PNIVEB8ITY OF CALIFORNIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA THE COLD STORAGE OF PEARS BY E. L. OVERHOLSER AND L. P. LATIMER BULLETIN No. 377 April, 1924 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY 1924 Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://www.archive.org/details/coldstorageofpea377over THE COLD STORAGE OF PEARS By E. L. OVERHOLSER and L. P. LATIMER The value of cold storage in the marketing of the pear lies primarily in prolonging the life of the fruit, and thereby extending the period of marketability. The placing of a part of the pear crop in cold storage, temporarily, to remove that portion from the market so as not to compete with the remainder, will probably become a growing practice. Pear production is increasing and as long as the necessity for disposing of the entire crop as soon as harvested remains, the market in some years may be overstocked and the prices low during the ' * peak period." This will be followed by a shortage of fresh pears and higher prices. According to Ramsey, McKay, Markell, and Bird 22 it would be nearly impossible to market the present apple crop without great loss to the growers and consumers except for the aid of cold storage. The deciduous fruit that can probably be next most satisfactorily cold- stored is the pear. Certain metabolic activities of the pear continue even after it is picked — the fruit respires or takes in oxygen from the air and gives off carbon dioxide and a small amount of water vapor. As a result of the metabolic activities, the tissue or flesh of the pear gradually breaks down, becomes dry and soft, and begins to decaj^. These metabolic processes are checked and the final breaking down of the tissue is delayed by placing the fruit in low temperatures, which do not freeze the tissue. METHODS OF EXPERIMENTAL PROCEDURE Experiments, therefore, have been conducted to determine the effects upon the storage behavior of pears, of certain factors, as follows : a. Storage temperatures. b. Maturity of fruit when harvested. c. Pear scald. d. Penicillium. e. Pollination. /. Ammonia fumes. g. Loss of moisture. Z UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Furthermore, the comparative keeping qualities of different varieties of pears in cold storage have been observed. Handling the Fruit. — The pears were picked, carefully placed in boxes, and in most cases brought into cold storage within six hours from the time of harvesting. In the case of fruit shipped from Davis and other points, the delay was short, usually not more than twenty- four hours. From each lot as received, ten specimens were taken and kept at room temperature (65° to 70° F.) to ripen. The remainder were divided between cold storage rooms of the various temperatures. These temperatures varied no more than 2° F. at any time. Methods of Observation. — At intervals of from two to four weeks, until they spoiled, ten pears were removed from each cold storage lot and placed at room temperature. Observations upon the fruits at room temperature were made every two or three days. At each observation the following points were noted: color of epidermis, color of flesh, stage of ripeness, flavor, quality, juiciness, defects; days required for ripening; days until valueless; general market condition ; and additional data that bore upon the problem. Definition of Terms "Optimum storage period" refers to the latest time of removal, which gave the best results in quality and time of holding up after removal from cold storage. "Maximum storage period" refers to the time beyond which it was considered unsafe to keep the fruit in storage, because of the likelihood of loss of quality, softening of texture, susceptibility to rot organisms, tendency to wilting, and rapidity of breakdown after removal, though it might still be in good condition. "Degrees of ripeness" were indicated by the following terms: 1. hard unripe 6. medium soft rip™ 2. firm unripe 7. soft ripe 3. firm ripe 8. past ripe 4. medium firm ripe 9. rotten 5. medium ripe "Texture" or relative juiciness was described by the following terms : 1. unusually juicy 4. moderately juicy. 2. very juicy 5. rather dry 3. juicy Bulletin 377] TH e COLD STORAGE OF PEARS 3 1 ' Quality ' ' or pleasantness of flavor was described by the following terms : 1. excellent 5. good to fair 2. very good 6. fair 3. good to very good 7. poor 4. good 8. very poor ''Days to ripen" refers to the number of days required for the fruit to attain a pleasing edible quality, either after harvesting or after removal from the storage temperatures. The condition corresponded to the degree of ripeness termed "medium firm ripe." "Failure in storage" signified the condition when the fruit, because of wilt, the growth of rot organisms, internal breakdown, and other limiting factors, became unfit for use. The fruit was considered valueless when ten per cent or more of the contents of a box became unfit for market. EXPERIMENTAL DATA The data concerning the behavior of varieties of pears in cold storage and the factors influencing their keeping quality, based upon from one to five years' work, are reported herewith. EFFECT OF TEMPEKATUKE UPON THE KEEPING OF PEAKS When the temperature at which fruits are stored is low, the life processes are retarded, but they do not cease, even though the tempera- ture is the lowest at which the fruit can be safely stored without permanently injuring the tissue. Cold storage is designed to check the ripening by a temperature that will not injure the fruit, thereby prolonging its life. Palladin 20 believes that respiration, since it is aided by, or possibly entirely dependent upon enzymes, is likely to be most active at about 75° F. He states that any lowering of this optimum temperature is followed by a retardation of the life processes of the organism. The metabolic activities of the fruit, which are a part of its life processes, require energy that is largely obtained by the utilization of the food materials stored within. Since low temperatures retard these meta- bolic activities, the life period of the fruit is correspondingly pro- longed. This is the basic principle upon which the preservation of fruit by means of low cold storage temperatures is founded. 4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Workers have differed with respect to the temperature recom- mended for storage of pears. Cooper 8 recommended 33° F., and stated 10 that 30° F. should be used only for pears to be kept for a long time, and that higher temperatures favor quality. Powell 21 recommended that pears be stored at a temperature of about 32° F., unless it was desired that the fruit ripen in storage, when temperatures of 36° F. to 40° F., or even higher, may be advisable. Lewis, et al 15 found that low temperature and high humidity, and high temperature and low humidity, were harmful to the ripening of the Bosc. Furthermore, Lewis, Magness and Gate 14 found with Bartletts that transferring pears from one storage temperature to colder storage temperature seemed definitely to check ripening for some time. They thought that suddenly changing the fruit from warm to cold storage after the ripening processes were proceding rapidly checked these processes to such an extent that ripening became slower than would be the case had the fruit been put in cold storage soon after being removed from the tree. TABLE 1 The Effect of Low Temperatures in Checking Ripening of Pears Temp, of Storage Opl imum Storage Maximum Storage Vanity Days to Opt. Storage Date Approx. Date Opt. Storage Days Mar- ketable after Removal at Opt. Stor. Date Days to Max. Stor. Date Approx. Date Max. Storage Days Mar- ketable after Removal at Max. Stor. Date 65° F. 45° F. 36° F. 32° F. 30° F. 65° F. 45° F. 36° F. 32° F. 30° F. 65° F. 45° F. 36° F. 32° F. 30° F. 65° F. 45° F. 36° F. 32° F. 30° F. 18 33 107 115 140 18 24 107 120 125 16 31 97 92 80 10 28 99 87 68 Sept. 16 Oct. 1 Dec. 15 Dec. 23 Jan. 17 Aug. 27 Sept. 3 Dec. 18 Dec. 31 Jan. 5 Sept. 15 Oct. 1 Dec. 6 Dec. 1 Nov. 19 Aug. 20 Sept. 7 Nov. 22 Nov. 10 Oct. 22 4 5 7 8 10 6 7 7 8 9 6 8 10 10 10 5 6 7 6 6 26 49 138 159 165 25 29 138 163 170 J9 37 134 127 120 24 34 112 121 119 Sept. 24 Oct. 17 Jan. 15 Feb. 5 Feb. 11 Sept. 3 Sept. 8 Jan. 18 Feb. 12 Feb. 19 Sept. 18 Oct. 7 Jan. 12 Jan. 5 Dec. 29 Sept. 3 Sept. 13 Dec. 5 Dec. 14 Dec. 12 3 4 5 Anjou 7 8 4 4 5 5 5 Bosc (0 6 Bosc 0) 7 Bosc (') 9 Bosc (') 6 Bosc (') 6 Howell (0 4 Howell C 1 ) .... 4 Howell (i) 5 Howell (J).... 5 Howell (') . . 5 0) Picked before proper ripeness. Magness 17 gives 30° F., or slightly below, as the best storage tem- perature for Bartletts. He found that Bartletts removed to tempera- tures of 60° F. to 70° F., after three months storage at 28° to 30° F., ripened satisfactorily and attained high quality. Bulletin 377] TH e cold STORAGE OF PEARS 5 The effect of low temperatures upon the keeping of pears is shown in table 1. In the investigations reported herewith, pears were placed in temperatures of 30°, 32°, 36°, 45° and 65° F. The data in table 1 indicate that pears picked at the proper stage of ripeness can be safely retained in storage at a temperature of 30° F. The fruit kept better and longer than at any of the higher tempera- tures. There is danger, however, attending storage at 30° F., in that it is near the critical temperature, below which injury to the fruit or actual freezing occurs. Wright and Taylor 28 give the freezing tem- perature of Bartlett pears as from 27.5° F. to 28.5° F. In commercial cold storage plants, with the difficulty of closely regulating the tem- perature uniformly throughout large rooms, the limits for tempera- ture fluctuations might not be sufficiently great. A temperature of 32° F. was found to be satisfactory except where the fruit was picked fairly green. The freezing point of most pears was sufficiently low to lessen the danger of storing at 32° F. It is interesting to note that fruit picked too green behaved better in storage at 36° F. than at 30° F or 32° F. At lower temperatures some varieties, when green, scalded more severely when, to check transpiration and wilting, the humidity was raised and the aeration was lessened. For example, the Howell at 30° F., developed a con- siderable amount of scald early in the season. Furthermore, the Bosc, picked when too immature did not ripen properly at 30° F. The fruit either developed a soft rot about the core, or wilted and remained firm and became insipid in flavor. At 36° F., however, similar specimens of Bosc gradually ripened and remained in marketable condition, except for slight wilting, for a longer period of time. The Forelle, Gray Winter, and Vicar, picked when relatively immature, also ripened best at 36° F. When green fruit was stored at 30° F., each week accentuated slight variations in the original degree of ripeness, seemingly because of unequal disturbances of the various ripening processes over a long period of time. This behavior was especially noticeable with the Louise variety. The Louise; for this test had been picked prematurely and was green when stored. It ripened satisfactorily both at room temperature and at a temperature of 36° F. Toward the end of its storage period at 30° F., however, the lots when removed exhibited various stages of ripeness from the yellow blush ripe to the grass green, hard unripe condition. 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He 11 suggested that the fruit should be harvested when the seeds turn brown. Stubenrauch and Ramsey 24 found that Bartlett pears picked when the fruit was still relatively immature deteriorated more rapidly than when picked later. They found that by leaving the fruit on the trees about two weeks longer, the season could be extended for from six to seven weeks. The suggestion was made that the number of pickings should be sufficient to allow all the fruit to mature on the tree. Magness 16 concluded that at the higher temperatures (70° F) early pickings kept longer than later pickings. At 40° F. storage, the early picked fruits scalded and became brown instead of ripening properly. The later pickings, however, ripened to full yellow and prime condition with almost no scald. Late picked fruit tended to become yellow more quickly than early picked fruit but remained firm in a prime eating condition for a longer period of time. An experiment to determine the effect of degree of ripeness at the time of harvest upon the keeping quality in cold storage and upon appearance and flavor was conducted by the writers. The Hardy, Bosc, and Cornice from the Santa Clara Valley were employed and were stored at both 32° F. and 36° F. The average cold storage behavior for the four seasons, 1919-20, 1920-21, 1921-22, and 1922-23, of the three varieties as influenced by the stage of development when picked are summarized in table 2. The height of the commercial harvesting period conformed to the second picking of each variety. The Bosc Variety. — The Bosc generally has a rich golden yellow skin almost entirely covered with a heavy brown or cinnamon russet. In the lots observed, however, a marked variation was noted in the character and color of the epidermis of the pears of the different pickings. Even after ripening, the pears of the first picking were only a pale yellow with but a few broken streaks of brown russet on the otherwise smooth surface of the skin. In ripened fruits of the third and fourth picking, the color was a rich golden yellow, and the epidermis was entirely covered with a cinnamon russet. The pears of the second picking, made at the height of the commercial harvest period, were intermediate in character between those of the first and of the third and fourth pickings. The fruit obtained at the first and second pickings was small and insipid in flavor. The fruits of the 8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION third and fourth pickings were larger, the flavor sweeter and more aromatic, and the quality of the best. Behavior at 32° F.—At 32° F.,the third and fourth pickings attained the best quality and richest flavor. The optimum and maximum storage dates were latest for the third picking, indicating that this picking was made at the most desirable stage of maturity for storage. The earlier the Bosc was picked, the greater the tendency for the variety to wilt in storage, especially in the long fleshy neck. There was, however, pronounced wilting at 32° F., with specimens of each of the pickings when the stem was injured (fig. 1). Behavior at 36° F. — A temperature of 36° F. was less satisfactory for storage of the Bosc than 32° F. The Bosc when picked at the optimum stage of development kept nearly six weeks longer at 32° F. than at 36° F. The Bosc specimens picked immaturely, however, had as late an optimum storage date at 36° F. as at 32° F., and likewise kept nearly as well at 36° F. as the third picking. Type of Failure. — At 32° F. the Bosc, especially when picked immaturely, generally failed from loss of moisture and wilting. The later pickings did not wilt so badly, but the tissue became soft and failure was due to internal breakdown. At 36° F., scald was the principal cause of failure and some rotting developed although the Bosc did not appear to be especially susceptible to the growth of rot organisms. The third picking of Bosc, made about ten days after the main commercial picking in the Santa Clara Valley, attained the most characteristic color, size, and general appearance, and kept to the latest optimum and maximum dates in storage (fig. 2). The Cornice Variety. — The first picking of Cornice was made when the fruit was relatively immature. The seeds were white and poorly developed, the flavor insipid, and the size inferior. The pears of the second picking were also small. They were, however, better colored and did not wilt so badly in storage. The quality attained was like- wise better, the flavor being sweeter, and the flesh more juicy ; the pears were, nevertheless, below the standard of quality for the Cornice. While the quality, flavor, texture, and juiciness of the pears of the third picking were better than at the previous picking, the size had only increased slightly. The fruit, however, appeared to be more mature. Cornice pears of the fourth picking were well colored, with a rich yellow ground color and a bright reddish overlay on one side. The quality and flavor were excellent. The size was nearly double that of the previous pickings, and the fruit was attractive and un- Bulletin 377] THE COLD STORAGE OF PEARS blemished. The pears of the fifth picking closely resembled the fourth, except that the specimens were more easily bruised and thus gave evidence of being overripe when harvested. Fig. 1. — Bosc pears after six weeks' storage, showing a tendency to wilt, especially when the stem is injured (center and lower). Normal pear (upper). The photograph was made at an early stage of storage. Behavior at 32° F. and 36° F. — The earlier the date of harvest of the first four pickings, the sooner the fruit failed in storage, both at 32° F. and 36° P. The failure of the first three pickings largely 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION resulted from wilting and scald. To a less extent, scald developed with the fourth picking. The fifth picking exhibited the least amount of wilting and scald, but failed in storage as a result of rotting about the bruised areas and softening and breaking down of the flesh. During certain seasons, the last, or fifth picking of Cornice, actually kept longer at 32° F. than the earlier pickings. At 36° F., however, the fifth picking always failed in advance of the fourth picking, indicating that overmaturity is more serious at 36° F. than at 32° F. \ k - j^Sfe; Mm ■'-■■■ 0M m\ B |{|WgS^s | jhi i|imj mii| mi, i m r 1 1 1 1 1,| H 1 1 1 1 m 1 j I • II 1 . 1 1 l s j M II u,i «ii Fig. 2. — The specimen on the left is a Bosc pear of the optimum picking made September 10. The one on the right is of the commercial picking (Sep- tember 1). The photograph taken January 15, illustrates the difference in size and also the degree of wilting when stored at 32° F. The pears of the fourth picking, made eleven days after the height of the commercial harvest period, were most satisfactory for storage, as indicated by the following characteristics: (a) Maximum weight, and size nearly double that attained at the time of the commercial picking; (b) excellent quality, sweet flavor and fine, melting, juicy texture; (c) highly colored, attractive fruit which retained its quali- ties for over five months in storage at 32° F., and which remained marketable for over two weeks after becoming ripe subsequently to removal from storage (fig. 3). Bulletin 377] TH e COLD STORAGE OF PEARS 11 The Hardy Variety. — The first and second pickings were undersized. The third picking was of good size, but the fourth and fifth pickings showed a marked increase in size of the fruit (fig. 4). The flavor of the fruit of the different pickings was as follows : First, acid to sub- acid and insipid ; second, sub-acid and aromatic ; third, sweet with almost no acidity. The pears of the third and fourth pickings were very juicy. Behavior at 32° F. and 36° F. — The quality attained by the Hardy pears stored in 32° F. was superior to that developed in 36° F. The pears stored at 32° F. were more juicy than pears kept at 36° F. At Fig. 3. — The specimen on the left is a Cornice pear of the commercial picking (September 10) and the one on the right is of the optimum picking made Sep- tember 21. The photograph taken on January 15, illustrates the difference in size and amount of wilting when stored at 32° F. 32° F. the first three pickings failed in storage because of wilting; the fourth and fifth pickings failed from internal breakdown and rot. At 36° F. the first two pickings wilted and scalded, but all the pick- ings were inclined to become rotten before wilting resulted. The commercial picking of the Hardy in the Santa Clara Valley has generally been completed by the first of September, or previous to the second picking of the experiment. The fourth picking, made about three weeks after the commercial picking, kept best in storage at both temperatures. The third picking, made ten days after the commercial picking, however, more nearly approached the keeping 12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION quality of the fourth picking at 36° F. than at 32° F. The size and flavor of the fourth picking was the best. The first and second pick- ings were made before the fruit was sufficiently mature for harvest, as evidenced by the severe wilting, small size, and inferior flavor. The fifth picking, while of large size and good quality, was made too late in the season for successful storage as indicated by the rapidity of ripening, breaking down, and rotting. Fig. 4. — The specimen on the right is the first picking of Hardy made August 22, nine days previous to the commercial picking. The specimen on the left is from the optimum picking made Septetmber 21. Note the difference in size and degree of wilting. The first picking never became marketable. Photo- graph taken January 15. Directions for Harvesting. — The evidence shows that immature pears do not keep so well as those which are firm and mature. Obser- vations during three seasons indicate a tendency in some sections of California to pick pears before they are sufficiently mature. The texture, flavor, quality, and market value of this immature fruit do not equal that of the better developed, properly matured fruit. The fruit, however, must not remain on the tree long enough to become overripe. Such fruit is nearer the end of its life limit and consequently deteriorates with even greater rapidity in cold storage than immature fruit. Bulletin 377] TH e COLD STORAGE OF PEARS 13 It is difficult to give directions that will enable a grower satis- factorily to determine the proper time each season to harvest his pear crop. Color, especially in the case of pears which have a red blush, seems to be correlated with maturity. For example, it is noticeable that such pears usually wilt or shrivel more on the uncolored side. As the pear attains maturity, as evidenced by the fading of the green or deepening of the yellow, there is deposited over the surface a layer of cutin. This cutin is a substance only slightly permeable to water. It acts as a protective wax-like covering and prevents the loss of water through the skin; and may also, to some extent, oppose the entrance of rot organisms. An indication of the best stage of maturity for harvesting pears is the shade of "ground" color of the fruit; that is, the color which underlies the red blush in the case of colored varieties, or the surface color of varieties that develop no red. The ' ' ground ' ' color, which is immature, becomes lighter in shade and assumes a faint yellowish tinge as the fruit approaches maturity. A pronounced yellow, how- ever, usually indicates overmaturity. Murneek 18 has devised a special apparatus for a "pressure" test which appears to be a practical means of measuring the stage of ripeness of pears, particularly Bartletts. He found that harvesting of Bartletts under Oregon conditions should commence when the pressure test with his apparatus indicated an average resistance of 35 pounds. The lower limit at which it is safe to pick Bartletts is 25 pounds. The Bosc, according to Murneek, during its picking season should register 20 to 24 pounds, as measured by his method. Other late fall or winter pears show different figures. EFFECT OF PEAR SCALD Pear scald is a dark brown or blackened condition of the skin, generally localized at first, but finally involving the entire surface of the fruit, rendering it unfit for the trade. As a rule the scald is superficial, rarely extending more than one-eighth of an inch beneath the surface. The authors observe that a peculiar flavor usually accompanies scald and could be detected before the tissues showed any discoloration. Pear scald is the result of unfavorable cold storage conditions, although maturity and weather at the time of harvest, delays in storing, and methods of handling also affect scald development. 14 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Temperature. — Observations during the past five years have shown that scald occurs when pears are kept at temperatures of 45°, 36°, 32°, and 30° F. Fruit not placed in cold storage, but ripened at room temperatures, did not develop scald; such fruit failed from internal breakdown, wilt, or rot. Pears stored at the higher cold storage temperatures, especially 36° F., scalded more severely and at an earlier date than fruit of the same lot held at 32° or 30° F. At a temperature of 45° F., before scald appeared, the quick germination of fungi spores and their subsequent rapid growth resulted in decay. Table 3 shows that a temperature of 32° F., as contrasted with 36° F., delayed the development of scald. With Cornice pears the delay was from four to eight weeks; with Bartletts about six weeks. TABLE 3 Effect of Storage Temperatures upon Development of Scald Date Picked Date of Development of Scald Variety 32° F. 36° F. Cornice Aug. 18 Aug. 29 Sept. 7 Sept. 17 Sept. 28 Wilt (no scald) Jan. 10 Wilt, very slight scald Dec. 15. (t (I Mar. 10 Jan. 7. it Feb. 10 Jan. 1. a No scald Bartlett (selfed) Aug. 24 Aug. 24 Jan. 1 Nov. 21. Bartlett (crossed) Jan. 2 Dec. 1. Aug. 18 Aug. 29 Sept. 7 Sept. 17 Aug. 18 Aug. 27 Sept. 7 32° F. Cause of Failure 36° F. Hardv Wilt Scald. a Wilt Scald. a Wilt Scald. u Rot Rot. Bosc Wilt; breakdown.... Wilt; breakdown.... Wilt; breakdown.... Scald. It Scald. it Scald. Scald frequently occurred at 36° F. ; at 32° F., with the same varieties, wilting occurred instead of scald. In this respect pear scald is analogous to apple scald. Before the actual appearance of scald in storage, it was possible to detect a peculiar taste in the fruit. This flavor indicated a rapid subsequent development of scald. Furthermore, fruit at this stage, Bulletin 377] THE COLD STORAGE OF PEARS 15 even though showing no scald in storage, developed the trouble within four or five daj^s after removal to room temperature. Thereafter con- siderable scald would appear in storage. Maturity at Harvest. — The effect of maturity at the time of harvest on susceptibility to scald was marked. With varieties susceptible to scald, it was found that fruit harvested when properly matured was less subject to scald than when picked relatively green, or overripe, as shown in table 4 and chart I. TABLE 4 Effect of Maturity at Time of Harvest upon the Development of Scald in Storage (1921-22) Variety Days to failure from scald Maximum storage date 32° F. 36° F. 32° F. 36° F. Bartlett (selfed) Aug. 24 Sept. 6 Sept. 16 131 132 107 88 Jan. 1 Jan. 15 Jan. 1 Oct. 21 a a Cornice Aug. 18 Aug. 29 Sept. 7 Sept. 17 Sept. 20 Wilt 134 183 146 Rot Wilt, slight scald. 108 122 106 Rot Jan. 10 Jan. 10 Feb. 20 Mar. 1 Feb. 20 Nov. 22 n Dec. 1 a Dec. 15 it Dec. 22 (< No picking. Hardy Aug. 18 Aug. 29 Sept. 7 Sept. 17 Wilt Wilt Wilt Rot 107 125 100 Rot Jan. 15 Jan. 15 Feb. 15 Jan. 15 Nov. 10 te Jan. 1 it Dec. 15 Nov. 15 The first picking of Cornice pears wilted, while the last picking failed from rot. The Hardy pears likewise showed a tendency to rot when picked late. Magness 17 states that the earlier picked fruit scalds. The results obtained at this Station showed this to be true when excessive wilting did not occur. Table 4 also shows that the more immature fruit generally scalded sooner after harvest than did the properly matured fruit ; over mature fruit, however, scalded more rapidly and severely than either. Days to Failure from Scald 388ig§3ig§§S§§ g Bulletin 377] T he COLD STORAGE OF PEARS 17 Certain varieties were notably more susceptible to scald than others. Data for four years showed the Bartlett to be most subject to scald of the varieties studied. The Cornice was next and was closely followed by the Louise and Clairgeau in degree of susceptibility. Furthermore, such varieties as the Bordeaux Vicar, and Pound, of rather low quality and rarely attaining a pleasing eating condition, were found to be subject to scald in storage. The Hardy was also sometimes affected. The Easter Beurre, Forelle, P. Barry, Anjou, and other long keeping varieties on the other hand were apparently immune. There is evidence that the region where grown may have some influence on the occurrence of scald. For example, most pickings of pears grown at Santa Clara, California, during 1922-23 showed severe scalding after removal from storage by the middle of January. The Cornice pears obtained from Davis, however, did not show signs of scald until March 15. Bartlett pears obtained from Antelope Valley, having an elevation of 3000 to 4000 feet and high summer tempera- tures kept two months longer without scalding than those grown at Niles near the coast. Another interesting feature noted was the manner of scalding with the Bordeaux and Pound pears in the box. Upon removing them from the box during the early stages of scald, it was noticed that the pears first scalded where they had been in contact with the sides of the box or with each other. A similar effect was noted in the case of the same two varieties, and also of the Clairgeau when scalding occurred after removal from storage. The parts of the fruit lying against the container and against one another scalded first. This is comparable to apple scald where ventilation retards the development of the trouble by permitting the escape of the injurious gases produced. 7 EFFECT OF BLUE MOLD Blue mold (Penicillium sps.) may seriously affect pears in storage and is the principal mold making appreciable growth at temperatures of 32° F. Varietal Susceptibility. — Susceptibility to blue mold differed greatly with the variety of pear. The Columbia, Alencon, and Seckel, apparently on account of the character of the tissues and epidermis, were relatively immune to the disease. Columbia pears were free from blue mold infection after sixteen months' storage at 32° F. However, 18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION after this period of storage the flesh had become browned, the pulp dry, and the quality poor. The Seckel pears also broke down internally rather than molded. The Onondaga, Flemish, and Diel were susceptible to attacks by blue mold at 32°, 36°, and 45° F. The higher the temperature, the greater the susceptibility; this trouble was generally the limiting factor in lessening their storage period. At temperatures of 36° and 45° F., the Easter Beurre was also susceptible to the growth of blue mold (fig. 5). Other varieties, such as Urbaniste and Howell, were susceptible, under certain conditions, but not to the same degree. Fig. 5. — Easter Beurre pears showing characteristic type of failure in storage at 36° F., from blue mold (Penicillium expansum Link). The Winter Nelis, P. Barry, Forelle, Hardy, Cornice, Bose, and Glout Morceau were midway in degree of resistance as contrasted with the groups just discussed, although they were attacked under con- ditions favorable for mold growth. In general, all varieties molded when the fruit was bruised and sufficient moisture was available. Temperature. — Brooks and Cooley, 5 studying the development of Penicillium expansum Link, on apples found, according to the tem- perature, a difference (a) in time necessary for infection to take place; Bulletin 377] THE COLD STORAGE OF PEARS 19 and (&) in the rapidity of growth thereafter with different varieties. A consistent correlation between growth and temperature in general was found to exist. They also noted that at 32° F., P. expansum made a quicker germination and more rapid early growth than any other fungus studied. They stated that this fact helped to explain its common appearance in cold storage. They found that 68° F. was optimum for the development of blue mold. At 86° F. on the Winesap, growth was scant. At 32° F. the diameter of rot caused by P. expansum was 10 mm., eight weeks after inoculation; while at 41° F. the diameter of rot was 55 mm. It took more than two weeks for the rot to commence growth below 50° F., but between 50° F. and 68° F. there was great accelera- tion in the rate of development Eustace 12 found that at a temperature of 31° F. the growth of blue mold (P. glaucum) was not so effectively checked as that of other organisms and that considerable damage, therefore, resulted in cold storage by the growth of this fungus. He found that at 34.7° F. it took about twenty times as long for the spores to germinate as at 71.6° F., which was the optimum temperature. Blue mold occurred at all temperatures commonly used for storing fruits. At the lower temperatures, however, the growth and develop- ment of blue mold spores and mycelium was so retarded that the damage to fruits from a commercial standpoint was far greater at temperatures of 36° F. and above. The data obtained by the writers pertaining to the effect of tem- perature upon the growth of blue mold are given in table 5. TABLE 5 Effect of Storage Temperature upon the Growth of Blue Mold (Penicillium sps.) on Pears (1921-22) Variety Tempera- ture Date value- less from blue mold growth 32° F. No mold 36° F. Nov. 21 32° F. Jan. 1 36° F. Dec. 10 32° F. Apr. 1 36° F. Jan. 10 32° F. No mold 36° F. Feb. 10 Date of maximum storage Bartlett (selfed) Bartlett (selfed) Onondaga Onondaga Diel Diel Easter Easter Jan. 1 (scald) Nov. 21 Jan. 1 Dec. 10 Apr. 1 Jan. 10 May 1 Feb. 10 20 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Selfed Bartlett pears of the first picking at 36° F. showed growth of blue mold by November 21, while at 32° F. no mold occurred; failure at that temperature, however, resulted from scald on January 1. Upon the Onondaga, blue mold developed twenty days later at 32° F. than at 36° F., while upon the Diel it was delayed about eighty days. With the Easter at 36° F., mold developed by February 10, while at 32° F. no mold had occurred as late as May 1. Maturity at Time of Harvest. — Late pickings were generally more susceptible to blue mold than earlier pickings. Earlier pickings of Easter Beurre pears developed no mold, while late pickings were quite subject to the rot. The early picked fruit tended to wilt and this lessened the occurrence of mold, probably because of the lack of favorable moisture conditions. At 32° F., during the 1922-23 season, the Bloodgood picked July 6 failed from wilt October 20 ; the second picking, July 13, failed from blue mold December 1. In general, it was only the latest picked fruit that molded badly. Wounds, bruises, and delay in getting into storage greatly increased the damage from Penicillium sps. Most varieties possessing a tough, well cutinized epidermis, free from bruises or scars, were rarely destroyed by mold in storage. Specimens of the same varieties, how- ever, with skin punctures developed blue mold. In addition the developing rot and exuding juice produced conditions so favorable for mold growth that adjacent sound fruits also became quickly infected. These observations are borne out by other investigators. Brooks, Co'oley, and Fisher 7 working with apples, state that the germ tubes of blue mold did not penetrate the sound skin of the fruit, but gained entrance through wounds resulting from mechanical injury or from insects. However, when a sound apple was imbedded in the remains of a rotten one the disease apparently penetrated the skin without a puncture. Delay in storing after harvest hastened the time when fruit in cold storage was rendered unfit by mold. Brooks and Cooley 5 showed that fruit picked and inoculated October 19 by puncture with the spores of blue mold and placed in storage immediately at 32° F. developed no rot as late as February 28. However, when storage was delayed seven days after inoculation, considerable rot had developed by February 28. This resulted because the spores had developed suffi- ciently at the higher temperature previous to storage to permit subsequent growth after being stored. Bulletin 377] the cold storage op pears 21 EFFECT OF POLLINATION Bartlett pears in the Antelope Valley frequently set fruit partheno- carpically or without the development of seeds. Certain growers of that section have in some instances been opposed to provision for cross- pollination, because they felt that seed development lessened the keeping quality of the fruit. Chart II. — Showing the keeping quality of seeded and seedless Bartlett pears at storage temperatures of 32° and 36° F. "Op," optimum storage date; "M," maximum storage date. During the season of 1921-22, tests were conducted to determine the effect of pollination upon the keeping quality. Bartlett pears were obtained from Littlerock,* a desert region of from 3000 to 4000 feet elevation. Three different pickings were made of both hand-crossed fruit (Bartlett x Winter Nelis) and fruit which had set partheno- carpically (self pollinated). The data obtained are presented in table 6 and in chart II. * The writers desire to express thanks to Mr. M. W. Dula, who made the hand crosses of Winter Nelis upon Bartlett and who supplied the fruit from Littlerock, California. 22 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION < O* H i PQ M o P O n o 0) P 1 o m a a a be d«« cs P=h" fa fa fa ptj fa fa fa' oooooooo MCD(N(N(NCO(NiM WWWCOWOOCOM Days to value- less OOOO^^ffllNOM 5° d p -a OQiOOtOOOOCO 03 P H00NNOC300O3 woocooiooicooi i-H i—l i—l rH i— 1 P 1— 1 1— IIOtHOi— 1 lO ifl 0) p bO c9 i-i o CQ S J '+3 a O Days to value- less 0> P (NOOOCOOCSCOCO P lOr-l»Oi— li— li— 1»00 i— 1 OQ i— 1 i-H i—l Days to value- less 1> 1> io CO CO CO « d gH a P -c O O 00 T-H i—l O O 00 i-H i-H 0>U i-Hi-HtNCO'-H'-IIMCO OS Selfed.... Selfed.... Selfed.... Crossed. Crossed. Crossed. Crnsspd > Bulletin 377] TH e COLD STORAGE OF PEARS 23 Observations. — The cross-pollinated pears, because of the large amount of tissue comprising the core, had less edible flesh than the fruit which set parthenocarpically (fig. 6). The data showed that the crossed Bartletts matured earlier than the selfed fruit. This was indicated by the fact that at 36° F., on November 16, the box of first picking of selfed pears showed scalding to the extent of from 95 to 98 per cent, whereas the crossed Bartletts had just begun to scald. Later in the season it was found that the selfed Barletts at 32° F. showed scalding fully three weeks before the crossed Bartletts. Fig. 6. — Bartlett pears self-pollinated (left), cross-pollinated (right), showing the relative proportion of edible tissue in each. Facts tending to confirm the belief that the selfed pears matured more slowly on the tree than the crossed pears were as follows : (a) The early date of scalding indicated immaturity, (b) The crossed Bart- letts colored and ripened in storage before the selfed. (c) The first pickings of crossed pears kept better than the first picking of selfed, because the former were nearer the proper stage of maturity while the latter were immature. The last picking of the crossed pears kept but a relatively short time, because they were approaching over- ripeness, while the selfed were still at the proper stage of maturity. The facts indicate that the crossed pears were in an optimum condition for storing at a time midway between the first and second pickings. The selfed Bartletts were in an optimum condition for storing two weeks later, at a time when the crossed pears were too mature for successful storage. 24 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The results showed that with the early picked fruit, the cross- pollinated pears kept the longest. Wth fruit picked relatively late, however, the self -pollinated pears had an optimum date nearly two months later and a maximum date two weeks later. A difference in methods of spoiling was noted. The breakdown in selfed pears, which were removed from storage and ripened, was characterized by a browning and softening of the tissue commencing at the surface of the fruit and progressing inwardly until the entire specimen was spoiled. The cross-pollinated specimens broke down at the core first, and the browning and softening of the tissue progressed outwardly. Apparently crossed pears should be picked about two weeks earlier than selfed pears. The difference between the shapes of crossed and selfed Bartletts (fig. 7) aids in distinguishing them. At each picking only pears of a uniform stage or ripeness, which are sufficiently mature, should be harvesetd. EFFECT OF AMMONIA FUMES UPON PEAKS Anhydrous ammonia is the g*as most frequently employed to obtain refrigeration. Notwithstanding care exercised by men in charge of plants, leaks may occur with certain types of equipment, and ammonia fumes may thus unavoidably gain entrance to storage rooms. Hence it becomes of interest to note the effect of ammonia gas upon the fruit. Pears contain a substance that behaves similarly to a vegetable litmus by becoming dark when alkaline and colorless when acid. The behavior is apparently similar to that found for apples by Overholser and Cruess. 19 Ammonia gas gives alkaline reaction. Since the fumes are quite soluble in fruit juices, they may be absorbed through the lenticel-like openings, or ' ' dots ' ' of the epidermis, sufficiently to bring about an alkaline condition in local areas. The oxidation processes in pears also proceed more rapidly when the medium is slightly alkaline than when it is acid, as is normally the case with the tissues of pears. Furthermore, the concentration of ammonia may become sufficiently great to act deleteriously by increas- ing the permeability of the cells and thus disorganizing the protoplasm and permitting the mixing of the oxidizing enzyme and substrate. Hence fruit subjected to ammonia gas or fumes may also darken by oxidation, but the discoloration thus produced is apparently distinct from that immediately effected by alkalinity. The two colors, however, are inseparable upon the basis of appearance. Bulletin 377] THE COLD STORAGE OF PEARS 25 Fig. 7. — Self -pollinated Bartlett pear (left), cross pollinated specimen (right), showing characteristic shape of each. it. V Fig. 8. — Vicar pear (left) and Col. Wilder (right), showing the effect of ammonia fumes upon firm unripe fruit. 26 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Figure 8 shows the characteristic appearance of pears subjected to ammonia gas. The cells immediately adjacent to the lenticel-like opening's of the epidermis first exhibited crimson colored rings about the lenticels that quickly became black. The depth of penetration, except upon prolonged exposure, was from three to five layers of cells. Upon continued exposure for from five to seven days, darkening took place to a depth of one-half inch, although the fibro-vascular bundles were darkened to a greater depth. Effect of Stage of Maturity when Harvested. — Cornice pears picked at four different stages of maturity were exposed to ammonia fumes. The later, better matured pickings were more slowly affected than were the earlier pickings, as shown in table 7. TABLE 7 Effect of Maturity of Comice Pears when Harvested upon Susceptibility to Ammonia Fumes Picking Date Harvested Time for first dark spots to appear Time for numerous spots Time for general darkening of surface to occur 1st Aug. 18 Sept. 7 Sept. 17 Sept. 28 60 minutes 75 minutes 125 minutes 195 minutes 125 minutes 115 minutes 195 minutes None 140 minutes 2nd 146 minutes 3rd 210 minutes 4th 285 minutes Similar observations with other varieties indicated that pears picked in a green condition were more seriously affected by ammonia fumes than specimens picked in a more ripened state. Histological examination of the epidermis of the different pickings of Comice did not show any significant variation in the thickness of deposition of cutin or in the size of the lenticel-like openings. There was a difference in the number of lenticels per square centimeter, averaging 35 in the first picking and 27 in the fourth. This, however, would not appreciably affect the rapidity of darkening of tissue about the individual openings. Nevertheless, the lessened rapidity of pene- tration of the ammonia gas in the case of the later pickings indicate a more complete sealing of the epidermis as maturity progressed. Difference in Varietal Susceptibility. — Four pickings each of Hardy and Comice were contrasted with respect to the varietal sus- ceptibility to ammonia fumes. The time required for the effect to become apparent was averaged for the four pickings of each variety, as shown in table 8. Bulletin 377] THE COLD STORAGE OF PEARS 27 TABLE 8 Difference in Varietal Susceptibility of Comtce and Hardy Pears to Ammonia Fumes (Average of Four Pickings) Variety Average time for first dark spots to appear Average time for general darkening of surface to Average area of lenticel openings in epidermis Average frequency of lenticel openings Cornice. Hardy.. 132 minutes 42 " 213 minutes 51 .063 sq. mm. .30 " " 31 per sq. mm. 21 " " " The Hardy showed a more rapid penetration of the ammonia fumes than the Cornice. The lenticel areas of the Hardy darkened over three times as rapidly as the Cornice, and the entire epidermis was blackened about four times as rapidly, indicating that the absorption proceeded at an accelerated rate. Furthermore, the Cornice exhibited an inter- mediate stage where the black dots became numerous, and subsequently the entire epidermis darkened. The entire epidermis of the Hardy, however, quickly darkened after the appearance of the first black dots. This difference in varietal susceptibility may be accounted for by the fact that the lenticel-like openings of the Hardy were nearly five times the diameter of those of the Cornice. Furthermore, the thickness of cutin covering the epidermis of the Hardy was about one-third that of the Cornice, and the evidence indicated that the ammonia fumes penetrated the layer of cutin in the Hardy. The presence of moisture increased the seriousness of the effects of ammonia fumes. Pears that were badly wilted and which had a dry surface were not so susceptible to ammonia fumes as those with a moist surface. LOSS OF MOISTURE IN RIPENING Interesting data pertaining to decrease in weight of Bartlett pears during ripening through transpiration losses of moisture are available through the Cooperative Cannery at San Jose, California.* During the 1922 season about seven tons of pears were handled. As deliveries of fruit were made, samples of 25 pounds were removed. Each sample was placed two layers deep in a lug box. The boxes were piled nine high, with space between each stack, in a sample room having ample ventilation. The average period for ripening was nine days from the time of harvest. The loss from rot was almost nil. The decrease in weight through loss by transpiration during the nine days was 5.23 per cent or about 104 pounds per ton. * Furnished through the courtesy of Dr. T. D. Stewart, Dept. of Chemistry, University of California. 28 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION The authors found that the actual moisture loss, however, varied with the variety and the stage of maturity when harvested, as shown by the data in table 9. Fruit of each picking was chosen at random immediately after harvest and placed at room temperature, having a relative humidity of about 55 per cent. Samples averaging 1000 kilo- grams were employed. TABLE 9 Percentage Loss of Moisture from Pears during a Eipening Period of Twenty Days (1921) Variety Picking Date of picking Per cent moisture lost Hardy 1st 2nd Aug. 18 Aug. 29 Sept. 7 Sept. 17 Aug. 18 Aug. 29 Sept. 7 Aug. 18 Aug. 29 Sept. 7 Sept. 17 13.7 it 12.9 tt 3rd 12.8* n 4th 10.5 Bosc 1st 12.3 u 2nd 11.6 It 3rd 9.1* Comice 1st 11.4 tt 2nd 9.7 n 3rd 9.2 n 4th 7.2* Most satisfactory picking for storage. Of the three varieties tested, the Hardy lost the largest percentage of moisture and the Comice the least. The earliest pickings of each variety lost the greatest quantities of moisture, and the later pickings least. Storage for Canning. — In canning the pear crop it is often of value to place a portion in cold storage, during the peak period to lessen possible spoilage and to enable peaches and other more perishable products to be canned first. The retention of pears for a certain period of time in cold storage does not lower their quality for canning purposes. The Bartlett, if properly picked, has an optimum date, not earlier than October 15 when stored at 30° F., and it appears that a portion of the crop could be held in canning condition until the apricots, plums, and peaches had been canned. Magness 17 found that storing the Bartlett for optimum periods of time did not injure its quality for canning. Bulletin 377] TH e COLD STORAGE OF PEARS 29 VARIETAL BEHAVIOR IN COLD STORAGE The data concerning the behavior of varieties of pears in cold storage, obtained during the seasons of 1918 to 1923, inclusive, are presented in table 10. The varieties are described in the order of their optimum storage dates, those with the latest dates being described first. 1. Doyenne d 'Alencon The Alencon was obtained from Niles and from Davis for two seasons. Its average picking date was September 28. The excessive wilt, and the fact that the fruit did not ripen when removed from storage at the beginning of the season, during the first season's observation, indicate that this variety was picked too early. The fruit was picked later during the second season (October 17) and kept to a late date. The quality of the Alencon was low, the fruit being coarse and flavorless. Behavior at 32° F. — The quality, poor at first, became fairly good after three months' storage. Until that time the fruit did not ripen when removed from storage. The fruit, prior to January 2, was dry ; after that date a little juice was present. The optimum and maximum date for the two seasons of 1921 and 1922 was May 1, or 215 days after harvest. The quality, up until May 1, was as good as ever attained but thereafter failure rapidly resulted from mold. Hence the optimum and maximum storage periods were made to coincide. Cause of Failure. — Failure in storage of early picked fruit resulted from wilt. Wilt determined the maximum date of storage. Fruit late picked was attacked by Penicillium. 2. Lawrence This variety was harvested at Niles and was stored at 32° F. during two seasons. The average picking date was September 21. The fruit was of medium size, uniform in shape, and of superior quality. It, however, did not color up well when ripe, remaining greenish or becoming only a pale straw color. It was one of the best varieties for retention in cold storage, and appeared desirable for the home garden. For a late shipping or storage pear it also appeared worthy of trial in California, 30 UNIVERSITY OF CALIFORNIA— EXPERIMENT STATION ft . o Eh o OQ 1-1 w eg 53 Hi H pq h< 6 S B .5 ^ If 5 =3 a 5 ^ i» ,P £ c Pl, pl, Pm & m a o •2 ^ J tJ Ph f> t> CO if . •3 Q 1 1 '3 -^ Ph pq - o s ^ 2 5 ,0 "1 "P«i £& 2 +? CO ^ ££ M O N » O) iO r^OCOTttO iOMT|tMiOffi<*ionilOOHO)OONNMiOWHCOMS^^- ^-iCO (NINNNHHININNNININHHWrilNNHMHOIHHHri >>>>>>:>> l_J WW u hH Wi M< -j Ml >1 M M-. k_, QJ 0) I— I »— I M W w M U M W< NOOOIKDnM^NNMOO (M O lO O 00 loniooMMnoooOHCoioin^NcccoooNntooo HOOOOONMiOC^MCDOiCOMtOTtl't'tMHINfOMCOHO) (N(NrHi-,r-l ; i-li-Hi-(i-(^Hr-(^lrHi-(r-(r-(rHT-li-Hi-HrHi-l r-H ,-H k2 &J5MS,£J3J2£u^'£'Sa;a3a;a3a3'£ 3 3 2 2 -l i-H rH t^ 1-4 rH r-l^r-lrHC^ ,-, ,-t ,-, rH tN H i-t * £ ffl W pq «. ^ Bwq Ph W O £ o s o S 3 a i* Bulletin 377] THE COLD STORAGE OF PEARS 31 o XI M 03 o QJ d o d d o Tl XI — < OS -Q r* n o si Bl d 0) rM a 09 ia 2 d o £ 3 Tl £ 73 -s 03 u £ o d O o "5 3 '5 0) 2 2 o o 03 go >> o 2 '£ fin t o £ - o '5 2 o 7. O P4 i i *«■«■*•** PQ 02 M rj 3 *-" Pi ^ 3 * .2 <-T O o> [_, c3 O tf p., pq (s< tf o£ >0000(NOrH COOO>-hOOcDOOCOOOt}< : .-i CO *# CO 00 f> d ^ > ci +; ^ +j li n ^!0O»O«0)T(((NNffiNt0OnMONO«^IN00OK5O(0Ttl 1 — I ' — I ' — I « — 1 ' — I ' — I lH l-H ,-( .-ll-HCl.-l.-l.-l.-l r-( ,-H l-l r-l ,-H eMiom-oeNcoo^ : o o n «; « : co : n >o n * : io o r-< IC' t^ b- oo to «4 *J +J *> hJ *i *; hJ +=• *>* "S, a m j>> QQQQ£;z;£;z;£££££00000000000£ffi<<^ OOltMOfflWNN ^MMHNONMOlHffi 00 "0 N O) N TfiOlHOHMijtWOO^OONO 3 3 3 ffiOD b b h 1f©iO(ONHNH^ « s ^ « O (H £ >, § « ! '3 9 o \r (h a) _ 3 SS o 0) o U w a. S t 3 -d h 3 2 T3 n ft 6 O h 73 d S^ d StSai s .Opx;5ooSt3 pqtfwPQfepqOpqOO^oSt-lOm^^ 32 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Behavior at 32° F. — At 32° F. the Lawrence kept remarkably well, retaining its good qualities unimpaired until April 11, 203 days after harvest. The maximum storage date, June 1, was more than seven months after harvest. 3. P. Barry The P. Barry was obtained from Niles for two seasons with an average picking date of September 18. The fruit was packed loosely in boxes. One portion was stored at 32° F. and the other at 36° F. In cold storage the fruit of this variety retained its flavor and melting, buttery, juicy texture long after most other pears had lost these qualities. It also had an optimum storage period about six months in length. Of the marketable pears of good quality, it ranked second to the Lawrence as a long keeper. The fruit ripened evenly in storage. It has been recommended as a good shipper and keeper by several authorities, 2 ' 3 and is the best of the B. S. Fox creations. The P. Barry probably was a trifle immature when harvested in 1921, as evidenced by the delay in ripening without storage. The marked acidity noted at first and the slight amount of shriveling occurring when ripened late in the storage season, were perhaps further evidences of premature picking. Behavior at 32° F. — At 32° F. the optimum storage date of the P. Barry was March 22, or 185 days after harvest. The maximum date was May 20. Without storage the P. Barry required twenty-four days to ripen and kept fourteen days more before becoming valueless. The first removal at 32° F. was inferior in quality to later removals. The intensity of the acid flavor diminished during the season and the sweetness increased. The combination of acid and sugar was improved by storage at 32° F. Behavior at 36° F.—At 36° F. the optimum date was February 20 and the fruit was of excellent flavor. The quality from this date on, however, was inferior to that of the fruit held at 32° F. At 36° F. the flavor was less acid than at 32° F. The maximum date, as deter- mined by the poorer flavor and softer texture, was April 1. Never- theless, its quality remained good. The fruit, however, was too soft to handle successfully. Cause of Failure. — Failure in storage resulted from Penicillium. There was no scald or wilt noticeable in storage. On removal from storage, failure resulted by the tissues becoming soft and the surface somewhat wrinkled. Bulletin 377] THE C0LD storage OF PEARS 33 4. FORELLE The Forelle was received from Davis and Niles and was observed during four seasons. The average date of harvest was September 16. This variety kept better at 36° F. This, however, might not have been the case had it been picked more mature. Although of attractive appearance and sweet flavor, the variety was surpassed in quality of flesh and texture among other long-keeping varieties by "Winter Nelis. In Germany it is a favorite, widely planted variety. 13 Reimer 25 states that it is more susceptible to blight than any other variety. Behavior at 32° F. — At 32° F. the Forelle was one of the longest keepers. The optimum date averaged March 15, the maximum date was May 17. The quality developed, when stored at 32° F., was good. The texture was crisp and the juiciness medium. On removal from storage early in the season, the Forelle was tough and did not ripen. After two months' storage the fruit ripened fairly well, being at its best after January 1. Behavior at 36° F. — At 36° F. the Forelle attained a better quality than at 32° F. The texture was not so coarse. It ripened on removal from storage one month earlier than at 32° F. The removal that was made the first week in October ripened in good condition. During the season of 1921-22 the end of the optimum period was February 20, ten days later than at 32° F. The maximum was about May 1. Cause of Failure. — Failure after removal from storage was caused by internal breakdown and wilt. Failure in storage resulted from scald and Penicillium. 5. Columbia The Columbia was obtained during the 1921-22 season from the Santa Clara Valley, and was picked on September 18. One box of carefully wrapped and packed fruit was stored at 32° F. This pear, of varieties under observation, was one of the more desirable for storage. None of the other varieties were so free from mold or rot. The Lawrence, Dearborn Seedling, and P. Barry retained their good flavor longer than the Columbia, but were more perishable when ripe. With the exception of the Block "18," the Columbia remained in a marketable condition for a longer period after removal from storage than any other variety under observation during 1921-22. At the optimum date, five days were required for ripening and sixteen days more for failure to occur. 34 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The dark colored, rather coarse flesh and abundance of grit cells, on the other hand, were undesirable characteristics. Another undesir- able feature was the non-uniformity of ripening after removal from storage. This was more noticeable in the earlier than in the later removals. One to two weeks' difference in the time of ripening was noted in pears removed from storage at the same time. This marked variation was not observed in any other variety. Behavior at 32° F. — At this temperature the variety kept excep- tionally well. The flavor and quality of the flesh improved in storage and on March 1 was very good. In the removal made on March 27 the flavor was still rich, but the fruit had become drier and slightly astringent. The optimum date, determined by the loss of its highest quality, was March 15, or 178 days after the fruit had been picked. The maximum date was April 1. The fruit appeared normal from the outside, but was found to have suffered severely from internal break- down. Hence poor fruit might easily be placed on the market and appear in prime condition to the eye. Cause of Failure. — Failure after removal resulted from drying of tissues, causing them to become mealy. No mold or scald developed in storage or after removal. 6. Block "18" The Block "18" was obtained from Santa Clara during the season of 1921-22, on October 24. The fruit was received wrapped, in a standard pack, and was stored at 32° F. The variety possesed a splendid appearance. It had a smooth skin, uniform shape, and freedom from blemishes. It was also valuable in that it developed a richer flavor than other pears of the Oriental type. The defects noted were coarse flesh and numerous grit cells, and as a result it was not so promising for storage as several other varieties. Behavior at 32° F.— The variety kept satisfactorily at 32° F. The maximum date, April 15, was determined by the quality and flavor, which was fairly good, but below that of previous removals. The external appearance, however, was still good. The optimum storage date, March 10, at 32° F. was exceeded only by Lawrence, Doyenne d'Alencon, Dearborn Seedling, P. Barry, and Columbia. The number of days to the optimum date, however, was only 133, because of the late harvest date of October 24. The fruit remained marketable for three weeks after removal from storage on the optimum date. Bulletin 377] TH e COLD STORAGE OF PEARS 35 Furthermore, the maximum date, while late in the season, was only 169 days after harvest. This period was exceeded in number of days by twenty-one other varieties. Type of Failure. — Failure after removal from storage resulted from internal breakdown and rot at the core. No scald or wilt occurred, and mold only in a few instances. 7. Vicar op Winkpield The Vicar of Winkfield was obtained from Niles during the seasons of 1921-22 and 1922-23. This variety, although large and attractive, was of inferior quality and was of value primarily for culinary pur- poses. The Vicar of Winkfield has been recommended 1 as a variety for distance shipment. Behavior at 32° F. — At 32° F. observations were made on fruit harvested September 29, 1923. The fruit was apparently in good con- dition for storage, having attained full size. The optimum storage date was March 1, 153 days after harvest, and the maximum date June 10, eight months after harvest. Failure in storage resulted from attacks of Penicillium, accom- panied by scald and breakdown. 8. Winter Nelis Winter Nelis pears were obtained from Niles, Santa Clara, Davis, and Helendale. The dates of harvest were as follows: from Niles, September 7; from Santa Clara, September 15; from Helendale, October 15; from Davis, October 29. The average harvest date, for five seasons, was September 22. The Winter Nelis, because of the retention of its good flavor and texture in storage until a late date, was a valuable variety for storage. Winter Nelis pears picked as late as October 29 kept in the best con- dition. Those from Niles, picked on September 7, did not attain such rich flavor, nor were they so buttery as the later picked pears. This indicated the advantage of permitting Winter Nelis to become well matured before harvesting. Behavior at 32° F— At 32° F. the Winter Nelis kept well and retained a quality of "very good" until near the end of its keeping period. This variety was one of the longest keeping pears at this temperature. It remained in a marketable condition for sixteen days when removed from storage on the optimum date, which averaged about March 1. The maximum date was about April 25. 36 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Behavior at 36° F. — x\t this temperature the Winter Nelis was an excellent keeper, and had an optimum storage date of March 1. The Winter Nelis kept three weeks longer than the Easter Beurre at this temperature. Cause of Failure. — At 36° F. failure was caused by mold and rot. At 32° F. less mold or wilt occurred. 9. Brettonneau This variety was observed only during the season of 1922-23. The date of harvest was October 5. The Brettonneau pears were large in size. The quality was poor, resembling the Pound in this respect. It never became suitable for eating out of the hand. It required seventy- five days for the fruit to ripen after harvest, at room temperature, and thereafter the fruit remained marketable for ninety days. Behavior at 32° F. — At this temperature failure resulted from wilting. At the optimum date, February 22, the fruit remained in good condition for sixty days after removal from storage. The maximum storage date was June 15. 10. Emile d'Heyst This variety was obtained from Niles during the season of 1922-23. The fruit was of such low quality — below even the Vicar of Wink- field — that a description is not merited. At 32° F., February 20 was the date of optimum storage and May 1 the date of maximum storage. 11. Beurre Diel The Beurre Diel was picked at Niles on September 3. One portion of this lot was stored at 32° F. and another at 36° F. Behavior at 32° F.—At a temperature of 32° F. the Beurre Diel kept satisfactorily. Scald was first noticed on the more exposed fruit in the box on April 1. The fruit was gritty early in the season, but this was less noticeable after a short period of storage. The grittiness, however, was never sufficiently pronounced to be serious. During storage a quality of "very good" was acquired. The flavor was sub- acid when ripened without having been in storage. As the season progressed and subsequent removals of the fruit were made, a richer and sweeter flavor was noted. The fruit was very juicy, even in the last removal. Its behavior in storage was good, with the retention of quality and juiciness. Bulletin 377] TH e cold STORAGE OF PEARS 37 The optimum storage date was February 20. The maximum date, April 1, was 210 days after harvest, and while the flavor at the time was "very good," scald had developed. A temperature of 32° F. effectively checked ripening and prevented the development of Penicillium on the fruit of the Beurre Diel. At 36° F., however, infection and growth by molds was pronounced. -•'-■ km W ^F Fig. 9. — Beurre Diel, showing characteristic type of failure occurring at 36° F. The late date of the optimum period and the absence of wilt or mold at 32° F., together with the fact that its appearance remained excellent, indicated that this variety might be desirable for storage. Behavior at 36° F. — The color developed at this temperature was unsatisfactory, being yellow and mottled with green. The fruit was ripe by November 15. Nevertheless, removals made after this date attained better quality than those made earlier. Scald, noticed January 10, marked this as the maximum storage date. Cause of Failure. — Failure when ripened out of storage was in the form of internal breakdown. Failure in storage at 32° F. was caused 38 UNIVERSITY OF CALIFORNIA.- —EXPERIMENT STATION by scald. At 36° F. failure was due to a spotting of the fruit as illustrated in figure 9. Some scald also occurred at this temperature, and considerable Penicillium developed. 12. Dearborn Seedling This variety, one of the earliest to be harvested at Niles, was observed during two seasons. The average picking date was August 6. The fruit was nearly ripe when harvested and was stored at 32° F. The fruits of this variety, although small, were uniform in size, shape, and color, attractive in appearance, and pleasing to eat. The quality was delicate, juicy and sweet. Failure resulted from stem end rot. Behavior at 32° F.—At this temperature the fruit kept remarkably long, and remained in good condition until the middle of February. The quality remained nearly unchanged throughout the storage season. 13. Japanese (Pyrus seroiina) This species of pear was observed during the season of 1922-23. The date of harvest was September 29. The pears during their optimum period of storage at 32° F. were of very low quality, being similar to the Kieffer in this respect. This fruit was subject to attacks from Penicillium and also tended to wilt after long storage. 14. Pound • The Pound was harvested September 29, and observed during the season 1922-23. At 32° F. the fruit kept until February 15, when failure resulted from the appearance of scald. The Pound was one of the largest pears, and also one of the lowest in quality. It was not a dessert fruit and could be recommended only for cooking purposes. 15. Hugo The Hugo was obtained from Niles. It was picked September 1. As the supply was limited all the fruit was stored at 32° F. Behavior at 32° F.—At 32° F. the Hugo kept better than the Beurre d'Anjou. The maximum date for the former was March 20, as com- pared with February 26 for the latter. Hugo kept three weeks longer than the Beurre d'Anjou. The maximum date was determined by the fact that on March 20, the Hugo had become dry and mealy. Bulletin 377] TH e cold STORAGE OP PEARS 39 The Hugo may be recommended as a variety suitable for storage. It was slightly better than the Beurre d 'An jou in this respect. It also possessed a richer flavor and finer texture, and when ripened, the bright yellow color was more attractive than the duller yellow of the Beurre d'Anjou. 16. Glout Morceau Glout Morceau pears were received from Davis. Niles, and Santa Clara. The average date of picking for three seasons was about September 15. The Glout Morceau showed promise as a variety for storage because of its firm skin, sweet flavor, long keeping qualities, and freedom from mold and rot. It should not be picked too immature. Thomas 25 describes this variety as variable but excellent when fully grown. The tree is vigorous and productive, 26 and the fruit is fairly good for shipping and is in demand on the London markets. 1 Behavior at 32° F. — Before storage, the Glout Morceau did not ripen satisfactorily. It was not until the removals of October and later that the pear became pleasing to the taste. The optimum date was February 6, and the maximum date March 26. On certain years those from Davis did not ripen well. In the last removal they became sweet, but some scald had developed. Each lot removed, colored up yellow and became sweet. The flesh, however, remained very firm and tough. Cause of Failure.— Failure in storage was mainly from wilt. This indicated that the fruit from the interior valley was too green when picked. Internal breakdown occurred in the pears obtained from the coastal sections when brought out of cold storage and ripened at room temperature. 17. Winter Bartlett The Winter Bartlett was obtained from Niles for two seasons. It was picked on September 12. Behavior at 32° F. — The Winter Bartlett kept satisfactorily at 32° F. except when picked too green. In such a condition the fruit wilted at an early date. It became yellow in storage and reached the end of the optimum storage period February 1. The maximum date of April 22 was determined by scald in green fruit and by core rot or internal breakdown in the more matured pears. In spite of the fact that the pear became wilted, the quality and flavor, which was fairly good, remained the same. The length of the maximum keeping period was 222 days. 40 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION Although the flavor was good, the unattractive appearance of the fruit because of wilt, when picked immaturely, lowered its market quality. 18. Urbaniste The average picking date for this variety, during the seasons of 1921-22 and 1922-23 was September 11. The Urbaniste, with two season's observations, ranked high as a variety suitable for storage. In general characters the fruit resembled the Hugo. At 32° F. the average optimum date, February 1, and the maximum date, April 1, were later than for most other varieties. In flavor and quality it was superior to the Beurre d'Anjou, which it also resembled. Thomas 25 noted that the Urbaniste in unfavorable locations had only fair quality. Weldon 20 stated that it possessed only medium quality in California. This statement did not apply to the pears of fine quality obtained from Niles. Cause of Failure. — Slight wilting in storage was in evidence toward the end of the storage period. The flavor remained ' ' very good ' ' and pleasing. Failure upon removal from storage was due to internal breakdown. 19. Zoe The Zoe was obtained from Niles. The date of picking was Sep- tember 1. This was a good variety but without special merit when compared with some of the standard varieties. Behavior at 32° F. — The Zoe was slow to ripen without storage. It held up from ten to twelve days when removed from storage, on the optimum date, January 15. The flavor was "sugar sweet/' during the storage period. The quality remained "good." The fruit was very juicy at first, but only "medium juicy" at the maximum date, March 15. Cause of Failure. — Failure on removal from storage was charac- terized by wilt and drying out of the tissues. Failure in storage was caused by wilt. 20. Easter Beurre The Easter Beurre was obtained from both the coastal and valley regions. The average picking date for the six seasons was Sep- tember 14. The Easter Beurre was a good keeping variety at 32° F. It was inferior in quality and flavor, however, to other long-keeping sorts such as Winter Nelis and Lawrence. Bulletin 377] TfIE CO ld STORAGE OF PEARS 41 Behavior at 32° F. — The Easter Beurre pears under observation at 32° F. were slow in ripening. Many of the specimens did not ripen. Only those specimens that were most mature, ripened. On January 3, the optimum date, they ripened in ten days after removal and spoiled ten days later. They kept in good condition at this temperature until April 7. Behavior at 36° F. — At 36° F. the maximum storage period of the Easter Beurre was February 10. This date was 160 days after the fruit was picked. This variety proved to be susceptible to Penicillium mold at 36° F. The fruit became ripe in storage at this temperature on January 20. This date was six weeks later than the optimum date of the Winter Nelis stored at 36° F. When removed from the 36° F. room, the fruit rapidly decayed through the growth of Penicillium. This was not the case with pears taken from the 32° F. room. Cause of Failure. — Failure at 36° F. was caused by Penicillium. The characteristic method of failure is illustrated in figure 5. After ripening at 36° F. the fruit was easily attacked by mold. This accounts for the short time between the maximum and optimum dates at 36° F. Pears removed from storage at 32° F. failed from internal breakdown. 21. Doyenne du Comice Doyenne du Comice pears were obtained from Santa Clara and Davis. Six seasons' observations were made. The average picking date was September 5. Behavior at 32° F. — The average optimum storage date of this high quality pear was January 3, or 120 days after harvest. The maximum date was February 14, or five months in storage. Behavior at 36 F. — At 36° F. the average optimum storage date was November 17, or 67 days after harvest. The maximum date was December 16, or 97 days after the fruit entered storage. Cause of Failure. — Scald and rot were the limiting factors in storage at both 32° F. and 36° F. See pages 8 to. 10 for further dis- cussion of the Doyenne du Comice. 22. Kieffer The Kieffer was obtained from Niles and Davis. The average pick- ing date was August 24. The pears were stored at 32° F. only. The fruit was small to medium in size, and of poor quality. In flavor the fruit was pungent and at all times sub-acid. In color it was yellowish green. 42 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Behavior at 32° F. — The average optimum and maximum storage dates were January 1 and March 15, respectively. At no time during the storage period did the fruit 'become suitable for eating out of hand, nor did it ever approach even the low standard of quality recognized for this variety. The best stage of ripeness appeared in the third removal from storage, the fruit becoming fairly good in quality about November 23. 23. Beurre d 'Anjou The Beurre d'Anjou was obtained from both the coastal and interior valley sections for six seasons. The average harvest date was August 13, which proved to be, in most seasons, several weeks too early. This variety may be recommended because of its popularity, appearance, and good keeping qualities. It is free from fungous diseases and relatively free from rot. Thomas 25 states that "the hardiness, uniformity, reliability, excellence and long keeping qualities of the Beurre d 'Anjou render it one of the most valuable of all pears. ' ' Behavior at 32° F. — The flavor and quality improved in storage and were best about November 1. At that date the fruit was extremely juicy, and the texture, quality, and flavor were excellent. The flesh tended to become a little grainy towards the end of the season. The average optimum and maximum dates at 32° F. were Decem- ber 24 and February 26, 133 and 197 days, respectively, from the time of harvest. Behavior at 36° F. — At this temperature the variety kept remark- ably well. The quality of the pears kept at 36° F. was inferior to that of the pears at 32° F. ; less juice was present. A comparison of the effects of the two temperatures showed 32° F. as the better. Cause of Failure. — The Anjou pears were not subject to mold. The characteristic mode of failure when removed from storage was internal breakdown. In storage, failure was characterized by a rot commenc- ing at the base of the stem where it joined the epidermis. 24. Beurre Bosc The Beurre Bosc was obtained from Davis and the Santa Clara Valley, and was observed for six seasons. The average picking date was August 28. The variety was stored at both 32° F. and 36° F. The Beurre Bosc, on account of its attractive appearance and its retention of flavor, was a good variety for storage. In certain seasons the flesh was a trifle coarse, an objectionable feature, but not a characteristic of the variety. Bulletin 377] TH e COLD STORAGE OF PEARS 43 Behavior at 32° F. — At this temperature the optimum date was about December 22 ; the maximum storage date was February 8. Behavior at 36° F. — At 36° F. the more mature specimens of Beurre Bosc kept for a shorter period of time than at 32° F. The quality of the mature Beurre Bosc pears developed at 36° F. was somewhat inferior to that developed at 32° F. With the prematurely picked Beurre Bosc pears, however, the fruit was better in both respects at 36° F. than at 32° F. Type of Failure. — The type of failure was wilt and internal break- down at 32° F., and scald at 36° F. The Beurre Bosc proved to be relatively free from mold in storage. See pages 6 to 8 for further discussion of the Beurre Bosc. 25. White Doyenne The White Doyenne was obtained from Niles for three seasons. The average picking date was September 12. This variety retained its good qualities in cold storage to a high degree. It should not be harvested when too green or too ripe. Behavior at 32° F. — Upon removal from storage the W T hite Doyenne attained a quality of "very good," but remained so only four or five days after ripening. It then became dry and mealy. The optimum storage date was December 1, and the maximum February 23. Cause of Failure. — In storage the variety was attacked by mold. There was also loss from wilting and internal breakdown. 26. Dana Hovey The Dana Hovey was obtained from Niles for four seasons. The average date of harvest was September 14. The fruit was picked and packed loosely in the box without being wrapped. This variety, being compartively late in date of ripening would, the indications were, have kept better if picked a week or so later. Evidence of premature picking was the slight amount of wilting that occurred during storage, and the length of time — fourteen days — it required for ripening without storage. Behavior at 32° F. — The entire lot was stored at 32° F. The length of the maximum storage extended over a period of 165 days, and the date was recorded as March 1. The rich flavor and high quality of the Dana Hovey was impaired more by storage than was the case with many other varieties. This was the chief reason for placing the optimum date as December. At that time a quality of ' ' best ' ' was noted for the last time. The fruit 44 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION was very juicy but became slightly drier during storage. The quality was so high to begin with that although impaired, it was still rich and sweet on February 1. The variety ranked close to the Seckel pear in quality. Upon removal from storage at the optimum date, this variety held up for fourteen days in good condition. 27. Commerce The Commerce was obtained from Santa Clara during the season of 1921-22. The date of picking was September 18. One box of carefully packed, wrapped fruit was received. The Commerce ranked high among the varieties desirable for storage, and retained its good qualities. "When in a ripe condition, its flesh and delicate skin necessitated care in handling. Its grittiness was also somewhat objectionable. Behavior at 32° F. — This variety was stored only at 32° F. It behaved creditably and proved to be one of the better keepers. This was remarkable since the fruit was ripe in storage by January 15. It was apparently in nearly the same condition on April 1 as on the former date. Before being stored this variety ripened in thirteen days and was valueless six days later, nineteen days in all. After nearly three months' storage at the optimum date, the fruit ripened in three days and became valueless thirteen days later, sixteen days in all. Storage until the optimum date, therefore, did not materially shorten the keeping period after removal. Cause of Failure. — Failure after removal was occasioned by internal breaking down of the tissues. 28. Gr,vy Winter This variety was obtained from Niles and observed during two seasons. The average date of harvest was September 12. It was stored at 32° F. Behavior at 32° F. — The variety kept well in storage until Decem- ber 19, 98 days after harvest. Failure resulted from breakdown. The fruit was round and completely and smoothly russeted. The flesh was delicate, aromatic, buttery, and melting. 29. Duchesse d'Angouleme The average picking date for the Angouleme from both Davis and Niles was August 30, The varietal behavior was observed during five seasons. Bulletin 377] TH e cold STORAGE OF PEARS 45 Behavior at 32 F. — At this temperature there was little difference in the length of time that the pears from Davis and Niles remained in a marketable condition. The average optimum storage date was December 3 ; the maximum date, January 23. Failure resulted from scald about February 1 in both cases. 30. Louise Bonne de Jersey The average harvest date of the Louise Bonne de Jersey was Sep- tember 9. It was obtained both from Davis and Niles, The deficiency in this variety was the rather short period of time the fruit remained in a marketable condition after removal from storage. Otherwise this pear was commendable for storing until Christmas. Thomas 25 men- tioned the fact that the variety is exceedingly productive. Behavior at 32° F. — The fruit of this variety was extremely juicy at first but became drier after two months' storage at 32° F. Behavior at 36° F. — At 36° F. the Louise Bonne de Jersey was ripe in storage about November 6. Cause of Failure. — This variety was attacked by molds in storage, and failed from wilt and rot. Failure after removal was due to internal breakdown. 31. Winter Seckel Winter Seckel was received from the Santa Clara Valley. It was picked on October 7 and stored at 32° F. Behavior at 32° F. — The Winter Seckel ripened in storage within two to three weeks. Quite remarkable was the fact that it remained thus in excellent condition until January 1, approximately three months, at which date scalding and internal breakdown occurred simultaneously. Storage for three weeks seemed to improve the quality somewhat, and lengthened by four days the period of time for which it might be kept when removed from storage. This variety kept in good con- dition for from eight to twelve days after removal from storage. It reached a quality designated as "very good" to "best," and a flavor rich and spicy, resembling the true Seckel, although more nearly approaching the flavor of the Dana Hovey. 32. Howell The Howell was obtained from both Davis and Niles and was observed during six seasons. The average harvest date was August 20. The chief defect of the Howell variety was the short period during which it retained its good qualites after becoming ripe. 46 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The Howell pears from the interior valley matured earlier in the orchard than those from the coastal section. They were also larger, juicier, sweeter, and more attractive when grown in the warmer interior valley. They did not, however, keep as long as when grown in the coastal section. The trees of this variety w T ere free from insects and diseases. Weldon 20 stated that it was, however, subject to blight. Behavior at 32° F. — The optimum storage date was November 15, and the maximum date was December 9, ah average of 102 days after harvesting. At the maximum storage date the quality was good, although not equal to the quality earlier in the season. Behavior at 36° F. — At this temperature the Howell pear proved to be a poor keeper. It ripened quickly in storage. Upon removal, both the Davis and Niles pears were worthless in four days on account of internal breakdown. Cause of Failure. — During the season of 1921-22, the pears from Davis failed because of internal breakdown, perhaps because of over- ripeness at the time of harvest. Those from Niles failed from the same cause. The fruit would, from surface appearance, apparently be in prime condition, while inspection of the interior would disclose internal breakdown in an advanced stage. Late in the storage period, round spots resembling a dry rot appeared on the fruit. The Howell was subject to the attacks of blue mold and was also injured by pressure in the box when approaching ripeness. At 36° F. the Howell from Niles was severely attacked by blue mold. Scald also appeared to a considerable degree upon this variety. 33. Onondaga The Onondaga was obtained from Niles for two seasons. The average date of picking was September 1. Two boxes of this variety, were available for storage. One was stored at 32° F., the other at 36° F. The shortness of the optimum storage period, and the susceptibility to molds, especially when bruised, placed the Onondaga as one of the poorer keepers. It was inferior in quality and flavor, becoming some- what astringent. Thomas 25 also noted that this pear was sometimes astringent. Weldon 20 claimed that it was of no value in California. Behavior at 32° F. — The behavior of this variety in storage was unfavorable. The optimum date at 32° F. was November 15, and the maximum date December 20. The pears were subject to mold and decay in storage. Furthermore, mold always caused failure after removal from storage. The fruit was as susceptible to attack by mold as any of the varieties. Bulletin 377] T he cold STORAGE OF PEARS 47 Behavior at 36° F. — The optimum date at 36° F. was November 1, 59 days from the date of picking. The maximum date was February 1. 34. Beurre Hardy The Beurre Hardy pears were obtained from Davis and Santa Clara. The average date of harvest for the six seasons was August 21. The fruit, however, was somewhat immature for best keeping quality in cold storage. A portion was stored at 32° F., and another at 36° F. Behavior at 32° F. — At 32° F. the Beurre Hardy retained its good qualities for a considerable period of time. The average optimum storage date was November 9. The average maximum storage date was December 31. Behavior at 36° F. — At 36° F. the keeping period of the Beurre Hardy was short. The average optimum keeping date was October 20. The maximum storage date was December 20. See pages 11 and 12 for further discussion of the Hardy. 35. Seckel The Seckel was obtained from both Davis and Niles. The average harvest date for four years was August 18. The quality and flavor of this pear were impaired by cold storage. The pears being in a semi-ripe condition soon passed their best stage in storage. Behavior at 32° F. — A marked difference was noted between the behavior of Seckel pears exposed to the relatively dry air of the storage room and those that were well covered. In the case of the former, wilting occurred as early as December 1, while those well protected were in good condition three weeks later. The average optimum storage date was November 1, and the maximum date December 19. 36. Beurre Clairgeau The Beurre Clairgeau pears used in the experiment were obtained from Davis, Niles, and Santa Clara. The average date of harvest during six years' observation was August 15. All were stored at 32° F. There are so many good varieties of pears that it seemed undesir- able to search for any special merits in such a poor variety as the Beurre Clairgeau. Sinclair 2 ^ recommended it for cooking. Behavior at 32° F. — In the observations made, the quality of the Clairgeaus from Santa Clara was noted as "very good" for the variety, when ripened without storage; as "good" in the first 48 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION removals, after being kept in storage for from eight to fourteen weeks. After this period the pear was nearly worthless as far as marketability was concerned. In the lot from Niles the quality was fairly good, but after six weeks' storage it became only fair and later quite poor. The lot from Davis kept longer and better, bringing the average maximum date to January 23. Cause of Failure. — The Clairgeau variety kept satisfactorily in storage and no defects were noticed until scald suddenly made its appearance about January 10, and the entire box rapidly became affected. 37. Flemish Beauty The Flemish Beauty was observed four seasons. The average harvest date in the interior valley was August 6 ; in the coastal section about September 1. The color was yellow, the skin was heavily russetted, the size was medium large, and the flavor was sweet and aromatic. Behavior at 32° F. — The optimum storage period of the Flemish Beauty was about October 29 ; the maximum December 29. After the optimum storage period the flavor became less pronounced and the quality dropped from "very good" to "good" and later to only "fairly good." The fruit that remained in good condition was ripe in storage by January 1, and broke down rapidly after removal. The amount of juice decreased rapidly during storage. 38. Bartlett The behavior of the Bartlett pear in cold storage was observed for six seasons. Fruit was obtained from various sections of the state. From three to five pickings were made each season. The average pick- ing date was August 24. The Bartlett was not a suitable variety for long storage. It was subject to scald and could not be recommended as a variety to be kept for the holiday trade. There were many other varieties that were less perishable under storage conditions than the Bartlett. Behavior at 32° F. — The average optimum storage date was October 29, or 66 days after harvest. The maximum storage date was December 18, 116 days after harvest. Behavior at 36° F. — At this temperature the average optimum storage date was October 11, or 46 days after harvest. The maximum storage date was October 24. Bulletin 377] the cold STORAGE OF PEARS 49 Cause of Failure. — At both 32° F. and 36° F., the fruit became ripe in storage; scald rapidly made its appearance and soon involved the entire lot. The effect of various factors upon the keeping quality and upon scald is described elsewhere in this publication. Pig. 10— Bartlett (left), Chadbourne (right), harvested August 9, 1923, at the optimum picking date for both. 39. Chadbourne This variety, obtained during the seasons of 1922-23 and 1923-24 at Niles, was stored at 32° F. The Chadbourne was discovered on the J. R. Chadbourne ranch at Suisun, California, and was propagated by George C. Roeding at Niles. It appeared to be a bud variation of the Bartlett. It was thought to be earlier than the Bartlett, as it attained Bartlett size two weeks in advance of that variety. When at the proper maturity for harvest, however, the Chadbourne was a larger and somewhat rougher pear than the Bartlett (fig. 10). This would lower its value as a variety suitable for canning. Behavior at 32° F. — During the season 1922-23, the first picking was made July 12, and the second July 22. For the fruit thus harvested the average optimum date was September 30 and the maximum storage date about October 8. The second picking was superior in color, texture, and flavor. The behavior and appearance of both, however, indicated immaturity at the time of harvest. 50 UNIVERSITY OF CALIFORNIA—EXPERIMENT STATION During the season of 1923-24 the fruit was harvested later. The picking dates were July 24 and 31, and August 9. The Chadbourne harvested July 24 were fully as large in size as the Bartlett harvested two weeks later. Behavior at 36° F. — During the season 1923-24 the fruit harvested August 9 kept later and better than that harvested earlier. The first picking tended to wilt slightly in storage; scald occurred about December 20. The second picking showed signs of scald by January 8, while the third picking was yellow ripe and still in good condition on that date. The results of the experiment indicated that although the Chadbourne attained a size equal to that of the Bartlett fully two weeks in advance it should be harvested at approximately the same time as the Bartlett. When harvested at that stage of maturity, the Chadbourne, in size, quality and color, surpassed the Bartlett grown in the same region. An excellent feature of the Chadbourne was that the fruit, although it frequently attained considerable size, did not drop prematurely from the tree. 40. Le Conte The average picking date of this variety for four years was August 13. The variety was stored at 32° F. It has little commercial value in this state. Its principal value lies in the fact that it is resistant to blight, especially in the warmer sections east of the Rockies. Behavior at 32° F. — Le Conte was found to keep only a short time in storage, the tissues turning brown and the fruit becoming valueless generally as early as November 26. 41. Clapp Favorite This variety was observed for four seasons. The average picking date was July 14. This variety was rather perishable for retention in storage. It was, however, a pear of high quality and was excellent as a dessert fruit when not stored. It was made attractive by its red blush, large size, and good form. Behavior at 32° F.—At 32° F. the Clapp Favorite had an optimum storage date of October 2, and a maximum storage date of November 1. Failure in storage resulted from rot, wilt, scald, Penicillium, and breakdown. 42. Idaho One year of observation showed this variety to be a short keeper. The fruit, although large and resembling Duchesse dAngouleme in character of flesh and flavor, was typically apple-shaped, with an Bulletin 377] the cold STORAGE OF PEARS 51 irregular surface. Its inferior quality when compared with many other varieties and its short keeping period would probably prevent it from becoming a commercial possibilty in California. 43. Bloodgood Five years' observation of the Bloodgood obtained from Davis showed an average picking date of July 18. At a temperature of 32° F. the average optimum date was Sep- tember 7, while the maximum was October 15, or 85 days after harvest. Storage at 36° F. was unsatisfactory, because of the early date at which the fruit failed. Failure in storage resulted from wilt in immature pickings, and rot and mold in pickings made at a more matured stage. Bloodgood has little value as a commercial fruit because of its small size and poor quality. 44. Other Varieties The varieties Gifford, Madeleine, Lawson, Lincoln, Margaret, Fame, Col. Wilder, Rossenay, B. S. Fox, and Colorado Seedless, as shown in table 10, were of inferior keeping quality. SUMMARY A. Causes of. the Spoiling of Pears in Storage 1. Scald, manifested by a darkening of the epidermis, occurred with certain varieties of pears when stored at low temperatures, namely 45°, 36°, 32°, and 30° F. Fruit not placed in cold storage but ripened at room temperature did not develop scald. 2. Blue mold (Penicillhim sps.) was the principal mold making appreciable growth at a temperature of 32° F. It made more rapid development at 36° and 45° F. 3. Internal breakdown or softening of the tissues was noted in many varieties at all temperatures used (30°, 32°, 36°, 45° F.), and also at room temperature (65° F.). 4. Wilting occurred with all varieties harvested in a very green stage of maturity and occasionally with more matured fruit. Wilting was more common at 32° F. and 30° F. than at higher temperatures for the same variety. 5. Ammonia fumes, when anhydrous ammonia is employed to obtain refrigeration, may sometimes unavoidably gain entrance to 52 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION storage rooms. When pears were exposed to ammonia fumes the cells immediately adjacent to the lenticel-like openings of the epidermis became black in color. Upon prolonged exposure, the depth of penetration and area of surface blackened increased. B. Summary of Observations. Factors Affecting Rate of Spoiling in Storage 1. Temperature. Pears kept better and longer at 30° F. to 32° F. than at 36° F. to 45° F. when harvested at the proper stage of maturity. The average maximum keeping period of the four varieties. Beurre d'Anjou, Doyenne du Cornice, Beurre Bosc, and Howell, at 30° F., was 143 days; at 45° F., the average maximum keeping period was 37 days. When fruit was picked in too green a stage of maturity it generally kept better and attained a more desirable quality when stored at 36° F. than at lower temperatures. This was particularly true With Beurre Bosc, Forelle, Gray Winter, and Vicar of Winkfield. Pears held at 36° F. scalded more severely and at an earlier date than at 30° or 32° F. At 45° F., decay generally resulted before scald developed. The blue mold (Penicillium sps.) occurred upon certain varieties of pears at all of the storage temperatures utilized. The lower temperatures, however, delayed its appearance and retarded its growth, as for example, the Easter Beurre at 36° F. developed blue mold by February 10, but at 32° F. developed no mold as late as May 1. 2. Degree of maturity at time of harvest. The average maximum storage period of the Beurre Bosc, Doyenne du Cornice, and Beurre Hardy, picked during the height of the com- mercial harvest, was 141 days at 32° F. When harvested about two weeks later at a somewhat more advanced stage of maturity, they kept for 158 days or nearly two and one-half weeks longer, and suffered less from wilt and scald in storage. Overripe fruit, however, was more objectionable than underripe fruit and deteriorated with even greater rapidity in cold storage than immature pears. Overripe fruit was more susceptible to the attacks of blue mold than prematurely picked fruit. The immature fruit generally scalded sooner after harvest than did the properly matured fruit; overripe fruit, however, scalded more rapidly and severely than either. Bulletin 377] THE C0L1> storage OF PEARS 53 Pears picked in an immature condition were more susceptible to ammonia fumes than when well matured. 3. Variety. Susceptibility to scald of the varieties studied was found to be in about the following order : Bartlett, Louise Bonne de Jersey, Beurre Clairgeau, Duchesse de Bordeaux, Vicar of Winkfield, Pound, Beurre Hardy. Beurre Hardy was the least susceptible but was somewhat variable in this respect. The varieties which exhibited considerable resistance to the develop- ment of scald were : Easter Beurre, Forelle, P. Barry, and Beurre d 'Anjou. Certain varietal suceptibility in storage to blue mold (Penicillium sps.) was indicated. The Columbia, Doyenne d'Alencon, and Seckel, of the varieties studied, were relatively immune to the blue mold. The varieties relatively susceptible were as follows: Onondaga, Flemish Beauty, Beurre Diel, Easter Beurre, Urbaniste, and Howell. 4. Care in handling at harvest and delay in placing in storage. Wounds, bruises, and delay in placing in storage greatly increased the subsequent susceptibility in storage of pears to the attacks of mold. 5. Cross-pollination. Cross-pollinated Bartlett pears matured earlier than self -pollinated specimens, and this occasionally indirectly affected the keeping quality. CONCLUSIONS AND RECOMMENDATIONS 1. Cold storage may be utilized for holding temporarily the crop of some varieties of pears. 2. Low temperature was an important factor in retarding the ripening of pears and in controlling the development of rot organisms. 3. The effect of degree of maturity at time of harvest upon the size, flavor, and keeping quality was found to be marked. Apparently there has been a tendency to harvest many pears prematurely. 4. When picked two weeks after the commercial harvest period for the variety, the Beurre Bosc, Doyenne du Cornice, and Beurre Hardy attained a "very good" to "excellent" quality as contrasted with a "fair" to "good" quality. The fruit was also of larger size and had a more attractive apearance. 54 UNIVERSITY OF CALIFORNIA— EXPERIMENT STATION 5. The pears susceptible to scald showed a tendency to scald first at points in contact with the sides of the container or with other pears, indicating one important advantage of aeration. 6. The blue mold ( Penicillmm sps.) occurred upon certain varieties of pears at all of the storage temperatures utilized. The lower tem- peratures, however, delayed its appearance and retarded its growth, as for example, the Easter Beurre at 36° F., developed blue mold by February 10, but at 32° F. had developed no mold as late as May 1. 7. There were varietal differences in susceptibility to ammonia fumes, apparently resulting from difference in size and number of the lenticel-like openings and the development of the cutin. 8. The average loss in weight of Bartlett pears during a nine-day ripening period after harvesting was about five per cent, this loss resulting chiefly from transpiration. 9. During a twenty-day ripening period the loss in weight was greater with the earlier pickings of pears than with the later pickings of the same variety. 10. Data indicated that when properly harvested and quickly stored at temperatures of 30° to 32° F., the Bartlett from certain sections could be held in storage for several weeks and still be in good condition for canning. 11. Of the pears studied those exhibiting most satisfactory keeping qualities in storage were the Doyenne d 'Alencon, Lawrence, P. Barry, Forelle, Columbia, Block "18," Vicar of Winkfield and Winter Nelis. 12. The pears unsuitable for storage were the Madeleine, Lawson, and Bloodgood. 13. A detailed account of the storage behavior of each of forty- three varieties of pears is presented. ACKNOWLEDGMENTS The writers desire to express their appreciation to the following individuals, who at one time or another, helped in harvesting the fruit, controlling the temperatures, making observations, and tabulating data: Professors G. L. Philp, F. W. Allen, and Messrs. R. H. Taylor, M. J. Heppner, J. L. Quail, and V. B. Claypool. The writers also wish to acknowledge the suggestions and kindly help received from Dr. J. C. Whitten up to the time of his death. Especial thanks are extended to Mr. George C. Roeding for his kind cooperation in permitting fruit to be harvested from the variety collection at Niles. Thanks are also due Mr. V. T. McCurdy of Santa Clara, for his cooperation which permitted the harvesting at different stages of maturity of the Hardy, Cornice, and Bosc. Bulletin 377] THE COLD STORAGE OF PEARS 55 BIBLIOGRAPHY i Anonymous. Pears (Dessert) to Grow for Shipping from Australia to London. Agr. Gaz. New South Wales, 2: 283. 1891. 2 Catalogue of Fruits — American Pomological Society, U. S. Dept. Agr., Div. Pomology, Bull. 8: 1-63. 1899. 3 Descriptions of Varieties of Pears. Annual Report, Calif. State Bd. Hort., 359. 1892. 4 Descriptions of Fruit Growing at the Agassiz Experimental Farm. Canada Experimental Farms Reports, Agassiz, B. C. 1900. s Brooks, Charles, and Cooley, J. S. Temperature Relations of Apple Rot Fungi. Jour. Agr. Res. 8: 139-164, pis. 1-3, 25 figs. 1917. 6 Brooks, Charles, Cooley, J. S., and Fisher, D. F. Nature and Control of Apple Scald. Jour. Agr. Res. 18: 211-240, 2 figs. 1919. * ■ Diseases of Apples in Storage. U.S. Dept. Agr. Farmers' Bull. 1160: 1-24, 26 figs. 1920. 8 Cooper, M. Influence of Cold Storage on the Pear. 425-454. Chicago, 1914. » Cold Storage of the Bartlett Pear. Cold 2: 172. 1911. io Storage of the Bartlett. Cold 3: 271. 1912. ii The Proper Time for Picking. Cold 4: 216. 1913. 12 Eustace, H. J. Investigations on Some Fruit Diseases. New York Exp. Sta. (Geneva) Bull. 297: 31-48, 7 pis. 1908. isLauche, W. Deutsche Pomologie, 2: 100 pis. Berlin, 1882. 1 4 Lewis, C. I., Magness, J. R., and Cate, C. C. Preliminary Report of Pear Harvesting and Storage Investigations in Rogue River Valley. Ore. Agr. Exp. Sta. Bull. 154: 1-20, 3 tables. 1918. is Lewis, C. L, Murneek, A. E., and Cate, C. C. Pear Harvesting and Storage Investigations in the Rogue River Valley (2nd Rept.). Ore. Agr. Exp. Sta. Bull. 162: 5-39, 12 figs, 21 tables. 1919. 16 Magness, J. R. Investigations in the Ripening and Storage of Bartlett Pears. Jour. Agr. Rec. 19: 473-500, 8 figs. 1920. it The Handling, Shipping and Cold Storage of Bartlett Pears in the Pacific Coast States. U. S. Dept. Agr. Bull. 1072: 1-16, 1 table. 1922. is Murneek, A. E. A New Test for Maturity of the Pear. Ore. Agr. Exp. Sta. Bull. 186: 1-28, 9 figs., 22 tables. 1921. is Overholser, E. L., and Cruess, W. V. A Study of the Darkening of Apple Tissue. Cal. Agr. Exp. Sta. Tech. Paper 7: 1^0. 1923. zopalladin, V. I. Plant Physiology. 1-320. Philadelphia, 1918. 2i Powell, G. H., and Fulton, S. H. Cold Storage with Special Reference to the Pear and Peach. U. S. Dept. Agr., Bur. Plant Ind. Bull. 40: 1-26, 7 pis. 1903. 56 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 22 Ramsey, H. J., McKay, A. W., Markell, E. L., and Bird, H. S. The Handling and Storage of Apples in the Pacific Northwest. U. S. Dept. Agr. Bull. 587: 1-32, 8 pis., 5 tables. 1917. 23 Sinclair, J. M. Victorian Fruit in London. Jour. Dept. Agr. Victoria 2: 149-157. 1903. 24 Stubenrauch, A. V., and Eamsey, H. J. Bartlett Pear Precooling and Storage Investigations in the Rogue River Valley. U.S. Dept. Agr., Bur. Plant Ind. Cir. 114: 19-24. 1914. 25 Thomas, J. J. The American Fruit Culturist. 491-544, figs. 636-735. New York, 1911. 26Weldon, G. P. Pear Growing in California. Mo. Bull. Cal. Com. Hort. 7: 219-410, 186 figs, 1918. 27 Wickson, E. J. California Fruits. 1-286. San Francisco, 1914. 28 Wright, R. C, and Taylor, G. F. The Freezing Temperatures of Some Fruits, Vegetables, and Cut Flowers. IT. S. Dept. Agr. Bull. 1133: 1-8, 3 tables. 1923. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION No. 253. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. 261. Melaxuraa of the Walnut, "Juglans regia." 262. Citrus Diseases of Florida and Cuba Compared with those of Califoruia. 263. Size Grades for Ripe Olives. 268. Growing and Grafting Olive Seedlings. 273. Preliminary Report on Kearney Vine- yard Experimental Drain. 275. The Cultivation of Belladonna in Cali- fornia. 276. The Pomegranate. 277. Sudan Grass. 278. Grain Sorghums. 279. Irrigation of Rice in California. 280. Irrigation of Alfalfa in the Sacramento Valley. 283. The Olive Insects of California. 285. The Milk Goat in California. 286. Commercial Fertilizers. 287. Vinegar from Waste Fruits. 294. Bean Culture in California. 298. Seedless Raisin Grapes. 304. A Study of the Effects of Freezes on Citrus in California. 312. Mariout Barley. 317. Selections of Stocks in Citrus Propa- gation. 319. Caprifigs and Capriflcation. 321. Commercial Production of Grape Syrup. 324. Storage of Perishable Fruit at Freezing Temperatures. 325. Rice Irrigation Measurements and Ex- periments in Sacramento Valley, 1914-1919. 328. Prune Growing in California. 331. Phylloxera-Resistant Stocks. 334. Preliminary Volume Tables for Second- Growth Redwood. 335. Cocoanut Meal as a Feed for Dairy Cows and Other Livestock. 336. The Preparation of Nicotine Dust as an Insecticide. 339. The Relative Cost of Making Logs from Small and Large Timber. 343. Cheese Pests and Their Control. 344. Cold Storage as an Aid to the Market- ing of Plums. BULLETINS No. 347. 348. 349. 350. 351. 352. 353. 354. 355. 357. 358. 859. 360. 361. 362. 363. 364. 366. 367. 368. 369. 370. 371. 372. 373. 374. 3 75. 376. Almond Pollination. The Control of Red Spiders in Decidu- ous Orchards. Pruning Young Olive Trees. A Study of Sidedraft and Tractor Hitches. Agriculture in Cut-over Redwood Lands. California State Dairy Cow Competition. Further Experiments in Plum Pollina- tion. Bovine Infectious Abortion. Results of Rice Experiments in 1922. The Peach Twig Borer. A Self-mixing Dusting Machine for Applying Dry Insecticides and Fungicides. Black Measles, Water Berries, and Related Vine Troubles. Fruit Beverage Investigations. Gum Diseases of Citrus Trees in Cali- fornia. Preliminary Yield Tables for Second Growth Redwood. Dust and the Tractor Engine. The Pruning of Citrus Trees in Cali- fornia. Fungicidal Dusts for the Control of Bunt. Turkish Tobacco Culture, Curing and Marketing. Methods of Harvesting and Irrigation in Relation to Mouldy Walnuts. Bacterial Decomposition of Olives dur- ing Pickling. Comparison of Woods for Butter Boxes. Browning of Yellow Newtown Apples. The Relative Cost of Yarding Small and Large Timber. The Cost of Producing Market Milk and Butterfat on 246 California Dairies. Pear Pollination. A Survey of Orchard Practices in the Citrus Industry of Southern Cali- fornia. Results of Rice Experiments at Cor- tena, 1923. Sun-Drying and Dehydration of Wal nuts. CIRCULARS No. No. 70. Observations on the Status of Corn 161. Growing in California. 164 87. Alfalfa. 165. 111. The Use of Lime and Gypsum on Cali- fornia Soils. 166. 113. Correspondence Courses in Agriculture. 167. 117. The Selection and Cost of a Small 170! Pumping Plant. 127. House Fumigation. 172. 129. The Control of Citrus Insects. 173. 186. Melilotus (ndica as a Green-Manure Crop for California. 174. 144. Oidium or Powdery Mildew of the Vine. 178. 151. Feeding and Management of Hogs. 179. 152. Some Observations on the Bulk Hand- ling of Grain in California. 184. 153. Announcement of the California State 190. Dairy Cow Competition, 1916-18. 193. 154. Irrigation Practice in Growing Small 198. Fruit in California. 199. 155. Bovine Tuberculosis. 201. 157. Control of the Pear Scab. 202. 158. Home and Farm Canning. 160. Lettuce Growing in California. 203. Potatoes in California. Small Fruit Culture in California. Fundamentals of Sugar Beet Culture under California Conditions. The County Farm Bureau. Feeding Stuffs of Minor Importance. Fertilizing California Soils for the 1918 Crop. "Wheat Culture. Th-' Construction of the Wood-Hoop Silo. Farm Drainage Methods. The Packing of Apples in California. Factors of Importance in Producing Milk of Low Bacterial Count. A Flnck of Sheep on the Farm. Agriculture Clubs in California. A Study of Farm Labor in California. Syrup from Sweet Sorghum. Onion Growing in California. Helpful Hints to Hog Raisers. County Organizations for Rural Fire Control. Peat as a Manure Substitute. CIRCULARS — Continued No. 205. Blackleg. 206. Jack Cheese. 208. Summary of the Annual Reports of the Farm Advisors of California. 209. The Function of the Farm Bureau. 210. Suggestions to the Settler in California. 212. Salvaging Rain-Damaged Prunes. 214. Seed Treatment for the Prevention of Cereal Smuts. 215. Feeding Dairy Cows in California. 217. Methods for Marketing Vegetables in California. 219. The Present Status of Alkali. 220. Unfermented Fruit Juices. 228. Vineyard Irrigation in Arid Climates. 230. Testing Milk, Cream, and Skim Milk for Butterfat. 231. The Home Vineyard. 232. Harvesting and Handling California Cherries for Eastern Shipment. 233. Artificial Incubation. 234. Winter Injury to Young Walnut Trees during 1921-22. 235. Soil Analysis and Soil and Plant Inter- relations. 236. The Common Hawks and Owls of Cali- fornia from the Standpoint of the Rancher. 237. Directions for the Tanning and Dress- ing of Furs. 238. The Apricot in California. 239. Harvesting and Handling Apricots and Plums for Eastern Shipment. 240. Harvesting and Handling Pears for Eastern Shipment. 241. Harvesting and Handling Peaches for Eastern Shipment. 243. Marmalade Juice and Jelly Juice from Citrus Fruits. 244. Central Wire Bracing for Fruit Trees. 245. Vine Pruning Systems. No. 247. 248. 249. 250. 251. 252. 253. 254. 255. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. 269. 270. 271. 272. 273. 275. Colonization and Rural Development. Some Common Errors in Vine Pruni»g and Their Remedies. Replacing Missing Vines. Measurement of Irrigation Water on the Farm. Recommendations Concerning the Com- mon Diseases and Parasites of Poultry in California. Supports for Vines. Vineyard Plans. The Use of Artificial Light to Increase Winter Egg Production. Leguminous Plants as Organic Fertil- izer in California Agriculture. The Control of Wild Morning Glory. The Small-Seeded Horse Bean. Thinning Deciduous Fruits. Pear By-products. A Selected List of References Relating to Irrigation in California. Sewing Grain Sacks. Cabbage Growing in California. Tomato Production in California. Preliminary Essentials to Bovine Tuber- culosis Control. Plant Disease and Pest Control. Analyzing the Citrus Orchard by Means of Simple Tree Records. The Tendency of Tractors to Rise in Front; Causes and Remedies. Inexpensive Labor-saving Poultry Ap- pliances. An Orchard Brush Burner. A Farm Septic Tank. Brooding Chicks Artificially. California Farm Tenancy and Methods of Leasing. Saving the Gophered Citrus Tree. Marketable California Decorative Greens. lOm-9,'24