UNIVERSITY OF CALIFORNIA PUBLICATIONS. COLLEGE OF AGRICULTURE. AGRICULTURAL EXPERIMENT STATION, BERKELEY, CALIFORNIA. CALIFORNIA PEACH BLIGHT By RALPH E. SMITH. Assisted by E. H. Smith, T. F. Hunt, and B. J. Jones. BULLETIN No. 191. UNIVERSITY OF CALIFQKJ>OA (Berkeley, Cal., September, 1907.) . iqq A D V COLLEGE OF AGRICULTURE SACRAMENTO: DAVB W. W. SHANNON, : : : : SUPERINTENDENT state printing. 1907. BENJAMIN IDE WHEELER. Ph.D., LL.D., President of the University. EXPERIMENT STATION STAFF. E. J. WICKSON, M.A., Director and Horticulturist. E. W. HILGARD. Ph.D.. LL.D., Chemist. • W. A. SETCHELL. Ph.D., Botanist. ELWOOD MEAD. M.S., C.E.. Irrigation Engineer. C. W. WOODWORTH, M.S., Entomologist. R. H. LOUGHRIDGE, Ph.D., Agricultural Geologist and Soil Physicist'. (Soils, Alkali.) M. E. JAFFA, M.S., Nutrition Expert, in charge of the Poultry Station. G. W. SHAW. M.A.. Ph.D., Agricultural Technologist, in charge of Cereal Stations. GEORGE E. COLBY, M.S., Chemist. (Fruits, Waters, Insecticides.) RALPH E. SMITH, B.S., Plant Pathologist and Superintendent of Southern California Pathological Laboratory and Experiment Stations. A. R. WARD, B.S.A., D.V.M., Veterinarian and Bacteriologist. E. W. MAJOR. B.Agr., Animal Industry and Manager of University Farm. F. T. BIOLETTI, M.S., Viticulturist. (Grapes, Wine and Zymology.) H. M. HALL, M.S., Assistant Botanist. H. J. QUAYLE, A.B., Assistant Entomologist. W. T. CLARKE, B.S., Assistant Horticulturist and Superintendent of University Extension in Agriculture. JOHN S. BURD, B.S., Chemist, in charge of Fertilizer Control. C. M. HARING, D.V.M., Assistant Veterinarian and Bacteriologist. E. B. BABCOCK, B.S., Assistant Plant Pathologist. E. H. SMITH, M.S., Assistant Plant Pathologist. J. W. MILLS, Assistant Horticulturist, ) CUrus Experiment station, Riverside. T. F. HUNT, B.S., ) H. J. RAMSEY, M.S., Assistant Plant Pathologist, I Southern California Pathologi- C. O. SMITH, M.S., " " " j cal Laboratory. Whittier. R. E. MANSELL, Assistant in Horticulture, in charge of Central Station Grounds. GEO. W. LYONS, B.S., Assistant in Soil Laboratory. RALPH BENTON, B.S., Assistant in Entomology. A. J. GAUMNITZ, M.S., Assistant in Cereal Investigations. HANS C. HOLM, B.S., Assistant in Zymology. P. L. McCREARY, B.S., Laboratory Assistant in Fertilizer Control. C. WESTERGARD, B.S., Assistant in Farm Mechanics. M. E. STOVER, B.S., Assistant in Agricultural Chemical Laboratory. D. L. BUNNELL, Clerk to the Director. JOHN TUOHY, Patron, \ Tu]SL re Substation, Tulare. J. T. BEARSS, Foreman, ) J. W. ROPER, Patron, ) E. C. MILLER, In charge, $ University Forestry Station, Chico. ROY JONES, Patron, \ University Forestry Station, Santa Monica. N. D. INGHAM, Foreman, S f VINCENT J. HUNTLEY, Foreman of California Poultry Experiment Station, Petaluma. The Station publications (Reports and Bulletins), so long as avail- able, will be sent to any citizen of the State on application^ CALIfORNIA PEACH BLIGHT By RALPH E. SMITH. Assisted by E. H. Smith, T. F. Hunt, and B. J. Jones. The disease which forms the subject of this bulletin has come to be a well- j known factor in peach-growing in practically every part of California where the fruit is extensively grown. While its general occurrence has been experienced only during the past few seasons, the disease has become so abundant and its effects so extremely disas- trous that almost every peach-grower has come to know it and see the necessity of finding some immediate preventive treatment in order to save .his trees from actual destruction. The present publication aims to present the results of three years' experience and experimentation in the control of this trouble, showing the almost absolute success with which the disease has been controlled by treatment. The work has been unusually satisfactory in this respect, and it has apparently been fully demonstrated that by proper attention the grower can fully protect his trees and crop from the effects of the blight at a minimum expense. Peach "blight' has been so frequently and fully discussed and described in our horticultural journals and meetings during the past two years that it seems scarcely necessary to consider in detail the nature and history of the disease at this time. So unusually sudden and pronounced have been the effects of the trouble in practically all the peach-growing sections, and so widely have methods of control been demonstrated and urged upon the growers by agents of the Experiment Station and others, that we have no plant disease in the State which is better known or for which control methods are more generally applied than this. This disease appears to have been present in the State for some time. Professor Pierce records it as occurring previous to 1900,* and some growers recognize the trouble as one with which they have been familiar for a number of years. It was in the spring of 190-4, how- ever, that the "blight" began to attract much attention. The injured condition of many trees at that time was very evident. This was particularly the case in the Sacramento, San Joaquin, and Suisun valleys. A spotting, gumming, and death of the buds and twigs, * Pierce, Newton B. Peach Leaf Curl. Bull. 20, Div. Veg. Phys. and Path., U. S. D. A., 1900, p. 179. 62354 71 UNIVERSITY OV CALIFORNIA KXPKHIM10NT STATION. particularly on the lower part of the trees, appeared in some abun- dance at that time. The winter of 1905 was a very wet one, and the blight increased greatly that spring. By the middle of February, 1905, it was evident in many places that a fresh infection had taken place and the growers began very generally to see the necessity of finding means of controlling this new disease. Since another even more seri- ous orchard disease, the pear blight, Avas making its first appearance FIG. 1. Peach twigs affected by "blight." in much of the same territory at the same time, the peach trouble was considerably overshadowed for the time. The writer first became familiar with the disease as a serious matter in the fall of 1904, since which time the matter has been under observation and experiment by the Station to a considerable extent, culminating in the general cam- paign of control in the fall of 1906. The blight was extremely preva- lent in the spring of 1906, and somewhat less so, but still very destruc- tive indeed in 1907. Tin- large acreage of peaches which received Bulletin 191. CALIFORNIA PEACH BLIGHT. 75 timely spraying previous to the latter season rendered the effects of the disease much less noticeable. In the unusually wet spring of 1905, it was noticed generally in the Sacramento, San Joaquin, and other valleys that peach trees were affected to an alarming extent with some unusual condition. The trouble consisted in the dying of FIG. 2. Peach orchard, showing typical blight effect. the buds on the fruiting wood, spotting of the green twigs, and drop- ping or non-development of the young leaves and fruit. Particularly noticeable, and the most prominent feature of the disease, was a copi- ous "gumming," or exudation of masses of gelatinous sap from the twigs, originating in the dead spots and buds. This gumming was extremely abundant in wet weather all over the one-year-old fruiting twigs of affected trees, and with the blighted leaves and fruit and (6 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. spotted, leafless, dead or dying twigs and shoots, gave the tree a most distressing and alarming appearance. The crop was entirely ruined in badly affected orchards and the trees brought into an extremely weakened condition. (Figs. 1 and 2.) This describes, in a general way, the nature of this disease. It is readily distinguished from any other peach trouble by the features mentioned. It is essentially a winter or early spring disease of the fruiting twigs, the one-year-old wood which is- the valuable part of the FIG. 3. Effect of blight on fruit of peach. tree. This growth becomes killed all through the tree, except in the very top, and very serious loss and injury result. Most of the infection takes place in the winter, before the new growth starts, on twigs which were healthy and free from the trouble at the end of the ing season the previous fall. The new fruit becomes affected to some extent, as shown in Fig. 3, but the principal damage is done by the killing of the buds and whole twigs at a period previous to the deyelopment of fruit. During 1905 and 1906 the disease occurred in greater abundance. appearing in all the peach-growing sections. Santa Clara County and the southern California peach sections were the last affected, but the Bulletin 191. CALIFORNIA PEACH BLIGHT. 77 blight now occurs in both regions. The losses occasioned by the ' * blight ' ' have been enormous, particularly in the seasons above mentioned when FIG. 4. Peach tree sprayed in December, 1905. Photo taken in May, 1906. Compare with Fig. 2. climatic conditions were particularly favorable and little was done to check the disease. Indeed, it may truthfully be said that in the sum- mer of 1906, after two years of active prevalence of the "blight," the f« UNIVERSITY OV CALIFORNIA — EXPERIMENT STATION. peach orchards of the Sacramento and San Joaquin valleys, the main commercial acreage of the State, would have been in an absolutely ruined and unproductive condition without some means of checking the disease. The trouble was abundant in every orchard, all varieties were more or less affected, and the younger growth, which in the peach bears the fruit, had been almost completely killed and further development FIG. 5. Effects of blight. prevented. With the disease unchecked peach-growing was appar- ently at an end. THE CONTROL OF THE BLIGHT. Most fortunately, under these serious conditions, there has been evidence almost from the first that the disease could be successfully controlled. When, in 1904 and 1905, the blight began to be abundant enough to attract notice, it was evident to all who observed the matter closely that the usual practice of peach spraying in February or March was too late to check infection by this disease. Twigs which were sound and healthy in December were found to be spotted with infection \>y the first of February. Evon with the heaviest and most Bulletin 191. CALIFORNIA PEACH BLIGHT. 79 thorough spraying with Bordeaux mixture, or lime, salt and sulfur, applied at the usual time, the gumming produced by the blight would be found breaking out directly through the spray coating on affected twigs, and the disease was not checked in the least by the application. Knowing the cause of the disease to be a parasitic fungus, and with this habit of midwinter infection and development suggested by the FIG. 6. Results of December spraying. Compare with Fig. 5. experience of 1904 and 1905, the idea became quite general by the fall of 1905 that spraying in December would be the most promising time for successful control. The disease being new, and the fall season of 1905 an exceptionally dry one, the majority of the growers held to the hope that the blight would not occur again as before and took no unusual means for its control. Several in the Suisun Valley, however, and a few in the San Joaquin and elsewhere, sprayed their trees in December, and when the very severe development of the disease came on in February, 1906, the results were most complete and striking, showing in general that one thorough spraying early in December with the Bordeaux mixture absolutely prevented the disease. (Fig. 4.) sM UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. After December results were not so good, and gradually deteriorated up to February, from which time on sprayed trees were no better than FIG. 7. Effects of blight on fruiting twigs, 1906. onsprayed in respect to this disease. One orchard, sprayed mostly in December, but finished out Late in January, showed a decided differ- ence in the two portions. Spraying in December was perfectly sue- Bulletin 191. CALIFORNIA PEACH BLIGHT. 81 cessful; in January partially so, and in February and March without effect on this disease. The blight was so bad in unsprayed or late- FIG. 8. Twigs from December-sprayed tree, 1906. sprayed orchards, with the crop and foliage almost entirely gone, and all the growth on those sprayed in December perfect, particularly the lower, inner, blight-susceptible fruiting twigs, that one seldom sees — UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. so striking a contrast in the treatment of any plant disease. Abundant comparison was available between trees of the same variety, age, and condition. (Figs. 5 and 6.) Effect on Curl Leaf Equally Good.— The writer took some pains to note in this connection the effect of this early spraying on curl leaf, inasmuch as any peach treatment must take this disease into consid- eration. (Fig. 7.) So far as could be judged, the effects were equally good, and the disease controlled as well as by the usual later spraying. The fine condition of a block of December-sprayed Susquehannas was especially noticed, while uhsprayed trees on this and even less curl- susceptible varieties were badly affected by c,url leaf wherever the blight fungus had left any leaves on the tree. (Fig. 8.) To summarize: Unsprayed trees were very badly affected by blight and curl leaf. Trees sprayed in December were free from any disease. Trees sprayed late in January were somewhat affected by blight, but free from curl leaf. Trees sprayed in February and early March were free from curl, but no better than the unsprayed in regard to blight. In the light of these results and in view of the serious and demoral- ized condition of the peach industry in the spring of 1906, a thorough campaign of peach-spraying and experimentation was planned by the Station for the season of 1906-07. So bad was the condition of prac- tically every orchard that it was not deemed sufficient to simply carry out a few limited demonstrations and experiments. In order to meet the situation adequately it was necessary that practically every grower in the principal sections be personally visited and instructed in the best method of procedure, in order that no further time be lost. In accordance with this plan assignments were made to Messrs. Jones and Hunt to the Sacramento and San Joaquin valleys, respectively, to urge the growers to spray in November and December, to instruct and assist the inexperienced in proper methods of work, and to follow up the work done and the results accomplished. Series of experiments were also carried out, in spraying at different seasons, for blight control. In addition to the Station efforts, great good was accomplished by the Boards of Horticulture in many of the counties along the same line. Early spraying was urged upon the growers at every opportunity by these men in the valley counties and elsewhere, and many a 1907 crop is the result of their efforts. The State Commissioner of Horticulture was a] so active in spreading the propaganda. As a result of this effort and the very serious condition of the peach orchards, spraying in November and December, 1906, was almost uni- Bulletin 191. CALIFORNIA PEACH BLIGHT. 83 versal in the San Joaquin and Sacramento valleys. Such a concerted and general effort has rarely been made in the attempt to control any plant disease. From October to March the Experiment Station repre- sentatives were constantly in the field in the upper San Joaquin and lower Sacramento, our greatest peach sections. The recommendation made was' to spray between November 15 and December 15, with Bordeaux mixture of the strength 30-35-200 (Milestone, lime, water). The work was entirely new to many of the growers, particularly in the San Joaquin Valley, where there had been little cause for spraying peaches hitherto, and much time was spent in instructing the inex- perienced in making the mixture and applying it to the trees. The fact that four hundred spray pumps were sold at one small town, as recorded by a horticultural paper, indicates both the extent of the operations and the fact that it was new to most of the growers. Natu- rally, under these circumstances, many mistakes were made and much poor spraying resulted. Another season will certainly find the grow- ers much better prepared to spray their trees properly. Weather con- ditions also were most unfavorable to spraying at the desired time, on account of continuous rain. The condition of the trees resulting from previous attacks of the disease was also to be considered. To one familiar with the state of a large part of our peach orchards in the spring of 1906 it would seem little short of miraculous to have any- thing like a full crop in 1907 on the same trees, and in fact even less surprising if the trees had all died. With all the lower twig growth killed, most of the leaves fallen in early summer, the crop almost entirely on the ground, no wood developing for a new crop, and the whole life of the tree confined to a few straggling twigs in the top, the outlook at the end of last season was indeed discouraging. Still further trouble was caused by a shortage of bluestone, many being totally unable to procure the material, and, if at all, only at an exorbitant price. All in all, therefore, the results of the past season may be taken as a very conservative basis for future calculations. The time suggested for spraying was chosen, as already shown, on the basis of the limited experience of the previous season and the known fact of the time of infection. After following the matter carefully for several seasons it has appeared that each year about the first week in January the signs of the disease make their appearance. At this time the indications of the blight of the previous year are very abun- dant everywhere in the shape of dead, cankered spots on the growth of the preceding year. From these spots copious gumming begins with the winter rains. Up through December, however, the new growth of th^ season, the young twigs which bear the fruit buds, are green and vigorous, save for a very few occasional blight spots which may have formed early in the preceding summer. The buds are alive and vigor- 84 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. ous, and on what bearing wood there is the indications are in no way other than tor a good crop. In the ease of very heavy rains previous to the first of Jan- uary there may be considerable infec- tion even before that date, as oc- curred in Decem- ber to some extent during the past season, but the main infection ap- pears to come on quite uniformly at about the time of the new year. From this time on through the winter further infection is abundant and rapid, occurring in proportion to and along with the rainfall. Up to December 15th al- most every twig is green, sound, and unaffected. With abundant rain be- fore or about that time the brown, or at first reddish, dead spots begin to appear, especially at the base of the buds just where they join the twig. (Fig. 7.) In this way the buds are killed and the crop as well as the growth for the next year is destroyed. This has not, in our observations, become abundant until January 1st, about which time the infection occurs very rapidly. In this way twigs which were entirely sound late in December may have almost all their buds and the twig itself killed, spotted, and gumming six weeks later. The results of spraying in the fall of 1906 became very apparent by February 1st. Trees well sprayed before the infection started had the twigs and burls still alive and sound, while unsprayed trees were show- FIG. 9. Unsprayed trees, 190' Bulletin 191. CALIFORNIA PEACH BLIGHT. 85 ing very bad infection and gumming. In one case the writer saw an orchard on January 8th which was just then being sprayed, and in which the work was stopped before completion, on account of rain. On the last rows sprayed, as well as on those unsprayed, the blight spots were appearing in great abundance on the twigs, breaking out directly through the spray in numerous cases, and it was most evident that so far as blight was concerned the best time for treatment had passed, though spraying might still prevent further infection, which might result from more rain. A very important complication must be considered in spraying for blight control; this is the occurrence of another peach disease, the Curl Leaf. The effects of this trouble are too well known in Califor- nia to need descrip- tion. The control of the disease is very successfully accomplished by spraying in Feb- ruary or March, just before the buds unfold, but a time which, as has already been shown, is too late for . blight preven- tion. In the expe- rience of 1905 the one fall spraying controlled both dis- eases — a most satis- factory condition. In the spring of 1907, however, a very virulent at- tack of curl leaf occurred, especially in the lower Sacra- mento Valley, while the blight fungus proved somewhat less active than in the previous season. The result of this is plainly shown by the results of spraying, FIG. 10. Tree sprayed in November, 1906, and February, 1907. •M UNIVERSITY OV CALIFORNIA — EXI'KKl.MKNT STATION. viz: that the November or December application did not entirely hold the curl Leaf in cheek, although as successful as before with the blight. Consequently some orchards sprayed properly and successfully for blight were badly injured by curl leaf, while others sprayed later were protected from curl leaf and left in better condition at the end of the sea- son than those in which the blight alone was con- trolled. All that had been expected of the blight treat- ment held good when its effects w r ere differentiated from those of the other disease, but the necessity of two sprayings rather than one for the positive control of both diseases has become evident. The following table gives in con- densed form the record of a number of typical orchards in the regions FIG. 11. Left side of tree sprayed in December, 1906, right side unsprayed. where our work was centered. The column of formulas expresses the amount of bluestone, lime, and water used in each instance. The names of varieties are abbreviated as follows: .C, Crawford; CI, Crawford Late; E, Elberta; F, Foster; G, Georgia; Ha, Hale; H, Henrietta; I, Imperial; L, Lovell; Mc, McDevitt; Ma, Mary's Choice; Mu, Muir; 0, Orange; P, Phillips; Sa, Salway; Su, Susquehanna; T, Tuscan; W. Wheatland. In orchard No. 1, for instance, Muirs, Lovells, and Elbertas were sprayed December 22d and in February, each time with Bordeaux Bulletin 191. CALIFORNIA PEACH BLIGHT. 87 mixture made with 30 pounds of bluestone, 30 pounds of lime, and 200 gallons of water. The acreage represented in this table is about 2,500. The orchards sprayed in the fall of 1906 for blight control, as a result of the efforts FIG. 12. Twigs from sprayed and unsprayed trees, 1907. of the Experiment Station and others, amounted certainly to ten times this amount, or 25,000 acres at a very conservative estimate, as there are at least 50,000 acres of bearing peaches in the area under observa- tion and an unsprayed orchard was very much the exception. The data given in the table are representative of average conditions, taking UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. the orchards as they come, from which it appears that most of the orchards were sprayed, and a very large majority at the proper time and with good results. Cases like Nos. 89 and 124 show the loss of practically the whole crop where no spraying was done, and Figs. 9, 10, 11 and 12 indicate plainly the comparative results of proper spraying and no treatment. Fig. 11 is particularly suggestive, showing on the same tree a heavy crop and full foliage on one side, which was sprayed, and the complete blighting and ruining of the crop on the other side, which received no treatment. In view of these results a saving of $20 per acre is cer- tainly a moderate estimate, which on the acreage stated would amount to a gain of $500,000 in the season's crop, not considering the saving of the trees and possibilities of even better results in the future. As a matter of fact the saving effected might reasonably be estimated as the difference between no crop at all and a large and profitable one, as well as the saving of the trees themselves, in which case the figures would rise very much higher. As the whole expense to the State and counties for this saving was probably not over $1,500, the practical value of this work is quite apparent. RECORD OF TYPICAL PEACH SPRAYING, 1906-07. No. Locality. Varieties Bordeaux Formula. uaies. Results and Remarks. 1 Hanford.- 2 3 4 5 " 6 7 9 10 11 12 13 li i.-, 16 17 Mu, L, E Mu Mu, E, T, P, H,Mc Mu, L, Su, Sa, P, O Mu, E Young trees F, Mu,L, E, O E, P, W, Mu Mu, C, S .-.. Mu, E, P.... Mu — Mu. E, T, L Mu, E Mu,E,Cl,Sa Mu, CI, Su, E Very old tre<-s 30-30-200 30-35-200 24-40-200 30-36-200 30-40-200 30-35-200 30-35-200 20-20-200 30-30-200 30-35-200 20-25-200 30-40-200 32-32-200 40-48-200 16-20-200 32-36-200 30-35-200 30-35-200 20-20-200 Dec. 22, '06 Feb. '07 Dec. 5, '06 Nov. 15, '06 Dec. 26, '06 Dec. 5-30, '06 Dec. '06 Dec. 8-30, '06 Feb. '07 Dec. 1-20, '06 Feb. '07 Dec. 7, '06 Jan. 2, '07 Dec. 1-30, '06 Dec. 12-22/06 Nov.29-Dec. 10, '06 Dec. 8-15, '06 Feb. '07 Dec. 15-18, '06 Nov. 20, '06 Jan. 5, '07 Dec. '06 Feb. '07 Trees in fine shape. Big crop. No blight. Big crop. No blight. Little or no blight. Fine crop. Little blight on old trees. Some curl leaf. Fine crop. Old trees ; considerable blight Poor spraying in part. Trees in tine condition. No blight. Very little blight. Good crop. Trees look tine. Good crop. Very little blight. Poor job first spraying; second good. Big crop. Trees tine. Very little blight. Trees look well. No blight. Trees fine. Young trees. No blight. No blight. Little blight in very old trees ; others good. Poor work at first, but repeated. No blight. Best crop ever had. Trees fine. Very little blight. Heavv crop. Very bad in 1905-6. Bulletin 191. CALIFORNIA PEACH BLIGHT. 89 RECORD OF TYPICAL PEACH SPRAYING, 1906-07 -Continued. No. Locality. Varieties. Bordeaux Formula. Dates. Results and Remarks. 32 Dinuba ... Mu,L 40-48-200 Dec. 17, '06 Poor spraying. Trees and crop poor. Some blight; much curl leaf. 33 " Mu, E, I, P, O 40-48-200 Dec. 13, '06 Elbertas curled badly. Very poor spraying. Some blight. Very little blight. Good crop. 34 " Various 24-24-200 Dec. 8, '06 Feb. 22, '07 35 " Mu, C, E.__ 25-25-200 Dec. 19-30, '06 Little blight. Some curl on Elbertas. 36 u Mu, L, P.... 36-36-200 Dec. 24, '06 Feb. 15, '07 Little or no blight. Good crop. 37 " Mu, L 36-36-200 Dec. 12, '06 Feb. 15, '07 No blight. Good crop. 38 " Mu, L, P,0, T, E, W 28-32-200 Dec. 1, '06 Feb. 15, '07 No blight. Good crop. 45 Armona _. Mu, E, L.__. 28-40-200 Dec. 22, '06 No blight. 46 " Mu, E, L.._. 28-40-200 Dec. 29, '06 No blight. A little curl leaf. 47 « Su, Sa, CI... 28-40-200 Dec. 20, '06 Little or no blight. 48 " Mu, L, E.._. 30-44-200 Dec. 29, '06 No blight. 49 " Mu, E. C, O, Su 24-28-200 Dec. 5-24, '06 A little blight and much curl leaf. 50 " Mu,C,0,Sa, Su, CI 24-40-200 Dec. 10-19, '06 No blight. 56 Kingsburg O, Mu, Sa, F, Su 40-48-200 Dec. 16. '06 No blight. Big crop. A few trees not sprayed have no crop and bad blight. Very little blight Good crop. 57 " Mu, O, T, C, Su Mu, 0, P.... 48-48-200 Dec. 15, '06 58 " 36-40-200 Nov. 20, '06 No blight. Heavy crop. 59 « T, P, 0,Mu, L,Su Mu, O, E, F. 36-40-200 Dec. 12, '06 No blight. Fine crop. 60 " 40-48-200 Dec. 15, '06 No blight. Fine crop. 61 C( C, L, O 36-40-200 Dec. 18, '06 Did poor iob. Much blight. Verv light crop. 72 Del Key... Mu,C,0,Sa, 30-35-200 Dec. 17, '06 ! Very 'little blight. Fine crop. Su, P 20-20-200 Feb. 15, '07 1 73 Visalia P 40-48-200 Dec. 1, '06 One row poorly sprayed, badly blighted. On the rest no blight. Trees badly injured by standing- water. 74 (< P,0 40-48-200 Nov. 27, '06 75 " Ma, Mu, O, E, C,Sa, P Mu, Su, O... 48-48-200 Dec. 12, '06 Very poor work. Much blight. 84 Selma 40-48-200 Sept. 1, '06 Poor spraying. Considerable Jan. '07 blight and light crop. 85 " P, 0, Mc__„ 32-42-200 Dec. 14, '06 No blight; a little curl leaf. 20-20-200 Feb. '07 Fine crop. 86 ii Mu, C, O.... 30-35-200 Dec. 20, '06 Poor job. Much blight. Fair 89 Sultana... Unknown. ... Not spra crop, yed.. Trees badly blighted. Very little fruit. 109 Yuba City. T, Mc, 0, F, 20-20-200 Sept. 25, '06 Badly affected with blight and Mu, curl leaf. 109 A 24-24-200 Sept. 25, '06 Showed some advantage over last in blight, but bad with curl leaf. 109 B " " 20-20-200 Sept. 25, '06 Feb. 13, '07 Much better than last, espe- cially in regard to curl leaf. 109 C w ' (< 20-20-200 Oct. 24, '06 Little blight, but bad with curl leaf. Somewhat better than last re- 109 D K « 30-35-200 Oct. 24, '06 garding blight. 90 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. RECORD OF TYPICAL PEACH SPRAYING, 1906 07— Continued. No. 110 110 A 110 B 111 1112 112 A 113 113 A 114 114 A 115 115 A 115 B 116 117 118 119 120 121 122 122 A 123 124 124 A 125 142 12*; 127 127 A Loealitv Varieties Yuba Citv T. Me, O, F. Mu T, Mc Bordeaux Formula. Dates. P. Me.... P, Mc... Unknown .. Mu, I, Ha .. T,Mc,0,W, Mu C . Marysville Chico Red Bluff Oakdale .. Unknown .. Unknown .. Mu, 0,T.__. P P C, Su, G .... Apricot Unknown Unknown Unknown Unknown Unknown Unknown Various... F Mu Bidwell... Various.. . 20-20-200 30-35-200 30-35-200 30-35-200 30-35-200 30-35-200 30-35-200 30-35-200 30-35-200 30-35-200 Not spra 36-40-200 36-40-200 36-40-200 Mu. C, Ma, CI Cling 30-35-200 40-60-200 . 40-60-200 60-72-200 36-36-200 30-35-200 36-36-200 30-35-200 Unknown Unknown Rex Unspray Unspray Unspray Unknown ! Feb. 13, '07 Dec. 1, '06 Jan. '07 Feb. '07 Feb. 15, '07 Nov. 27 to Dec. 20, '06 Mar. 6, '07 Nov. 20, '06 Nov. 20, '06 Nov. 20, '06 Mar. 1, '07 Mar. 13, '07 yed Feb. 10, '07 Jan. 18, '07 Jan. 18, '07 Feb. 10, '07 Nov. '06 Feb. 10, '07 Nov. 7, '06 Results and Remarks. Dec. 7, Feb. 5, Feb. Nov. 10, Nov. Feb. Feb. ed ed ed '(it; '07 '07 '06 '06 ; 07 '07 Nov. '06, to Mar. '07. Jan. 10, '07 Dec. 7, '06 Dec. 14, '06 Considerable blight. Good control of curl leaf. Very free from blight; con- siderable curl leaf. More blight than last. Less fruit. Less curl. Very bad with blight. Free frbm curl. Blight very bad. Good con- trol of curl leaf. Very little blight, or curl leaf. Even less blight infection than last. Very little blight; considerable curl leaf. Free from blight and curl leaf. Blight very bad; very little curl leaf. Blight and curl leaf very bad. Some blight, but fairly good. Quite bad with blight and curl leaf. Less curl leaf than last. Fine condition. No blight or curl leaf. Crop spoiled by rain, but full bloom and foiiage. No' blight. Blight very bad. Blight very bad. Very little blight. Very little blight. Part of same orchard as last. Blight much worse. Twigs already infected. Blight abundant. Blight and curl very bad. No crop. Blight less than last. Curl very bad. Light crop. Blight and curl very bad. Excellent blight and curl leaf control by fall and spring spray. Considerable previous blight infection. Checked bv spray. No blight. Part of same orchard as last. Rain Dec. 10. Some infec- tion on these. The records in this table represent sprayings with various strengths of Bordeaux mixture, in a number of sections of the Sacramento and Joaquin valleys, at limes ranging from September to March, and Bulletin 191. CALIFORNIA PEACH BLIGHT. 91 on all the usual varieties of peach. A study of this table gives a clear idea as to the most successful manner of treatment. Time of Spraying for Blight Control. — September was too early and February and March too late. Spraying in the latter part of October seemed effective, and from then on to the middle or last of December the best results of one application were secured in preventing blight infection. The attacks of curl leaf complicated matters. In many cases a com- plete blight control, obtained by early spraying, was nullified by unchecked attacks of the other disease. Spraying in November and December did not altogether hold the curl in check, while the February and March applications did so perfectly. It therefore seems best in the future to advise two sprayings, one early and one late, to insure freedom from both diseases. As a third peach pest, the Peach Worm may be controlled by spray- ing with lime, salt, and sulfur just before the buds open, a treatment that is equally efficacious for curl leaf, we suggest this for the second spraying rather than Bordeaux mixture.* Kind of Mixture.— Practically all these results refer to Bordeaux mixture. We have reason to feel sure that lime, salt, and sulfur spray would give equally as good results, but for the blight alone the more easily prepared Bordeaux is usually preferable. Proportion of Mixture. — We have not laid great stress on the exact formula for the Bordeaux mixture to be used. Where the mixture was properly prepared very little difference in the results has appeared, whether it was 20-20-200, 30-35-200, or very much stronger as some have used it. Ordinarily the 20-20-200 formula is probably strong enough and affords some saving of material over a heavier application. A mixture containing more copper and lime remains longer on the tree, however, is not as quickly washed off by rain, and shows more plainly on the tree just how thoroughly it has been covered. We would therefore advise the use of the lesser strength only when mate- rials are very high and scarce or where the workmen are particularly adept in applying the spray perfectly. For average conditions we pre- fer the 30-35-200 for the early application. Preparing the Mixture.— The preparation of Bordeaux mixture has been described almost too frequently to need repetition. The lime should be of the best and perfectly unslaked, and slaked in a consider- able amount of the water and stirred and strained to make a perfectly smooth whitewash. The bluestone is to be dissolved in water, a stock * See Bulletin No. 144, California Experiment Station. 92 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. solution of known strength being most convenient. In mixing the two, plenty of water should be used to keep them well diluted, and the mixture well churned together, strained, and diluted with the remainder of the water. Relation of Spraying and Pruning.— The early time of spraying recommended for blight control is apt to find the trees unpruned and with considerable foliage still on the branches. This at first seemed a serious obstacle to some, but experience has shown that even in -this condition the trees may be sprayed with perfect success, provided a thorough job is done. It is very desirable to have the trees pruned before spraying, and this should be done if possible, but spraying should on no account be delayed beyond the proper time because the trees are not pruned. If the pruning can not be clone in time the spraying should proceed very thoroughly, and the pruning done later. Application of the Spray.— Instances like Nos. 32, 33, 61, and 73, of the table, show the results of poor spraying. Many growers went over their trees a second time, on being shown their mistakes. The effort should be made, above all, to cover all the branches and fruiting twigs completely with the spray. The inexperienced workman soaks the trunk and main limbs, but leaves untouched much of the small growth which bears the fruit and which the blight particularly affects. In order to check the blight infection on the twigs, those twigs must be completely covered with spray before infection occurs. The least portion of a twig left uncovered is as exposed to infection as though there w T as no spray on the tree at all. An experienced and conscientious sprayer goes over his tree systematically and completely, leaving no portion uncovered and yet wasting no material. E elation of Peach Varieties to Infection.— We have been able to find no fixed rule as to the relation of the different peach varieties to the blight. In some sections or seasons one kind has been much the worst, while in another quite a different condition held good. No variety has been at all immune to the trouble, but all quite badly affected. Bulletin 191. CALIFORNIA PEACH BLIGHT. 93 THE PEACH BLIGHT FUNGUS. The fungus causing the so-called "blight," or "shothole fungus," has been identified by us as Coryneum beyerinkii Oud. This has been mentioned frequently as doing damage in this country, though never to nearly so great an extent as in California. Trabut reports the same fungus as occurring extensively in Algeria in 1904, on apricots, peaches, and cherries. 4 McAlpine, 3 in discussing the shothole fungi of the stone fruit, describes the fungus Clasterosporium carpophilum (Lev.) Aderh., which he consideres identical with Coryneum beyerinkii. Our fungus appears to be correctly classified as Coryneum, in that the spores are given off in distinct aggregations from a special stroma. This char- acteristic separates it definitely from Clasterosporium, which is among the Hyphomycetes. Otherwise, so far as can be observed from descrip- tions and plates, the Clasterosporium of McAlpine is identical with our Coryneum. So far as mycological characters show, there is only one species of Coryneum on the various stone fruits in California. We are not yet ready to report upon the matter, however, from the standpoint of cross-inoculation, as experiments are still in progress. The mycelium producing' the spots on peach leaves and shoots during the winter, fruits by means of spore pustules which occur as minute black specks (four or five) near the center of the more or less circular spot. The tissue of the leaves so affected soon drops out, so that it is often difficult to find the conidia at this season of the year, especially where only the young, spotted shoots are at hand. The spots on the bark are more often sterile, which is sometimes true of the leaf spots as well. By the end of the infection period, however, the spores have become quite abundantly scattered about on the twigs. The fertile spots, on sectioning, show distinct pustules with well-developed stro- mata, which push out until the epidermis is ruptured, after which the short conidiophores with their olive-colored elliptical spores appear as dense clusters on the surface. (Fig. 13.) Especially on twigs from which the affected leaves have fallen the eonidia are found in abundance about the leaf scars and roughened portions of the bark during the spring and summer. (Fig. 14, c.) If a late rain occurs they germinate, causing new infection on the remain- ing leaves, and are ready with the fall rains to infect and kill outright many of the newly formed buds. 1 Mich. Agr. Exp. Sta. Bull. 103, p. 57. 1894. 2 Ohio Agr. Exp. Sta. Bull. 92, p. 225. 1898 and other State Bulletins. 3 Fungus Diseases of the Stone Fruits in Australia and their treatment, bv D. McAlpine. March, 1902. 4 Le Coryneum, Maladie des Arbres a Noyaux, in Bulletin Agricole de l'Algerie et de la Tunisie. No. 10, May, 1904. By Dr. Trabut. 94 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. Though many of the eonidia thus distributed are those which fall from the spots on leaves and green bark, it was found that these eonidia FIG. 13: Longitudinal section through a Coryneum pustule on peach spot. Bulletin 191. CALIFORNIA PEACH BLIGHT. 95 reproduced themselves more or less with moisture on the dead outer cells of the older twigs. This occurs often as a mold-like growth on the surface of the bark, much as in artificial media. Characteristic pustules are found on the leaf scars, however, some- times in considerable abun- dance. The life history of the Coryneum, then, as shown by our experience, is as follows: The spores, scat- tered profusely over the limbs, germinate as soon as enough rain has fallen to wet them up thoroughly, usually in December or January. Spores lying on the green bark of new shoots penetrate the tissue and cause the characteristic spotting, the mycelium from each germinated spore killing a small area of the bark. Spores lying about the bud scales produce a mycelium which penetrates and kills outright both the bud and quite an area of surrounding bark, the spot extending from one-fourth to ,one inch in length. On the spots spore pustules are developed, the conidio- phores being produced on a stroma under the epi- dermis which is ruptured by the spores. (Fig. 13.) When the buds which have survived the winter attack unfold in the spring, the leaves are very generally affected by the fungus, causing small dead areas in the leaf tissue, which soon dry up and fall out, causing the so-called "shothole" effect of the leaf. Pustules are also found on the leaf spots. In the majority of seasons the new infection ceases at the end of April. In seasons where a late rain occurs in spring, however, the spores produced on FIG. 14. Coryneum spores: a, from petri dish colonies in agar; b, from prune agar tube cultures; c, from pus- tules on peach bark. (All drawn to same scale.) 96 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. the winter infection germinate instead of remaining dormant till fall or winter, and not only leaves, but the new shoots and even the young fruit become spotted at this time. The mycelium in the newly affected tissue produces spores in turn, thus furnishing a fresh supply for the winter attack. The alarming phase of the fungus, economically, is this winter kill- ing of the buds, together with the area of the bark about the bud which is involved in the destruction. As new growth proceeds the tension FIG. 15. Dried petri dish culture in agar, showing colonies. Natural size. which is set up between the dead and the growing bark surrounding it causes a fissure, from which the gum is exuded. This gumming from lesions around the dead buds is chiefly confined to the new wood, since, where the tree has sustained the attack sufficiently, old wounds are more or less healed over at the time of the next year's flow. This attempt at healing on the part of the tree causes the cankers so often found on the Limbs of affected trees. Where the vitality of the tree is low, however, from the loss of buds, leaves, and sap for perhaps several consecutive years, there are sometimes "gumming" wounds left in the older wood. Bulletin 191. CALIFORNIA PEACH BLIGHT. As yet we have failed to procure abundant growth in culture from spores taken from the bark or leaf. This is to be accounted for, at least in part, by the fact that the copious gum exuded from the cankers of the diseased bark produces an abundance of mold spores of various kinds besides bacteria and yeasts, which outgrow the Cory- neum in initial cultures. Moreover, during the winter and spring the surface of the tree is often moist and sticky throughout from escaping sap, in which many of the spores have already germinated. The fact remains, however, that mature spores under seemingly favorable con- ditions in whatever season usually fail to grow in culture when taken from the tree. Often only one colony is secured out of a dozen or more petri dish cultures in peach or ordinary agar. Once secured in culture, however, it can be reproduced readily in either of the above named media. It also grows luxuriantly on sterilized peach twigs in tubes. The colonies in agar petri dish cul- ture are black, with distinct zones of conidia, the col- onies being submerged in the medium. (Fig. acid agar slants the fungus produces a black posed almost entirely of spores. The mycelium, in culture, is colorless. On sterile twigs distinct pustules are formed, as in Fig. 16, which appear to the naked eye as black specks on the epidermis. The size of the pustule is more or less uniform, both in natural infection and in twig cultures, measurements varying from 100 m to 166 pi with pustules observed. Shape is somewhat cubical or rounded. The spores as occurring naturally do not vary materially in length from those in agar plates, the minimum length being 17 pi, maximum 44 yu, average 30-40 pi. Width in " natural" spores, however, is uniformly about 13 yu, $nd number of cells 3 or 4, rarely 5, while in FIG. 16. Microphotograph of Coi pustule on sterilized peach twig. 15.) On prune or surface crust com- sparingly produced 98 UNIVERSITY OP CALIFORNIA EXPERIMENT STATION. agar colonies width is about 6 //, and number of cells from 3-12, usually 6 or 7. On sterile twigs the spores do not average more than 20 jjl in length, and range from 3 to 6 cells, usually 4. (See Fig. 16.) The peach trouble identified as being caused by Helminthosporium carpophilum (Lev.) in this country (see cit. 1, 2, 3) is stated by Mc- Alpine to be identical with his Clasterosporium. In our work we have found the spores of agar cultures particularly suggestive of this type, being narrow, of uniform width, and often nearly oblong in shape. In short, there appear to be two types of spores belonging to the peach Cory iicum, one borne on a distinct stroma in pustules, elliptical and confined to three or four cells, the others of hyphomycetous origin, more or less oblong, and from 3 to 12 cells. (Fig. 14.) Vuillemin in 1890 described a new species of Ascospora {A. beyerinkii Yuill.) which he considered to be the perfect form of Coryneum beyerinkii. Up to the present time we have found no indication of an ascomycetous stage of any kind. The conidia appear to live over the dry, summer season, lodged in the bud scales and bark, as previously described. That it is possible for the spores to live several months in a dry condition has been proved by laboratory experiments. Of the various molds encountered in a study of the diseased tissue, sooty mold and a species of Phyllosticta have been found most con- stantly in connection with it. The former spreads itself over the sur- face of the dead spots, often rather soon after infection, forming a single layer of connected cells, which give off bud conidia in the manner characteristic of this class of fungi. The Phyllosticta is found more often on spots which are thoroughly dead and dry, the whole surface being dotted with the small pyenidia, which give off minute, unicellular conidia from short conidiophores. The writer has found no fungus associated with the Coryneum which could readily be confused with it as the cause of peach blight. RECOMMENDATIONS FOR PEACH BLIGHT AND CURL LEAF CONTROL. Spray thoroughly with Bordeaux mixture between November 1st and December 15th. The work may begin as early as October 25th. Use 30 pounds of bluestone and 35 pounds of quicklime to 200 gal- loos of water. If materials are very high, somewhat less may be used, down to 20-20-200. Prune if possible before spraying, but do not delay the work on account of pruning. About February 15th, or just before the buds open, spray again with Bordeaux, 20-20-200, or lime, salt and sulfur. STATION PUBLICATIONS. 99 STATION PUBLICATIONS AVAILABLE FOR DISTRIBUTION, REPORTS. 1896. Report of the Viti cultural Work during the seasons 1887-93, with data regarding the Vintages of 1894-95. 1897. Resistant Vines, their Selection, Adaptation, and Grafting. Appendix to Viticultural Report for 1896. 1898. Partial Report of Work of Agricultural Experiment Station for the years 1895-96 and 1896-97. 1900. Report of the Agricultural Experiment Station for the year 1897-98. 1902. Report of the Agricultural Experiment Station for 1898-1901. 1903. Report of the Agricultural Experiment Station for 1901-1903. 1904. Twenty-second Report of the Agricultural Experiment Station for 1903-1904 TECHNICAL BULLETINS— ENTOMOLOGICAL SERIES. Vol. 1, No. 1 — Wing Veins of Insects. No. 2 — Catalogue of the Ephydridae. BULLETINS. Reprint. Endurance of Drought in Soils of the Arid Region. No. 128. Nature, Value and Utilization of Alkali Lands, and Tolerance of Alkali. (Revised and Reprint, 1905.) 133. Tolerance of Alkali by Various Cultures. 140. Lands of the Colorado Delta in Salton Basin, and Supplement. 141. Deciduous Fruits at Paso Robles. 142. Grasshoppers in California. 147. Culture Work of the Substations. 148. Resistant Vines and their Hybrids. 149. California Sugar Industry. 150. The Value of Oak Leaves for Forage. 151. Arsenical Insecticides. 152. Fumigation Dosage. 153. Spraying with Distillates. 154. Sulfur Sprays for Red Spider. 156. Fowl Cholera. 158. California Olive Oil ; its Manufacture. 159. Contribution to the Study of Fermentation. 160. The Hop Aphis. 161. Tuberculosis in Fowls. (Reprint.) 162. Commercial Fertilizers. (Dec. 1, 1904.) 163. Pear Scab. 164. Poultry Feeding and Proprietary Foods. (Reprint.) 165. Asparagus and Asparagus Rust in California. 166. Spraying for Scale Insects. 167. Manufacture of Dry Wines in Hot Countries. 168. Observations on Some Vine Diseases in Sonoma County. 169. Tolerance of the Sugar Beet for Alkali. 170. Studies in Grasshopper Control. 171. Commercial Fertilizers. (June 30, 1905.) 172. Further Experience in Asparagus Rust Control. 173. Commercial Fertilizers. (December, 1905.) 174. A New Wine-Cooling Machine. 175. Tomato Diseases in California. 176. Sugar Beets in the San Joaquin Valley. 177. A New Method of Making Dry Red Wine. 178. Mosquito Control. 179. Commercial Fertilizers. (June, 1906.) 180. Resistant Vineyards. 181. The Selection of Seed-Wheat. 182. Analysis of Paris Green and Lead Arsenate. Proposed Insecticide Law. 183. The California Tussock-moth. 184. Report of the Plant Pathologist to July 1, 1906. 185. Report of Progress in Cereal Investigations. 186. The Oidium of the Vine. 187. Commercial Fertilizers. (January, 1907.) 188. Lining of Ditches and Reservoirs to Prevent Seepage and Losses. 189. Commercial Fertilizers. (June, 1907.) 190. The Brown Rot of the Lemon. 1 • UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. CIRCULARS. No. 1. •i 3. 4. 5. 7. 9. 10. 11. 12. 13. 15. 16. 17. 18. 19. 20. 21. Texas Fever. Blackleg. Hog Cholera. Anthrax. Contagious Abortion in Cows. Remedies for Insects. Asparagus Rust. Reading Course in Economic Entomology. (Revision.) Fumigation Practice. Silk Culture. The Culture of the Sugar Beet. Recent Problems in Agriculture. What a University Farm is For. Notes on Seed-Wheat. Why Agriculture Should Be Taught in the Public Schools. Caterpillars on Oaks. Disinfection of Stables. Reading Course in Irrigation. The Advancement of Agricultural Education. Defecation of Must for White Wine. No. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. Pure Yeast in Wineries. Olive Pickling. Suggestions Regarding Exam- ination of Lands. Selection and Preparation of Vine Cuttings. Marly Subsoils and the Chlo- rosis or Yellowing of Citrus Trees. A Preliminary Progress Report of Cereal Investigations, 1905- 1907. Preliminary Announcement con- cerning Instruction in Practi- cal Agriculture upon the University Farm, Davisville, Cal. White Fly in California. The Agricultural College and Its Relationship to the Scheme of National Education. White Fly Eradication. Packing Prunes in Cans. Cane Sugar vs. Beet Sugar. Copies may le had on application to Director of Experiment Station, Berkeley, Cal.