UNIVERSITY OF CALIFORNIA • COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA BLACKEYE BEANS IN CALIFORNIA W. W. MACKIE BULLETIN 696 February, 1946 UNIVERSITY OF CALIFORNIA • BERKELEY, CALIFORNIA CONTENTS History and origin of the Blackeye bean 3 Spread of cowpeas in the United States 4 Climatic conditions governing Blackeye production 6 Rainfall in Blackeye areas 8 Frosts and winds 10 Distribution of Blackeye-bean culture 10 San Joaquin Valley 11 Sacramento Valley 12 Southern California 12 Coastal counties 13 Culture 13 Spacing 13 Fertilization 14 Crop rotations 14 Nodule cultures 15 Seed treatment 16 Irrigation 16 Growing Blackeye beans by dry farming 18 Harvesting 18 Uses of Blackeye beans as covercrop and forage 20 Intercultures with Blackeye beans 22 Blackeye seed and varietal purity 22 Breeding for disease-resistant Blackeye beans 22 Technique of breeding 24 Factors involved in breeding for disease resistance 26 Size of seed 26 Shape of seed and quality of seed coat 26 Vine shape and size 28 Maturity 29 Inheritance of characters found in hybrid Blackeyes 29 Mode of inheritance of characters 29 The Fj, or first generation 30 The F 2 , or second generation 30 Factors affecting disease resistance to cowpea wilt, charcoal rot, and root- knot nematode 32 Nature of resistance 33 Tests with disease-resistant Blackeye hybrids in other states 34 Maturity of hybrid Blackeyes 35 Comparative yields of Blackeye hybrids 36 Disease-resistant Blackeye hybrids released to farmers 37 Diseases of Blackeye beans 41 Diseases found in California 41 Diseases not occurring in California 44 Insects and other pests causing economic damage 45 Price, production, and marketing of Blackeye beans 46 Marketing Blackeye beans 48 Market grades 50 Uses of Blackeye beans 51 Blackeyes as snap beans and sprouts 51 Cooking of Blackeye beans 51 Blackeyes parboiled 51 Blackeyes baked 52 Other uses for Blackeye beans 52 Discussion and summary 52 Literature cited 53 BLACKEYE BEANS IN CALIFORNIA 1 W. W. MACKIE 2 What is the Blackeye, a bean or a pea ? In the southern states, where it is contrasted with the garden, or English, pea, it is called a pea. In general over the United States it is known as a cowpea, but in California it is known only as the Blackeye bean (Wells, 1941). 3 In the South, where it is more generally cultivated than elsewhere, it is used both as a green pea in the garden and as a field crop. The seed is used as a popular food for human consumption, and the forage is either used as pasture and feed for stock, or it is plowed under to enrich the soil. In California the crop is grown almost exclusively as a dry bean, cultivated and harvested like other bean crops of the state. For this reason it is classified under the tariff as a bean (U. S. Tariff Commission, 1920). The large acreage of Blackeyes in California (estimated ten-year aver- age of over 50,000 acres producing 792,000 one hundred-pound sacks in 1944) 4 is grown mainly for shipment to the markets of the southern states where the bean is used as food and as seed. HISTORY AND ORIGIN OF THE BLACKEYE BEAN Botanically the Blackeye is neither a pea nor a bean but is a member of a distinct genus of the pea family, distinguished by its value as a food and as a forage plant. Undoubtedly it originated in central Africa, in which region only are the wild plants or species found (Piper, 1913). From central Africa the plant spread through Egypt to Asia and to the Mediterranean region where it was well established in remote times. To the species Vigna sinensis is given the name cowpea, a species that includes the varieties now extensively under cultivation. Two other cultivated species, V. Catjang, or catjang cowpea, and V. sesquipedalis, the asparagus, or yard-long, bean, differ from ordinary cow- peas in the shape and length of their pods as well as in their usually smaller seeds. Abundant evidence exists that all three species should be classified as one (V. sinensis) because all of them cross readily. The same is true for their wild progenitors. Other species of this group of legumes, notably V. latea, appear to be true species which the writer has not been able to cross after many years of trials. The haploid chromosome number for all species of the genus is 12 (Senn, 1938). That the cowpea has been under cultivation for centuries is evidenced by its widespread culture in ancient times in Africa, Asia Minor, India, China, and in the Mediterranean region, where it was described by the earliest Roman writers. It is still grown in Italy where the Blackeye is known by the same name as the kidney bean (Phaseolus vulgaris) from America which largely supplanted it. The Blackeye was probably introduced into the American colonies, for Sloane — a pre-Linnaean botanist — describes the bean there in 1 Eeceived for publication March 5, 1945. 2 Agronomist in the Experiment Station, Emeritus. 3 See "Literature Cited" for complete data on citations, referred to in the text by name of author and date of publication. 4 Westan Bean News. 2 p. Published by The Westan Bean Growers Association, Wesley, California. August 19, 1944. (Processed.) [3] 4 California Experiment Station Bulletin 696 1707 (Wight, 1907). Later importation undoubtedly arrived with slaves from Africa. Introduction of the Blackeye into Virginia was made by General Wash- ington, and the use of the name cowpea is ascribed to Thomas Jefferson, who believed the bean was a native of America, because it was extensively used by the Indians ( Carrier, 1923 ) . SPREAD OF COWPEAS IN THE UNITED STATES From the recorded beginning in 1707, the cowpea in 1919 covered 1,500,000 acres producing 750,000 tons of hay and 3,000,000 bushels of seed (Piper, 1924). By 1940 some 5,020,000 acres were grown in the United States (Cali- TABLE 1 Acreage and Yield per Acre of Cowpeas* for Seed by States, Average 1929 through 1938 State Acreage harvested Yield per acre acres 48,000 174,000 143,000 10,000 32,000 161,000 108,000 83,000 40,000 26,000 133,000 52,400t bushels 7.7 5.7 5.9 8.8 5.4 5.7 5.8 6.9 8.5 5.5 Texas 7.0 20. Of * United States Department of Agriculture. Agriculture Statistics 1941:307. 1941. t Estimated. fornia excluded) ; of these, 1,385,000 acres produced 8,712,000 bushels of seed, or 6.3 bushels per acre. In addition, on an estimated 67,240 acres California produced 1,923,333 bushels of Blackeyes, or 11.5 bushels per acre. The production of Blackeye beans in California is attributable entirely to the sale of the greater part of the crop for human consumption to the southern states, and with limited quantities to Puerto Rico and Cuba. This competition with the southern states is possible because of the higher yields obtained in California (11.5 bushels per acre as compared with 6.3 bushels in the South) and because of the excellent quality produced by the practically rainless sum- mers that favor brightness of seed. In contrast to the California-grown Blackeyes, the cowpeas grown for seed in the southern states are not classed as beans (Morse, 1920& ) . There, because of the small area plantings and the rainy summers that cause poor quality and severe weevil attacks, the market for cowpeas does not compare favorably with that of the California Blackeye (XL S. Dept. Agr. Yearbook of Agriculture, 1941 ) . The cowpea is recognized, however, as the most important legume grown in the southern states where it is extensively used for green manuring and for stock feed. The 1,385,000 acres of cowpeas grown and harvested for seed in the southern states (Barr, 1923) yielded an average of 6.3 bushels per acre valued Blackeye Beans in California at $1.38 a bushel, or a total value of $12,040,000. The crop of cowpeas harvested for seed occupied 27.5 per cent of the 1940 acreage and was distributed as fol- lows : used for seed, 32 per cent; fed to livestock, 20 per cent; used on farm, 8 per cent ; and sold, 40 per cent. In contrast, the California-grown Blackeye is sold as a dry bean and shipped to the southern states mainly for human con- ;shp Ca/iforma 8/ackffi/e #eg/'aas- 1943 crop Sacrammfa &//ea $£ t mo -i »-i i c i »-I »-h © I I I I I I I I I I I I COOO©Tt<©CO t>-' CO o 31 03 3 §a &3 eocOrteot^'-ic 3 «OCOO5t^(M00"5T-l-i r-i CN I + I ++++++ + + — i-hco NONOOOlOOiniOW " I " CN i*< 00 I CM CO i-H Si d^l-c^o^ &3 if §a sa o3 a) sa — iOCOCS-h^-h— <©©-h © co ° + + + + + ' + + + + I + CO *< I © -*> CO © U0 _ ^< ■* •* O iO I t*< co »o ■>* -<*< * 2 il sa ^ 2 §a >-i ° cd r CT2 >* i-H O CO I CO fc, O O O O O — i OCO I W W * OO tO N 00O-^t— COON*tDMl«lO k* id co co c ° I I I I I I I I + I I + r--*iO«5COOll5rt «03^HOOt^05U0l0O5^H-HC0 o o at > C c u c c cr CD O O c $ a SC 09 U 0) J* at pq CD 1 a 2 J > t I pq > c s 1 c 03 3 .. " - ' . ' ' ' ■■ ' ■" " ! .'' ' ■'.' ;4 "M^iSMk'-ff^^f- , ' % /rvj/^VO'/;/.' \,. ; ,; ; ;#l ..-'■:**■*• ** ,* ; - ,; • ' ' , j? *' "j ' ; * ■::■■■■ . ■ . , ,, %0%u;- : &, /VPp%* a**-:^w,> 111 , l>: ::: '": : f |f^4i*;'"' ' ■ ■■"■■ ^r.'^- llS:Kfl3i Sk" • - - ?" .'%. s ;'.:; ;.""'\. ' \* ■ - ^^? *-^a ^i 3-'*.;, <** iSr-i *sK '-■'". ' "'■".'• ■.■■■■■■>.■. ■■''■■ Mf: Fig. 9. — The Iron cowpea, a disease-resistant variety. resistant to cowpea wilt, charcoal rot, and root-knot nematode. The Iron cow- pea is unlike the Blackeye in many characters (figs. 9 and 10). It is late in maturing, unusually viny, and yields a small crop of very hard, small, brown seeds unfit for human consumption. Like the California Blackeye, however, the Iron cowpea is resistant to shattering. 24 California Experiment Station Bulletin 696 Breeding for disease-resistant varieties cannot be considered as permanent when a resistant variety is secured. Not only is the variety itself subject to vari- ation through mutation and field hybridization (Mackie and Smith, 1935) but the disease itself is subject to the same variations. It may be that a highly resist- ant variety (immunity is rarely attained) may suddenly show marked sus- ceptibility after having been resistant for a long period. Such conditions are usually caused by a newly risen and virulent form of the disease. This appears to have been true of California Blackeye 5. Although this variety did not have the highest possible resistance, it did produce satisfactory crops, but now it shows considerable susceptibility to cowpea wilt, although continuing its re- sistance to root-knot nematode. At present all the nematode-resistant hybrid Hi ... ■ Fig. 10. — Iron cowpen with a strong vigorous root. varieties appear fixed for nematode resistance, but it has been shown that the root-knot nematode has a number of strains that vary in virulence (U. S. Agri- cultural Research Administration, 1943) ; these strains appeared when some of the nematode-resistant beans were tested in the southern states. Conversely, nematode-resistant bean varieties of the southern states when grown in Cali- fornia have succumbed to nematode attacks. In order to note the changes in the battle of resistant host to attacking parasite, constant vigilance must be main- tained by renewed breeding against the parasitic forms of these diseases as they appear. TECHNIQUE OF BREEDING The first artificial crosses between Iron and the Blackeye were made between the hours of 9 a.m. and 4 p.m., during the warmer part of the day, upon the advice of prominent cowpea breeders (see also Spillman and Sando, 1930; Oliver, 1910; Capinin, 1935). Of more than 2,000 crosses made at Hilmar, Merced County, only one was successful. In the following summer, similar crossings were made at Davis. Here artificial crosses were begun at early day- light and continued until 4 p.m. From sunup until about 8 : 30 artificial cross- ing was very successful, but before and after these periods, no viable crosses Blackeye Beans in California 25 were obtained. Because the pollen of cowpeas does not float in the wind, it was not necessary to cover the emasculated flowers. Within 24 hours after the cross- ing, which was made immediately after emasculation, the successful ones could be detected. Natural crossing in Blackeyes rarely occurs in California (Mackie and Smith, 1935) because the pollen, being sticky and heavy, does not float in the wind. The dry air in the areas where the Blackeye is grown favors immediate pollination. In many of the southern states, where humidity is high throughout the day and night, considerable cross-pollination occurs. For this reason, seed of cowpea varieties of southern origin, grown for forage and green-manure crops in California, have been found unsatisfactory. This applies especially to iMmmmmmm^i * .... - ? ^P- f \ iv -.:.; ' ; ■ v; ■ < ■;:„ ' ." '• "*&%r <*•& s*\fc i§p* \ /■ Wm ' i$? ; v*' 1^ >^& ''*7JH& ' w^iBKI Fig. 11. — Eight, Iron cowpea resistant; center, common California Blackeye bean susceptible and dead; and left, disease-resistant hybrids. Shafter, California. such varieties as Iron, Brabham, and Victor (Piper, 1924), which are grown on soils infested with root-knot nematodes and cowpea wilt. The stocks of these varieties used for breeding were purified and tested under severe disease at- tack. The Victor variety was rejected because of extreme shattering of the seed (Hayes and Garber, 1921) and the Brabham because it was less disease resist- ant than the Iron, which is the parent of both these varieties (Piper, 1912). Iron does not shatter, but it is a poor yielder in spite of its high disease re- sistance. The tests of the F x and succeeding generations were made on the farm of J. J. Anderson, near Hilmar, in soil where cowpea wilt, root-knot nematode, char- coal rot, and other diseases had long attacked and injured the Blackeye crop. At close intervals, susceptible California Blackeyes were planted throughout the plots in the breeding tests to keep the attacks of these diseases at full viru- lence (fig. 11). The common practice of flooding the crop was followed to maintain the maximum disease attack. To secure a disease-resistant Blackeye as nearly as possible like the Blackeye of commerce, the F t plant (fig. 12) was crossed back to the California Black- eye. The backcrossing of F t plants was continued to the fourth and sixth gen- 2(3 California Experiment Station Bulletin 696 erations. Only those crosses made on disease-resistant plants were continued. Most of these backcrossed survivals varied in many respects from the Cali- fornia Blackeye, including maturity, size, and shape of vine and seed. FACTORS INVOLVED IN BREEDING FOR DISEASE RESISTANCE Size of Seed. — Because of different genes for size carried by the parents, it was possible to increase the size of the seed to that of both parents combined. The largest-sized seed, however, was usually too coarse, inclined to split and to discolor, and was frequently twisted or otherwise undesirable in shape. Ex- cessively large seed usually has a hollow space between the two cotyledons, which induces excessive cracking and splitting during threshing. Fig. 12. — An Fj hybrid between California Blackeye bean and Iron cowpea. Shape of Seed and Quality of Seed Coat. — Variations from the desired kid- ney shape (fig. 13) including long, cylindrical, blunted ends, flat, twisted, and other types were eliminated, as were variations from the bright white color desired, such as cream, yellow, gray, or dappled. Skin texture expressed in the size and form of the wrinkles from coarse to smooth was similarly made to con- form to the accepted trade standards. The seed coat of the Blackeye is sharply divided into the white area and the small black area surrounding the hilnm, called the "eye." The desired white seed coat is finely wrinkled whereas the black seed coat forming the "eye" is smooth. The difference in wrinkling lies in the palisade cells, which are turgid and regular for the colored area and irreg- ular in form and turgidity for the wrinkled white seed coat (Mann, 1914) . The wrinkled seed coat imbibes water much more rapidly than does the colored, smooth seed coat ; this greatly improves the cooking and eating qualities over the self-colored, smooth seed-coated cowpeas. Although cracked skin frequent- ly was caused by cultural practices and weather conditions, it was found to be inherited and controlled, to a large extent, by breeding. Blackeye Beans in California 27 AIDING BUCKETS* FOR RESISTiOICE TO mUl, WMkfWn * AND 0K*8C0A£ 101 BLACKHY1 9 Fimt BACK.CRC5SS? BLA^KIYE § * ^,8***^ % .ECOKD BACKCaOSSt BLACFTfE $ x FIHST 8ACH&J 1 ^rjr m>\ \V- V# Pig. 13. — Breeding Blackeye beans resistant to cowpea wilt, root-knot nematode, and charcoal rot. 28 California Experiment Station Bulletin 696 Vine Shape and Size. — Vine shape and size are important to the farmer. Large flat vines that appear early in the season prohibit the operations of the cultivator and are also difficult to harvest. The fact that the shape and size of the vine is inherited (figs. 9, 14, and 15) permits staple selection of the desired Fig. 14. — Blackeye 8149. Butte County, California. Fig. 15—California Blackeye no. 5 (8145), earliest of California Blackeye x Iron hybrid. It is resistant to root-knot nematode and cowpea wilt, but is susceptible to charcoal rot. oval, upright types (Harland, 1919&, 1920) . Although bush types found in the common bean and lima beans have not been found in the Blackeye, an oval, up- right form, similar to the California Blackeye, has been isolated frequently. This form is recessive, as are the bush types, and therefore remains fixed. The flat and intermediate forms were eliminated by selection except where the large viny types were continued in order to form forage or covercrop varieties. Blackeye Beans in California 29 Maturity. — Time of maturity is definitely inherited. In the ¥ 1 generation, late maturity was found to be dominant and identical with that of the late Iron parent, but in the F 2 and later generations early-maturing types were isolated as recessives. "When the inheritance of seed size, seed shape, seed color, seed- coat wrinkling, maturity, and vine shape and size were fixed in the hybrid varieties, the inheritance of disease resistance under different cultural condi- tions was carefully studied. INHERITANCE OF CHARACTERS FOUND IN HYBRID BLACKEYES The inheritance of seed-coat colors, patterns, and eyes has been well worked out by several plant breeders and geneticists (Orton, 1908; Spillman and Sando, 1930; Harland, 1919a; Capinin, 1935) checking their behavior. These inheritances were checked but no outstanding differences were noted. Disease resistance in the various crosses behaved likewise, establishing the dominance of disease resistance in the F 1? or first generation (fig. 12) . The ratio of resistance to diseases in the following generations was impossible to deter- mine owing to three major and many minor diseases always present and active. The use of the backcross method of breeding to secure rapidly the qualities of the desirable Blackeye parent further prevented genetic studies of disease .inheritance. Although the Iron cowpea shows only slight formation of small nematode galls, the hybrids of Iron and susceptible varieties do not display the same high resistance. Another species of the same genus (Vigna lutea) has proved, over many years of tests, to be free from the numerous diseases attacking the cow- pea and entirely free from nematode galls (fig. 16) . For several years, attempts to secure crosses have failed. It may be, however, that other methods of cross- ing will be found to be successful. Other species of this genus from Africa, where it is indigenous, may be found that could be successfully used in breed- ing for disease resistance in cowpeas. MODE OF INHERITANCE OF CHARACTERS In crossing the California Blackeye and the Iron cowpea, the Blackeye was used as the female parent because of its greater number of available blossoms, the large size of its flowers, and the more certain setting of its seed. The California Blackeye has a normal size index of 24.0, a kidney-shaped seed with a finely wrinkled seed coat of bright white, except for a small black "eye" surrounding the hilum. The leaves are light green and remain active until killed by frost or diseases. The pod is green, thin skinned, bears 8 to 10 seeds, and is nearly straight with but slight curving. It does not shatter under normal conditions. The vine is small, oval, upright, and bushlike. It is best adapted to rows spaced 30 inches apart. The Iron-cowpea seed has a size index of 11.0, is kidney shaped with a thick, tough seed coat devoid of wrinkles, and is tan or brown. Many hard seeds are formed that survive the winter in the soil and volunteer in the spring. The vine is large, wide spreading (12 feet or more under good soil conditions) (fig. 9) , oval, upright, and bears very dark-green leaves. The root is extremely large (often 3 to 4 inches in diameter at the maximum) (figs, 10 and 17) , with very 30 California Experiment Station Bulletin 696 thick bark in which disease resistance appears to be located. The size and the deep penetration of the root indicate a perennial habit that cannot be deter- mined because frost ends the life of the plant before the end of the first year. The pods are almost straight, shatter resistant, and bear from 10 to 14 seeds. The Iron cowpea is highly resistant to charcoal rot, root-knot nematodes, cow- pea wilt, and cowpea mosaic, as well as to several other minor diseases. The F x , or First Generation. — The haploid chromosome number of the cow- pea is 12 (Senn, 1938) . The size of the ¥ x seed is intermediate or almost exactly half the size of the combined weight of both parents (fig. 13) . The shape of the Fig. 16. — Vigna lutea, a species closely related to cowpeas. It is resistant to fungus diseases, red spider, wireworm, and root-knot nematode. No viable crosses with Black- eye beans have been secured, even with years of trials. seed is similar to that of both parents, namely kidney. In color the seed coat is black, with small, reddish mottlings or flecks expressive of the dominance of both black color and mottling. The seed coat, like that of the Iron parent, is smooth, thick, and devoid of wrinkles. The size and vigor of the vine are greater than that of the Iron parent (fig. 12). In form, the vine closely resembles the Iron parent; the leaves are dark green, the roots large with thick bark, and the maturity late— all characters of the Iron. The pods are nonshattering like those of the Iron parent; and the yield, like the size of the seed, equals the combined yield of both parents. Disease resistance in the F t is exactly like that in the Iron. The F 2 , or Second Generation. — The size of the F 2 seed varies from smaller than the Iron to one half larger than the Blackeye parent, indicating at least two factors for size. The shape of the seed varies widely from almost round to long cylindrical with twists, blunt ends, and splits. Multiple factors for shape and size are indicated. Blackeye Beans in California 31 Color caused by anthocyanin and a melaninlike substance (Mann, 1914) is represented in several forms : solid or self-colored — black, brown, or buff, ma- roon, blue or purple, red, cream and white, and mottled, including Holstein, necked, eyed (colored about the hilum) in many sizes and forms. The mode of inheritance of these colors has been clearly set forth by Spillman and Sando (1930) andHarland (1919a). The size and shape of the vine varies widely. The mode of inheritance could not be accurately determined because of multiple disease attack, but forms appeared, varying from the bushlike to the very flat, prostrate types with al] kinds of intermediates. Only those adapted to tillage machinery were pre- served. 17. — Roots of Blackeye hybrids (California Blackeye x Iron). Left to right: Chino 3, Blackeye 8147, Blackeye 8149, Blackeye 7711, and Chino 2. The eyed character was inherited at a 3 : 1 ratio of self-colored to eyed types, the eyed form being recessive (Spillman, 1911). At least 13 different eyed forms were noted, many of which were heterozygous and separated usually in a monogenic ratio. The small blackeye form, desired by the trade, was found to be recessive to the large and variable-shaped eyes and was easily maintained in the backcrossing. Rusty, yellow, and gray coloring in Blackeyes caused by pigments in the palisade cells of the seed coat or in the layer cells directly below them, is inher- ited. Some hybrids, sound in other respects, were rejected for this reason. Dark- green leaf color appeared to be linked with colored seed coats. Yield and size of vine were not linked or definitely associated. No attempt was made to deter- mine mode of inheritance for maturity, but fixed selections of wide variation were secured, ranging from a period shorter than the early Blackeye parent to later than the late Iron parent. Anthocyanin color (red or purple) in pods, stems, and leaves, is inherited. An absence of this coloring results in a pure light green. Inheritance ratios in disease resistance could not be genetically determined because of constant mul- tiple-disease attacks. Beginning with the fourth and sixth backcrosses, thousands of disease-resist- ant plant selections were tested under severe disease attack in the plant-to-row 32 California Experiment Station Bulletin 696 plots. The best of these were increased and placed with bean farmers. These first distributions were not fixed in all characters, but further selections involv- ing hundreds of plants from each variety were tested. These followup tests resulted in varieties much improved in resistance to disease attack, especially cowpea wilt. FACTORS AFFECTING DISEASE RESISTANCE TO COWPEA WILT, CHARCOAL ROT, AND ROOT-KNOT NEMATODE Cowpea wilt is not only carried in the soil but is seed-borne from outside contamination, especially during threshing (Kendrick, 1931). Considerable variations in resistance in the new hybrid varieties were found for different Fig. 18. — Background of pigeon peas resistant to root-knot nematode. Foreground, partially resistant Blackeye hybrids and one highly resistant Blackeye hybrid at back. localities and different cultural practices. Before wilt-resistant varieties were made available, the usual practice in the Blackeye area of the San Joaquin Val- ley consisted in preirrigating the land, then cultivating and seeding. No fur- ther irrigation was given. The resulting crop depended upon the fertility of the soil, its water-holding capacity, and the degree of soil infestation from wilt. The same conditions prevailed with root knot caused by the root-knot nema- tode. Where these two diseases occurred, subsequent irrigation after the Black- eye crop was up usually caused the destruction of a large part of the crop. Under dry-land conditions (not irrigated) cowpea wilt and nematode injury usually were not markedly apparent. With the introduction of new disease- resistant varieties, irrigations were applied in ever-increasing numbers and with larger quantities of water after the Blackeyes came up. Because of the abundance and cheapness of gravity water, the flooding method of irrigation is used in the San Joaquin Valley irrigation districts of Manteca, Modesto, Turlock, and Merced. Flooding not only weakens the vines by depriving the roots of oxygen for a period, but provides the most favorable conditions for cowpea wilt, nematodes, and many other diseases (fig. 18). In the counties of Blackeye Beans in California 33 the southern part of the San Joaquin Valley and in southern California, where the water is furnished by pumping from wells, the furrow method of irrigation is practiced ; this method uses a much smaller quantity of water and does not materially disturb the supply of oxygen to the plant roots. In areas thus irri- gated, the disease-resistant varieties showed no measurable loss in yield, al- though evidence of cowpea wilt and nematode attack was always present. Charcoal rot depends on entirely different conditions of soil and tempera- ture than do cowpea wilt and nematodes (Tompkins and Gardner, 1935 ) . High water content of the soil and low soil temperatures that follow depress the char- coal-rot fungus, but relatively dry soils and high temperature favor it. For these reasons, charcoal-rot causes severe damage to Blackeyes in unirrigated or lightly irrigated soils. Charcoal-rot spores are widely distributed, making attacks possible wherever temperature and moisture conditions are favorable. Nature of Resistance. — The resistance to cowpea wilt and root-knot nema- todes appears to be caused by suberin, a substance common to most plants. The Iron cowpea has the ability to rush suberin promptly to the wounded area from surrounding cells, already high in suberin content, in sufficient quantity to check the disease attack. The cowpea-wilt fungus enters the plant through the root hairs or surface of the roots broken by diseases such as stem canker (sore shin) , or by mechanical injury. The root-knot nematode penetrates the cortical tissue and fastens itself upon the woody, or stelar, structure of the stem where the greatest injury occurs. In resistant varieties, like the Iron and its hybrids, the nematode, soon after entering the soft cortex, is met with highly suberized cell walls that effectively prevent the nematodes from reaching the stele, or woody stem. 5 The ability of the Iron to suberize cortical cells appears to be heritable and therefore transmittable to its hybrids. Resistance to cowpea wilt is dominant at the proportion of 3 resistant to 1 susceptible (Hawthorne, 1943) . Charcoal rot caused by Sclerotium bataticola (Mackie, 1932) has not been found to attack the Iron cowpea except where the cortex has been mechanically penetrated to the stele. Where such an injury occurs, the vine may be severely damaged by the fungus. In hybrids of Blackeye and Iron, many were secured that are resistant to charcoal rot, cowpea wilt, and nematode attack, whereas others were found to be resistant to cowpea wilt and nematodes but susceptible to charcoal rot. For example, California Blackeye no. 5 is resistant to cowpea wilt and nematodes but susceptible to charcoal rot, whereas California Black- eye no. 1 is resistant to all three. Apparently resistance to cowpea wilt and charcoal rot is attributable to different factors. Dry soils and high tempera- tures favor charcoal rot (Kendrick, 1933; Tompkins and Gardner, 1935), whereas soils naturally moist or irrigated repress charcoal attack which is caused, undoubtedly, by the lowering of temperatures through evaporation. In reducing the number of Blackeye hybrid varieties, selection for disease resistance, high yield, good marketing quality of seed, early maturity, resist- ance to shattering, and for small to medium size of vines, was rigidly applied. Some hybrids produced very high yields but were dropped because of poor quality of seed or poor disease resistance. The old California Blackeye pos- sessed all the desirable qualities (Morse, 1920tf ) , except disease resistance, and 5 Arzberger, E. G. A comparative morphological study of cowpea roots resistant and non- resistant to nematode infestation. Unpublished manuscript. 34 California Experiment Station Bulletin 696 was used as the ideal to be attained in the disease-resistant hybrids. None of the hybrids possessed superior yielding ability to the California Blackeye ; this fact was shown repeatedly when none of the three diseases attacked it. Tests with Disease-Resistant Blackeye Hybrids in Other States. — The major market for California Blackeyes is found in the southern states, where they are consumed or used as seed. The diseases that attack Blackeyes in California like- wise occur in the southern states; it follows naturally that farmers in these states would expect the disease-resistant hybrids that were successful in Cali- fornia to be successful in the south. The producers of resistant varieties in California hoped to find a profitable market for their seed. In anticipation of these demands, the most promising Blackeye hybrids, still somewhat hetero- TABLE 7 Maturity of Sixteen Hybrid Varieties Compared with California Blackeye 8274 Variety no. Days re- quired beyond those of Blackeye 8274 Variety no. Days re- quired beyond those of Blackeye 8274 8274 (common California Blackeye) 8130 8135 4 10 10 8 7 6 6 8149 8152 Chino 1 (Calapproved as California 6 8 8137 (Calapproved as Blackeye 7) 4 8140 Chino2 5 Chino 3 6 eye 5) 20-20 6 8146 M32 8 8147 7711 14 8148 zygous, were placed with the experiment stations in eleven of the southern states for testing. The difficulties arising from attempting to adapt varieties bred and tested for adaptation to California conditions, at once became apparent. Sandy and loamy soils are exclusively used for Blackeyes in California, whereas many heavy soils are planted to cowpeas and Blackeyes in the South. The dry, rain- less, growing season of California contrasts sharply with the summers of the southern states where the rainfall is heavy. The rainy summers foster many diseases, including bacterial blights, leaf spots, mosaics, and root rots, which do not occur in the dry California summers. Cowpea wilt and root-knot nema- todes, which do occur in both areas, are known to include a number of forms, some of which are not common to either area. Charcoal rot normally does not appear in the perfect form in California but does appear in the eastern areas. The Iron, or disease-resistant parent, besides being resistant to cowpea wilt, common root-knot nematode, and charcoal rot, has also been found resistant to cowpea mosaic and bacterial blights. If the hybrids of California Blackeye and the Iron cowpea in a heterozygous condition could be tested for adaptation under eastern or southern conditions, the seed could be produced abundantly in California where the yields appear to be much higher. Seed produced in rainless summers will be free from bac- terial blight, from many leaf spots and other diseases until reinfested under southern conditions. Blackeye Beans in California 35 In view of these preliminary tests in the southern states it appears inadvis- able to import in large quantities seed of California-produced disease-resistant varieties without dependable tests under southern conditions. Tests conducted over several years in northeastern Texas (Johnson, 1944) with these hybrids and the plant selections from them, established outstanding disease-resistant varieties of high productivity and seed quality. In recent years, however, the demand for seed of the disease-resistant Blackeye 5 has increased in the south- ern states to the extent of several carloads a year. TABLE 8 Fields of Blackeye Hybrids Compared with Common California Blackeye 8274 on Farms in Merced and Stanislaus Counties, 1939 Variety no. Yield per acre on farm A at Keyes Percentage yield of hybrid to California Blackeye 8274 Yield per acre on farm B at Hilmar Percentage yield of hybrid to California Blackeye 8274 8274 (common California Blackeye) 100-pound bags 10.1 25.6 19.0 14.9 24.6 16.6 * 25.4 per cent - 100 353 188 147 203 164 251 100-pound bags * 19.9 17.2 23.2 21.6 25.1 20.4 27.5 per cent 8130 8135 8137 8140 8145 8148 8149 Variety no. Yield per acre on farm C at Winton Percentage yield of hybrid to California Blackeye 8274 Yield per acre on farm D at Hilmar Percentage yield of hybrid to California Blackeye 8274 100-pound bags 12.0 24.0 21.0 22.5 21.0 19.0 per cent 100 200 175 187 175 158 100-pound bags 8.6 18.6 10.1 32.4 15.0 22.3 per cent 100 8135 211 8137 8140 117 380 8145 174 8149 260 * Dashes indicate data not available; crop at farm B completely destroyed by diseases. Maturity of Hybrid Blackeyes. — Early maturity is desirable when Black- eyes are grown for grain. Early maturity is usually antagonistic to yield but the combination of early maturity and yield was secured in a considerable num- ber of hybrids. The maturity of a variety alters with the year, the date of planting, the type of soil and its fertility, and irrigation practice. All the hy- brids, if not seriously attacked by diseases, continue to grow and put out new leaves and flowers until killed by frost. On the contrary, the common California Blackeye tends to mature at an early date, especially when attacked by dis- eases. Most of the hybrid varieties placed with farmers possess the quality of continuous blooming, although the major part of the crop matures at a definite date. Where a further setting of pods continued, there occurred a serious reduc- tion in quality of the seed through discoloration by moisture from dews and rains, and by evaporation from the growing plants. Usually after the seed is sufficiently mature to show clearly the outline of the "eye" the bean will mature 36 California Experiment Station Bulletin 696 to the point where it will yield a good marketable product. The seed harvested in a more immature condition will usually be blown out in the threshing, or be removed in recleaning before marketing. These reasons make it advisable for the Blackeye farmer to cut his crop as soon as the first full setting is mature. A measure, to apply generally, of the exact number of days from planting to maturity of the Blackeye cannot be given because of the many factors in- volved. The earliest maturing variety, Blackeye 8274, was used as the basis for Fig. 19. — Disease resistant Blackeye hybrid yielding 4,200 pounds per acre as con- trasted with 700 pounds per acre' for California Blackeye beans in adjacent plot. comparison.' The relative, or comparative, difference in maturity compiled for data from plots in several parts of the state over a period of years is given in table 7. Comparative Yields of Blackeye Hybrids.— The yield of Blackeye beans per acre in California cannot be given because no authentic records exist of the acreage grown each year. In the Turloek-Modesto area the yields have been estimated at 12 bags per acre under normal conditions. Attack by disease prob- ably reduces this estimate. At the inception of Blackeye culture in this area, 20 bags per acre are given as the high point of production. With the introduction of the new disease-resistant hybrid Blackeyes, 20 bags per acre are commonly secured with exceptional yields of double this quantity (table 8). Test yields in small plots duplicate these records (fig. 19) . Wilt-resistant hybrids derived from crosses between California Blackeye and Virginia Blackeye (a cowpea-wilt-resistant variety) gave rise to a number of hybrids highly resistant to wilt (Kendrick, 1936). Under severe nematode attacks all hybrids succumbed. Some of these wilt-resistant varieties produced good yields where nematodes were not a factor, but the trade objected to the Blackeye Beans in California 37 size, shape, and quality of the beans. Excessive vine growth on many of these hybrids was objectionable. None of these wilt-resistant hybrids has persisted. Among the hybrid varieties tested, the farmers generally preferred nos. 8145 (California Blackeye 5) and 8140. Variety 8145 is very early and has the up- right, small vine of the common California Blackeye and therefore does not disturb the cultural practices usually followed in growing and harvesting Blackeyes. Variety 8140, even though it matures a little later and is more viny, has many of the characters of the common Blackeye. Both varieties are high yielders of good-quality seed. Where cowpea-wilt attack was severe, both varie- ties suffered with consequent crop losses. Yet both varieties had passed cowpea- wilt-resistant tests in the plots. It is suggested that there may be forms of cow- pea wilt to which these varieties are not resistant. Where these varieties were grown without irrigation after planting no especial cowpea-wilt injury oc- curred. When the new disease-resistant Blackeye varieties appeared, farmers increased the number of irrigations to 3 or more after the beans were up. The usual method consists in retaining a flood of water between borders. This prac- tice favored the attacks of both cowpea wilt and nematodes. Under the furrow method of irrigation the injury to vines did not occur to any measurable extent. On tests covering several years, some of the hybrid Blackeyes that grew with greater vigor proved to be highly resistant to cowpea wilt and nematodes under the flooding system, whereas other varieties succumbed. All of these varieties mature a few days later than the 8145 and 8140 and their vines are larger and more vigorous, but they produce good crops where the more susceptible hybrids fail. These resistant varieties are being increased for distribution. DISEASE-RESISTANT BLACKEYE HYBRIDS RELEASED TO FARMERS After four to six backcross generations of disease-resistant hybrids, suffi- cient fixity was secured to warrant distribution of seed to farmers (fig. 16). These resistant varieties were not entirely fixed in all characters but were of good marketing quality, superior yield, and were highly disease resistant. Per- haps because of the influence of backcrossing, none of the hybrid varieties were as resistant to the three diseases under test as the resistant Iron parent. In the advance of disease, the California Blackeye established itself in com- petition with many other Blackeye varieties. The seed is medium in size with a standard index of 24.0 when soil and cultural conditions are favorable. (The index is the weight in grams of 100 seeds.) Under unfavorable conditions and disease attack, the size index may drop to 18.0 and the seed coat and color dete- riorate. For this reason the trade prefers somewhat larger-sized seed which is thought to be produced by fertile soil, good cultivation, and freedom from dis- ease. The size of the seed in the hybrid varieties distributed to farmers is mainly attributable to inheritance. The size of the California Blackeye vine is small and the shape upright with no marked side spreading (fig. 20). It is one of the earliest of the Blackeye varieties. These qualities that afford easy cultivation and easy, early harvest are favored by the farmers who dislike the larger, more vigorous, new disease- resistant hybrid varieties. Recent breeding operations on the original hybrid 38 California Experiment Station Bulletin 696 Fig. 20. — Center two rows, California Blackeye beans dead from diseases; disease-resistant hybrids are on both sides. Hilmar, California. Fig. 21. — California Blackeye no. 7. This variety is resistant to root-knot nematode, cowpea wilt, and charcoal rot. stocks have produced varieties superior in yield and disease resistance to the earlier distributed hybrids. Some of these are almost as early as the California Blackeye and retain the same erect form of vine. Other varieties, later and more viny and prolific, are more difficult to harvest. Modern bean cutters adapted to all types of tractors, however, remove this difficulty. Blackeye 20-20 has a coarse seed-coat texture of dull color; the size of its seed is large, with an index of 31.0. The vine is medium in size, and matures medium early, with good yield. Disease resistance is good but not fixed. Objec- tions to the marketing quality caused its rejection. Blackeye Beans in California 39 Fig. 2 2. -^California, Blackeye no. 1. Four backcrosses. Common Blackeye bean failed to produce a crop. Fig. 23. — Blackeye 7711 very resistant to root-knot nematode, cowpea wilt, and charcoal rot. This variety is highest in yield and latest in maturity of the Blackeye x Iron hybrids. No backcross. Blackeye M 32 has a coarse, but well-wrinkled seed coat, dull yellowish or rusty in color, and medium-sized seed with an index of 26.0. The large, vigor- ous, upright, medium-maturing vine is highly resistant to cowpea wilt and root-knot nematode. Blackeye M 32 was dropped because of poor seed-coat color. 40 California Experiment Station Bulletin 696 Blackeye 8130 produces seeds normal in size (index 24.0) , with good wrinkles and of bright white color. The vine is medium sized and semierect. It is highly disease resistant. Blackeye 8135 produces seed above medium in size (index 28.0) , with satis- factory wrinkles and color, and of medium early maturity. The vine is red stemmed, large, and flat. The disease resistance is good but the split seed coats and prostrate vine caused it to be rejected. Blackeye 8137 has a larger than medium seed (index 26.0) with good wrinkles and a bright white color ; it has some twisted seed. The vine is me- dium early, upright and vigorous. It possesses good disease resistance and be- cause of its vigor grows well in a wide range of soils. Rigid selection produced a satisfactory variety which was Calapproved and distributed as California Blackeye 7 (fig. 21). Blackeye 8140 has a larger than medium seed somewhat more oblong than the California Blackeye; it is variable in shape and size, with satisfactory wrinkling but dull white in color. The vine is flat and wide spreading, yielding well. Under severe cowpea-wilt attack it is badly injured ; for this reason it was not certified. Blackeye 8145 produces a seed somewhat larger than California Blackeye with an index of 26.0. The shape, color, wrinkles, and "eye" are identical with the California Blackeye. The vine has the same upright posture, small size (fig. 15), and early maturity as the Blacke3 r e parent but, in addition, is resistant to cowpea wilt and nematodes. Under certain attacks it succumbs to wilt and nem- atodes and is also susceptible to charcoal rot. Because of its close resemblance to the California Blackeye, it is popular with the farmers and was certified as California Blackeye 5. It is the most extensively grown variety. Attempts to secure greater disease resistance by selection failed because it is fixed for this character. Blackeye 8146 has a very large seed (index 32.0) with excellent wrinkles, a bright color, and medium maturity. The vine is large, flat, and vigorous, yield- ing well. The large seed is inclined to twist ; it possesses hollow centers that are likely to crack during threshing. Blackeye 8147 has a large (index 30.0) , well-shaped seed with good wrinkles and color. The leaf color is dark green and the vine medium in size, upright and vigorous. The yields are high and the maturity medium early. Selections have greatly improved its resistance to cowpea wilt and nematodes. Blackeye 8148 has a large seed (index 31.0) well wrinkled and of good color. The vine is large, vigorous and erect, oval in form. Its disease resistance and yield are high. Blackeye 8149 has a large seed (index 29.0), but smaller in size than the Blackeye hybrids whose hollow seeds are prone to crack during threshing. The vine is vigorous, oval, upright, and medium early in maturity. Its yield and disease resistance are superior to the varieties described above for the per- fected form finally secured by selection (fig. 14) . Blackeye 8152 bears a seed (index 26.0) larger than standard (index 24.0), well wrinkled, and bright white in color. The vine is large, vigorous, upright, medium in maturity, and very disease resistant. It has produced well in north- eastern Texas. Blackeye Beans in California 41 California Blackeye 1 possesses a large seed (index 28.0), somewhat oblong, with fine wrinkles and a very bright white color. It is resistant to both cowpea wilt and nematodes and, in addition, is highly resistant to charcoal rot. Resist- ance to charcoal rot makes this variety suitable for dry-land farming where charcoal rot is likely to occur. The variety is certified (fig. 22) . Chino 2 closely resembles California Blackeye 1 in size, color, and wrinkles of seed, but it differs in the size and behavior of the vine, which matures slight- ly later than California Blackeye 5 (8145). The vine is more vigorous than California Blackeye 5 and greatly to the improvement of the crop, tends to spread sufficiently to fill spaces left vacant. It also is superior in disease resist- ance to California Blackeye 5. The improvement was brought about by plant selection of unfixed material. Blackeye 7711 is a dual-purpose variety — a high yielder of excellent-quality seed. The seed is above medium in size (index 26.0) and somewhat oblong. The vine has all the vigor and size of the Iron-cowpea parent and is superior to all other hybrids in disease resistance. The vigor and disease resistance of the Iron parent are preserved by omitting the backcrossing practiced in the breeding of the other hybrids. As a result of several years of plant selection, it has also outyielded all other hybrids in the final form. Blackeye 7711 (fig. 2) is very drought resistant and has produced consistently on good soil under dry-land farming. It is also a good producer on heavy soils and offers promise on old riceland. The objections lie in its late maturity and in its large vine which offers difficulties in harvesting. Bean cutters designed for attachment to tractors re- move this difficulty. The variety is certified but the later improvements have not yet reached certification (fig. 23) . DISEASES OF BLACKEYE BEANS DISEASES FOUND IN CALIFORNIA 6 In breeding for resistance to the three principal diseases of Blackeye beans in California, the presence of other diseases that may become important, when the principal ones are subdued, must be considered. A list of the diseases al- ready encountered in California follows (Harter and Zaumeytr, 1944 ; Ander- son, etal, 1926) : Cowpea wilt (Fusarium oxysporum f. tracheiphilum) Charcoal rot (Sclerotium bataticola, Macrophomina pliaseoli) Stem canker, scab, or sore shin (Rhizoctonia solani) Dry root rot, or fusarium root rot (Fusarium solani f . phaseoli) Sclerotinia wilt, or cottony rot (Sclerotinia sclerotiorum) Southern wilt, or southern blight (Sclerotium Rolfsii) Verticillium wilt, or verticilliosis (V erticillium albo-atrum) Cotton root rot (Phymatotrichum omnivorum) Black root rot (Thielaviopsis basicola) Powdery mildew (Erysiphe polygoni) Eust (Uromyces vignae) Pythium spp. Curly top (a virus disease of sugar beets and other crops caused by Eutettix tenellus) Root-knot nematode (Heterodera marioni) Aphid spot (caused by the lygus bug) Crumple leaf (a physiological disease — effect of low temperature) For the identification of certain of these diseases, the author is especially indebted to W. C. Snyder and J. B. Kendrick of the Division of Plant Pathology. 42 California Experiment Station Bulletin 696 Cowpea wilt, caused by Fusarium oxysporum f . tracheipMlum, is confined to cowpeas. It is carried by diseased straw or upon the surface of beans, but is not borne internally in the seed. It lives over in the soil where it attacks the Blackeye seedling. The early attacks show in the wilted seedling, but later the lower stem and root become swollen with blackened inner bark which extends well up the plant. Resistant varieties comprise the only means of control. A number of these are available. Charcoal rot, caused by Sclerotium oataiicola {Macrophomina phaseoli), attacks a considerable number of crops and occurs in practically all areas of the state. High temperatures and unirrigated land favor the fungus, but irri- gation and subsequent evaporation reduce the temperature and the disease. The disease manifests itself when the plant approaches maturity. Diseased plants show small black sclerotia imbedded in the bark of the stems and roots. Disease-resistant varieties offer the only economic solution (Andrus, 1938). One of those varieties resistant to charcoal rot is California Blackeye 1 (Young, 1937 ; Tompkins and Gardner, 1935) . Stem canker, scab, or sore shin, caused by Ehizoctonia solani, is present in all arable soils. This fungus is favored by cool weather and abundant mois- ture. Early plantings may be entirely destroyed by unfavorable weather. Seed planted early should always be dusted with Spergon, Semesan, or some other effective treatment. Spergon is favored because it is only slightly toxic to nodule bacteria. Excessive irrigation may continue the attacks until the plant matures. The disease is detected by the rusty or brick-red color of the diseased bark of the roots and the swollen, thickened skin. Seedlings dying from scab drip when squeezed, in contrast with dry rot which does not drip. Dry root rot, or fusarium root rot, is caused by Fusarium solani f . phaseoli. This disease is found in all Blackeye areas (Weimer and Harter, 1926) but causes minor injury in the interior valleys. A reddish or rusty color is noted on the root bark and interior of the stem of attacked plants. The greatest in- jury appears in the seedling stage but the injuries may continue until the crop matures. Seed treatment with Spergon is beneficial for early planting. No resistant varieties are available. Sclerotinia wilt, or cottony rot, caused by Sclerotinia sclerotiorum, attacks vines close to the surface of the soil, usually girdling the root in a pattern that resembles mouse damage. White fungus mycelium is usually present at the soil surface, but in the soft central pith of the stem large black sclerotia are often found. No resistant varieties are available. By ridging the row of vines to keep water away from the root crown, or by providing a dry surface soil, this disease can usually be prevented. Southern wilt, or southern blight, is caused by Sclerotium Bolfsii. This disease is mainly spread by sugar beets but attacks many other crops. Crop rotation and the use of nitrogenous fertilizers reduce the attacks (Leach and Davey, 1934) . The presence of black sclerotia serves to identify the disease. Verticillium wilt, or verticilliosis, caused by Verticillium albo-atriim, affects a number of crops, including cotton and tomatoes (Baker, Snyder, and Han- sen, 1940) . The vines show a yellowing of the leaves and give poor yields. Ver- ticillium wilt is usually not a serious disease on Blackeyes. No remedy is known ; only resistant varieties escape the disease. Blackeye Beans in California 43 Cotton root rot is caused by Phymatotrichum omnivorum. This disease, found attacking cotton and many other crops in Texas, New Mexico, and Ari- zona, is apparently indigenous to these regions. It has been identified in iso- lated areas in southern California. The fungus destroys the smaller rootlets and invades the vascular system, causing wilt and death of the plant. An oil-spot spread follows initial infestation. As it is carried in the soil by the sclerotia, crop rotation with resistant crops is indicated. If cotton root rot is suspected, the nearest agricultural commissioner should be notified. Black root rot, caused by Thielaviopsis basicola, attacks Blackeyes and is identified by a blackening of the stem. It attacks other crops also. At present the damage to Blackeyes is restricted. Powdery mildew, caused by Erysiphe polygoni, is usually most severe in coastal fields under the influence of summer fogs, but it may also occur in the interior valley late in the season if too much water has caused excessive growth and, as a consequence, excessive shade. A bluing of the stems and leaf ribs, usually accompanied by characteristic powdery leaf surface, indicates mildew. Sulfur dusted on the afflicted plant in the forenoon, before winds occur, ordi- narily stops the mildew. Rust, caused by Uromyces vignae, infrequently appears on the leaves of Blackeyes in fields in the southern part of the state but not elsewhere. The crop damage is slight. Pythium wilt, caused by Pythium spp., is severe when too much water is applied to the crop causing a drop in temperature ; otherwise the wilt causes little damage. Curly top, a virus disease carried by the beet leafhopper, Eutettix tenellus, attacks a number of crops including Blackeye beans (Severin and Henderson, 1928) and common beans. Blackeye fields in the San Joaquin Valley have been ruined by curly top, a disease recognizable by a peculiar down cupping and curling of the leaves. The flight of the beet leafhopper has been seen confined, by a canal, to one side of a field ; in this area the crop was badly damaged, where- as the rest of the field remained normal. No remedy is suggested because curly top in Blackeyes occurs very irregularly. Aphid spot is a term given to the yellowish disfiguring spots sometimes found on the seed coats of the Blackeye. The disfigurement adversely affects the sale of the beans. No damage from aphids has been indicated. The yeast spot, caused by the fungus Nematospora phaseoli (Wingard, 1922a, 19225), has not been identified in California. Recently, it has been demonstrated that the attacks by lygus bugs (Baker and Snyder, 1945) are the cause of aphid spot. The new insecticide DDT has proved economically effective against lygus bugs. Some of the hybrid Blackeyes also seem to be resistant. Crumple leaf is caused by temperatures lower than those normally required for healthy vigor, such as cold spring weather in the interior valleys and in all coastal valleys subject to cool summer temperatures because of the fogs. This leaf trouble may be confused with curly top which, when contrasted with the irregular crumpling from cold, differs decidedly in cupping effect. In the inte- rior, with the change from cold temperatures to normal heat, crumple leaf dis- appears. In the coastal valleys, it persists and definitely reduces the yield and quality of Blackeyes. 44 California Experiment Station Bulletin 696 Root knot, caused by the nematode Heterodera marioni, is undoubtedly the worst disease of Blackej^es. It is widespread and thrives in sandy soils usually preferred by the Blackeye (U. S. Agricultural Research Administration, 1943 ) . Nematodes attack in irrigated soils, but seldom enter dry soils not subject to irrigation. In the San Joaquin Valley, where Blackeye beans follow uprooted peach, fig, walnut, or almond orchards, or vineyards, nematodes invariably occur. As the root-knot nematode occurs in more than 2 million acres of per- haps the best soils of the state, it may be considered a menace to Blackeyes planted in irrigated soil. Chemicals applied to the soil have proved to be very expensive and of temporary benefit only. The one effective remedy to root-knot nematode lies in the use of resistant Blackeye varieties. A number of these vari- eties are now being grown in all the Blackeye areas. DISEASES NOT OCCURRING IN CALIFORNIA The following list includes diseases attacking cowpeas in other states, but not in California (Harter and Zaumeyer, 1944 ; Anderson et al., 1926) : Pod and leaf blight (Cladosporium vignae) Leaf spots (Cercospora vignae, C. cruenta, C. dolichii, Amcriosporium oeconomicum) Anthracnose (Collet otrichum lindemuthianum) Phytophthora, or downy mildew (Phytophthora phaseoli) Yeast spot (N ematospora phaseoli) Bacterial canker spot (Bacterium vignae) Bacterial blight (Bacterium phaseoli) Cowpea mosaic (cucumber mosaic) Pod and leaf blight, caused by Cladosporium vignae, occurs in eastern states but seldom in California, except in coastal areas subject to summer fogs (Gard- ner, 1925). Leaf spots, caused by Cercospora vignae, C. cruenta, C. dolichii, Amerospor- ium oeconomicum, are not likely to occur except under unusually moist con- ditions. Anthracnose, caused by Collet otrichum Had cm nth ian um, appears as blotches or sunken spots on pods and leaves. The disease occurs only under rainy condi- tions or sprinkling which simulates rain. It is not likely to be found in Cali- fornia. Phytophthora wilt, or downy mildew, is caused by Phytophthora phaseoli. This disease causes considerable injury when overirrigation is practiced. Yeast spot, caused by a fungus N ematospora phaseoli, has not been found in California and is not likely to occur except under rainy conditions ( Wingard, 1922a, 19226). Bacterial blight, caused by Bacterium phaseoli, and bacterial canker spot, caused by B. vignae (Hoffmaster, 1944) , probably will not occur except under unusually rainy conditions, which are not found in California in summer (Burkhalter, 1944). Cowpea mosaic, which occurs in the southern and eastern states, has not been found in California. As it is not seed-borne, it cannot be brought in by seed. Cucumber mosaic, spread by insect vectors, appears responsible for the disease. Most cowpea varieties are susceptible (Chester, 1939; Briant and Martyn, 1929). Blackeye Beans in California 45 INSECTS AND OTHER PESTS CAUSING ECONOMIC DAMAGE Although many insects attack Blackeyes, relatively few cause much damage. These insects are listed with the standard control measures. When other insects appear, the entomologists of the California Agricultural Experiment Station should be consulted (Essig and Hoskins, 1934) . The red spider (Tetranychus althaea) and similar mites sometimes attack Blackeyes but not to the same extent as they attack common beans. As soon as the infestation appears, sulfur dust should be used in a combination of 90 parts of fine dry sulfur to 10 parts of finely ground dry lime. If the area is small and isolated, the sulfur should be used for a considerable depth adjacent and should be repeated in about 2 weeks. Bean thrips (Hercothrips fasciatus), apparently a native of the state, may be expected in any area since it survives on a number of weed hosts (Bailey, 1937). By eliminating prickly lettuce (Lactuca scariola) and sow thistle (Son- chus oleraceus) the worst hosts of the bean thrips are removed. Blackeyes are fairly resistant to bean thrips, especially when the fields are well irrigated and the Blackeye plants kept in a healthy growing condition. Thrips do not propa- gate in sandy soils as freely as in heavy soils that crack and permit the larvae to penetrate, where they pupate and later emerge to attack the Blackeyes. The presence of thrips can be detected by the numerous black, shiny spots of excre- ment. When these insects attack in large numbers, they should be sprayed with a highly refined commercial oil emulsion at 2 per cent concentration, to which has been added % pint of nicotine sulfate (40 per cent) in 100 gallons of emul- sion (Bailey, 1937). The lima bean pod borer (Etiella zinckenella) prefers lima beans but is known to attack Blackeyes. The small gray moth lays its eggs on the green pod. There is no known practical control. The sugar-beet wireworm (Limonius calif ornicus) attacks early-planted Blackeyes, but after the soil becomes warm the wireworms usually drop below the planting level of the seedling beans. No remedy is known (Stone, 1941). Corn earworm (Heliothis armigera) may attack limas and Blackeyes but usually in such small numbers that the attack is of little economic importance. The cowpea weevil (Acanthoscelides obtectus) causes considerable damage to Blackeyes ; not only does it lay its eggs on the bean pods and beans in the field as soon as they mature, but it also continues to lay eggs and infest Black- eyes in the warehouse where it continues, generation after generation (Lar- son and Fisher, 1938). The most effective method of control lies in harvesting and threshing the Blackeyes as soon as they are ripe ; this should be followed promptly by fumigation at the warehouse or wherever they are stored. Carbon disulfide is commonly used. The fumigation chamber should be tight, with the temperature 65° F or more. From 10 to 20 pounds of carbon disulfide should be used for every 1,000 cubic feet of space, depending upon how tight the cham- ber is and how well filled it is with beans. A minimum exposure of 24 hours, and usually an exposure of 48 hours, is required. Carbon disulfide gas is heavier than air, with a boiling point at 115° F ; its high degree of inflammability neces- sitates great care in keeping lighted lanterns, pipes, cigarettes, and cigars away from chambers being fumigated. 46 California Experiment Station Bulletin 696 Methyl bromide (Linsley and Michelbacher, 1943) is a very effective fumi- gant without the inflammable qualities of carbon disulfide. It is dangerous to human beings if the fumes are breathed into the lungs, however, but it is not harmful to food products. It has a boiling point of 40° F but is most effective above 60° F. It should be used only by experienced persons. The minimum dos- age per 1,000 cubic feet is 1 pound. It is slow acting but very effective against both insects and their eggs. Chloropicrin (tear gas) is very effective, evaporates slowly, but is a poison- ous gas that should be used only by experienced persons. It should be used at a temperature not less than 70° F. Many reports of injury to seed germination have been received and, for this reason, it is not recommended for Blackeyes to be used for seed. Sources of cowpea- weevil infestation should be removed early to prevent con- tinuing generations of weevils. Unharvested Blackeyes, stack bottoms where beans are threshed or recleaned, refuse dumps about warehouses or buildings or exposed, unfumigated stores of seed, all contribute to the spread of weevil infestation and should be eliminated as promptly as possible. In this way a great part of the field infestation can be prevented. In some counties, local ordi- nances enforce the destruction of all Blackeye straw and refuse by April 15 to prevent weevil spread (Larson and Fisher, 1938) . The Angoumois grain moth (Sitotroga cerealella) , common in all grain, also attacks stored Blackeyes. It is controlled by the same fumigation methods used to control the cowpea weevil. Bean aphid (Aphis rumicis) may collect in spots, damaging the tender plant tips. Dusting with 5 per cent nicotine or using nicotine and casein spray will check them. Root-knot nematodes (Heterodera marioni) are very destructive to Black- eyes. Sandy soils in which Blackeyes are usually grown also favor nematodes, whereas heavy soils retard them. In many areas the root-knot nematode has long been established in peach, walnut, and fig orchards, in vineyards, and in alfalfa and cotton fields where these crops are injured but do not die. Black- eyes following them may be injured or destroyed. Root-knot nematode is not controlled by long flooding and is only temporarily controlled by chemicals at prohibitive expense (Brown, 1933) . The only practical remedy lies in breeding for resistant varieties (Tyler, 1944) . This has been done and is discussed under "Breeding for Disease Resistance in Blackeyes." PRICE, PRODUCTION, AND MARKETING OF BLACKEYE BEANS The price and production of Blackeye beans from 1909 to 1943 are given in table 9. Under normal conditions, the price of Blackeyes varies inversely with production ; that is, when production is low the price is high and vice versa. Exceptional variations were caused by war, such as the demand for beans cre- ated by "World War I ; the boom in prices that followed lasted until the depres- sion, beginning in 1929. Prices of Blackeyes were high during that time, with slight exceptions in 1921, 1922, 1926, and 1927 (fig. 24). The price since has varied according to supply and demand until the effect of World War II influ- enced the markets. This condition was stabilized by the fixing of prices for Blackeye Beans in California 47 TABLE 9 Production and Price of Blackeyes in California, 1909 through 1943* Year Field-run yield t Price 1910 1911 1912 1913 1914 1915 1916 1917, 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 100-pound bags 80,000 100,000 225,000 204,000 80,000 150,000 405,000 275,000 300,000 463,000 200,000 180,000 400,000 300,000 275,000 250,000 400,000 460,000 300,000 428,000 514,000 852,000 459,000 275,000 587,000 525,000 615,000 705,000 857,000 512,000 573,000 1,154,000 704,000 733,000 896,000 dollars 4.65 5.85 3.80 3.30 5.50 5.25 3.75 6.80 8.20 4.80 7.20 6.45 4.55 4.76 6.76 9.64 5.72 3.89 4.93 9.47 8.36 3.33 3.35 2.92 4.04 4.55 4.99 2.91 3.87 4.56 2.76 5.02 5.80 5.80 * Data from: Wellman, H. R., and E. W. Braun. Beans (series on California crops and prices). California Agr. Exp. Sta. Bui. 444:18, 61. 1927. United States Department of Agriculture. Agriculture Statistics 1940:302. 1940; 1944:275. 1944. Pacific Rural Press, annual issues, t Yields quoted in field run. Recleaning reduces the total as follows: 1934 through 1938, five-year-average field run was 655,000 one hundred-pound bags: recleaned was 612,000. Percentage reduction was 6.5. 48 California Experiment Station Bulletin 696 /90S /9/0 /9/S /920 /925 /930 /S35 /940 /94S Fig. 24. — Production and price of Blackeye beans in California, 1909 through 1943. TABLE 10 Proportion of Blackeye Beans to Total Bean Production in California, 1931 through 1943* Year Blackeye beans Total beans Proportion of Blackeyea to total 1931 ' 100-pound bags 459,000 275,000 587,000 525,000 615.000 765.000 857.000 512.000 573.000 1,154,000 704,000 740.000 890,000 100-pound bags 3,467,000 2,484.000 3,520,000 3,684,000 3,966,000 4,081,000 5,369,000 4,501,000 3.991.000 5,490,000 5.139,000 4,894,000 5,169.000 per cent 13.2 1932 11.1 1933... 16 7 1934 14.3 1935 15 5 1936 18.7 1937 1938 1939 16.0 11.2 14 3 1940 1941 21.0 13 7 1942 15.1 1943 17 2 Average 1931-1943 15.2 * [Clarke, L. M.j Bean production by varieties for California and other leading states, p. 2. California Crop and Livestock Rept. Serv. 1944. (Mimeo.) Blackeyes, U. S. no. 1 grade, in 100-pound bags by the O. P. A. (Office of Price Administration) at $5.80 in 1944 and $6.20 in 1945. MARKETING BLACKEYE BEANS Blackeyes grown in California are marketed almost entirely in the southern states where their value as food is appreciated because of long acquaintance with the crop. The high quality of the California-grown crop is attributable to Blackeye Beans in California 49 55 50 45 <0 ! 35 30 35 1 /5 /O — — — J ~Tc?fa/ dear? pre •>dt/cf/or? - \ / - \ / - - - ) \ - V\J V/ Z \J~-3/#c/x ~ 1 1 1 1 eye proo't/cf/o/7 1 1 1 1 l 1 l I /930 /935 /940 1945 Fig. 25. — Production of Blackeye beans to total bean production in California, 1931 through 1943. the rainless summers that are not encountered in the southern states. The cli- matic conditions likewise favor the use of labor-saving* machinery in cultural and harvesting operations. The extent of Blackeye culture in California is definitely limited by the re- stricted marketing area so that the price and production follow each other closely in an inverse ratio. This relation does not necessarily hold true for other beans, such as the Pink, Pinto, and Red Kidney, which are grown in other states and have a wider market. The ratio of the Blackeye crop to the total bean crop 50 California Experiment Station Bulletin 696 of the state follows within fairly close limits. In other words, the conditions that increase or decrease the production of the bean crop of the state equally affects the Blackeye production (fig. 25) . Some Blackeyes formerly were imported from Mexico but this source has been shut off by the removal of American farmers from Mexico. Table 10 shows the proportion of Blackeyes to total bean production in Cali- fornia. The acreage of Blackeyes is not affected by the changes in the price of other beans because the areas where Blackeyes are principally grown are not well adapted to other beans. Over a thirteen-year period (1931 through 1943) Blackeyes comprised about 15 per cent of all the dry beans produced in the state. This proportion has gradually increased from 3.5 per cent in 1910 to 9.0 TABLE 11 Market-Grade Eequirements for Blackeye Beans Grade* Maximum limits of defects consisting of sound splits, damaged beans, contrasting classes, and foreign material Total defects t Contrasting classes Foreign material Stones Other classes that blend t U. S. no. 1 per cent 2.0 4.0 6.0 per cent 0.5 1.0 2.0 per cent 0.5 1.0 1.5 per cent 0.2 0.4 per cent 5 U. S. no. 2 10 U.S. no. 3. 0.6 15 * The following are further market-grade classifications: "U. S. Substandard shall include beans of any of these classes which do not come within the requirements of the specifications for the grades U. S. no. 1, U. S. no. 2, or U. S. no. 3, or for the grade U. S. Sample Grade." "U. S. Sample Grade shall include beans of any of these classes which are musty, or sour, or heating, or hot, or weevily, or materially weathered, or which are otherwise of distinctly low quality." t "The beans in the grade U. S. no. 2 of the class Blackeye may contain not more than 0.2 per cent, and the beans in grade U. S. no. 3 of this class may contain not more than 0.5 per cent of clean-cut weevil-bored beans." t "The beans in grade U. S. no. 1, U. S. no. 2, and U. S. no. 3 of any of these classes shall be well-screened hand- picked beans. Definition — hand-picked beans shall be beans of any class except Pinto, lima, baby lima, and mixed beans, which meet the grade requirements of any of the grades U. S. no. 1, U. S. no. 2, or U. S. no. 3, which have been hand-picked or otherwise processed so that they contain not more than 0.3 per cent badly damaged beans, nor more than 0.01 per cent contrasting classes, and not more than 0.01 per cent foreign material, and which do not contain any stones." per cent in 1918, 13.5 per cent in 1926, to a final average of 15.2 per cent. The proportion of Blackeyes tends to increase at the expense of other beans, espe- cially in hot areas in the San Joaquin and Sacramento valleys where land under irrigation is being increased (fig. 25) . No cooperative marketing organization exists at present for Blackeyes as it does for lima beans, but "pools" of Blackeyes are formed for sale of the crop in connection with the California Lima Bean Growers Association. This plan facilitates shipping mixed carload lots to the eastern markets. Otherwise the crop is marketed by well-established firms familiar with the California crop. MARKET GRADES The United States Department of Agriculture under the Agricultural Mar- keting Service has established market grades of beans, including Blackeyes (U. S. Dept. Agr. War Food Administration, 1944). The requirements are: Blackeyes may not contain more than 2 per cent of beans of contrasting classes and not more than 15 per cent of other classes that blend (table 11). When greater amounts are included the beans are classed as "mixed" and graded under this classification. Blackeye Beans in California 51 USES OF BLACKEYE BEANS BLACKEYES AS SNAP BEANS AND SPROUTS In the southern states, cowpeas (Blackeyes) are grown everywhere as a gar- den crop for their green pods and green beans which are harvested and con- sumed as snap beans. If the pods become too tough or stringy the green or immature beans are shelled out and cooked with the snap pods. Because of the high vitamin content (Reid, 1942), especially B x , green cowpeas are valuable in the diet during hot weather. Although Blackeyes have been grown in California for many years, the use of green Blackeyes as a vegetable has only begun. Recently, green Blackeye pods, or snaps, have begun to appear in the Los Angeles, Fresno, and San Francisco markets, where they ctf e in demand by consumers from the southern TABLE 12 Nutritional Analysis of Lima Pink, and Blackeye Beans Varieites Water Ash Protein Fat Fiber N-free extract* per cent 11.82 9.28 9.02 per cent 4.11 4.31 3.56 per cent 19.25 21.00 18.90 per cent 1.86 3.65 1.50 per cent 5.26 3.29 3.12 per cent 57.70 Pink 58.47 Blackeye 63.82 * N-free extract includes starches and sugars. states. The season may be extended by early and late plantings in thermal areas similar to the Coachella Valley. "When the merits of this vegetable are known, the demand should steadily increase. Sprouts from Blackeyes contain a high amount of vitamin C and fair amounts of B vitamins. Twenty -four hours after germination, the sprouts are ready for cooking. COOKING OF BLACKEYE BEANS Although California produces the greater part of the Blackeyes marketed for human consumption, relatively small quantities are consumed in the state. This condition is not traceable to the quality and nutritive values of the Black- eye but to the flavor which is as specific to it as the lima flavor is to the lima bean. The analysis of the nutritional qualities is given in table 12. The Blackeye bean is lower in indigestible ash and fiber and higher in starches and sugars (N-free extract) than the lima and Pink beans. It is also easier to cook. Like other beans the Blackeye is low in fat and is much improved when cooked with fat meat such as pork. The following methods of cooking put forth by the United States Department of Agriculture (Morse, 19205 ) will be found useful. Blackeyes Parboiled. — Soak in lukewarm water for several hours, or over- night, and simmer slowly at low heat until tender. Do not use soda in the water. Soaking and slow cooking will make the Blackeyes sufficiently tender. Season well. Pork fat, cheese, onion, green pepper, celery, or tomato combine well as seasoning (Windsor, 1918). 52 California Experiment Station Bulletin 696 Blackeyes Baked.— After the Blackeyes are cooked tender, the beans can then be baked or fried. To bake cowpeas add to 1 quart of parboiled Blackeyes % pound of salt pork, % teaspoon of mustard, % cup of molasses (preferably sorghum), salt, and a pinch of cayenne pepper. Cover with water and bake several hours. OTHER USES FOR BLACKEYE BEANS Blackeye beans were repeatedly reported to have been used for the making of gunpowder in World War I, as well as in World War II. A careful survey of the principal munition plants of the United States definitely disposes of this myth. The Blackeye bean is not used for gunpowder. Under war conditions and depressions Blackeyes have been roasted and used as a substitute for coffee (Robbins, 1917, p. 460-62) . DISCUSSION AND SUMMARY The Blackeye is a cowpea of African origin with definite adaptation and edible qualities but more closely resembling the bean than any other legume. In applying the tariff, the Blackeye is classed as a bean. After becoming well established in the southern states, it spread to California where it was found well suited to the warmer irrigated areas and, to a lesser extent, to dry-farmed areas. Climatic conditions that restrict common beans and lima beans, do not apply equally to Blackeyes. Large areas in the San Joaquin and Sacramento valleys and in similar regions are well adapted to Blackeyes. Cultural methods of soil preparation, irrigation, cultivation, and harvesting- are similar to those of other bean crops. Crop rotations with Blackeyes are more widespread and satisfactory than with other beans. Nodulation in Blackeyes is easily established and becomes permanent, although requiring a different culture from beans. The market for Blackeyes is confined almost exclusively to the southern states, with consequent restrictions on production and price. Because of rain- less summers, however, California almost exclusively holds the market for Blackeyes. Fungus and bacterial diseases and nematode and insect pests attack the Blackeye, but most of these attacks have been met by creating disease-resist- ant varieties, or by improving cultural practices under favorable weather con- ditions. Blackeye Beans in California 53 LITERATURE CITED Anonymous. 1944-45. Seed certification in California. 15 p. California Crop Improvement Association, Davis, California. Allen, O. N., and Ethel K. Allen. 1936. Koot nodule bacteria of some tropical leguminous plants: I. Cross-inoculation stu- dies with Vlgna sinensis L. Soil Sci. 42:61-74. Anderson, P. J., E. J. Haskell, W. C. Muenscher, Clara J. Weld, Jessie I. Wood, and G. H. Martin. 1926. Check list of diseases of economic plants in the United States. U. S. Dept. Agr. 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New, productive strains resist disease. South. Seeds- man 7(3) :24, 36. Kendrick, J. B. 1931. Seed transmission of cowpea fusarium wilt. Phytopathology 21:979-83. 1933. Seedling stem blight of field beans caused byBhizoctonia bataticola at high tem- peratures. Phytopathology 23:949-93. 1936. A cowpea resistant to fusarium wilt and nematode root knot. [Abstract.] Phyto- pathology 26:98. Larson, A. O., and C. K. Fisher. 1938. The bean weevil and the southern cowpea weevil in California. U. S. Dept. Agr. Tech. Bui. 593:1-70. Leach, L. D., and A. E. Davey. 1935. Soil amendments for southern sclerotium rot of sugar beets. [Abstract.] Phyto- pathology 25:896. Leonard, L. T. 1944. Methods of testing legume bacteria cultures and results of tests of commercial in- oculants in 1943. U. S. Dept. Agr. Cir. 703:1-8. Letjkel, R. W. 1942. Spergon as a seed disinfectant. Plant Disease Reporter [ Issued by U. S. Bur. Plant Indus.] 26:93-94. (Mimeo.) Linsley, E. G., and A. E. Michelbacher. 1943. Insects affecting stored food products. California Agr. Exp. Sta. Bui. 676:1-44. McClelland, C. K. 1937. Variety and inter-cultural experiments with cowpeas. Arkansas Agr. Exp. Sta. Bui. 343:1-15. 1940. Effects of interplanting legumes in corn. Arkansas Agr. Exp. Bui. 393:1-29. Mackie, W. W. 1932. A hitherto unreported disease of maize and beans. Ph}'topathology 22:637-44. Mackie, W. W., and F. L. Smith. 1935. Evidence of field hybridization in beans. Amer. Soc. Agron. Jour. 27:903-9. Mann, Albert. 1914. Coloration of the seed coat of cowpeas. Jour. Agr. Res. 2:33-56. Morse, W. J. 1920a. Cowpeas: culture and varieties. U. S. Dept. Agr. Farmers' Bui. 1148:1-26. 1920b. Utilization of cowpeas. U. S. Dept. Agr. Farmers' Bui. 1153:1-23. Oliver, G. W. 1910. New methods of plant breeding. U. S. Bur. Plant Indus. Bui. 167: 1-39. Orton, W. A. 1902. The wilt disease of cowpea and its control. U. S. Bur. Plant Indus. Bui. 17(Pt. I) : 9-22. 1908. The development of farm crops resistant to disease. U. S. Dept. Agr. Yearbook 1908:453-64. Blackeye Beans in California 55 1911. The development of disease resistant varieties of plants. Internatl. Conf . de Gene- tique 4:247-61. PlETERS, A. J. 1927. Green manuring principles and practice. 356 p. John Wiley and Sons, Inc., New York. N. Y. Piper, C. V. 1912. Agricultural varieties of the cowpea and immediately related species. U. S. Bur. Plant Indus. Bui. 229:1-160. 1913. The wild protype of the cowpea. U. S. Bur. Plant Indus. Cir. 124D: 29-32. 1924. Forage plants and their uses. 671 p. The Macmillan Company, New York. N. Y. Reid, Mary E. 1942. Effect of variations in light intensity, length of photo-period and availability of nitrogen upon accumulation of ascorbic acid in cowpea plants. Torrey Bot. Club Bui. 69:204-20. Bobbins, W. W. 1917. The botany of crop plants. 681 p. P. Blakiston's Son and Company, Philadelphia, Pa. Senn, H. A. 1938. Chromosome number relationships in Leguminosae. Bibliographia Genetica 12: 175-336. Severin, H. H. P., and C. F. Henderson. 1928. Some host plants of curly top. Hilgardia 3(13) :339-92. Spillman, W. J. 1911. Inheritance of the "eye" in Vigna. Amer. Nat. 45:513-23. Spillman, W. J., and W. J. Sando. 1930. Mendelian factors in the cowpea (Vigna sinensis). Michigan Acad. Sci., Arts, and Letters Papers 11:249-83. Stone, M. W. 1941. Life history of the sugar-beet wireworm in southern California. U. S. Dept. Agr. Tech. Bui. 744:1-87. Tompkins, C. M., and W. W. Gardner. 1935. Relation of temperature to infection of bean and coAvpea seedlings by Rhizoctonia bataticola. Hilgardia 9(4) : 219-30. Tyler, Jocelyn. 1944. The root-knot nematode. California Agr. Exp. Sta. Cir. 330 : 1-30. Revised. United States Agricultural Research Administration. 1943. Root-knot nematode studies. In : Report of the Administrator of Agricultural Re- search, p. 215-16. U. S. Govt. Printing Office, Washington, D. C. 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Pacific Rural Press, San Fran- cisco, California. 56 California Experiment Station Bulletin 696 Wight, W. F. 1907. History of the cowpea and its introduction into America. U. S. Bur. Plant Indus. Bui. 102:43-59. Windsor, Wenona. 1918. How to cook soybeans and cowpeas. Missouri Agr. Ext. Cir. 45:1-4. Wingard, S. A. 1922a. A yeast parasite on lima beans. [Abstract.] Phytopathology 12:47. 1922&. Yeast-spot of lima beans. Phytopathology 12:525-32. Young, P. A. 1937. Ashy-stem blight of blaekeye cowpea in Texas. Plant Disease Reporter [Issued by U. S. Bur. Plant Indus.] 21:279. (Mimeo.) 20m-4,'46(5871)