PUMPKIN AND SQUASH
Cucurbita spp., family CucurbitaceaeThere is no satisfactory association between the common and scientific names of pumpkin, squash, summer squash, winter squash, vegetable marrow (primarily a British term), cushaw (Louisiana French for "big pumpkin"), and ornamental gourds. Four species of Cucurbita of economic importance are involved: C. maxima Duch., C. mixta Pang., C. moschata Duch. ex Poir., and C. pepo L. Botanical identification of the specimens is according to the type of stem (trunk) or peduncle (flower stalk). To the general public, however, a plant, or its fruit, may be known as a squash or pumpkin to one individual and as a cushaw or gourd to another. Botanical classification is further complicated by the fact that all cultivars of the species will readily intercross (Tapley et al. 1937, Whitaker and Bohn 1950, Whitaker and Davis 1962*). The proposal by Whitaker and Davis to separate the species according to culinary usage has not been accepted.
From the pollination standpoint, the four species and their types and cultivars are subsequently treated herein as a unit, and are collectively referred to as "pumpkin and squash."
In addition to the use of pumpkin and squash as human food, they are also used as livestock food, some cultivars much more than others. Also, the seeds are eaten whole as a confection or crushed to extract the oil, which is about equal to peanut oil production on a per-acre basis. This oil is used as a high-quality liquid vegetable fat and as a sandwich spread (Curtis 1948). The fruit of plants more frequently known as gourds is used for containers, musical instruments, and ornamentation (Whitaker 1964).
Although the USDA, Agricultural Statistics, 1971, does not show the acreage devoted to these four species of cucurbits it gives the acres devoted to seed production and the volume of seed produced in 1969 as follows:
[gfx] fix chart below:
Crop Acres Lbs. seed X 1,000 Pumpkin 226 109 Squash: Summer 1,039 551 Winter 500 210
This amount of seed should be sufficient to plant several hundred thousand acres (Jones and Emsweller 1931, Thompson et al. 1955, Whitaker and Davis 1962*).
Pumpkin and squash are grown throughout the country, with Illinois, New Jersey, California, Florida, and Texas having the greatest acreage, although State positions vary from year to year because of season and market conditions (USDA 1964). Individual plantings usually range from home-garden size to about 40 acres.
Plant:
All of the Cucurbita spp. are annuals. Most of them are prostrate with trailing branches, reaching a length of 40 to 50 feet, but some have short, semierect stems (Castetter and Erwin 1927). The leaves are large, sometimes exceeding 12 inches across, and are borne on petioles up to 24 inches in length. The plants are susceptible to frost but do well in relatively cool climates. If the fruit is consumed in the immature stage, it must be harvested at frequent intervals. Otherwise, it is left to mature on the vine. The fruits vary greatly in size, from a few ounces to more than 100 pounds, and in shape from globular and oval to gooseneck, crookneck, and other grotesque shapes.
Inflorescence:
The flowers are large (to 3 inches), solitary, showy, creamy white to deep orange-yellow, and are open for only 1 day. Plants are normally monoecious, but hermaphroditic flowers occur (Jones and Rosa 1928*). Battaglini (1969) recorded 10 staminate flowers for each pistillate one. Staminate flowers are at the end of a thin stem, and have three anthers producing relatively large pollen grains (fig. 162). The morphology of the staminate flowers was described by Chakravarty (1958). Pistillate flowers are on a short peduncle, the style is thick, and the stigma two- lobed. The showy corolla of the pistillate flower is attached to the end of the easily recognizable ovary (Whitaker and Jagger 1937). Tapley (1923) recorded 24 to 34 pistillate blooms per squash plant with 5.5 to 43.7 percent set. Both pollen and nectar are produced in the staminate flowers and nectar in pistillate flowers. Verdieva and Ismailova (1960) stated that most bees visit the squash flowers for nectar only. Nectar is secreted from a ring of tissue surrounding the style and just inside the perianth tube. The ovary is divided into three to five carpels. Eisa and Munger (1968) reported that male and female sterility have been observed in C. pepo, and Scott and Riner (1946) reported male sterility in C. maxima.
The squash blossom is the emblem of fertility to the Hopi Indians of the Southwest, whose more expensive pieces of jewelry include the squash blossom necklaces.
[gfx] FIGURE 162. - Longitudinal section of reproductive portions of acorn squash flowers, x 2. A, Staminate, or male flower; B, pistillate, or female flower.
Pollination Requirements:
Because the anthers are in one flower and the stigma is in another, the mechanical transfer of pollen is essential to fruit set. Hayase (1953) stated that the seed number and fruit weight was increased in proportion to the amount of pollen deposited on the stigma. The period of receptiveness has not been thoroughly worked out. Sanduleac (1959) observed that honey bees worked the flowers most intensively from 6 a.m. to noon with maximum activity from 8 to 9 a.m. Amaral and Mitidier (1966) stated that the flowers of C. pepo open before sunrise and close by 11 a.m. Atwal (1970) recorded that pollinating insects visited the flowers from 7 to 10:30 a.m., "when the flowers began to close." Hurd (1966) noted that, depending upon the weather and season, the flowers of the host (cucurbits) open some time before daylight or shortly thereafter, and in hot weather they wither and close by 8 to 9 a.m., otherwise they may stay open until noon. Hawthorn and Pollard (1954*) also stated that the flowers open about 5 a.m. and close about noon. Pollination, therefore, is most effective in the early morningÑprimarily before 9 a.m. Bailey (1890) indicated that "squash" and "gourd" were self-sterile, but Bushnell (1920) stated that the 'Hubbard' squash was not self-sterile, and if there was sterility apparently it no longer existed.
Bailey (1937) further stated that in "gourds" it is doubtful whether there is ever impregnation between two flowers on the same plant because experimental efforts to do so are unsuccessful. He felt, therefore, that seeds of the "gourds" are always produced from crosses between two plants.
Pollinators:
Practically all authorities give primary credit to the honey bee in pollinating Cucurbita (Pammel and Beach 1894, Jones and Rosa 1928*, Jones and Emsweller 1931, Thompson et al. 1955, Whitaker and Davis 1962*, Battaglini 1969, Langridge 1952, Nevkryta 1953, Robinson 1952, Sanduleac 1959, Verdieva, and Ismailova 1960, Wolfenbarger 1962). Michelbacher et al. (1964) and Hurd (1966) credit both honey bees and wild bees. Some species of wild bees are most efficient pollinators of Cucurbita, but they are frequently so limited in number or in range as to be of no great economic significance. Durham (1928) gave some credit to the cucumber beetle; Tontz (1944) to ants; and Fronk and Slater (1956) to the wild bees, Peponapsis spp. and Zenoglossa spp., with a minor role played by Diabrotica spp. beetles. Hurd (1966) stated that "other insects are involved such as cucumber, scarab and meloid beetles, and flies and moths but to a lesser extent than are bees."
Michelbacher et al. (1964) concluded that even though honey bees are poorly adapted as pollinators of squash, pumpkin, and gourd, because of the small size of the insect and the relatively large pollen grains, still the importance of honey bees as pollinators of these crops should not be minimized. Langridge (1954) stated that if pollination was inadequate, the introduction of honey bees was the only solution.
For commercial production of Cucurbits, there seems little doubt that the honey bee is the only effective pollinator that can be provided in sufficient numbers for adequate pollination. Wadlow (1970) reported that with only about 1,000 colonies, at $10 per colony, he provided pollination for squash and other crops valued at over $1 million.
The value of bees as pollinators has been shown in terms of fruit produced. Wolfenbarger (1962) showed the following correlation between colonies per acre and increased production in baskets of squash per acre: No colonies provided, 148 baskets; one-half colony per acre, 155 baskets; one colony per acre, 161 baskets; two colonies per acre, 168 baskets; and three colonies per acre, 173 baskets. In open plots, he obtained 4.20 squash per yd2; whereas in plots caged to exclude bees, he produced only 0.82 per yd2. Verdieva and Ismailova (1960) reported 47 to 57 kg squash from plants pollinated by honey bees compared with 25 to 30 kg from plots pollinated by other (unspecified) methods. Nevkryta (1953) increased cucurbit production 3.0 to 3.4 times with increased bee activity, attributed to stimulative feeding of the bees. Battaglini (1969) recorded a set of 61.2 percent of pistillate flowers exposed to bees in comparison with a set of 6.8 percent of caged flowers. The agent responsible for the set of the caged flowers was not given.
Not only are bees largely responsible for the fruit set on standard cultivars, but their value is enhanced on plants in which hybrid vigor has been demonstrated. Curtis (1939) obtained 59 fruits from a hybrid compared to 25 and 27 from the two parents.
Hutchins and Croston (1941) also obtained significantly greater yields from 7 out of 10 crosses, and production of all crosses was significantly earlier than in the parental lines. With male sterility now available in Cucurbita (Eisa and Munger 1968), techniques involving the crossing of inbred lines by honey bees provide plant breeders with the opportunity to develop improved hybrid cultivars.
Pollination Recommendations and Practices:
Unfortunately, concrete data are scarce on the pollination of crops of the genus Cucurbita. As a result, most publications merely generalize with such statements as " . . . largely insect pollinated" (Thompson et al. 1955), "Transfer of pollen is usually accomplished by insects, chiefly honey bees" (Jones and Rosa 1928*, Purseglove 1968*), "Honey bees are the usual agents. .. " Hawthorn and Pollard (1954*), or "insect pollinated" (Whitaker and Davis 1962*). The "one colony of honey bees per acre" recommended for cantaloupe (McGregor and Todd 1952*) might be expected to apply to Cucurbita also, but proof should be established.
Sanduleac (1959) reported one to two colonies per 25 acres in the area of his test. Eckert (1959*) suggested that one strong colony per 2 acres of squash may be enough under irrigated conditions in California. Jaycox (1969) listed pumpkins and squash along with many other crops and generalized without supporting data that most crops require one strong colony per acre. Wolfenbarger (1962) showed continued increase in squash production in Florida up to three colonies per acre without hitting a peak in production.
Available evidence shows that the plants must be insect pollinated, and that honey bees are the chief pollinators. Detailed studies, correlating bee visits to flowers with yield, quality, and related factors have not been carried out. Where yields are low, an additional one to three colonies per acre should be provided for at least 3 years to determine their value. The literature indicates that colonies nearby are most effective.
LITERATURE CITED:
AMARAL, E., and MITIDIER. I. J.
1966. [POLLINATION OF SQUASH.] Anais, da Escola Superior de Agricultural "Lutz de Queriroz" Sao Paulo Univ., Piracicaba, Brazil 23: 121-128. [In Portuguese, English summary.]ATWAL, A. S.
1970. BIOLOGY, ECOLOGY AND UTILIZATION OF INSECTS OTHER THAN HONEYBEES IN THE POLLINATION OF CROPS. Final Res. Rpt. (1965-70) OF P.L. 480 project executed at Punjab Agr. Univ., Ludhiana (India), 115 pp.BAILEY, L. H.
1890. EXPERIENCES IN CROSSING CUCURBITS. N.Y. (Cornell) Agr. Expt. Sta. Bul. 25, pp.180-187.______ 1937. THE GARDEN OF GOURDS. 134 PP. The Macmillan Co., New York.
BATTAGLINI, M. B.
1969. [THE IMPORTANCE OF HONEYBEES FOR FERTILIZING CUCURBITA PEPO.] Apicolt. 35(1): 9-12. [In Italian.] AA-585/69.BUSHNELL, J. W.
1920. THE FERTILITY AND FRUITING HABIT IN CUCURBITA. Amer. Soc. Hort. Sci. Proc. 17: 47-51.CASTETTER, E. F., and ERWIN, A. T.
1927. A SYSTEMATIC STUDY OF THE SQUASHES AND PUMPKINS. Iowa Agr. Expt. Sta. Bul. 244: 107-135.CHAKRAVARTY, H. L.
1958. MORPHOLOGY OF THE STAMINATE FLOWERS OF THE CUCURBITACEAE WITH SPECIAL REFERENCE TO THE EVOLUTION OF THE STAMENS. Lloydia 21: 49-87.CURTIS, L. C.
1939. HETEROSIS IN SUMMER SQUASH (CUCURBITA PEPO) AND THE POSSIBILITY OF PRODUCING F1 HYBRID SEED FOR COMMERCIAL PLANTING. Amer. Soc. Hort. Sci. Proc. 37: 827-828.______ 1948. THE USE OF NAKED SEED IN CUCURBITA PEPO AS A SOURCE OF HIGH QUALITY LIQUID VEGETABLE FAT, AS A HIGH ANALYSIS PROTEIN, AS A NEW CONFECTION, AND AS A SANDWICH SPREAD. Amer. Soc. Hort. Sci. Proc. 52: 403-406.
DURHAM, G. B.
1928. POLLEN CARRIERS ON SUMMER SQUASH. Jour. Econ. Ent. 21: 436.EISA, H., and MONGER, H. M.
1968. MALE STERILITY IN CUCURBITA PEPO. Amer. Soc. Hort. Sci. Proc. 92: 473-479.FRONK, W. D., and SLATER, J. A.
1956. INSECT FAUNA OF CUCURBIT FLOWERS. Kans. Ent Soc. Jour. 29: 141-145.HAYASE, H.
1953. [CUCURBITA-CROSSES. IV. THE DEVELOPMENT OF SQUASH FRUIT AS AFFECTED BY PLACEMENT OF POLLEN ON STIGMA.] Hokkaido Natl. Agr. Expt. Sta. Res. B. 64: 22-25. [In Japanese, English summary.]HURD, P. D., JR.
1966. THE POLLINATION OF PUMPKINS, GOURDS AND SQUASHES (GENUS CUCURBITA). In 2d Internatl. Symposium on Pollination, London, 1964. Bee World 47 (supp.): 97-98.HUTCHINS, A. E., and CROSTON F. E.
1941. PRODUCTIVITY OF F1 HYBRIDS IN THE SQUASH (CUCURBITA MAXIMA). Amer. Soc. Hort. Sci. Proc. 39: 332-336.JAYCOX, E. R.
1969. BEEKEEPING IN ILLINOIS. Ill. Col. Agr. and Coop. Ext. Serv. Cir. 1000, 132 pp.JONES, H. A., and EMSWELLER, S. L.
1931. THE VEGETABLE INDUSTRY. 431 pp. McGraw-Hill Book CO., Inc., New York and London.LANGRIDGE, D. F.
1952. POLLINATION EXPERIMENT [ON PUMPKINS]: AGRICULTURAL DEPARTMENT'S WORK. Austral. Bee Jour. 33: 84.______ 1954. HONEY-BEES IN AGRICULTURE AND HORTICULTURE. Victoria Jour. Dept. Agr. 52: 113-116, 128.
MICHELBACHER, A. E., SMITH, R. F., and HURD, P. D., JR.
1964. BEES ARE ESSENTIALÑPOLLINATION OF SQUASHES, GOURDS AND PUMPKINS. Calif. Agr. 18(5): 2-4.NEVKRYTA, A. N.
1953. [INSECTS POLLINATING CUCURBIT CROPS.] 92 pp. [Kiev] Akad. Nauk Ukrain. SSR. [ In Russian.] AA153/61.PAMMEL, L. H., and BEACH, A. M.
1894. POLLINATION OF CUCURBITS. Iowa Acad. Sci. Proc. 2: 146-152.ROBINSON, F. A.
1952. THE USE OF HONEY BEES IN PRODUCTION OF CUCURBITS IN FLORIDA. Amer. Bee Jour. 92: 326 - 328.SANDULEAC, E.
1959. [DATA ON THE ENTOMOPHILOUS POLLINATION AND THE SELECTION OF CUCURBITACEAE.] Lucr. Stiint. Stat. Cent. Seri. Apic. 1: 129-132. [In Romanian.] AA-431/61.SCOTT, D. H., and RINER, M. E.
1946. INHERITANCE OF MALE STERILITY IN WINTER SQUASH. Amer. Soc. Hort. Sci. Proc. 47: 375-377.TAPLEY, W. T.
1923. THE FRUITING HABIT OF THE SQUASH. Amer. Soc. Hort. Sci. Proc. 20: 312-319.______ENZIE, W. D., and ESELTINE, G. P. VAN.
1937. THE VEGETABLES OF NEW YORK. V.1, pt. 4, 131 pp. Rpt. of the N.Y. State Agr. Expt. Sta. Ann. Rpt. for year ending June 30, 1935. J. B. Lyon CO., Albany.THOMPSON, R. C., DOOLITTLE, S. P., and CAFFREY, D. J.
1955. GROWING PUMPKINS AND SQUASHES. U.S. Dept. Agr. Farmers' Bul. 2086, 30 pp.TONTZ, C.
1944. ANTS PINCH-HIT FOR BEES. Gleanings Bee Cult. 72: 482.UNITED STATES DEPARTMENT OF AGRICULTURE.
1964. GROWING PUMPKINS AND SQUASHES. U.S. Dept. Agr. Farmers' Bul. 2086, 27 pp. (A revision of Thompson et al. 1955.)VERDIEVA M. G., and ISMAILOVA, M. K.
1960 [THE INFLUENCE OF BEE POLLINATION ON THE INCREASE OF THE CROP FROM FEED SQUASH.] Pchelovodstvo 37(9): 4041. [In Russian.] AA-951/63.WADLOW, R. V.
l97O. POLLINATION OF CROPS IN FLORIDA. In The Indispensable Pollinators, Ark. Agr. Ext. Serv. Misc. Pub. 127, pp. 61-63.WHITAKER, T. W.
1964. GOURDS AND PEOPLE. Amer. Hort. Mag. 43(4): 207-213.______and BOHN, G. W.
1950. THE TAXONOMY, GENETICS, PRODUCTION AND USES OF THE CULTIVATED SPECIES OF CUCURBITA. Econ. Bot. 4: 52-81.______and JAGGER, I. C.
1937. BREEDING AND IMPROVEMENT OF CUCURBITS. U.S. Dept. Agr. Yearbook 1937: 207-232.WOLFENBARGER, D. O.
1962. HONEY BEES INCREASE SQUASH YIELDS. Fla. Agr. Expt. Sta. Sunshine State Agr. Res. Rpt. 7(1): 15,19. 310
