Chapter 9: Crop Plants and Exotic Plants

RAPE³²Brassica spp., family Cruciferae
Two species of Brassica are known as rape, a word derived from the Latin word "rapum" meaning turnip. B. napus L. is known in Canada as the Argentine type of rape, and elsewhere as summer rape, winter rape, colza, colza-oil rape, or swede rape. B. campestris L. is known as field mustard, summer turnip rape, Polish rape, toria, and sarson. Sarson is somewhat different from toria for it has both yellow-seeded and brown- seeded cultivars.

Rape is not extensively grown in the United States, but there are about 4 million acres in nearby Canada. About 80 percent of this acreage is planted to B. campestris, 20 percent to B. napus. The oil, pressed from the seed, is used in margarine and shortenings and in salad and cooking oil. The quality of rape oil is equal to or better than soybean oil. Rapeseed meal has found wide acceptance as a food for many classes of livestock. The protein in rape is considered equivalent to that in soybean on a pound-for-pound basis (Downey et al. 1970). Yields reported from Canada range from 1,560 to 2,220 pounds seed per acre.
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³² See also, "Cole Crops," and "Mustard."

Plant:
Young rape plants look somewhat like young cabbage plants, with basal leaves 4 to 12 inches or more long and half as broad as long. The flower stalk of B. napus grows to a height of 2 1/2 to 4 feet, whereas B. campestris reaches only 1 l/2 to 3 feet. Rape is a cool-season crop but is susceptible to frost. The seeds of rape are drilled into the soil, just like wheat, either late in the fall (making it a sort of biennial) or early in the spring as an annual.

Inflorescence:
The plant is topped by a mass of golden yellow flowers that in bloom give the field a bright golden appearance.

The flowers are in elongated terminal racemes. There are the four characteristic cruciferous petals and, usually, six stamens, four projecting above the stigma and two shorter than the style. There are four partly concealed nectar glands, two on the inner side of the short stamens, the others between the insertions of each pair of long stamens (Knuth 1908*, p. 96). The latter nectaries become more accessible to bees as the flower matures (Meyerhoff 1958). The fruit is a slender silique or pod 2 to 4 inches long. Knuth (1908*, p. 76) stated that when the flower of B. napus opens, the anthers are still unripe, and those of the four long stamens lie close to the already mature stigma. Before the corolla has fully expanded, the anthers make a half turn and dehisce so the pollen-covered sides are turned outward. The anthers of the short stamens, 2 to 3 1/2 mm below the stigma, remain with their pollen-covered sides toward the style, but they lean outward. When the flower fades, the long stamens recurve, so that automatic self- pollination may occur if the plant is selfcompatible. Flowering extends from 22 to 45 days (Gerard and Cronan 1963, Radchenko 1964).

Rape produces nectar sufficiently to be considered a better honey plant than white or red clover (Hammer 1966). The nectar can be seen glistening in the bottom of the flower all day, and a colony of honey bees may store 15 to 33 pounds of honey per day (Palmer 1959). This, of course, would depend upon the strength of the colony, the number of flowers present, and weather conditions.

Pollination Requirements:
There seems little doubt that B. campestris or Polish rape requires insects for cross-pollination and seed production. Koutensky (1958) showed that production in fields with apiaries beside them was 2,095 kg/ha (1,844 lb/acre), but with apiaries 2.4 km (1.4 miles) distant the production was only 1,275 kg/ha (1,511 lb/acre). Pritsch (1965) studied the pollination of B. campestris in cages with bees compared to cages with bees excluded, although smaller insects had access to both cages, and obtained significantly greater production with bee pollination. Downey and Bolton (1961) reported that the yield of seed in fields stocked with bees was at least 30 percent higher than fields not supplied with bees. Downey et al. (1970) stated that B. campestris is almost completely self-sterile and bees must be provided. White (1970) reported that summer turnip rapes are almost completely cross-pollinated, the "true" rapes about one-third cross-pollinating and twothirds self-pollinating.

In the case of B. napus or Argentine rape, there is some question about the degree of benefit from insect pollinators. Knuth (l 908*, p. 98) reported that "according to some authors the plant is self-sterile," and insect visitation will increase seed production. According to Free and Nuttall (1968), Fujita (1939) reported that B. napus plants caged with bees produced 25 percent more seed than plants caged without bees. Von Rhein (1952) cited other workers who showed that bees caused 17.4 percent more seed per pod and 9.7 percent heavier seeds than were produced on plants not visited by bees. Louveaux and Verge (1952) reported a 50 percent increase in seeds per pod on plants growing near a large apiary as compared to plants caged to exclude bees.

Jenkinson and Jones (1953) reported that although the relationship of anthers to the stigma in individual flowers favors self-pollination, the presence of bees resulted in increased yields, for example, 8.8 seeds per pod with bees present versus 5.3 seeds per pod with bees excluded.

Downey et al. (1970) stated that B. napus is largely self-pollinated, and thus a good uniform set of seed can be obtained without bees. Turnip rape, however, is almost completely self-sterile and requires cross- pollination to set seed. Wind can carry pollen from one plant to another, but insects, particularly bees, are important. Experiments show that when fields of turnip rape (B. campestris) are stocked with bees, earlier and more uniform maturity results. Downey (1964) indicated that when bees were excluded from 'Arlo' cv. of rape only two-thirds as much seed set as when bees were present at flowering. Even so, he indicated that neither native bees nor honey bees were available in sufficient quantities for effective pollination of the large acreages of rape in Canada. Nothing was mentioned about transporting colonies to the fields that had low pollinator populations. The ratio of seeds per flower with bees present was 6.7 compared to 2.8 without bee visitation.

Koutensky (1959) reported that bee pollination increased seed yields of B. napus v. arvensis by 64 percent. Vesely (1962) reported that bee activity increased B. napus v. oleifera seed production by 25 percent and that cross-pollinated plants set the crop of seed and ceased flowering earlier than plants not visited by bees. Pritsch (1965) also reported significantly greater yield of seed in cages with bees than with bees excluded. Free and Nuttall (1968) reported a 13 percent increase in seed yield from cages with bees compared to cages without bees - an amount they did not consider of significance. Downey et al. (1970) indicated that B. napus was 70 percent self- pollinated. Mohammad (1935) stated that in toria and brown-seeded sarson 12 and 20 percent of bagged pods set, whereas 91 percent of yellow- seeded sarson in bags set. He also stated that plants from cross- pollinated seeds were more productive.

Meyerhoff (1954) conducted five tests over 3 years with 'Lembke's' winter rape. He concluded that honey bees increased the number of pods per plant by 53.2 percent, pod length by 6.1 percent, and seeds per pod by 12.6 percent. Zander (1952) also studied 'Lembke's' winter rape in one cage with bees, in one without bees, and an open plot. In mid-May, the plants in the cage with bees had set their seed crop and had ceased flowering, whereas the plants in the cage without were still in full bloom; the stage of the plants in the open was between that of the others. Latif et al. (1960) showed that rape seed production in fields with bees was more than double that in fields where bees (Apis cerana F.) were absent. Olsson (1955) also showed that rape was about one-third cross-pollinated in open fields, whereas white mustard was almost completely self-pollinated. The presence of bees in cages of white mustard doubled the number of seeds per pod and increased the pod set by 50 percent.

Vasil (1964) and Hasler and Maurizio (1949, 1950) have shown that boron, in some unknown way, influences the pollination of B. napus and other plants. More information in this area would be most helpful in understanding the pollination and fruit setting not only in the Brassicas but also in the pollination and fruit setting of other plants.

The above tests showed a benefit from bee pollination ranging from 13 to 64 percent more seeds per pod, and with earlier cessation of flowering. This would indicate that the crop is considerably benefited by insect pollination.

Olsson (1955) gave wind pollination some credit in the setting of rape seed, but most other researchers consider wind as only a minor factor.

Pollinators:
Rahman (1940) studied the pollinators of B. napus in India. He concluded that the dwarf honey bee of India (Apis florea F.), the wild bees (Andrena ilerda Cam. and Halictus sp.), and the fly (Eristalis tenex (L.)) were the most important pollinators.

Free and Nuttall (1968) studied the activity of honey bees on B. napus. They reported that all bees that visited the flowers collected nectar although some collected pollen also. All became covered with pollen, but some removed and discarded it. Those that collected the pollen did so primarily during the morning hours.

Honey bees are the primary pollinators of rape (Belozerova 1960, Nikitina 1950, Radchenko 1964, Vesely 1962). The plant is highly attractive to honey bees, providing both nectar and pollen, and the honey bee is of appropriate size for effective transfer of pollen from anthers to stigma. Hammer (1952) reported as many as 20,000 bees per hectare of rape in fields 31/2 to 4 km from the apiary. Each bee was returning to the hive with 30- to 60-mg loads of nectar, roughly half the weight of a worker bee.

Belozerova (1960) noted that B. napus had 2.326 mg nectar per flower at the beginning of bloom, 1.950 mg during the peak, and 1.350 mg per flower toward the end of blooming. He noted that 96.3, 95.3, and 72.9 percent of the floral visitors at the three different periods were honey bees. Other pollinators in India include Apis florea, A. dorsata, A. cerana, and Andrena ilerda (Kapil et al. 1969).

Pollination Recommendations and Practices:
Hammer (1963, 1966) recommended three colonies per hectare (1.5 colonies per acre); Radchenko (1964), two colonies per hectare (0.8 colony per acre); Downey and Bolton (1961), one colony per acre; White (1970), two colonies per acre; and Vesely (1962) three to four colonies per hectare (1.5 to 2 colonies per acre). Downey et al. (1970) stated that it is not necessary to provide bees to produce good seed yields, which is puzzling when it is remembered that 80 percent of the rape in Canada is B. campestris, which is largely self-sterile. White (1970) said that both summer turnip rapes and true rapes depend on bees for maximum production. The data indicate that a heavy bee population on rape would be beneficial, but no data establish the maximum floral visitation desired. Until more concrete data are available, the one to two strong colonies of honey bees per acre cited above would appear to be a logical usage.

The ideal pollinator population and proper distribution of colonies for most efficient pollination of rape needs to be determined.

LITERATURE CITED:
BELOZEROVA, E. I.
1960. [BEES INCREASE SEED CROP FROM WINTER RAPE.] Pchelovodstvo 37(9): 38-40. [In Russian.] AA-939163.

DOWNEY, R. K
1964. EFFECT OF BEES ON SEED YIELDS OF ARLO RAPESEED. Forage Notes 10: 1.

____ and BOLTON, J. L.

1961. PRODUCTION OF [POLISH AND ARGENTINE] RAPE IN WESTERN CANADA. Canada Dept. Agr. Res. Br. Pub. 1021, 19 pp.

____ PAWLOWSKI, S. H., and MCANSH, J.
1970. RAPESEED - CANADA'S "CINDERALLA", CROP. Ed. 2. Rapeseed Assoc. of Canada Pub. 8, 40 pp.

FREE, J. B., and NUTTALL, P. M.
1968. THE POLLINATION OF OILSEED RAPE (BRASSICA NAPUS) AND THE BEHAVIOUR OF BEES ON THE CROP. Jour. Agr. Sci. (Cambridge) 71: 91-94.

FUJITA, M.
1939. [INFLUENCE OF HONEYBEES ON THE FRUCTIFICATION OF RAPE.] Bul. imp. Zootech. Exp. Stn. Chiba-shi 34: 1. [ In Japanese. ]

GERARD, BROTHER, AND CRONAN, FATHER.
1963. RAPESEED - IOWA GOLD. Amer. Bee Jour. 103: 218-219.

HAMMER, O.
1952. [RAPE GROWING, BEES AND SEED PRODUCTION.] Dansk Landbr. 71: 67-69. [In Danish.] AA-122/54.

____ 1963. [SUMMER RAPE AS A COMPETITOR AFFECTING THE POLLINATION OF CLOVERS.] Dansk Froavl No. 14, 7 pp. [In Danish.] AA-425/68.

____ 1966. SOME PROBLEMS OF COMPETITION BETWEEN SUMMER RAPE AND CLOVER, IN RELATION TO POLLINATION. In 2d Internatl. Symposium on Pollination, London, 1964. Bee World 47, Supp. 1: 99-106.

HASLER, A., and MAURIZIO, A.
1949. [THE ACTION OF BORON ON SEED - SETTING AND NECTAR SECRETION IN RAPE (BRASSICA NAPUS L.).] Phytopath. Zeits. 15(2): 193-207. [In German, English summary.]

____ and MAURIZIO, A.
1950. [INFLUENCE OF VARIOUS NUTRITIVE SUBSTANCES ON THE DEVELOPMENT OF BLOSSOM, THE SECRETION OF NECTAR, AND THE SEED-YIELD, OF NECTAR PLANTS (ESPECIALLY SUMMER RAPE).] Schweiz Landw. Monatshefte 6: 201-211. [In German.]

JENKINSON, J. G., and JONES, G. D. G.
1953. OBSERVATIONS ON THE POLLINATION OF OIL RAPE (BRASSICA NAPUS) AND BROCCOLI (BRASSICA OLERACEA). Bee World 34: 173-177.

KAPIL, R. P., GREWAL, G. S., KUMAR, S., and ATWAL, A. S.
1969. INSECT POLLINATORS OF RAPE SEED AND MUSTARD. (Abstract) 56th Indian Sci. Cong. Proc., pt. 3, p. 509.

KOUTENSKY, J.
1958. [THE RESULTS OF THE POLLINATING WORK OF BEES.] Vcelarstvi 11(5): 72-73. [In Czech.] AA-70/60.

KOUTENSKY, J.
1959. [THE POLLINATING EFFECT OF THE HONEY BEE (APIS MELLIFERA L.) ON THE INCREASE IN RAPE AND WHITE MUSTARD YIELDS PER HECTARE.] Ceskoslov. Akad. Zemedel. Ved, Sborn. Rostlinna Vyroba 32(4): 571-582. [In Czech., English summary.]

LATIF, A., QAYYUM, A., and ABBAS, M.
1960. THE ROLE OF APIS INDICA IN THE POLLINATION OF [OIL SEEDS] "TORIA" AND "SARSON" (BRASSICA CAMPESTRIS VAR. TORIA AND DICHOTOMA). Bee World 41: 283-286.

LOUVEAUX, J. and VERGE, J.
1952. [RESEARCHES ON THE POLLINATION OF WINTER RAPE.] Apiculteur 96 (Sect. Sci.): 15-18. [In French. ] AA-213/53.

MEYERHOFF, G.
1954. [INVESTIGATION ON THE EFFECT OF BEE VISITS ON RAPE.] Arch. f. GeflugelZucht und Kleintierkunde 3(3/4): 259-306. [In German.] AA-99/59.

____ 1958. [BEHAVIOR OF BEES FORAGING ON RAPE.] Leipzig. Bienenztng. 72(6): 164-165. [In German.] AA-89/60.

MOHAMMAD, A.
1935. POLLINATION STUDIES IN TORIA (BRASSICA NAPUS VAR. DICHOTOMA PRAIN), AND SARSON (B. CAMPESTRIS L. VAR. SARSON PRAIN). Indian Jour. Agr. Sci. 5: 125-154.

NIKITINA, A. I.
1950. [HONEYBEES RAISE SEED YIELDS OF TURNIPS AND RUTABAGA.] PchelovodstVo 27(5): 271-274. [In Russian.]

OLSSON, G.
1955. [WIND POLLINATION OF CRUCIFEROUS OIL PLANTS.] Sverig. Utsadesforen. Tidskr. 65(6): 418-422. [In Swedish, English summary.

PALMER, S.
1959. A HONEY PLANT PAR EXCELLENCE. Gleanings Bee Cult. 87: 460-461.

PRITSCH, G.
1965. [INCREASING THE YIELD OF OIL PLANTS BY USING HONEY BEES.] Ved. Prace Vyzkam. Ustav. Vcelar CSAZV 4: 157-163. [In German.] AA-770/66.

RADCHENKO, T. H.
1964. [THE INFLUENCE OF POLLINATION ON THE CROP AND THE QUALITY OF SEED OF WINTER RAPE.] Bdzhil'nitstvo 1: 68-74. [In Ukrainian, Russian summary.] AA- 380/69.

RAHMAN, K. A.
1940. INSECT POLLINATORS OF TORIA (BRASSICA NAPUS LINN., VAR. DICHOTOMA PRAIN) AND SARSON (B. CAMPESTRIS LINN., VAR. SARSON PRAIN) AT LYALLPUR. Indian Jour. Agr. Sci. 10(3): 422-447.

RHEIN, W. VON.
1952. [RESULTS OF TRAINING BEES BY SCENT DURING THE 1952 RAPE FLOW.] Hess. Biene 88(8): 192-194, (9): 218-220. [In German.] AA- 220/53.

VASIL, I. K.
1964. EFFECT OF BORON ON POLLEN GERMINATION AND POLLEN TUBE GROWTH. In H. F. Linskens, ea., Pollen Physiology and Fertilization, pp. 107-119. Symposium held in August 1963 at Nijmegen Univ., The Netherlands.

VESELY V.
1962. [THE ECONOMIC EFFECTIVENESS OF BEE POLLINATION ON WINTER RAPE (BRASSICA NAPUS L., VAR. OLEIFERA METZ.).] Min. Zemedel. Lesn. a Vodniho Hospodar. Ust. Vedtech. Inform. Zemedel. Ekon. 8(9): 659-673. [In Czech., German summary.] AA-866/65.

WHITE, B.
1970. POLLINATION OF COMMERCIAL RAPE SEED CROPS. Australasian Beekeeper 72(4): 99-100.

ZANDER, E.
1952. [RAPE AND BEES.] Z. Bienenforsch. 1(8): 135-140. [In German.] AA-121/54.