Many fields here in southern France this spring are bright yellow, full of the plant called “colza.” This oilseed rape relative (Brassica napus L. var. oleifera) and hybrids are relatively new to this region. They require insect pollination, but the environmental conditions are often unstable when they bloom, meaning many pollinators are simply not available. Enter the one manageable pollinating insect vector, Apis mellifera, the honey bee. This insect is also used in sunflower seed production for oil, thus the event of January 9, 1997 in Toulouse, France called “A Day of Information Exchange Concerning the Pollination of Oil-Seed Crops.” This event was reported by F. Jéanne in Bulletin Technique Apicole (No. 93, Vol. 23 (1) 1996, pp. 7-22), published by the O.P.I.D.A. F61370 Echauffour, FRANCE, a cooperator with E.D.A.P.I .
This meeting, Mr. Jéanne says, was organized by l’Association Nationale des Agriculteurs Multiplicateurs de Semences Olégineuses (ANAMSO). Part of the event was a report of a survey of the ANAMSO membership concerning use of honey bees. Among those responding, 49.6 percent of colza growers used hybrid varieties, 40.4 percent used the original (classic) plant and rest used both. Of those growing the classic plant, 32.8 percent saw use of honey bees in pollination as advisable, 8.19 percent considered it mandatory. In hybrid production, 94 percent of growers used bees. For sunflower seed production, 56 percent considered honey bees mandatory in the pollination process.
Ninety percent of hives used in colza and sunflower seed production were there at the grower’s request, according to the survey. Eighty-three percent were rented by verbal agreement. The number of hives per hectare (2.47 acres) varied between one and five (one or two most frequent for colza; two for sunflower). The hives were generally moved in at grower’s request, but located by beekeeper preference. The average price was 136 FF (US$ 24) with a range of 50 FF (US$ 9) to 500 (US$ 89 ).
Pesticide treatments are necessary in colza, but the survey shows that over 90 percent of growers took necessary precautions when bees are present. These included selecting less toxic compounds and applying them when bees are not foraging. Warnings related to bee toxicity are routinely carried on the labels of products used in the field. Participants agreed that all the elements leading to a good pollination effort in colza were not known.
Jacqueline Pierre and Michel Renard, scientists from INRA (the French equivalent of USDA) presented their findings concerning colza pollination at the meeting. Colza is a hermaphroditic plant (has both female and male flowers). The stigma is receptive before the anthers begin to produce mature pollen. The stigma is good for only about six hours. One male flower produces about 100,000 pollen grains; one hundred are deemed sufficient for self-pollination in classic colza. For hybrid see, however, cross-pollination is needed between male and female varieties. These are planted in rows, one male to four female. Care must also be taken that competing crucifers, including other varieties of colza, are not nearby to ensure purity in the resultant seeds.
The most important condition for pollination in hybrid colza is synchronized flowering. Thus, it is essential that a complete pollination effort is maintained, according to authors. The presence of honey bees accelerates and stabilizes the pollination endeavor, and results in less risk of accidental pollination by undesirable varieties or related plants. Nectar collecting honey bees are those responsible for the pollination; this produces a greater effort in the field than if just pollen collectors were responsible. Because honey bees are generally faithful to one plant, it is advisable not to introduce them into colza plantings until at least 5 percent of the plants are in flower. Purity is essential in colza hybrid seed production; the quality of the seed also depends on choice of parents and conditions under which they are grown.
A paper presented by Minh-Há Pham-Delegue of INRA described results concerning the relationship of honey bees and transgenic colza. The development of transgenic varieties through genetic manipulation has provided some new properties to plants. These include production of protease inhibitors (PI) which confer resistance to fungi and insects. The overall strategy in this technology is to develop plants that require less insecticide use. In transgenic plants, however, chemicals produced by genes designed to inhibit insect feeding or prevent fungal growth may also affect pollinating insects in two ways according to the author:
1. Direct effect on colonies from proteins in nectar and pollen.
2. Indirect effect in foraging behavior by modification of nectar, pollen or other volatile substances.
The results of the studies reported by the author indicate significant differences in quantity of nectar found in various transgenic varieties. Other investigations on pollen composition and structure are continuing. Comparing volatile emissions between transgenic colza and control plants also indicates that genetic transformation can modify existent plant odors. In other studies, analysis of larval intestinal proteins of adult worker bees fed PI does not show a higher-than-normal level. In addition, no apparent toxicity was found when measuring bee mortality in the same way it is done for pesticides. Finally, no inter-genotypic preference by worker bees was found.
Colza is also now being grown across the southeastern United States. It is called canola and can produce a good honey crop as it does in France. I have seen relatively little information on the plant, but concerns about its culture and pollination are likely to be similar. A chapter dealing with canola is due to be published soon in an upcoming book authored by Drs. Keith Delaplane and Dan Mayer.
In a somewhat parallel study on sunflowers, the same author found that nectar composition played a role in pollinator selection, principally due to the amount of sweet found. The floral odors were also variable, resulting in the conclusion that selection of both male and female lines with similar nectar compositions and odors is necessary for optimum pollination by honey bees for production of hybrid seed.
In another paper “Honey Bees and Apiculture: Their Pollination Role,” F. Jéanne provided a discussion of the essential elements in pollination contracts. He concluded that commercial pollination is not the purview of the amateur beekeeper. The activity requires a full-time commitment from a professional beekeeper who can bring the three constituents of a successful hybrid-see pollinator together:
1. Strong hives.
2. Availability of colonies when and where the grower wants them.
3. Size enough to put many colonies on a pollination job.
For their own protection, Mr. Jéanne said, commercial pollinators must demand written contracts dictating when colonies are moved in and out and the number of pollinators (pollinating units) expected by the grower. The goal he said is not how many hives per/hectare, but the number of forager honey bees per unit area.