HAVE A THOUGHT FOR THE BEES

Press, 2 September 1977, Page 15

HAVE A THOUGHT FOR THE BEES

Kale, rape and turnip crops flower from September to January and the profusion of bright yellow blooms is very attractive to bees. The bees gather pollen and feed honey from the flowers and at the same time they cross pollinate them to ensure maximum seed yields.

The natural relationship between brassica plants and honey bees is, therefore, of mutual benefit to both growers and beekeepers, and it must be safeguarded. Unfortunately, all brassica seed crops are prone to attack by cabbage aphids, which may have to be controlled with an insecticide. If the systemic materials used are applied to flowering crops, the flowers remain toxic to bees for up to five days.

The solution to the problem of chemically controlling aphids without killing bees is to control them outside the flowering period and, as a rule, this can be done very successfully.

When spraying is not necessary before flowering, which it often isn’t, if a few aphid colonies are found during the flowering period spraying is rarely warranted until flowering has finished. It is illegal (under the Apiaries Act, 1969) for growers to use insecticides on flowering brassica crops or crops containing flowering weeds, unless a permit is ob-

tained from the Ministry of Agriculture and Fish eries.

Such permits are very rarely issued, because if a flowering crop was to be sprayed all hives of bees within a three kilometre

radius of the crop would have to be moved out of harm’s way. This is laborious, costly and very much against the interests of growers and beekeepers.

Spring-sown oil seed rape, which is being grown on an increasing scale, presents special problems. It flowers later than the other brassicas, in December or January, depending on thelocation and seasonal conditions. The usually * drier ground conditions at that time, coupled with higher

temperatures, can cause moisture stress in some crops. When this situation occurs affected crops become particularly vulnerable to aphid attack and they can suffer heavy levels of infestation. The fact that white clover flowers concurently with oil seed rape make the movement of hives away from crops an unacceptable proposition. White clover depends entirely on honey bees for pollination, and it is the main source of the honey crop.

Spraying of flowering oil seed rape crops is not permitted, and in fact it will not be permitted unless an insecticide can be found that can be used to control aphids without killing honey bees. Compared with the other brassicas, oil seed rape has a brief flowering period, and aphids can be satisfactorily controlled by using a granular systemic insecticide at sowing and spraying crops after

The accompanying item on crop spraying and protecting honey bees has been written by V. A. Cook, apiary instructor. Ministry of Agriculture and Fisheries, Oamaru.

flowering, where this is warranted.