When this happens, the hive is at a minimum greatly weakened and stressed by losing the field bees for a week or more. Residue-type pesticides also cause loss of successive generations. Hives weakened by pesticides often will not recover sufficiently before winter to survive. Beekeepers facing the continual depopulation of their hives stop keeping bees in the area, further depleting the pollination forces. This is one reason bees are moved in for pollination and then out after bloom, in spite of the inconvenience and cost.
Beekeepers can generally do nothing to prevent pesticide kills.
It is impossible to monitor spraying within a two mile radius of the hive. The low profit margin on honeybees also restricts the amount of monitoring of individual hives, thus delaying discovery of a pesticide kill until it is almost impossible to determine when it occurred, the pesticide used, and the source. Losses to predatory mites, drought, floods, and pesticide kills, all effect the beekeeper and pollination fees, which have doubled in northwestern USA in the last three years. The farmer and the bee man should be friends. If they aren't, neither one will be in business for long.