What is the main cause of bee poisonings related to insecticides?

The main cause of bee poisonings related to insecticides is primarily due to insecticides being applied during bloom. When insecticides are sprayed on flowering plants, bees can come into direct contact with the chemicals as they forage for nectar and pollen. This timing is critical because it coincides with the bees’ activity and their reliance on blooming plants for food sources. During this period, the risk of bee exposure to harmful chemicals significantly increases, leading to poisoning and adverse effects on bee populations.

In contrast, the other options, such as pesticides in soil or insecticides sprayed directly on nests, are less commonly associated with widespread bee poisonings during peak foraging times. These scenarios may be harmful but do not generally present the same level of risk to bees as applications made while plants are in bloom. Over-application of herbicides is also not a direct factor leading to insecticide-related bee poisoning, as herbicides primarily target plants and have different mechanisms of action that do not typically impact bees in the same manner as insecticides.