Beekeepers in Ohio benefitted from the generally mild winter of 2015-2016. In Columbus we lost less than 20% of our colonies over winter. Spring is the only reliably good season for bees in Ohio. Colonies that survived the winter and new colonies brought up from the Gulf Coast or California are currently in the process of harvesting nectar and pollen from spring-blooming trees and weeds. Little honey will be made from this spring bounty as most will be eaten by the bees themselves as they multiply and grow into large productive colonies that will be able to make a honey crop off of clovers, black locust, alfalfa and soybean in the coming months. Additionally, robust colonies will be needed to pollinate the fruit trees soon and pumpkins, squash and cucumbers later in the summer.
Spring build-up of honey bee colonies can be directly threatened by corn planting. Insecticide seed treatments used on corn seed generate an insecticidal dust when they are planted. Bees may encounter a cloud of insecticidal dust as they cross corn fields to visit the dandelions and blooming trees in field margins. Insecticidal dust can also settle on these flowers that bees are visiting. Insecticides formulated as dusts are the absolute worst for honey bees because they do not immediately kill the bees that encounter the insecticide. Rather than causing immediate death, the dust is packed up with the pollen and brought back to the colony where it is fed to young bees inside the colony.
In spring of 2015, we sampled pollen from ten bee yards in the counties west of Columbus. During corn planting, all colonies were bringing back pollen containing corn seed treatment insecticides. While no spectacular bee-kills were observed in our colonies, we did observe a significant increase in the number of dead bees appearing in front of colonies during the week of corn planting in 2015. While the long-term consequences of planting-related mortality are not clear, it is an unwelcome additional stress on bee colonies that are already under stress from mites, diseases and nutritional problems.
Corn growers can limit exposure of seed treatment dust to honeybees by 1) starting with clean and weed-free fields; 2) following recommendations for using talc; 3) avoid planting on windy days; and 4) following proper disposal procedures when finished.