Editor's note: Reed Johnson is the lead author on this article
Beekeepers in Ohio suffered substantial losses of colonies over the exceptionally long and cold winter of 2013-2014. Here in Wooster we lost more than half of our colonies and beekeepers around the state are reporting levels of winter kill in the 30-80% range. While the frigid temperatures played a substantial contributing role, losses were undoubtedly made worse by all of the problems facing bees today: parasites, diseases, pesticides, breeding problems, and a general lack of summer and fall forage.
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 are in the process of harvesting nectar and pollen from spring-blooming trees and weeds -- but little honey will be made. This spring bounty 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 possibly soybean in the coming months. Additionally, robust colonies are needed to pollinate the fruit trees soon and pumpkins, squash and cucumbers later in the summer.
This spring build-up of honey bee colonies can be directly threatened by corn planting. Insecticide seed treatments used on corn seed produce an insecticidal dust when they are planted. Depending on conditions, this insecticidal dust can settle on the flowering trees and weeds that bees are visiting. Insecticidal dusts are terrible for honey bees because they do not immediately kill the bees visiting flowers. Rather than causing immediate death, the dust is packed up with the pollen and brought back to the colony where it is can poison young and developing bees inside the colony.
In spring 2013 we sampled pollen from three bee yards in Madison, Union and Clark Counties. During corn planting all colonies were bringing back pollen containing corn seed treatment insecticides, sometimes at levels that would be expected to cause bee death. While no obvious bee-kills were observed in our colonies in 2013, we believe that different conditions during planting could have led to a different outcome. In 2013 corn planting in central Ohio coincided with the start of bloom for fruit trees and hawthorns – extremely attractive flowers for bees – which likely drew bees away from the riskier and somewhat less attractive dandelions, mustards and purple deadnettle growing in corn fields and on field margins. In some years planting may happen before or after fruit tree bloom when bees are intensely interested in weeds growing in and near fields. This may have been the case in Ohio in 2012 when planting started early and a number of bee-kill incidents were reported.