Matt O’Neal, Erin Hodgson, and Thelma Heidel-Baker
Department of Entomology
Iowa State University
For small farms that grow a diversity of fruit and vegetables, pollinators can be essential for crop production. Even though much of Iowa is committed to producing corn and soybeans, a remarkably diverse community of bees persists in the landscape. Although the conversion of native prairie to farmland has likely negatively affected this community, many species are still active and can contribute to crop pollination. In a recent research project directed by Matt O’Neal at Iowa State University, over 40 pollinator species were collected in soybean and corn. These included social bees like honey bees and bumble bees, as well as solitary bees and flies. Below, we describe several approaches to conserving bees so that small farms can get the most out of the service they provide.
What Farming Practices Hurt Bees?
Certain farming practices can be harmful to bees, such as removing native plants that provide food and shelter. Although corn and soybean do not require insect pollination to produce seed, many bees will forage in these crops for pollen and nectar. A landscape made up of mostly corn and soybean does not provide all the resources bees need to survive. These crops generally have a short window of pollen and nectar production, leaving pollinators without sufficient food for most of the spring and fall. Furthermore, removing perennial vegetation and tilling soil can disturb bees that build nests in the ground.
Most of the insecticides used in Iowa agriculture are highly toxic to honey bees and other pollinators. Pollinators are sensitive to insecticides and often die upon direct contact with broad spectrum products. The impact of insecticide exposure can be sublethal as well, as observed when bees are exposed to low doses through pollen and nectar.
What Can I Do to Help Pollinators?
A small acreage farm owner can take several practical steps to protect and enhance pollinators. These insects have two basic needs for survival: food and shelter. Pollinators need pollen and nectar throughout the spring, summer and fall. A best practice for helping pollinators is to plant a mixture of native, perennial plants that provide flowers throughout the growing season. Scientists at Michigan State University have tested many native plants commonly found in Midwestern prairies (http://nativeplants.msu.edu/plant_facts). Research conducted at ISU with the most attractive of these plants has shown that even a simple mixture of an early season blooming plant with a later season blooming plant can increase the abundance and diversity of bees. For example, planting Zizia spp. and cup plant will provide higher quality pollen and nectar compared to the crops grown commonly in Iowa, like corn, soybean, and alfalfa.
Not only do bees need food, but they also need shelter for nesting. By providing open areas (e.g., sandy ground, brush piles, etc.), ground nesting bee queens will be able to create a nest more easily. Some solitary bees nest in hollow plant stems or decaying wood. Providing artificial bee houses can encourage these pollinators to stay in an area and dramatically improve flower pollination.
How Can I Reduce Insecticide Exposure to Bees?
Anyone using an insecticide is required to follow the instructions on the label. These instructions likely include details on reducing bee exposure to insecticides, like when plants are blooming or when bees are actively foraging during the day. Furthermore, consider applying an insecticide only when needed. Instead of applying insecticides in a prophylactic manner, consider scouting fields and using density thresholds. Some pests can even be managed without insecticides.
Our understanding of pollinator biology, ecology and management is growing rapidly. Only a few decades ago did we think of the honey bee as the most important if not only commercial pollinator. Now there are commercial sources of other bees for farmers to use in their crops, and we have learned that native solitary bees are a significant source of crop pollination. Stay tuned for updates!