Farmers being observant with seed treatments at planting and pesticide applications during the growing season could minimize ill effects on bee populations, according to Iowa State University entomologists.

In a U.S. Department of Agriculture and Environmental Protection Agency report released last week, several possible causes of national decline in honeybees were outlined, including habitat loss, poor diet, diseases, parasites and pesticide exposure.

Research so far points to a combination of these factors that may be responsible for the 30 percent decline in honeybees annually since 2006.

Bees through their role in pollination are considered to be directly or indirectly responsible for about every third bite of food we eat, according to the USDA.

Crops that are predominantly pollinated by honeybees have an estimated value of more than $215 billion annually worldwide.

Matt O'Neal, Iowa State associate professor of entomology, and Erin Hodgson, assistant professor and ISU Extension and Outreach entomologist, said the insecticides are used to protect the germinating seed from pests.

They advised cleaning seed treatment residues from planting equipment away from fields and minimizing off-site dust movement from treated seeds.

By taking these precautions, farmers could help minimize bee exposure to a class of insecticides, called neonicotinoids, that some studies have identified as a particular concern.

Using the recommended rate of lubricants that aid the flow of seed through planters is another way to minimize exposure to bees, as well as being aware of wind speed and direction around flowering plants when applying pesticides, they said.

Alerting local beekeepers of upcoming pesticide applications is an important practice. The Iowa Department of Agriculture and Land Stewardship maintains an Iowa Sensitive Crops Directory that includes the locations of hives (http://www.iowaagriculture.gov/Horticulture_and_FarmersMarkets/sensitiveCropDirectory.asp).

O'Neal said farmers can encourage bee populations by growing native perennial plants around agricultural fields to improve foraging habitat. He includes specific recommendations in a recent ISU publication by the Leopold Center for Sustainable Agriculture: http://www.leopold.iastate.edu/pubs-and-papers/2013-01-conserving-beneficial-insects-native-plants.

Hodgson and O'Neal have written an article about bee health recommendations for Integrated Crop Management News: http://www.extension.iastate.edu/CropNews/2013/0508onealewh.htm.