Putting beneficial insects to work for you

Jamison Scholer, MDA Research Scientist, Jolene Warnke, UMN Pesticide Safety and Environmental Education Extension educator, and Tana Haugen-Brown, UMN Pesticide Safety and Environmental Education Extension educator

Responding to pest threats that emerge in your crop fields and supporting beneficial insects (predators and pollinators) living around your farm doesn’t need to be mutually exclusive. Thoughtful consideration of pesticide selection, use timing, and application method can give you the benefits of both. Supporting beneficial insects that call your lands home means more tools in your arsenal to maximize yields and minimize pesticide inputs when economic thresholds are followed. For example, in soybean, pollinator visitation can increase yield in many nectar producing varieties^{1, 2}. Maintaining untreated, uncultivated land around crop fields, such as field margins, ditches, conservation strips, etc., help support pollinators and predators that feed on crop pests and may reduce the need for pesticide inputs.

To support pesticide applicator’s efforts to use integrated pest management (IPM), the Minnesota Department of Agriculture has developed pollinator best management practices (BMPs): https://www.mda.state.mn.us/pesticide-fertilizer/best-management-practices-pollinators-their-habitat.

Ways to support beneficial insects

• Develop a pest management plan that incorporates a variety of pest management strategies.
  https://www.mda.state.mn.us/pesticide-fertilizer/how-practice-ipm
• Incorporate non-chemical control methods into your pest management plan to maximize the presence of beneficial insects that help control pest insects and weeds.
• Incorporate vegetative filter strips, grassed waterways, or other uncultivated lands adjacent to fields to support beneficial insects and to minimize erosion and pesticide movement.

Follow economic thresholds for target pests

An economic threshold, measured through pest scouting, indicates the timing of pesticide intervention that should prevent populations from increasing to levels that cause economic injury such as yield loss. Economic thresholds are conservative and deliberately set below the economic injury level to provide managers time to reduce pest populations before the risk of yield loss occurs.

• Consult with your local University of Minnesota Extension Office or independent crop consultant for specific pest thresholds.
• Resources for some Midwest pests:
  • Corn pests - https://extension.umn.edu/corn/corn-pest-management#leaf-feeders-and-defoliators-1209911
  • Soybean aphid - https://extension.umn.edu/soybean/soybean-pest-management
  • UMN Specialty Crop Guide - https://vegedge.umn.edu/pest-profiles
  • Midwest Vegetable Guide - https://mwveguide.org/

Selecting pesticide products

• Review the “Environmental Hazard” section of the pesticide product label for pollinator concerns and restrictions.
• When possible, consider products that have low residual activity to minimize impacts to beneficial insects.

Pesticide application and timing

• Follow label recommended nozzle type, boom height, spray buffer zone, and wind speed restrictions to minimize spray drift.
• Apply pesticides before 10 a.m. or after 5 p.m. when pollinator visitation is lowest.
• Apply pesticides when temperature inversions are not present.
• Avoid foliar applications when rain is forecast within 24-48 hours of application.
• Adopt new selective spray technologies when financially feasible.

References:

¹Forrester, K. C., Lin, C. H., & Johnson, R. M. (2024). Measuring factors affecting honey bee (Hymenoptera: Apidae) attraction to soybeans using bioacoustics monitoring. Journal of Insect Science, 24(2), 20.

²Lin, C. H., Suresh, S., Matcham, E., Monagan, P., Curtis, H., Richardson, R. T., & Johnson, R. M. (2022). Soybean is a common nectar source for honey bees (Hymenoptera: Apidae) in a Midwestern agricultural landscape. Journal of Economic Entomology, 115(6), 1846-1851.