Reducing risk to pollinators in and near soybean

Farm Forum

Insecticides are an important tool in the IPM toolbox for protecting crop yields from pests. However, we need to keep in mind that many of the insecticides we use to manage crop pests are also toxic to beneficial insects, such as predators and pollinators. This article will provide an overview of some considerations for reducing the risk of impacting pollinators (e.g., bees and some flies) when foliar insecticide applications are made to crops.

Pollinating insects can occur in and near soybean fields. For example, a study published in 2015 by entomologists from Iowa State University documented more than 30 species of bees in Iowa soybean fields. Most of the bees collected were wild or native bee species. Less than 1% of the bees collected were the European honey bee. The authors also found that the bees occurred in fields throughout the R1 to R6 soybean growth stages and that some of the most abundant bee species were collecting soybean pollen.

The risk of pollinators being impacted by insecticide applications is a function of the toxicity of the insecticide and the exposure of the pollinators to the insecticide. As mentioned above, many of the insecticides used from management of crop pests, such as soybean aphid, are toxic to pollinators. Labels for some products/formulations with high toxicity to bees will provide specific directions for minimizing risk to pollinators. In general, to reduce the risk of impacting pollinator when using foliar insecticides to manage soybean aphid, we need to consider steps to reduce the exposure of pollinators to the insecticides. Some steps to consider are:

• Inform beekeepers in the area about planned insecticide applications (i.e., products and schedules). In Minnesota, lists locations of some hives.

• The number of insecticide applications made across the landscape can be reduced by using economic thresholds (i.e., 250 soybean aphids per plant, with most plants infested, and aphid populations increasing) and other IPM tactics (e.g., aphid-resistant soybean varieties).

• Insecticide applications made to fields when pollinators are less active (i.e., early-morning or late-evening) are generally less harmful.

• Avoid applying insecticides when conditions, such as wind speed, will promote drift of the insecticide to sensitive habitats.