The following is an excerpt of the paper “The Effectiveness of Neonicotinoid Seed Treatments in Soybean,” published by Purdue University. The publication reviews current research on neonicotinoid’s efficacy, non-target effects and potential role in soybean production.
Neonicotinoid seed treatments offer soybean plants a narrow window of protection — a maximum of 3 weeks after planting (McCornack and Ragsdale 2006). As such, they can be useful for managing early-season pests in targeted, high-risk situations.
Examples of such high-risk situations include:
- Fields transitioning to soybean production from pasture, Conservation Reserve Program (CRP) land, or grassland to soybean production. Such fields tend to have higher populations of long-lived soil pests, such as wireworms or white grubs, which cannot be controlled with foliar insecticides.
- Fields with recently incorporated animal manure, green cover crops, or weeds. These fields tend to be more attractive to seedcorn maggot, because females lay eggs in rotting organic material.
- Second (double) crop or specialty (food-grade or seed) soybean. During soybean aphid outbreaks, aphids may migrate from mature soybean plants to colonize later-planted plants in a double-crop situation. In food-grade or seed soybean, early season insect pests can vector diseases that affect crop quality. For example, bean leaf beetle transmits bean pod mottle virus.
These high-risk scenarios are uncommon in northern states. Seed and seedling pests such as wireworms, white grubs, and seedcorn maggots rarely reach economically damaging levels in the vast majority of soybean field. Adult bean leaf beetles are frequently encountered in newly emerged soybean, but they rarely cause more than cosmetic injury to plants.
It is critical to remember that soybean plants are resilient and can tolerate considerable early-season damage without suffering economic loss. Recent field studies support this point: yield benefits attributed to neonicotinoid seed treatments are inconsistent or absent (Seagraves and Lundgren 2012; Gaspar et al. 2014, 2015). The U.S. EPA extensively reviewed published and unpublished data regarding the yield benefits and concluded that “neonicotinoid seed treatments likely provide $0 in benefits to growers” (USEPA 2014).