The Questionable Benefit of Neonicotinoid Seed Treatments to Soybeans
Posted: November 4, 2014
Insecticidal seed treatments are ubiquitous on corn seed, with about 95% of seed being treated with a neonicotinoid insecticide. For soybeans, the trend is moving in that direction with a higher percentage of soybean seeds being treated each year. As of 2012, the percentage of soybean seeds receiving a neonicotinoid insecticide is thought to have been around 40%. These insecticides target early season insect pests, like seedcorn maggot, wireworm, and bean leaf beetles, that are very sporadic in most years, and difficult to find in some.
Research that we have conducted at Penn State with soybeans in Lancaster and Centre Counties fails to consistently show yield benefits associated with insecticidal seed treatments. This lack of a yield benefit from neonicotinoid seed treatments on soybeans has also been found repeatedly by colleagues at Universities across the cornbelt. Layered on top of this lack of a yield benefit is mounting evidence that neonicotinoids from seed treatments can pollute water and decrease populations of native insects and even insect-eating birds. Recall also that Penn State research with these seed treatments has demonstrated that they exacerbate slug populations and the damage they cause.
Now the Environmental Protection Agency has published an analysis of the benefits of neonicotinoid seed treatments on soybeans. This report is available online. Here is the conclusion of the report: “EPA concludes that these seed treatments provide little or no overall benefits to soybean production in most situations. Published data indicate that in most cases there is no difference in soybean yield when soybean seed was treated with neonicotinoids versus not receiving any insect control treatment.”
(One of the reasons that EPA issued this report is to solicit comments from the public to see if they agree or disagree with the conclusions of the report. If you feel strongly, one way or another, you can visit the same website listed above and follow the “comment” link to provide your opinion.)
What does this mean for soybean growers of PA? It means that you are likely not getting much protection from the insecticidal portion of the treatments you are buying, and that you are likely to get the same yield by growing soybeans without insecticidal seed treatments. This does not mean that you have to leave your soybeans unprotected. Integrated Pest Management (IPM) is a proven approach to managing insect pests. If your soybeans develop damaging populations of insect pests, use IPM to determine if applying a treatment makes sense. As always, I encourage growers to use IPM and use insecticides only when they are likely to provide a return on the investment.