Insect Management: The Reality of Neonics as a Seed Treatment

Soybean seed treatments now routinely include a fungicide (usually 2 or 3) and an insecticide. The most common insecticides used come from the neonicotinoid chemistry family. The question circulating the past year is: Does this insecticide add any value and is it really needed? The EPA released a paper stating that in their survey of data it did not add any economic value and its use should be discontinued.

So twelve Corn Belt universities set out to “review the current research regarding the efficacy of these neonicotinoid seed treatments, their non-target effects, and the potential role for neonicotinoid seed treatments in soybean production.” I guess they didn’t want the EPA to have the last word on the efficacy and value of seed treatment. Their questions and comments are below.

Do Neonicotinoid Seed Treatments Work in Soybeans? “Neonicotinoid seed treatments offer soybean plants a narrow window of protection—a maximum of three weeks after planting. As such, they can be useful for managing early-season pests in targeted, high-risk situations.”

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 fields. Adult bean leaf beetles are frequently encountered in newly emerged soybeans, 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.”

Seed Treatments Not Timed for Major Pests. “Soybean aphid is the most important insect pest of
soybeans in northern states, and it is listed on labels for neonicotinoid seed treatments. Recall that neonicotinoid seed treatments protect soybean seedlings for a short time window after planting (approximately three weeks). However, soybean aphid populations usually increase in midsummer during the late-vegetative and bloom stages of soybeans. In other words, populations increase to threshold levels weeks after the short window that neonicotinoid seed treatments protect plants.”

The current use of neonicotinoid seed treatments in soybean and other crops far exceeds pest pressures. The authors summarized the review of their own science and experiences. “For typical field situations, independent research demonstrates that neonicotinoid seed treatments do not provide a consistent return on investment.”

The authors point out that these seed treatments do pose some risk to non-tar¬get insects through off-target move¬ment and environmental persistence. Of course, they are referring to bees as one example. And repeated use could bring about resistance. While they don’t say to discontinue their use, the authors advise growers to use good IPM practices that include scouting, identifying pests, treating only when the pest reaches an economic threshold, and incorporating an array of best management practices to keep insects at bay. Click here to read the full publication.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com.