Researchers Urge More Careful Use of Soybean Seed Treatments

February 17, 2016 03:12 PM
Researchers Urge More Careful Use of Soybean Seed Treatments

A new joint publication from 12 Midwestern universities suggests that soybean farmers are failing to use neonicotinoid soybean seed treatments properly. According to “The Effectiveness of Neonicotinoid Seed Treatments in Soybean,”  growers are overusing neonicotinoid seed treatments in soybeans.

It’s a different perspective on neonicotinoids, which the paper says is a valuable technology for growers. The researchers note in the publication that neonicotinoid seed treatments offer young soybean plants a three-week window of protection after planting. That can make them quite useful for managing early season pests.

However, the researchers also say the treatments’ usefulness is primarily confined to “targeted, high-risk situations” such as:

  • Fields that have recently been converted from CRP or grassland to soybean production.
  • Fields with animal manure, green cover crops or numerous weeds present.
  • Double-crop or specialty (food-grade or seed) soybean fields.

Other high-risk scenarios are relatively uncommon in Midwestern states where soybeans are grown. For example, wireworms, white grubs and seedcorn maggots do not often reach economically damaging levels. And adult bean leaf beetles tend to cause cosmetic damage only in newly emerged soybeans.

Unfortunately, these seed treatments have little value controlling one of the biggest soybean pests – the soybean aphid. Neonicotinoid seed treatments are labeled for soybean aphid, but thresholds usually occur midsummer, or weeks after the seed treatment’s window of protection has ended. Meantime, natural predators such as Asian lady beetle, parasitic wasps and others often suppress earlier season infestations of soybean aphid.

Chris DiFonzo, field crops entomologist with Michigan State University, says medical patients have an expectation to know why a doctor wrote a particular prescription, and that farmers should have the same expectation when considering insecticidal seed treatments and other crop inputs.

“Why shouldn’t we be equally as curious about the insecticides we use?” she says. “Insecticidal seed treatments control only a few types of insects well, and for only a short time after planting. I am not saying that neonic seed treatments aren’t justified – they just are not justified as often as they are used in soybeans.”

“That said, I recognize that it may not be easy to get seed treated with fungicide only, for example,” DiFonzo adds. “Many dealers offer only combo products, or only guarantee seed treated with a full package of insecticide and fungicide. If growers want more choice in seed treatment in the future, the message is they have to speak up and be persistent.”

The report also addresses several risks of neonicotinoid seed treatments, including toxicity to bees and other pollinators. The EPA is in the middle of risk-assessment reviews for all major neonicotinoids, including imidacloprid, clothianidin and thiamethoxam. Dockets of these assessments can be found at:

According to a Bayer response to the EPA report: “[Neonicotinoids] have been widely adopted by growers because of their favorable human and environmental safety profile, especially when compared to the older products they replaced. Neonics are critically important to today’s integrated pest management programs, allowing farmers to manage destructive pests, preserve beneficial insects and protect against insect resistance.”

The researchers in the 12-university report recommend an integrated insect pest management plan, including crop rotation, conservation of natural enemies, planting pest-resistant varieties, and scouting and applying insecticides at established thresholds.

To read the entire report, visit

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