You might want dig into the question of whether or not treating soybean seed with a neonicotinoid insecticide is a good idea this year.

Neonics (pronounced Nee-Oh-Nicks) were used on 40% of the soybeans and 80% of the corn in the U.S. in 2011.

Michael McCarville, a seed growth technical service manager for Bayer CropScience, which markets a neonic, says on average the compound increases soybean yields 2-2 ½ bushels per acre. It costs about $6-$10 per acre, depending on seeding rate.

Neonics are especially effective when planting early, when weather is cool and when you are cutting back on the seeding rate, he says.

But 12 universities have published a new bulletin that concludes, “For typical field situations, independent research demonstrates that neonicotinoid seed treatments do not provide a consistent return on investment.”

Neonics have been linked by environmental and conservation groups to honey-bee colony collapse disorder, Monarch butterfly caterpillar deaths and a loss of birds due to a reduction in insect populations. In 2013, the European Union and several non-EU countries restricted the use of certain neonics. Several groups have filed suits against the EPA for accepting allegedly inadequate studies on neonics’ environmental impact.

Misses mark
In the Dakotas, neonics aren’t much of a help against the worst soybean pest – aphids, says Janet Knodel, North Dakota State University Extension entomologist, and one of the bulletin’s authors.

Even though neonics are labeled for control of soybean aphids, the seed treatment wears off long before the soybean aphids show up in July and August.

You are better off spraying soybeans with a foliar insecticide when and if aphid populations reach the economic threshold level in July or August, she says.

For farmers in South Dakota, neonicotinoid seed treatments in soybean are capable of providing important early season management of soil dwelling insect pests such as wireworms, grubs, and seedcorn maggots, Adam Varenhorst, South Dakota State University Extension entomologist. “They can also provide management of early season defoliators such as bean leaf beetle adults. They should not be used as a management tool for late season pests including soybean aphids. Decisions to use these products for early season pests should be made based on previous insect pest pressure in the field, and whether field conditions at planting favor infestation,” he says

Key points
Key points from the report, include:

* Neonic seed treatments only protect soybean plants for about three weeks after planting 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 grasslands and fields fertilized with manure. These fields tend to have higher populations of long-lived soil pests, such as wireworms or white grubs, which cannot be controlled with foliar insecticides. “All of these high-risk scenarios are uncommon in northern states,” Knodel says. Seed and seedling pests such as wireworms, white grubs, and seed corn maggots rarely reach economically damaging levels in the vast majority of soybean fields. Adult bean leaf beetles are frequently encountered in newly emerged soybean, but they rarely cause more than cosmetic injury to plants. Soybean plants are resilient and can tolerate considerable early-season damage without suffering economic loss, she says.

* Neonic seed treatments may pose risks to non-target organisms in two basic ways: Off-target movement of planter dust and leaching from runoff and tile drainage. Planter dust contains high concentrations of neonic insecticides that can move beyond field margins and land on flowers and other vegetation, exposing non-target insects, including honey bees and other pollinators, to the insecticide. Because neonics are highly soluble and can move easily in water, residue in runoff and tile lines may collect in ponds, ditches or creeks. There it may affect arthropods, which form the basic on of complex food chain. Neonicotinoid residues also may be absorbed by plants, including milkweed, the food source for monarch butterfly caterpillars.

* There is a risk of insects becoming resistant to neonics. When growers repeatedly plant neonic-treated seeds in fields where no economic levels of target pests occur, the rate at which resistance to neonics will occur accelerates. Foliar neonics applied to soybean during the season will further increase pressure on pests to evolve resistance.

For more information, download the publication here