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Research Highlights

Research Highlights
New Study Confirms that IPM is a Better Pest Management Investment for Soybean Aphid than Seed Treatment

by Christian Krupke, Soybean Entomologist, Purdue University

We recently compared neonicotinoid seed treatment for managing soybean aphid to an integrated pest management (IPM) approach that included monitoring soybean aphids and treating with foliar-applied insecticide only when the economic threshold was reached. 

The two-year study, conducted on a large geographic area, confirmed earlier studies that even during periods of aphid infestation, neonicotinoid seed treatment produced the same yields as using no insecticide at all.

The grower-funded study was conducted in Indiana, Iowa, Kansas, North Dakota, South Dakota, Minnesota, and Wisconsin with checkoff funds provided by the North Central Soybean Research Program. The results were recently reported in the April 2017 issue of Pest Management Science.

We found that by the V2 stage, the amount of thiamethoxam, the neonicotinoid insecticide applied as a coating to soybean seeds, in plant tissue was statistically similar to plants grown from untreated seeds.  As a result, when soybean aphid populations reached threshold levels, from late July to August, the insecticide levels in tissues of neonicotinoid-treated soybean foliage were similar to plants grown from seeds without the insecticide.  Therefore, thiamethoxam concentrations in foliage are unlikely to effectively manage soybean aphids for most of the pests’ activity period across the region.

relationship between neonicotinoids and aphid populations

Both the IPM treatment and thiamethoxam-treated seed resulted in significant reductions in cumulative aphid days when soybean aphid populations reached threshold levels. But while the IPM treatment resulted in significant yield increases, the neonicotinoid treatment produced the same yields as using no insecticide at all.

The relevance of this information for soybean producers is that an IPM approach, combining scouting and foliar-applied insecticide where necessary, remains a better pest management investment for soybean aphid in the North Central region, both in terms of protecting the yield potential of the crop, and in terms of break-even probability for producers. This is important because millions of dollars are spent in the region each year for a pest management product (insecticidal seed treatment) that doesn’t deliver good value.