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IPM is a Better Pest Management Investment for Soybean Aphid than Seed Treatment
Fri, Dec 4, 2015
IPM is a Better Pest Management Investment for Soybean Aphid than Seed Treatment
Figure 1
by Christian Krupke, Soybean Entomologist, Purdue University

Neonicotinoid seed treatments of soybeans represent one of the largest uses of insecticides on a per acre basis in the United States. With funding from the North Central Soybean Research Program, we have attempted to rigorously examine the benefits of this approach for soybean aphid management. The project addressed several applied questions that are of interest to soybean growers in the Midwest: Do insecticidal seed treatments reduce soybean aphids throughout the season?  How long is thiamethoxam (the neonicotinoid in Cruiser®) present in plant tissues?  Do yield results justify the cost of insecticidal seed treatment?

In a three-year study conducted by soybean entomologists in seven participating states (IN, MN, ND, SD, IA, KS, WI), we did the following: (1) measured concentrations of thiamethoxam in CruiserMaxx®-treated soybeans in soybean foliage throughout the season; (2) documented soybean aphid populations and yield in 6 and 7 states in 2012 and 2013, respectively -- comparing CruiserMaxx®-treated soybean seed with naked seed (either untreated entirely, or with a foliar insecticide at aphid threshold; (3) performed an economic modeling analysis to determine the probability and amount of a net return on seed treatment vs. an IPM approach (a foliar insecticide at threshold).

Major findings:
  • In the absence of aphid pressure, thiamethoxam (Cruiser®) provides no yield benefits
  • Thiamethoxam levels plummet to background levels (i.e., levels in untreated plants) by the V2 stage, well before aphid populations peak for the summer (Figure 1).
  • Thiamethoxam is not present in soybean pollen, which is good news for pollinators
  • In our region, IPM (foliar at threshold) offers an average net return of $21.02/acre with a 94.5% probability of at least breaking even, while for Cruiser® seed treatment, the average net return is $6.02/acre with a 66.2% probability of at least breaking even.
The relevance of this information for soybean producers is that IPM is a better pest management investment in the North Central region.  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. For more information, view the webinar  Soybean Aphid Management Using Neonicotinoid-Treated Seed, hosted by the Plant Management Network.