Assessing the value and pest management window provided by neonicotinoid seed treatments for management of soybean aphid (Aphis glycines Matsumura) in the Upper Midwestern United States

This two-year study, performed in multiple Upper Midwest states, compared efficacy and value of managing soybean aphid with thiamethoxam coated seed to foliar applied insecticide triggered by an economic threshold (i.e. integrated pest management, IPM). Researchers also monitored plants grown from coated and uncoated seed to determine how long pest management effects persisted in the plants from seed coating (gauged by the amount of thiamethoxam found in leaves).

While both management techniques reduced cumulative days when aphid populations reached threshold levels, only the IPM method resulted in yield increases. Furthermore, net cost estimates for both pest management methods show that the IPM method was the most cost effective, whether aphid pressure was above and below economic threshold levels.

Regarding the coated seeds’ pest management effectiveness, the researchers found that coated seed had a limited efficacy window. More specifically, thiamethoxam levels sufficient to manage pests stayed in plants for two weeks after planting. That timeframe does not coincide with times when soybean aphid is at economically damaging levels (except for when farmers employ the uncommon practice of planting soybeans late). Researchers also noted that thiamethoxam levels in plants grown from coated and uncoated seed were comparable after the initial 2 week high-level window in plants grown from coated seed. Researchers suggested that the residues in plants grown from uncoated seed were caused by uptake of soil residues as the fields had been planted with coated seed in previous years.

Authors: 
Krupke, C. H., A. M. Alford, E. M. Cullen, E. W. Hodgson, J. K. Knodel, B. McCornack, B. D. Potter, M. I. Spigler, K. Tilmon, and K. Welch
Journal: 
Pest Management Science
Year published: 
2017