Management of soybean aphid in narrow row soybean production

Across the Midwest, soybean production has been complicated by the arrival of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae). The economic injury level for soybean aphid was published in 2007 establishing a framework for soybean aphid management. One of the limitations of this existing economic injury level for soybean aphid is that it was derived from research conducted in only 76 cm rows, and there are questions as to the applicability of the existing threshold to soybean planted in narrow (20 cm) rows. My goal is to determine if the rate of decrease in soybean yield from aphid injury in 76 cm rows is applicable to soybean produced in narrow rows (20 cm). To determine the effect of aphid injury on soybean planted in narrow rows three aphid infestation levels (aphid-free control, 250 aphids per plant, and untreated control) will be arranged in a split block randomized complete block design, with aphid infestation level as the main affect and row spacing as the split affect (20 cm and 76 cm). The design will be established at two locations within two states (Iowa and South Dakota). Aphids will be allowed to establish naturally, and populations will be maintained at the desired infestation levels using the insecticide lambda-cyhalothrin (234 ml per ha). Determining the effect of row spacing will either validate the existing economic thresholds or indicate that refinement of the existing threshold is needed for narrow row soybean production.