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Anthropod Management Tests



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Soybean grown in Iowa and most of the north central region of the United States has historically used low amounts of insecticide. However, the arrival of soybean aphid (SBA), Aphis glycines Matsumura, in 2000 has drastically changed soybean production. SBA causes direct economic yield losses from direct plant feeding. To date, SBA can be successfully managed by foliar insecticides, and timely scouting and applications will protect yield. Plots were established at the Iowa State University Northeast Research Farm in Floyd County, Iowa. Twenty five treatments were arranged in a RCB design with four replications (Table 1), and soybean (04RM148034 and 07JR801843) was planted in 30-inch rows using no-till production practices on 18 May. Each plot was six rows wide and 50 feet long. Only the CruiserMaxx Beans treatments contained an insecticide and fungicide seed treatment. There were two controls including an untreated control and ‘zero aphid’ control in which a tank-mix of insecticides (Warrior II + Lorsban Advanced) could be applied every time aphids were detected. Applications were made using a backpack sprayer and TeeJet (Springfield, IL) twinjet nozzles (TJ 11002) with 20 gpa of water at 40 psi. SBA were counted on randomly selected plants within each plot. The number of plants counted ranged from 20 to 5 depending on plant growth stage. All aphids (adults, nymphs and winged aphids) were counted on each plant. Summing aphid days accumulated during the growing season provides a measure of the seasonal aphid exposure that a soybean plant experiences. To estimate the total exposure of soybean plants to soybean aphid, we calculated ‘cumulative aphid days’ (CAD) based on the number of aphids per plant counted on each sampling date. Yields were determined by weighing grain with a grain hopper which rested on a digital scale sensor custom designed for each of the three harvesters. Yields were corrected to 13% moisture and reported as bushels per acre. One way ANOVA was used to determine treatment effects within each experiment and means separated using least significant difference (LSD) test (P = 0.05) in SAS. Data on accumulation of aphid days was log-transformed to meet the assumptions of ANOVA. Treatment impacts on yield were determined using untransformed data.


This article is from Anthropod Management Tests 37 (2012): F79, doi:10.4182/amt.2012.F79. Posted with permission.

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Entomological Society of America



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