Date of this Version
Soybeans are an abundant and valued agricultural crop in Nebraska and other parts of the world. Significant soybean aphid, Aphis glycines Matsumura, mortality has been observed in research plots adjacent to soybeans treated with chlorpyrifos in late July through August. The objectives of the study were to determine the efficacy of the chlorpyrifos vapor effect on A. glycines in adjacent untreated areas and assess the impact of the vapor effect on key biological control agents. Observation of A. glycines populations and sweep net samples for other arthropod species, including Oruis insidiosus, began weekly in mid to late July. When aphid levels reached economic thresholds, chlorpyrifos formulation Lorsban Advanced® was applied to designated spray areas. Weekly assessments continued to monitor populations both in the spray areas and at set distances from the spray areas. Results from the 2013 field season suggest an area of eight to sixteen rows may be left as untreated zones. Results from 2014 field season are inconclusive due to crop failure. Laboratory predation studies observed consumption rates of a key biological control agent, O. insidiosus. Studies measured life stage choice of A. glycines by O. insidiosus, consumption rates at each life stage, and video recordings were used to quantify behavior. There was no significant difference in a preference for A. glycines life stage by O. insidiosus (χ2 = 1.73, df = 2, P = 0.4204). Orius insidiosus consumes increasing numbers of aphids over a 24-hour period, consuming more early stage than late stage aphids, and more late stage than adult A. glycines. Behavior recordings suggest O. insidiosus returns to previously attacked, but unconsumed A. glycines.
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