Effects of thiamethoxam seed treatments on soybean aphid (Hemiptera: Aphididae) feeding behavior.
Since its discovery in North America in 2000, the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), has rapidly become an important pest of soybean [Glycine max (L.) Merrill], sometimes resulting in significant yield losses. Previous research has documented the toxicity of neonicotinoid seed treatments to soybean aphids, but control under field conditions has been inconsistent. Imidacloprid, a popular neonicotinoid insecticide, has been shown to exhibit antifeedant effects on aphids. Antifeedant activity has not been demonstrated for other neonicotinoids, including thiamethoxam. This research investigated the effects of a thiamethoxam seed treatment on soybean aphid feeding behavior by using electronic penetration graphs (EPG) to visualize stylet penetration behavior. Soybean aphid feeding behavior was assessed for 9 h on thiamethoxam-treated and untreated soybeans (V2 and V4 stages). Because results were inconclusive from initial experiments, a study was conducted to document the effects of thiamethoxam-treated soybeans on soybean aphid survival. The seed treatment was shown to negatively affect aphid survival at 4, 8, and 11 d after aphid introduction. A subsequent EPG study then was designed to document soybean aphid feeding behavior for 15 h, after an initial exposure of 9 h to thiamethoxam-treated soybeans. In this study, the exposed aphids exhibited significant differences in feeding behavior compared with those aphids feeding on untreated soybeans. Soybean aphids on thiamethoxam-treated soybeans spent significantly less time feeding in the sieve element phase, with a greater duration of nonprobing events. These studies suggest soybean aphids are unable to ingest phloem sap, which may be another important element in seed treatment protection.
Department of Entomology, University of Nebraska-Lincoln, 103 Entomology Hall, Lincoln, NE 68583, USA. mstamm3@unl.edu
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Stamm
Department of Entomology, University of Nebraska-Lincoln, 103 Entomology Hall, Lincoln, NE 68583, USA.
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Heng-Moss
Department of Entomology, University of Nebraska-Lincoln, 103 Entomology Hall, Lincoln, NE 68583, USA.
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Baxendale
Department of Entomology, University of Nebraska-Lincoln, Haskell Agricultural Laboratory, Concord, NE 68728, USA.
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Reese
Department of Entomology, University of Nebraska-Lincoln, 103 Entomology Hall, Lincoln, NE 68583, USA.
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Siegfried
Department of Entomology, University of Nebraska-Lincoln, Haskell Agricultural Laboratory, Concord, NE 68728, USA.
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Hunt
Department of Agronomy and Horticulture, University of Nebraska-Lincoln, 202H Keim Hall, Lincoln, NE 68583, USA.
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Gaussoin
Department of Statistics, University of Nebraska-Lincoln, 343B Hardin Hall North, Lincoln, NE 68583, USA.
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Blankenship
D000818:Animals; D001042:Aphids / Q000187:drug effects* / Q000502:physiology; D055724:Electrophysiological Phenomena; D005247:Feeding Behavior; D005260:Female; D007306:Insecticides / Q000633:toxicity*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000633:toxicity*; D010078:Oxazines / Q000633:toxicity*; D013025:Glycine max; D000077922:Thiamethoxam; D013844:Thiazoles / Q000633:toxicity*
D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010078:Oxazines; D013844:Thiazoles; D000077922:Thiamethoxam