Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice

Journal of Economic Entomology, Jun 2015

Adams, A., Gore, J., Musser, F., Cook, D., Catchot, A., Walker, T., Awuni, G. A.

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Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice

J. Econ. Entomol. Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice Department of Biochemistry 1 Molecular Biology 1 Entomology 1 0 Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Delta Research and Extension Center (DREC), Mississippi State University , Stoneville, MS 38776 , USA 1 Plant Pathology, Mississippi State University , MS 39762 , USA 2 Department of Plant and Soil Sciences, Delta Research and Extension Center (DREC), Mississippi State University , Stoneville, MS 38776 , USA Two experiments were conducted at the Delta Research and Extension Center in Stoneville, MS, during 2011 and 2012 to determine the impact of water management practices on the efficacy of insecticidal seed treatments targeting rice water weevil, Lissorhoptrus oryzophilus Kuschel. Larval densities and yield were compared for plots treated with labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin and an untreated control. In the first experiment, plots were subjected to flood initiated at 6 and 8 wk after planting. Seed treatments significantly reduced larval densities with the 8-wk flood timing, but not the 6-wk flood timing. Overall, the treated plots yielded higher than the control plots. In the second experiment, the impact of multiple flushes on the efficacy of insecticidal seed treatments was evaluated. Plots were subjected to zero, one, or two flushes with water. All seed treatments reduced larval densities compared with the untreated control. Significantly fewer larvae were observed in plots that received one or two flushes compared with plots that did not receive a flush. All seed treatments resulted in higher yields compared to the untreated control in the zero and one flush treatments. When two flushes were applied, yield from the thiamethoxam and clothianidin treated plots was not significantly different from those of the control plots, while the chlorantraniliprole treated plots yielded significantly higher than the control. These data suggest that time from planting to flood did not impact the efficacy of seed treatments, but multiple flushes reduced the efficacy of thiamethoxam and clothianidin. Lissorhoptrus oryzophilus; flood; flush; seed treatment - The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most widely distributed and destructive early season insect pest of rice, Oryza sativa L., in the United States (Cave et al. 1984, Way 1990, Saito et al. 2005) . Native to North America (Saito et al. 2005) , this insect has been associated with rice since the crop was introduced into the United States (Bowling 1957) . In 1976, the rice water weevil was accidentally introduced into Japan (Pathak and Khan 1994) . It has now spread to major rice producing regions of Asia, and is now regarded as a global threat to rice production (Pathak and Khan 1994, Heinrichs and Quisenberry 1999, Stout et al. 2002b, Zou et al. 2004a, Saito et al. 2005) . Adult rice water weevils overwinter in bunchgrass or in leaf litter in wooded areas and emerge from overwintering in early spring (Shang et al. 2004) . After emergence from overwintering, adults feed on the leaves of rice and other aquatic grasses and sedges in flooded or unflooded fields (Tindall and Stout 2003) . Adults feed on the upper surface of the foliage, leaving narrow longitudinal scars parallel to the venation of rice leaves (Sooksai and Tugwell 1978, Cave et al. 1984, Zou et al. 2004b) . Feeding by the adult is not economically important. Oviposition in rice commences upon establishment of the flood (Stout et al. 2002b) . Peak oviposition generally occurs 1 to 2 wk after the flood is established (Wu and Wilson 1997). Rice water weevil adults oviposit in leaf sheaths at or below the water line (Stout et al. 2002b) . Following eclosion, larvae mine leaf sheaths for a short period before crawling down the plant to feed on the roots (Grigarick and Beards 1965, Bowling 1972, Cave et al. 1984, Wu and Wilson 1997) . Larvae progress through four instars and a pupal stage on roots before emerging as adults (Cave and Smith 1983) . Larval and pupal stages of this insect are spent almost entirely in flooded or water-saturated soils, where larvae feed on or in the roots of their hosts (Zhang et al. 2006) . Feeding by rice water weevil larvae results in stunted root systems, reduced tillering, reduced number of grains per panicle, and reduced grain weight (Zou et al. 2004b) . Yield losses from larval feeding typically approach 10%, but can exceed 25% under severe infestations (Stout et al. 2000) . Water management practices have a direct effect on rice water weevil behavior in rice production (Webb 1914, Whitehead 1954, Morgan et al. 1989, Thompson et al. 1994, Rice et al. 1999, Stout et al. 2002b) . Presence of the flood is the most important external influence on the interaction between rice (...truncated)


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Adams, A., Gore, J., Musser, F., Cook, D., Catchot, A., Walker, T., Awuni, G. A.. Impact of Water Management on Efficacy of Insecticide Seed Treatments Against Rice Water Weevil (Coleoptera: Curculionidae) in Mississippi Rice, Journal of Economic Entomology, 2015, pp. 1079-1085, Volume 108, Issue 3, DOI: 10.1093/jee/tov095