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
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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)