Document Detail

Immediate and delayed mortality of Rhyzopertha dominica (Coleoptera: Bostrichidae) and Sitophilus oryzae (Coleoptera: Curculionidae) adults exposed to spinosad-treated commodities.
MedLine Citation:
PMID:  18613608     Owner:  NLM     Status:  MEDLINE    
A series of tests was conducted to characterize differences in the mortality of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), and rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), exposed to three commodities treated with a liquid and dry spinosad formulation. In laboratory bioassays, adults of the two insect species were exposed to untreated wheat, Triticum aestivum L., corn, Zea mays L., and sorghum, Sorghum bicolor (L.) Moench., and to commodities treated with 1 mg (AI)/kg of liquid and dry spinosad formulations. Mortality was assessed from independent samples examined at specific time intervals to determine immediate mortality and after 24 h of recovery on untreated grain at 28 degrees C and 65% RH to determine delayed mortality. Comparison of the time required for 50% (LT50) and 95% (LT95) mortality indicated that R. dominica adults were consistently and significantly more susceptible (died quickly) than S. oryzae adults when exposed to spinosad-treated commodities. In general, the toxicity of liquid and dry spinosad formulations was similar against R. dominica or S. oryzae. The toxicity of spinosad to each species varied slightly among the three commodities, and there were no consistent trends to suggest that spinosad was more effective on one commodity versus another. LT50 values based on immediate mortality for R. dominica on all commodities ranged from 0.45 to 0.74 d; corresponding values based on delayed mortality ranged from 0.04 to 0.23 d, suggesting delayed toxic action of spinosad in R. dominica. LT50 values based on immediate and delayed mortality for S. oryzae on all three commodities treated with the two spinosad formulations were essentially similar and ranged from 2.75 to 4.56 d. LT95 values for R. dominica based on immediate mortality on spinosad-treated commodities ranged from 1.75 to 3.36 d, and those based on delayed mortality ranged from 0.49 to 1.88 d. There were no significant differences in LT95 values based on immediate and delayed mortality for S. oryzae on spinosad-treated commodities, and the LT95 values ranged from 7.62 to 18.87 d. The toxicity of spinosad was enhanced during a 24-h holding period after removal from spinosad-treated commodities only against R. dominica adults, and possible reasons for increased postexposure mortality of R. dominica adults after brief exposures to spinosad warrant further study.
Anna Iversen Getchell; Bhadriraju Subramanyam
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of economic entomology     Volume:  101     ISSN:  0022-0493     ISO Abbreviation:  J. Econ. Entomol.     Publication Date:  2008 Jun 
Date Detail:
Created Date:  2008-07-10     Completed Date:  2008-08-07     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985127R     Medline TA:  J Econ Entomol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1022-7     Citation Subset:  IM    
Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506-2201, USA.
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MeSH Terms
Beetles / drug effects,  growth & development*
Drug Combinations
Insecticides / toxicity*
Life Cycle Stages / drug effects
Macrolides / toxicity*
Oryza sativa / parasitology*
Sorghum / drug effects
Triticum / parasitology*
Zea mays / parasitology*
Reg. No./Substance:
0/Drug Combinations; 0/Insecticides; 0/Macrolides; 0/spinosad

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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