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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICALLY-BASED TECHNOLOGIES FOR MANAGEMENT OF CROP INSECT PESTS IN LOCAL AND AREA-WIDE PROGRAMS Title: Using stable isotope analysis to examine the fall armyworm (Lepidoptera: Noctuidae) host strains in a cotton habitat

Authors
item Nagoshi, Rodney
item Adamczyk, John
item Meagher, Robert
item Gore, Jeffrey
item Jackson, Ryan

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2007
Publication Date: November 1, 2007
Citation: Nagoshi, R.N., Adamczyk Jr, J.J., Meagher Jr, R.L., Gore, J., Jackson, R.E. 2007. Using stable isotope analysis to examine the fall armyworm (Lepidoptera: Noctuidae) host strains in a cotton habitat. Journal of Economic Entomology. 100(5):1569-1576.

Interpretive Summary: Spodoptera frugiperda (J.E. Smith; Lepidoptera: Noctuidae) or fall armyworm is an important agricultural pest of a number of crops in the western hemisphere, including cotton. Two morphologically identical host strains of fall armyworm exist that differ in plant host usage and habitat distribution. The corn (C) strain is the primary pest of corn, while the rice (R) strain is the majority population infesting rice and turf grass. The strain infesting cotton has not been identified in the United States. We used stable isotope methods combined with the molecular analysis of strain-specific markers to determine whether one or both strains infest cotton grown in the Mississippi delta. The results indicate that the majority of the fall armyworms arising from cotton are of the C-strain. The population distribution patterns observed were consistent with corn providing an important source for the fall armyworm strain infesting cotton and suggested that late season populations in the Mississippi delta may be migrants from more northern corn areas. These results have potential importance for growers of Bacillus thuringiensis (Bt) toxin expressing cotton varieties with respect to accessing the need for refuge areas.

Technical Abstract: Spodoptera frugiperda (J.E. Smith; Lepidoptera: Noctuidae) or fall armyworm is an important agricultural pest of a number of crops in the western hemisphere, including cotton. Two genetically distinct but morphologically identical strains (R-strain and C-strain) exist that differ physiologically and behaviorally. With the increased use of Bacillus thuringiensis (Bt) toxin expressing cotton varieties and the necessity of assuring adequate refuge areas to prevent the spread of Bt toxin resistance, an understanding of the noncotton plant hosts available for the fall armyworm population infesting cotton is critical. Stable isotope analysis combined with the molecular analysis of strain-specific markers was used to determine whether one or both strains infest cotton grown in the Mississippi delta. The results indicate that the majority of fall armyworm adults present during the early cotton growing season arise from C4 plants (e.g., corn, sorghum) and that the only strain developing on cotton (a C3 plant) in substantial numbers is the C-strain, whose primary plant host is corn. The population distribution patterns observed were consistent with corn providing an important refuge for the fall armyworm strain infesting cotton and suggested that late season populations in the Mississippi delta may be migrants from more northern corn areas.

Last Modified: 11/22/2014
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