Journal of Economic Entomology (2004) 97, 2154-2159

Fangneng Huang, Bhadriraju Subramanyam and Michael D. Toews (2004)
Susceptibility of laboratory and field strains of four stored-product insect species to spinosad
Journal of Economic Entomology 97 (6), 2154-2159
Abstract: Two field strains of the Indianmeal moth, Plodia interpunctella (Hübner); red flour beetle, Tribolium castaneum (Herbst); and lesser grain borer, Rhyzopertha dominica (F.), and one field strain of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), were collected from hard red winter wheat stored on farms in northeastern Kansas. Fifty eggs of P. interpunctella and 25 beetle adults of each species were exposed to 100 g of untreated wheat or wheat treated with various rates of spinosad, to determine susceptibility of the field and corresponding insecticide-susceptible laboratory strains. Mortality of beetle adults and P. interpunctella larvae was assessed after 7 and 21 d postinfestation, respectively. Field strains of P. interpunctella, C. ferrugineus, and T. castaneum were less susceptible to spinosad than the corresponding laboratory strains. The LD₅₀ and LD₉₅ values for P. interpunctella and C. ferrugineus field strains were 1.7-2.5 times greater than values for corresponding laboratory strains. Adults of both laboratory and field strains of T. castaneum were tolerant to spinosad, resulting in <88% mortality at 8 mg/kg. The LD₅₀ and LD₉₅ values for the field strains of T. castaneum were 2.0-7.5 times greater compared with similar values for the laboratory strain. The field and laboratory strains of R. dominica were highly susceptible to spinosad, and one of the field strains was relatively less susceptible to spinosad than the laboratory strain. Our results confirm a range of biological variability in field populations, which is consistent with findings for other compounds, and underscores the need to adopt resistance management programs with stored grain insect pests. The baseline data generated on the susceptibility of the four insect species to spinosad will be useful for monitoring resistance development and for setting field rates.
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Full text of article
Database assignments for author(s): Fang Neng Huang, Michael D. Toews, Bhadriraju Subramanyam

Research topic(s) for pests/diseases/weeds:
control - general
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Tribolium castaneum	Stored grain	U.S.A. (mid N)
	Tribolium castaneum	Stored grain	U.S.A. (mid S)
	Plodia interpunctella	Stored grain	U.S.A. (mid N)
	Plodia interpunctella	Stored grain	U.S.A. (mid S)
	Rhyzopertha dominica	Stored grain	U.S.A. (mid N)
	Rhyzopertha dominica	Stored grain	U.S.A. (mid S)
	Cryptolestes ferrugineus	Stored grain	U.S.A. (mid N)
	Cryptolestes ferrugineus	Stored grain	U.S.A. (mid S)