Evaluating Penetration Ability of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) Larvae into Multilayer Polypropylene Packages.

The larvae of the Indian meal moth, Plodia interpunctella (Hübner), can invade or penetrate packaging materials and infest food products. Energy bars with three polypropylene packaging types were challenged with eggs (first instars), third instars, and fifth instars of P. interpunctella to determine package resistance at 28 °C and 65% r.h. The packing types were also challenged with two male and two female pupae of P. interpunctella under similar conditions in order to determine which package provided the greatest protection against larval penetration. Samples infested with eggs, third instars, and pupae were evaluated after 21 days and 42 days to count the number of larvae, pupae, and adults found inside the packages. Packages challenged with fifth instars were observed after 21 days to count the number of larvae, pupae, and adults inside each package. The number and diameter of the holes were determined in each package, followed by the amount of damage sustained to the energy bar. Third and fifth instars showed a higher tendency to penetrate all of the packaging types. First instars showed a reduction in package penetration ability compared with third and fifth instars. The increase in exposure time resulted in an increase in the damage sustained to the energy bars. Among packaging types, the thickest package (Test A) was most resilient to penetration by all of the larval stages. In conclusion, energy bar manufacturers need to invest more effort into improving packaging designs, creating thicker gauge films, or advancing odor barrier technology, in order to prevent penetration and infestation by P. interpunctella larvae.

Efficacy of a New Deltamethrin Formulation on Concrete and Wheat Against Adults of Laboratory and Field Strains of Three Stored-Grain Insect Species.

Efficacy of the suspension concentrate formulation of deltamethrin (Centynal) was evaluated at labeled rates on concrete surfaces and hard red winter wheat against 12 field strains of the red flour beetle, Tribolium castaneum (Herbst); six strains of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.); and four strains of the lesser grain borer, Rhyzopertha dominica (F). The time for ≍100% mortality of adults of laboratory strains was first established by exposing them to deltamethrin-treated concrete at the highest labeled rate of 0.02 g(AI)/m(2) for 1-24 h. On concrete, deltamethrin did not provide complete mortality of adults of T. castaneum and O. surinamensis field strains, but was effective against R. dominica strains. Mortalities of two strains each of T. castaneum and O. surinamensis were significantly lower than that of the corresponding laboratory strains. On wheat treated with 0.5 mg(AI)/kg of deltamethrin, the 7- and 14-d mortalities of four to six T. castaneum field strains, three O. surinamensis strains, and one R. dominica strain were significantly lower than that of the corresponding laboratory strains. Even at twice the labeled rate on wheat, the 7-d mortalities of three strains each of T. castaneum and O. surinamensis were significantly lower than the corresponding laboratory strains. Except for one T. castaneum and two O. surinamensis strains, the reduction in adult progeny production on deltamethrin-treated wheat relative to that on untreated wheat was 92-100%. Reduced susceptibility in field strains may be due to low levels of tolerance or resistance to deltamethrin.

Variation in susceptibility of laboratory and field strains of three stored-grain insect species to ß-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to concrete surfaces.

BACKGROUND: The efficacy of commercial formulations of ß-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to clean, concrete surfaces similar to that of empty bins against field strains of stored-grain insects is unknown. We exposed adults of 16 strains of the red flour beetle, Tribolium castaneum (Herbst); eight strains of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.); and two strains of the lesser grain borer, Rhyzopertha dominica (F.), collected mainly from farm-stored grain in Kansas, USA, to ß-cyfluthrin and chlorpyrifos-methyl plus deltamethrin applied to concrete surfaces and determined knockdown and mortality. RESULTS: Knockdown and mortality differences among species and strains to the insecticides tested were significant. Mortality of all species was less than that of knockdown, suggesting recovery when placed on food after insecticide exposure. ß-Cyfluthrin was effective against R. dominica but ineffective against T. castaneum and O. surinamensis field strains. Chlorpyrifos-methyl plus deltamethrin was only partially effective against field strains of the three species. CONCLUSION: Reduced susceptibility in field strains may be due to inherent formulation deficiency and low levels of tolerance or resistance to ß-cyfluthrin. No single insecticide provided adequate control of the three species tested.

Variation in susceptibility of field strains of three stored grain insect species to spinosad and chlorpyrifos-methyl plus deltamethrin on hard red winter wheat.

Spinosad and chlorpyrifos-methyl plus deltamethrin efficacy at labeled rates on hard red winter wheat were evaluated against 11 field strains of the red flour beetle, Tribolium castaneum (Herbst); six strains of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.); and two strains of the lesser grain borer, Rhyzopertha dominica (F.), collected mostly from farm-stored grain in Kansas. Adults were exposed to wheat treated with spinosad at 1 mg (active ingredient)/kg or chlorpyrifos-methyl plus deltamethrin at three plus 0.5 mg (active ingredient)/kg. Adult mortality was assessed after 7 and 14 d and progeny production after 42 d. Spinosad did not provide complete mortality or progeny suppression of T. castaneum and O. surinamensis field strains, but was effective against R. dominica strains. Chlorpyrifos-methyl plus deltamethrin produced complete mortality and progeny suppression of field strains all three species. The two least susceptible T. castaneum and O. surinamensis strains and the two R. dominica strains were chosen for dose-response tests only with spinosad. The LD99 values for T. castaneum and R. dominica field strains were similar to that of the corresponding laboratory strains. Corresponding values for the two O. sturinamensis field strains were significantly greater (approximately 6 times) than the laboratory strain. The effective dose for progeny reduction (ED99) of only one R. dominica field strain was significantly greater (approximately 2 times) than the laboratory strain. The baseline susceptibility data of field strains of three insect species to spinosad will be useful for monitoring resistance development when this product is commercially released as a grain protectant.