F.H. Arthur

Monitoring Tribolium castaneum (Coleoptera: Tenebrionidae) in Pilot-Scale Warehouses Treated with Residual Applications of (S)-Hydroprene and Cyfluthrin

Abstract Pilot-scale warehouses, artificially infested with all life stages of Tribolium castaneum (Herbst), were used to evaluate the efficacy of two contact insecticides, (S)-hydroprene and cyfluthrin, and to determine the effect of insecticide treatments on insect captures in food- and pheromone-baited pitfall traps. Two application strategies were compared; insecticides were applied at the labeled rate either around the inside perimeter of the warehouse or in a band around the base of shelf units containing discrete food patches (10 g of wheat flour) infested with T. castaneum. Insect populations were assessed weekly for 6 wk by recording number of dead adults on the warehouse floor; number of larvae and adults captured in pitfall traps; and number of larvae, pupae, and adults recovered from food patch samples. There were significantly more dead adults in warehouses treated with cyfluthrin than with (S)-hydroprene or water (control treatment). However, food patch samples showed no detectable differences in quantity of larvae, pupae, or adults among any treatments. Pitfall traps detected fewer larvae starting the fourth week of the study in the warehouses treated with cyfluthrin around the shelf perimeter. Rate of larval capture in traps increased overall with increasing larval populations, but it was more pronounced in traps located closer to the food patches. Number of adults captured in pitfall traps reflected adult mortality in cyfluthrin-treated warehouses. Capture of larvae and adults was greater near the source of the infestation than elsewhere in the warehouse, suggesting that trapping data should be considered when precision targeting insecticide applications in the field.

Monitoring Tribolium castaneum (Herbst) in pilot-scale warehouses treated with β-cyfluthrin: are residual insecticides and trapping compatible?

Integrated pest management strategies for cereal processing facilities often include both pheromone-baited pitfall traps and crack and crevice applications of a residual insecticide such as the pyrethroid cyfluthrin. In replicated pilot-scale warehouses, a 15-week-long experiment was conducted comparing population trends suggested by insect captures in pheromone-baited traps to direct estimates obtained by sampling the food patches in untreated and cyfluthrin-treated warehouses. Warehouses were treated, provisioned with food patches and then infested with all life stages of Tribolium castaneum (Herbst). Food patches, both those initially infested and additional uninfested, were surrounded by cyfluthrin bands to evaluate if insects would cross the bands. Results show that insect captures correlated with population trends determined by direct product samples in the untreated warehouses, but not the cyfluthrin-treated warehouses. However, dead insects recovered from the floor correlated with the insect densities observed with direct samples in the cyfluthrin-treated warehouses. Initially, uninfested food patches were exploited immediately and after six weeks harbored similar infestation densities to the initially infested food patches. These data show that pest management professionals relying on insect captures in pheromone-baited traps in cyfluthrin-treated structures could be deceived into believing that a residual insecticide application was suppressing population growth, when the population was actually increasing at the same rate as an untreated population.

Methodology for assessing rice varieties for resistance to the lesser grain borer, Rhyzopertha dominica

Abstract Several physical and chemical attributes of rice were evaluated to determine which character would be best to use to assess multiple rice varieties for resistance to the lesser grain borer, Rhyzopertha dominica (F.). Laboratory tests were conducted on single varieties of long-, short-, and medium grain-rice to develop procedures and methodologies that could be used for large-scale screening studies. Progeny production of R. dominica was positively correlated with the percentage of broken hulls. Although kernel hardness, amylose content, neonate preference for brown rice, and adult emergence from neonates varied among the three rice varieties tested they did not appear to be valid indicators of eventual progeny production, and may not be useful predictors of resistance or susceptibility. Soundness and integrity seem to be the best characters to use for varietal screening studies with R. dominica.

Susceptibility of eggs and adult fecundity of the lesser grain borer, Rhyzopertha dominca, exposed to methoprene.

Abstract A series of tests were conducted to determine the susceptibility of eggs and neonates of the lesser grain borer Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae = Bostrychidae), exposed to the insect growth regulator, methoprene, on filter paper and on rough rice. In the first test, the hatch rate of eggs exposed on filter paper treated with methoprene at the label rate of 0.003 mg [AI]/cm2 when used as a surface treatment in structures was 52.0 ± 7.3% compared to 93.0 ± 3.3% on untreated controls. In the second test, eggs were exposed to a dose-response series of 0.00003 to 0.03 mg[AI]/cm2. Egg hatch was directly proportional to concentration and ranged from 85.0 ± 2.0% on untreated controls to 26.7 ± 8.3% at the highest concentration tested. In the third test, 1 ppm of methoprene was sprayed on long grain rough rice (paddy) (Cocodrie variety), and then individual kernels were cracked and an egg of R. dominica was placed directly on the kernel. On untreated rice kernels, 67.5 ± 11.6% of the eggs hatched and were able to bore inside, and all of these larvae emerged as adults. In contrast, 40.0 ± 5.3% of the eggs placed on treated cracked kernels were able to develop to where the larvae were visible through X-ray detection, but none emerged as adults. In the final test, newly-emerged adults were exposed on rough rice treated with 1 ppm methoprene. The number of eggs from adults on untreated rice was 52.1 ± 4.3 eggs per female, and on treated rice the average egg production was 12.5 ± 1.1 eggs per female. Methoprene applied on a surface or on rough rice affected development of egg hatch also reduced fecundity of parent adults exposed on the treated rough rice.

Contact Toxicity of Deltamethrin Against Tribolium castaneum (Coleoptera: Tenebrionidae), Sitophilus oryzae (Coleoptera: Curculionidae), and Rhyzopertha dominica (Coleoptera: Bostrichidae) Adults

Abstract This study was conducted at Oklahoma State University, Stillwater, OK, to evaluate the response to deltamethrin concentrations for adults of three stored-product insects, Tribolium castaneum (Herbst), Sitophilus oryzae (L.), and Rhyzopertha dominica (F.). In insect toxicological studies, knockdown is the state of intoxication and partial paralysis as a result of exposure to an insecticide. Deltamethrin concentrations ranging from 0.48 to 140 mg/m2 (1 to 3,000 ppm) were sprayed on glass Petri dishes. After the dishes dried, 20 adult insects of each species were placed on the treated dishes to determine the contact toxicity of deltamethrin. Assessments for knockdown were made at 15-min intervals for up to 8 h after initial exposure and then again after 24 or 48 h. Insects were then transferred to clean untreated Petri dishes with diet and observed from 0.5 to 72 h. Mortality was assessed 72 h after transfer to untreated dishes with food material. Deltamethrin was highly effective against all three species tested and achieved 99% knockdown of insects of all species within 4 h after exposure at concentrations ≥1.2 mg/m2. Although some insects recovered from initial knockdown at concentrations ≤48 mg/m2, nearly all the insects were killed at 140 mg/m2 when exposed for 48 h. LC95 values for all species tested, for the 48-h exposure period, were <140 mg/m2, the concentration of deltamethrin that could potentially be present in new ZeroFly Storage Bag fabric. ZeroFly bags are used for stored-product insect pest control.

Evaluation of Pyrethroid Insecticides and Insect Growth Regulators Applied to Different Surfaces for Control of Trogoderma granarium (Coleoptera: Dermestidae) the Khapra Beetle

The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a serious pest of stored products and is the only stored product insect pest that triggers a quarantine response when it is found in the United States. The larvae of T. granarium feed on a wide range of dry food products of plant and animal origin, including cereals, dried fish, and museum specimens. In this study, we evaluated the residual efficacy of two pyrethroid insecticides, deltamethrin and cyfluthrin, applied on concrete, wood, painted wood, vinyl flooring tile, and metal surfaces using small and large T. granarium larvae. Residual efficacy of two insect growth regulators (IGRs), methoprene and pyriproxyfen was also evaluated on concrete, metal, and wood surfaces. In both studies, larvae were exposed with provision of a food source on the treated surfaces and residual assays were conducted at 0 months (1 d), 1, 2, and 3 months post treatment. In general, both of the pyrethroids provided a high level of control of T. granarium larvae, though small larvae were much more susceptible than large larvae. The IGRs were comparatively less effective, with more larval survival and adult emergence of exposed larvae compared with the pyrethroids. Residues of the pyrethroids and IGRs were most persistent on the metal surface. Results can be used to help to control and eradicate infestations of T. granarium when they are detected in the United States.