Insecticides for empty grain bins

In this column, Blossom Sehgal, a graduate research assistant in the Department of Grain Science and Industry, Kansas State University (KSU), Manhattan, teamed up with Milling Journal’s regular contributor Bhadriraju Subramanyam (Subi), a Don Wilbur Sr. Endowed Professor of Postharvest Protection, Department of Grain Science and Industry, KSU, to explain their key findings from evaluating the effectiveness of two insecticides for treating empty bins

Efficacy of ozone against phosphine susceptible and resistant strains of four stored-product insect species

Citation: Xinyi, E., Subramanyam, B., & Li, B. (2017). Efficacy of ozone against phosphine susceptible and resistant strains of four stored-product insect species. Insects, 8(2). doi:10.3390/insects8020042The efficacy of ozone was evaluated against four economically-important stored-product insect species at 27.2 °C and 20.4% r.h. Adults of phosphine-susceptible laboratory strains and phosphine-resistant field strains of the red flour beetle, Tribolium castaneum (Herbst), saw-toothed grain beetle, Oryzaephilus surinamensis (Linnaeus), maize weevil, Sitophilus zeamais Motschulsky, and rice weevil, Sitophilus oryzae (Linnaeus), were exposed in vials to an ozone concentration of 0.42 g/m3 (200 ppm) for 1, 2, 3, 5, 6, 8, 10 and 12 h with 0 and 10 g of wheat. Initial and final mortalities were assessed 1 and 5 d after exposure to ozone, respectively. After an 8–12-h exposure to ozone, initial mortality of Sitophilus spp. and O. surinamensis was 100%, whereas the highest initial mortality of T. castaneum was 90%. A 3–4-h exposure to ozone resulted in 100% final mortality of Sitophilus spp., whereas O. surinamensis required a 6- to 10-h exposure to ozone. Adults of T. castaneum were least susceptible to ozone, and after a 10-h exposure, mortality ranged between 82 and 95%. Time for the 5 d 99% mortality (LT99) for adults of laboratory and field strains of Sitophilus spp., O. surinamensis and T. castaneum were 2.00–5.56, 4.33–11.18 and 14.35–29.89 h, respectively. The LT99 values for adults of T. castaneum and O. surinamensis were not significantly different between bioassays conducted with 0 and 10 g of wheat. The LT99 values for the laboratory strains of Sitophilus spp. in the absence of wheat were significantly lower than those obtained in the presence of wheat. Both phosphine-susceptible and -resistant strains were equally susceptible to ozone. Ozone effectively suppressed adult progeny production of all four species. Ozone is a viable alternative fumigant to control phosphine-resistant strains of these four species. © 2017 by the authors; licensee MDPI, Basel, Switzerland

Evaluating Penetration Ability of \u3ci\u3ePlodia interpunctella\u3c/i\u3e (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 partial treatment of wheat with spinosad against Rhyzopertha dominica (F.) adults

The efficacy of partial treatment of wheat with spinosad against adults of the lesser grain borer, Rhyzopertha dominica (F.), was evaluated by mixing spinosad-treated and untreated wheat kernels in varying proportions. Spinosad was applied to wheat kernels either by dipping in 1 mg (a.i.) mlˉ¹ spinosad solution for 1 minute or admixed with dry and liquid spinsoad formulations at 0.1 and the labeled rate of 1 mg (a.i.) kgˉ¹ of wheat. In the kernel dipping method, the percentage of kernels treated was increased from 10 to 100 in 10% increments, while keeping the total number of kernels at either 10 or 100. The mortality of introduced adults in independent samples was observed over time at 1 to 209 h post-infestation. In the admixture method, the percentage of spinosad-treated wheat ranged from 10 to 100 in 10% increments by varying amounts of spinosad-treated and untreated wheat to form a total of 50 g. Mortality of introduced R. dominica adults was determined after 1, 3, 5, and 7 d. In the kernel dipping method, there was an inverse relationship between lethal times for 50 and 95% mortality of R. dominica adults and percentage of kernels treated. In the admixture method, adult mortality increased with an increase in spinosad rate, exposure time, and percentage of kernels treated. The liquid formulation was more effective against R. dominica than the dry formulation. At the labeled rate of 1 mg (a.i.) kgˉ¹, treating 20 to 90% of the kernels with liquid or dry formulation of spinosad was as good as treating 100% of the kernels in controlling R. dominica adults within 3 to 5 d. In practical situations where uneven distribution of spinosad on kernels is expected, complete control of R. dominica adults can be achieved if more than 50% of the kernels receive spinosad treatment