2011 Annual Report
1a.Objectives (from AD-416)
Evaluate efficacy of potential alternatives to the use of methyl bromide as a structural treatment and improve Integrated Pest Management (IPM) programs for stored-product insect pests in food facilities such as wheat flour mills, rice mills, pet food facilities, and their associated warehouses with the goal of reducing the number of methyl bromide critical use exemptions (CUEs) requested or the amount of methyl bromide used.
1b.Approach (from AD-416)
A four part approach, based on priorities identified by stakeholders at the NP308 program review, will be used to meet this objective. (1) Obtain information on the field efficacy of alternative structural treatments, such as sulfuryl fluoride or heat, compared with methyl bromide. (2) Evaluate the impact of some alternative tactics, such as reduced-risk aerosol insecticides or targeted treatment with residual contact insecticides, as part of an IPM or systems approach to eliminate the need for, or reduce the frequency of, fumigations or other structural treatments. (3) Develop improved monitoring tools and strategies to evaluate the need for and effectiveness of different management tactics to improve the implementation of an IPM program (in association with Gainesville). (4) Develop models using the above information with which to determine optimal management strategies using methyl bromide alternatives.
This report documents progress for Project 5430-43000-028-00D, Development of Integrated Pest Management Programs to Reduce Methyl Bromide Fumigations for Control of Insects in Postharvest Structures, which started May 2008. Under Objective 1, significant progress was made in understanding stored-product insect population dynamics in commercial food facilities such as mills, processing plants, and warehouses and the impact of treatment with alternatives to the structural fumigant methyl bromide (MB) such as the fumigant sulfuryl fluoride (SF), use of high temperature treatments, or Integrated Pest Management (IPM) programs. Stored-product insect monitoring, emphasizing red flour beetle, before and after treatment was conducted in multiple commercial food facilities. In collaborative research with scientists at Kansas State University, impact of localized heat treatments on pest populations was evaluated in commercial facilities and experimental studies were conducted to determine the effects of flour residue depth on survival of red flour beetles during heat treatments. Spatial variation in the impact of fumigation was evaluated in a flour mill to determine critical control points where populations rebound after treatment. Evaluation of a previously developed risk threshold was conducted for other food facilities to determine how widely it could be applied. This research is supplying critical information to managers on treatment efficacy and the factors that impact efficacy in food facilities and also providing information to validate population models developed in Objective 4. Under Objective 2, significant progress has been made on determining the impact of reduced-risk insecticides on pest insect populations. Studies were conducted with a new neo-nicotenoid insecticide to evaluate its effectiveness against different developmental stages of the red flour beetle, and the detrimental effects of exposure to an insect growth regulator insecticide on individuals that survive was studied. New studies were initiated to examine the impact of regular aerosol applications of pyrethrin and insect growth regulator insecticides on long-term population growth of red flour beetles in small-scale storage facilities. The more effective use of these insecticides as part of an IPM program could reduce the need to conduct structural fumigations, facilitating the phase-out of methyl bromide. Under Objective 4, to better understand how different alternatives to MB affect population rebound following treatment, a model for red flour beetle population dynamics in flour mills was developed previously. Significant progress has now been made on incorporating MB and SF fumigation treatments into the model, and currently model predictions are being validated using field data from flour mills. The model will provide important information for managers to determine optimum integrated pest management strategies for flour mills. The research conducted in this project will contribute to the development of more effective pest management programs with the potential benefit of reducing the number of MB critical use exemptions requested or the amount of MB used.
Flour spills reduce the ability of heat treatments to kill red flour beetles in mills. The phase-out of the fumigant methyl bromide in the United States, because of its adverse effects on stratospheric ozone, has generated renewed interest in using heat treatments for insect control in flour mills. However, flour that accumulates inside of mills can potentially insulate the beetles and reduce the effectiveness of these heat treatments. ARS scientists in Manhattan KS, in collaboration with researchers at Kansas State University, investigated the influence of residual flour depth on mortality of red flour beetle eggs and adults during heat treatment of a flour mill. The protective effects of flour residues on insect mortality during the heat treatment were much greater for adults than for eggs. Flour depths of 1 inch or greater had less than 10% adult mortality. This study provides important information for mill managers about the importance of sanitation prior to heat treatments in flour mills that will increase the effectiveness of these treatments.
Sulfuryl fluoride fumigation reduces red flour beetle populations in rice mills. In rice mills, the fumigant insecticide sulfuryl fluoride is a potential alternative to methyl bromide, whose use as a fumigant in mills is being phased out. To evaluate efficacy of this new fumigant in commercial rice mills, ARS researchers in Manhattan, KS, conducted red flour beetle monitoring in four rice mills and before and after nine fumigations with sulfuryl fluoride. There was a reduction in average number of beetles captured per trap after treatment of 81% and an average reduction in probability of capturing a beetle in a trap of 63%. These results are similar to that reported for methyl bromide fumigation in wheat mills. Population rebound rates after fumigation in rice mills tended to be slower than in wheat mills after methyl bromide fumigations, but this may reflect differences in the population growth potential in these two types of mills. Understanding how structural fumigations impacts pest populations is important for both the assessment of methyl bromide alternatives and the development of more effective integrated pest management programs.
Red flour beetle developmental stages vary in susceptibility to new insecticide. A new insecticide, chlorfenapyr, kills the red flour beetle, a major pest of stored products, but there is no information on how well it works in the presence of a food source. ARS researchers in Manhattan, KS, exposed adults, larvae and pupae on a concrete surface that was partially treated with chlorfenapyr and had food in the untreated area. They demonstrated how the more mobile adults were better able to escape exposure and survived to lay eggs in the food, while the less mobile larvae were more susceptible and usually died before reaching the adult stage, even if they reached the food in the untreated area. The insecticide persisted on the concrete surface and control of larvae lasted for several weeks. When insecticides are applied in commercial food facilities not all areas are treated and refugia from exposure exist, thus understanding how effectiveness is impacted by these refugia is important for implementing management programs.
Cigarette beetle egg stage is most tolerant to heat treatments. Methyl bromide was widely used in food processing and storage facilities for the suppression of stored-product insect pests, but its use as a structural fumigant is being phased out. Heat treatments are a potential alternative, but little information is available on their effectiveness against the cigarette beetle, a pest associated with food-processing facilities. ARS researchers in Manhattan, KS, in collaboration with Kansas State University, evaluated the susceptibility of all cigarette beetle developmental stages to elevated temperatures and determined that the egg stage was the most tolerant stage and that the time to kill 99% of eggs at 122°F was 190 minutes. Determining the most tolerant stage provides the target temperatures and exposure times need to provide control, thus this study provides valuable information for managers and pest control professionals using heat treatments to control cigarette beetles in food-processing facilities.
Insect growth regulators reduce potential for red flour beetle population growth. Red flour beetle is a major pest of the flour milling industry, and with the phase-out of methyl bromide there is need to evaluate the effectiveness of alternative management tools. Insect growth regulators cause the death of immature insects, but survivors may also have reduced fitness that could enhance the effectiveness of these treatments. ARS scientists in Manhattan, KS, exposed larvae and adults of the red flour beetle to wheat treated with growth regulators. Exposure of adults did not reduce their subsequent reproduction. However, when exposed to growth regulators, male larvae were less likely to survive to the adult stage compared to female larvae. In addition, adult males that survived exposure to growth regulators as larvae produced less offspring than unexposed males. Results show the nonlethal effects of growth regulators potentially increase the impact insecticide treatments have on population growth rates, thus making them more effective than initially estimated at managing pest populations.
Jenson, E.A., Arthur, F.H., Nechols, J.R. 2010. Methoprene and synergized pyrethrins as an aerosol treatment to control Plodia interpunctella (Hubner), the Indian meal moth (Lepidoptera: Pyralidae). Journal of Stored Products Research. 46(2):103-110. doi: http://dx.doi.org/10.1016/j.jspr.2009.11.002.
Toews, M.D., Campbell, J.F., Arthur, F.H. 2010. The presence of flour affects the efficacy of aerosolized insecticides used to treat the red flour beetle, Tribolium castaneum. Journal of Insect Science. 10:196. Available online: www.insectscience.org\10.196.
Throne, J.E., Arbogast, R.T. 2010. A computer model for simulating population development of the Indianmeal Moth (Lepidoptera: Pyralidae) in stored corn. Journal of Economic Entomology. 103(4):1503-1507.
Yu, C., Subramanyam, B., Flinn, P.W., Gwirtz, J.A. 2011. Susceptibility of Lasioderma serricorne (F.)(Coleoptera: Anobiidae) life stages to elevated temperatures used during structural heat treatments. Journal of Economic Entomology. 104(1):317-324. doi: http://dx.doi.org/10.1603/EC10067.