2009 Annual Report
1a.Objectives (from AD-416)
The goal is to maximize the effect of physical, chemical, and biological stressors to control stored-product insects in raw grains and processed grain products. Stored-product insect pests reduce the quality of stored grain and grain-related products in the U.S. and in the world. We will identify new methods of controlling insect pests in stored products, targeting controls to specific sites or areas, and determining how insect immune systems can be exploited to improve efficacy of new control strategies. We will identify and refine alternative insecticides, biologically-based control methods, and physical controls to manage stored-product insect pests. We will evaluate selective targeted controls and application strategies to manage insect pests in different stored-product systems.
1b.Approach (from AD-416)
Laboratory and field experiments will identify new biologically-based methods and reduced-risk insecticides to control stored-product insect pests, evaluate synergistic and additive effects from selected control agents, and to further refine physical controls, such as heat and aeration, to modify storage environments. Laboratory and field tests will investigate targeted applications of control agents, detect pathogen virulence in field populations of stored-product insects, and examine new methods for using pathogenic controls to regulate pest populations in stored products. Our research will also include detailed analysis of the cuticular lipids in the insect cuticle, and analysis of how these properties affect their response to various control agents. We will investigate how insect immune responses are regulated and how physiological responses can be interrupted and manipulated to enhance efficacy of control agents. Our research will provide new methods to control insects in raw grains and processed grain products, strategies for integrating different control agents, information on using targeted controls for specific areas within stored-product facilities, and knowledge of how the insect immune system could be exploited to improve control from reduced-risk insecticides and insect pathogens. Results will provide practical information for minimizing risk, quality deterioration, and economic damage caused by stored-product insects.
Our research has shown that insect growth regulators, alone or in combination with either pyrethrin or pyrethroid insecticides, will control Indianmeal moth eggs and larvae. These insect growth regulators may be used in combination with other control strategies, including inert dusts, microbial pathogens, and fungal pathogens, to manage insect pest populations in bulk grains, flour mills, and processed food warehouses. We have shown that suction aeration may be preferable over standard pressure aeration for cooling wheat during the summer months, and that controlled aeration will effectively manage insect pest populations in rice stored in Texas. We have shown that dietary stress improves the efficacy of a mycoinsecticide. We are also making progress in quantifying the genetic responses of stored-product beetles to selected insecticides and microbial pathogens. Normalization reference genes for RT-qPCR have been established, documented changes in gene expression induced by fungal pathogens, and are currently conducting experiments with silencing of key genes.
New insecticide to control Indianmeal moth larvae. Methoprene is an insecticide that is used in pest management programs for stored grains, and works by inhibiting the molting process of insect larvae. Methoprene is effective on stored-product beetles, but there is comparatively less data regarding effectiveness on the Indianmeal moth. ARS scientists in Manhattan, Kansas, conducted tests by exposing eggs or larvae of the Indianmeal moth on packaging materials or flooring surfaces treated with methoprene. Eggs of the Indianmeal moth were not susceptible to methoprene. However, depending on the specific packaging material and the time of exposure, larvae were susceptible and most of them did not reach the adult stage after they were exposed to methoprene. An economic analysis showed the risks and benefits associated with methoprene treatment, and results of the tests and the budget analysis show that methoprene could be used in pest management plans to control larvae of the Indianmeal moth.
Dietary stress improves mycoinsecticide efficacy. The fungi that are pathogenic for insects provide a safe approach to controlling pests. The insecticidal fungus, Beauveria bassiana, is being considered as non-chemical control for insect pests of stored products including the red flour beetle for which it is less effective than for most insects. Certain stresses on insects render them more susceptible to fungal disease. Restriction of access to food by sanitation is an important stress-inducing means of insect management. Similarly, the nutritional content of various foods is a determinant of insect vigor and success on different commodities. This study investigated the effect of dietary stress on the efficacy of B. bassiana for red flour beetles. When beetle larvae were deprived of food for various periods of time they were more susceptible to fungal infection than when provided a constant food supply. Larvae that were reared on a rice diet were more susceptible than those reared on wheat flour. The addition of protease inhibitors to flour also increased fungal efficacy. Dietary stress, whether by food deprivation, suboptimal food quality or inhibition of gut digestive proteases significantly affected developmental rate and efficacy of B. bassiana. This research helps to create strategies for non-chemical methods to control insect pests in stored commodities.
Aeration controls insects in stored grain. Using low-volume ambient air to cool stored grain is a common management practice in the southern plains, but little research has been done recently to determine if the direction of airflow makes a difference regarding the cooling patterns. ARS scientists in Manhattan, Kansas, conducted a study by using suction aeration, pulling air downward through the grain mass, as compared to pressure aeration, the standard strategy of pushing cool air upward through the grain mass. Results of a two-year study show that temperatures on the upper surface of the grain mass were consistently cooler with suction aeration than with pressure aeration. The resulting insect pest populations were also generally lower in the bins with suction versus pressure aeration. Results demonstrate that using suction aeration would cool the upper surface zone of the grain mass, which is vulnerable to insect infestation, and could reduce the need for additional pesticide inputs through this reduction in pest pressure.
Lord, J.C. 2009. Efficacy of Beauveria bassiana for control of Tribolium castaneum with reduced oxygen and increased carbon dioxide. Journal of Applied Entomology. 133(2): 101-107. Doi: http://dx.doi.org/10.1111/j.1439-0418.2008.01322.x.
Chanbang, Y., Arthur, F.H., Wilde, G.E., Throne, J.E. 2008. Control of Rhyzopertha dominica (F.) in stored rough rice through a combination of diatomaceous earth and varietal resistance. Insect Science. 15(5): 455-460. Doi: http://dx.doi.org/10.1111/j.1744-7917.2008.00233.x.
Lord, J.C. 2009. Beauveria bassiana Infection of Eggs of Stored-Product Beetles. Entomological Research 39: 155-157.
Arthur, F.H., Yang, Y., Wilson, L.T., Siebenmorgen, T.J. 2008. Feasibility of automatic aeration for insect pest management for rice stored in East Texas. Applied Engineering in Agriculture 24: 345-350.
Park, S., Arthur, F.H., Bean, S., Schober, T.J. 2008. Impact of differing population levels of Rhyzopertha dominica (F.) on milling and physicochemical properties of sorghum kernel and flour. Journal of Stored Products Research 44: 322-327.
Arthur, F.H., Liu, S., Zhao, B., Phillips, T.W. 2009. Residual efficacy of pyriproxyfen and Hydroprene applied to wood, metal, and concrete for control of stored-product insects. Pest Management Science. 67(7): 791-797. Doi: http://dx.doi.org/10.1002/ps.1756.
Chintzoglou, G., Athanassiou, C.G., Arthur, F.H. 2008. Insecticidal effect of spinosad dust, in combination with diatomaceous earth, against two stored-grain beetle species. Journal of Stored Products Research. 46(4): 347-353. doi: http://dx.doi.org/10.1016/j.jspr.2008.03.005.
Toews, M.D., Arthur, F.H., Campbell, J.F. 2009. Monitoring Tribolium castaneum (Herbst) in Pilot-Scale Warehouses Treated with B-Cyfluthrin: Are Residual Insecticides and Trapping Compatible?. Bulletin of Entomological Research. 99(2): 121-129. Doi: http://dx.doi.org/10.1017/s0007485308006172.