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United States Department of Agriculture

Agricultural Research Service

2010 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.

3.Progress Report
This is the final report for the Project 5430-43000-025-00D terminated in April 2010. All experiments described in the Project Plan for Project 5430-43000-025-00D were completed. This project is continued in the Bridging Project 5430-43000-029-00D.

The results of the 5-year plan were extensive and substantial. Aeration is an under-utilized pest management strategy to manage temperature in stored grains, and our studies showed the potential for the expanded use of aeration to control insect pests of stored rice. In addition, suction aeration gave quicker cooling of the top layer of stored wheat during the summer months when compared to standard pressure aeration, resulting in improved insect control. We also showed that rice varieties with a greater percentage of splits and cracks were more likely to be infested with the lesser grain borer. Varietal resistance could be integrated with other methods for control of stored-product insects. We have shown that insect growth regulators and diatomaceous earth, an inert dust, could be used instead of conventional insecticides to protect stored wheat and also stored rice from insect damage. These growth regulators could be combined with other reduced-risk insecticides, microbial pathogens, or fungal pathogens to enhance insect control. Several new insecticides and insect pathogens were evaluated for control of stored-product insects. Registration for the contact insecticide chlorfenapyr was expanded to include flour beetles.

We demonstrated that various stresses, including reduced oxygen and desiccation, enhance the efficacy of a fungal biological control agent for several stored-products pests. We demonstrated enhanced efficacy of the fungus Beauveria bassiana for red flour beetles under dietary stress, and further, that the fungus, itself, can contribute to dietary stress because it deters feeding. We found that B. bassiana and two other fungal species were lethal to the larvae of the hide beetle, an emerging pest species. Of several substrates that were tested, only wood, on which the spores of all three species die quickly, had an impact on the performance of the fungi. We developed an immunoassay to detect beetle infections with a naturally occurring protozoan pathogen of insects and used it to test seven rusty grain beetle laboratory cultures from the US and elsewhere, all but one of which were infected with the pathogen. Another protozoan pathogen of beetles was found in a new host and, after bioassays and genetic analysis, was transferred to the appropriate genus.

1. Biological insecticide spinosad controls lesser grain borer. Spinosad is a biological insecticide that is being evaluated for insect control in stored grains, but there is no information as to the effectiveness of this insecticide if grains receive only partial treatment. ARS scientists in Manhattan, KS, conducted laboratory tests by exposing lesser grain borers, rice weevils, and several psocid species to different amounts of treated wheat mixed with untreated wheat. Partial treatments were effective for the lesser grain borer but not as effective for rice weevils or psocids. Results show the effectiveness of spinosad will depend on the target species, the depth of the treated layer, and the upward or downward mobility of the insect species.

2. Psocid susceptibility varies with insecticide. Psocids, or booklice, are emerging pests in stored products, including stored grains, but new data indicate psocids are tolerant to insecticides used to control other stored-grain insect pests. We evaluated several grain protectants registered in the United States for control of different psocid species. On wheat and rice, the insecticide chlorpyriphos-methyl + deltamethrin (Storicide II®) was generally more effective in controlling adults and reducing progeny production than either spinosad or pyrethrum, and pirimiphos-methyl (Actellic®) was more effective on corn than spinosad or pyrethrum. Our results show that if psocids are the target pests on wheat and corn, the insecticides that will give the best control are Storicide II on wheat and Actellic on corn.

3. Surface treatments with methoprene are not completely effective for lesser grain borer control. Grain protectants can be used to treat the top portion of a grain mass during storage, but there is little information regarding control of insects using this method. ARS scientists in Manhattan, KS, conducted laboratory studies using the insect growth regulator methoprene, which affects immature stages of insects but not adults, to determine if treating the top of portion of wheat, rice, and corn would control the lesser grain borer, an important economic pest of stored grains. In wheat and rice, the layer treatments were not as effective as whole-grain treatment, but there were fewer progeny produced as the application rate of methoprene increased. However, on corn the partial treatments were as effective as the whole-grain treatment. Results show that partial layer treatments with methoprene can be used to control lesser grain borers on corn but not on wheat and rice.

4. Catmint oil potential new repellent for flour beetles. Repellents are used in insect pest management programs for some insect species but there are few repellents that can be used for stored-product insects. ARS scientists in Manhattan, KS, evaluated two types of oils made from catmint plants as repellents for the red flour beetle and the confused flour beetle. Visual assessments and video recordings were used to evaluate the reactions of the beetles to the repellents. Simple visual assessments were inconclusive, but the video recordings showed that both oil products were more repellent to the red flour beetle than to the confused flour beetle. Red flour beetles would avoid the area that was treated with the oils. The results show that the catmint oil products are effective as repellents for the red flour beetle.

5. Fungus deters feeding by the red flour beetle. Beauveria bassiana, a fungus that is commercially produced for biological control, has previously been shown to be more efficacious for red flour beetles when they are under dietary stress. ARS scientists in Manhattan, KS, demonstrated that the presence of the fungus in a beetle food source reduces feeding and slows larval development. This means that the fungus causes population development effects beyond simply killing the target insects. It also could have a negative impact on the proposed use of the fungus in self-exposure traps for spreading the fungus among insect populations.

6. Symbiotic fungus identified in mealworms. ARS scientists in Manhattan, KS, found an unusual symbiont in nervous tissue, fat body, and male reproductive tissue of the yellow mealworm. Its identity as a fungus that is distinct from known species was established by sequencing a key diagnostic gene. This is a rare case of transmission from male to female during mating with apparent transfer to the eggs as they are deposited. This research will improve the understanding of transmission of diseases that are carried by insects.

Review Publications
Arthur, F.H., Casada, M. 2010. Directional Flow of Summer Aeration to Manage Insect Pests in Stored Wheat. Applied Engineering in Agriculture 26: 115-122.

Lord, J.C., Hartzer, K.L., Toutges, M.J., Oppert, B.S. 2010. Evaluation of Quantitative PCR Reference Genes for Gene Expression Studies in Tribolium castaneum After Fungal Challenge. Journal of Microbiological Methods. 80: 219-221.

Athanasiou, C.G., Arthur, F.H., Throne, J.E. 2009. Efficacy of Grain Protectants Against Four Psocid Species on Maize, Rice, and Wheat. Pest Management Science. 65: 1140-1146.

Arthur, F.H. 2009. Efficacy of Chlorfenapyr Against Adult Tribolium castaneum Exposed on Concrete: Effects of Exposure Interval, Concentration, and the Presence of a Food Source After Exposure. Insect Science. 16: 157-163.

Arthur, F.H., Johnson, J.A., Neven, L.G., Hallman, G.J., Follett, P.A. 2009. Insect Pest Management in Postharvest Ecosystems in the United States of America. Outlooks on Pest Management. 20: 279-284.

Last Modified: 3/2/2015
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