1a. Objectives (from AD-416):
Objective 1: Improve and develop new monitoring strategies for stored-product insects, and improve methods for interpretation of monitoring information to aid in pest management decision making. Sub-objective 1.1: Determine relationships between outside trap captures and movement into and out of storage structures. Sub-objective 1.2: Develop and improve pheromone-based monitoring programs for stored-product insects. Objective 2: Improve and develop decision-making tools for management of stored-product insect pests. Sub-objective 2.1: Develop simulation models for insect pests of stored commodities. Sub-objective 2.2: Develop models to estimate risk of grain damage based on sampling data for insects. Objective 3: Characterize the biology of and develop management strategies for new insect pests of stored products. Sub-objective 3.1: Evaluate and develop potential attractants for stored- product psocids. Sub-objective 3.2: Evaluate response of psocid pests of stored products to temperature, moisture, and dockage gradients. Sub-objective 3.3: Determine optimal conditions for rearing hide beetles. Objective 4: Improve control strategies for insect pests of conventional and organic stored commodities, including insecticides, microbial agents, natural enemies, and physical control such as aeration and heat. Sub-objective 4.1: Assess new insecticides, microbial agents and natural enemies to control insects in stored products. Sub-objective 4.2: Develop physical methods to control insect pests of stored products. Objective 5: Identify potential genomic and proteomic targets in stored-product insect pests that can be exploited for control. Sub-objective 5.1: Obtain genetic information from stored-product insects and perform insect- and tissue-specific functional genomics and proteomics profiling to identify new potential control targets. Sub-objective 5.2: Exploit the Tribolium genome sequence to identify new control strategies for coleopteran stored-product pests.
1b. Approach (from AD-416):
This project is one of two projects within the ARS that focuses on stored product insect pests of raw grain, milling and processing facilities, and grain-based finished food products. The overall goal of the project is to refine and improve management of these pests and mitigate product loss through an approach that emphasizes cooperative research among several sub-disciplines of stored-product entomology. Research will focus on improving insect detection and monitoring, increasing efficiency of pest management strategies, improving our knowledge of pest biology, and using genomics to discover totally new ways to control these pests. Much of the research is applicable to organic, as well as conventional, commodities, and some of the research deals with new pests of stored products (often referred to as emerging pests). Specific knowledge gaps being addressed are a need: to determine how resident insect populations impact pest management; for better insect attractants for monitoring pest populations; for computer models to aid in decision making for pest management; to determine environmental conditions that attract insects to commodities; to assess new insecticides for insect control; to optimize grain cooling and commodity freezing for insect control; and to identify vital genes that can be targeted for insect control. This project builds upon the results from three previous projects, and the expected benefits of this new project will enhance management of stored-product insects and ensure the quality and safety of the U.S. grain supply and grain-based finished food products.
3. Progress Report:
Under Objective 1, significant progress was made in improving and developing new monitoring strategies for stored-product insects and interpretation of monitoring information to aid in pest management decision making. Distribution of captures of insects in traps inside and outside of food facilities was assessed, and physical and environmental factors associated with locations with greater capture were determined. Under Objective 2, significant progress was made in improving and developing decision-making tools for management of stored-product insects. Optimal number of traps needed to monitor red flour beetles was assessed in small-scale studies, and relationship between number of insects captured and population size was evaluated. We showed that adult and larval red flour beetles cannibalized eggs and pupae, but rate of cannibalization by females decreased as level of flour conditioning increased, but male cannibalization was not affected. Under Objective 3, significant progress was made in characterizing biology of and developing management strategies for new insect pests of stored products. Psocids are emerging insect pests, and we showed that they can orient to different temperature gradients in bulk grain, which provides insight for monitoring programs. Attraction of psocids to different commercial lures was assessed. The hide beetle is another emerging pest, and hide beetle colonies were established from a field population. Tests were done to assess development of hide beetle on different food sources. Under Objective 4, significant progress was made in improving and developing new control strategies for insect pests of conventional and organic stored commodities. Results of studies with aerosols and contact insecticides show psocids are more difficult to kill than beetles. Other tests show that microbes in the gut of hide beetles help reduce mortality from insect pathogens. We showed that neo-nicotenoid and pyrolle insecticides are less effective for control of hide beetles compared to flour beetles. Related tests showed that female lesser grain borers may be less susceptible than males to the grain protectant insecticide Storicide II®. Under Objective 5, significant progress was made in identifying potential genomic and proteomic targets in stored-product insect pests that can be exploited for control. We showed that the expression of many enzyme transcripts is decreased in insects that are stressed through exposure to toxins, so digestion is reduced and leads to increased mortality. However, encoding chymotrypsin enzymes are increased when insects are stressed, indicating that this specific genetic pathway can be targeted for control using microbial insecticides and inhibitors. Gene sequencing and bioinformatic analysis was initiated for the lesser grain borer, and bioinformatic analyses are being conducted for chitin assembly genes in the red flour beetle. In addition, there is a gene called Medea4 that is sometimes expressed in the red flour beetle. When this gene is present it can cause mortality, and experiments are being conducted to clone this gene and determine feasibility of using it as a control agent for red flour beetles.
1. Beetle trap catch correlated with trap density. Pheromone and food-baited traps are widely used to monitor red flour beetle populations in food processing facilities, but the number of traps needed to accurately detect pest activity and the relationship between capture in traps and beetle density were unknown. ARS scientists in Manhattan, KS, conducted a study using large experimental chambers where beetle population size could be controlled. Beetle captures increased with trap density but the rate of increase slowed at about 1 trap per about 100-150 square feet (10-15 square meters), which suggests this may be the most efficient trap density to use in a facility. When trap density was held constant and number of beetles was varied, captures increased linearly with density enabling a mathematical formula to be used to estimate beetle density based on trap capture. These findings are being validated using field-collected data, but provide critical information to improve the implementation and the interpretation of red flour beetle monitoring programs.
2. Psocids are tolerant to aerosol insecticides. Psocids (insects which are also called booklice) are pests of stored grains and grain products in most of the world, and they have natural tolerance to some of the insecticides used for control of other stored-product insect pests, such as beetles and moths. Aerosol insecticides are used in flour mills and warehouses to control beetle and moth pests, but their effect on psocid pests needs to be determined. ARS researchers at Manhattan, KS, evaluated two commonly used aerosol insecticides, methoprene and esfenvalerate, applied alone and in combination for control of four species of stored-product psocid pests. However, the aerosols did not provide effective control of the tested psocid species. This study shows that psocids may be tolerant to these aerosol insecticides when applied at rates that are normally effective for control of other stored-product insect pests. This information will help pest managers choose appropriate control strategies for psocid pests.
3. Gut microbe protects beetles from disease. Insect pathogens and microbial insecticides offer natural pest control and safe alternatives to chemical insecticides, but their impacts are limited. ARS scientists in Manhattan, KS, conducted experiments with hide beetles, emerging pests of a variety of stored commodities, and discovered that nearly ubiquitous gut-inhabiting organisms of insects have two countervailing effects. They have a small retardant effect on growth rate, but when infections are heavy they provide protection from some orally transmitted pathogens. Both effects are thought to be the result of obstruction of access to the gut wall. This research provides a basic understanding of a possible impediment to natural pest suppression and the use of microbial agents and will help to improve the arsenal of non-chemical approaches to control insect pests in stored commodities.
Arthur, F.H., Ondier, G.O., Siebenmorgen, T.J. 2012. Impact of Rhyzopertha dominica (F.) on quality parameters of milled rice. Journal of Stored Products Research. 48(1): 137-142. doi: http://dx.doi.org/10.1016/jspr.2011.10.010.