March 2013
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Methodology for Determining Susceptibility of Rough Rice to Rhyzopertha dominica (L.) and Sitotroga cerealella (Olivier)
There are few recent tests that evaluate susceptibility of stored rice to stored-product insects. We evaluated different long grain rice varieties for susceptibility to two major insect pests, the lesser grain borer and the Angoumois grain moth, using different methods. Adult lesser grain borers were first exposed on the rice varieties, then removed. Adult feeding caused the varieties to become more susceptible to larval feeding, which in turn increased progeny production. Some varieties were more susceptible than others to the lesser grain borer. Since adult Angoumois grain moths do not feed, we exposed mating pairs of adults to produce larvae that would infest the rice. All varieties were susceptible to damage caused by larval Angoumois grain moth, including those that did not support lesser grain borer growth and development. Results show that varietal susceptibility to stored-product insects may differ with insect species.
• Frank Arthur, 785.776.2783, Frank.Arthur@ars.usda.gov |
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January 2013
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Potential for Hypobaric Storage as a Phytosanitary Treatment: Mortality of Rhagoletis pomonella in Apples and Effects on Fruit Quality
Storage under low oxygen conditions increases the shelf life of fresh fruits and vegetables and is being used increasingly for that purpose on a commercial basis. It is known experimentally to kill insects as well and has been researched as a treatment to kill insects that may be present in fruit exported to areas where those insects do not exist and might become established. However, that application is not used commercially. Low pressure is a way of achieving low oxygen storage. Although it has been researched considerably for use against stored-product insects, little research has been done for control of quarantine pests of significance on fresh fruits and vegetables and no research that we are aware of has been done for control of an internal feeder in a fruit, which are the most important and difficult to manage quarantine pests. This research investigated low pressure to kill eggs and larvae of the apple maggot (Rhagoletis pomonella) in apples. Infested apples were exposed to two pressures, 3.33 and 6.67 kPa (kilopascals) (0.5 to 1 pound per square inch), in jars at 25 and 30°C (77 and 86°F) for 3-120 hours. Mortality of eggs and larvae increased with increase in time of exposure. Apples exposed to 3.33 kPa at 25 and 30°C for 3 and 5 d were unaffected for aroma and taste, although in ‘Red Delicious’ but not ‘Golden Delicious’ apples the internal and external appearances were affected. Eggs and larvae were all killed at conditions that did not affect ‘Golden Delicious’. Use of low pressure for disinfestation and preservation of apples is a potential, non-chemical treatment for exported fruit.
• Guy Hallman, 785.776.2705, Guy.Hallman@ars.usda.gov |
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December 2012
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The Case for a Generic Phytosanitary Irradiation Dose of 250 Gy for Lepidoptera Eggs and Larvae
Ionizing radiation is being used increasingly as a phytosanitary treatment to overcome biological barriers to trade in agricultural products. Generic treatments (one dose is used for a group of commodities and/or quarantine pests) allow for broader application. A generic dose of 250 Gy is proposed for all eggs and larvae of the insect Order Lepidoptera, a key group of quarantine pests. The measure of efficacy of this treatment is prevention of emergence of normal-looking adults when the most radiotolerant stage, late larva, is irradiated. This dose is supported by many studies comprising 29 species in 10 lepidopteran families, including some of the most important families and species of quarantine importance. Two of the studies found that doses >250 Gy were necessary, but they are contradicted by other studies with the same species showing that <250 Gy is adequate. In comparison a dose of 150 Gy for Tephritidae (fruit flies) was accepted by APHIS and the International Plant Protection Convention when only 14 species were studied and a number of studies did not support that low of a dose. A dose of 250 Gy for all Lepidoptera eggs and larvae gives a liberal margin of error that no insects in the group will survive the treatment.
• Guy Hallman, 785.776.2705, Guy.Hallman@ars.usda.gov |
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November 2012
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Transcript Analysis and Expression Profiling of Three Heat Shock Protein 70 Genes in the Ectoparasitoid Habrobracon hebetor (Hymenoptera: Braconidae)
The Indianmeal moth is a major pest of stored grain and processed commodities. There is a small wasp that does not sting humans but parasitizes the Indianmeal moth, and releasing these parasitic wasps would be an environmentally friendly way to control the Indianmeal moth. But, there is currently no way to store these wasps for when they are needed for controlling the Indianmeal moth. We previously showed that the wasp can enter reproductive diapause (a resting stage where they don’t produce offspring) when reared at low temperature and short photoperiod, and diapausing females have a higher rate of survival during cold storage and lay more eggs after cold storage than nondiapausing females. Heat shock proteins (HSPs) are known as chaperones that help with folding of other proteins when cells are under environmental stresses, and HSPs are essential for cold survival during insect diapause. We identified three HSP genes in the wasp, and characterized their expression levels during exposure to cold. Knowing how heat shock protein genes respond to cold stress may allow enhancement of diapause and prolonging the duration of low-temperature storage of insects by finding ways to artificially control the expression of these genes.
• James Throne, 785.776.2796, James.Throne@ars.usda.gov |
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October 2012
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Control of Stored Product Pests by Ionizing Radiation
The use of food irradiation is increasing in the world because it can assist in solving some food problems such as food-borne illness and quarantine of agricultural commodities. This review article focuses on the use of irradiation in stored products for pest control. The doses required to control stored product pests range from 50 Gy for yellow mealworm to 450 Gy for Angoumois grain moth. Although small amounts of grain and pulses are irradiated in the world today, that amount is increasing, especially in Asia. Thirty three countries permit irradiation of some stored products with 14 permitting it for all stored products. One area that may show promise for use on exported grain is to prevent seeds from invasive plants from growing.
• Guy Hallman, 785.776.2705 Guy.Hallman@ars.usda.gov |
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Characterization of cDNAs Encoding Putative Serine Proteases and their Transcriptional Responses to Cry1Ab Protoxin in the Gut of Ostrinia nubilalis Larvae
Insect proteases affect the efficacy of insecticidal microbial toxins, such as those from the bacterium Bacillus thuringiensis (Bt). Thus, understanding the expression of protease genes in a target pest is important to more effectively design and deploy Bt toxins. Larvae of the European corn borer, a major target of Bt transgenic corn, express a suite of proteases at various locations in the gut. Our data suggests that protease genes can be grouped by genetic relatedness and expression patterns in the gut. We found that some protease genes were increased in expression when larvae were exposed to toxin. These data represent the most comprehensive study to date on larval gut proteases and the effect of Bt toxin on gene expression in the European corn borer. The data can be used to improve transgenic constructs for efficacy and durability in the field.
• Brenda Oppert, 785.776.2780, Brenda.Oppert@ars.usda.gov |
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June 2012
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Sampling Stored Product Insect Pests: A Comparison of Statistical Sampling Models to Maximise Pest Detection
Pest Management Science Sampling stored grain for insect pests is critical for maintaining grain quality and to determine if insect control is necessary. To develop the best sampling protocol for stored grain it is important to select a statistical model that explains how the insects are distributed in the grain, because the model can be used to predict the number of samples necessary to detect insects in the grain. In collaboration with scientists from Queensland University of Technology and Kansas State University, we compared the accuracy of four different statistical models to detect insects in grain. Of the four models, the compound model performed the best under both high and low insect densities. The findings from this study will be used to improve insect pest management programs for stored grain.
• Paul Flinn, 785.776.2707, Paul.Flinn@ars.usda.gov |
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April 2012
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Residual Efficacy of Methoprene for Control of Tribolium castaneum (Coleoptera: Tenebrionidae) Larvae at Different Temperatures on Varnished Wood, Concrete, and Wheat
The insecticide methoprene is an insect growth regulator that affects molting and development of immature insects. It has been evaluated as an aerosol insecticide but it has not been sufficiently examined as a residual surface treatment. We conducted studies by spraying concrete and wood surfaces with methoprene and holding these surfaces at different temperatures, with or without flour, for up to 24 weeks. We then added flour to the bare surfaces or removed the aged flour and added new flour, and then added larvae of the red flour beetle to determine adult emergence. Methoprene applied to wood gave excellent residual control of the red flour beetle, but, on concrete, residual control declined with time and the presence of flour on concrete during aging reduced the effectiveness of the insecticide. Persons responsible for insect pest control can utilize these results to integrate methoprene into their management programs for the red flour beetle.
• Frank Arthur, 785.776.2783, Frank.Arthur@ars.usda.gov |
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Genomic and Proteomic Analyses of the Mode of Action of the Insect Growth Regulator Diflubenzuron in Tribolium castaneum
The insect exoskeleton (cuticle) has many unique functions vital for insect survival, and is therefore an attractive target for new biopesticide design. One of the older pesticides, diflubenzuron, has already been shown to disrupt insect cuticle, but exactly how this occurs has never been demonstrated. We used modern genomic techniques to assess the effects of diflubenzuron toxicity on gene expression for 11,000 of the 16,000 total genes in the red flour beetle genome. Interestingly, genes for metabolism of chitin (a component of insect cuticle) were not affected, but cuticle proteins did show abnormal expression. Genes for diflubenzuron detoxification showed increased activity. This work demonstrates the complexity of diflubenzuron’s mechanism of toxicity, which could explain why this mechanism has remained elusive for decades. Modern genomic technology should enable this mystery to be solved, opening the door for better design of biopesticides that target the insect cuticle.
• Richard Beeman, 785.776.2710, Richard.Beeman@ars.usda.gov |
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