2010 Annual Report
1a.Objectives (from AD-416)
Investigate, develop and evaluate the use of predators, parasitoids, entomopathogens, feeding stimulants or deterrents, cultural controls, host resistance, and other environmentally -friendly tactics in IPM programs for Colorado potato beetle, corn rootworm and other chrysomelid pests.
Develop methods for improved management of gypsy moths in non-forest and newly infested forested areas of the United States, particularly mating disruption techniques.
1b.Approach (from AD-416)
Characterize and develop new tactics to manage chrysomelid leaf beeetles, particularly Colorado potato beetle and corn rootworms, and in labratory, semi-field and field experiments, evaluate various methods of deployment, such as primary toxicants or pathogens, habitat augmentation, conservation biocontrol, baits or other attracticidal formulations, or incorporation in crop or trap plants. Studies will encompass biology, host specificity, behavior, non-target effects and environmental impact of biological control agents and other tactics. Studies will be conducted in cooperation with U.S. Forest Service "slow the spread" national Gypsy Moth Project and partners to disrupt gypsy moth mating.
During fiscal year 2010, research progress was made towards developing effective, environmentally sound biological controls, through natural and biotechnological methods, for use against agricultural pests. To address our goal of characterizing natural enemies which function as biological controls of pests, we determined the effect of non-prey foods on consumption of target pest prey by generalist predators, and their ability to digest prey and non-prey foods based on life stage. This is very important to determining the role for non-prey food such as pollen, nectar, and possible supplements in lab or field settings, on the predatory behavior of generalist or omnivorous predators. We also determined whether mass collection of predators for molecular gut-content analysis has the potential to compromise resulting data by contaminating the predators’ surfaces with exogenous DNA from other animals collected at the same time. Finding that it did, they developed a simple and rapid laboratory protocol to inactivate contaminating DNA. Adoption of this inactivation step enables mass collection of the large numbers of predators needed for meaningful ecological research without fear of contamination by exogenous DNA.
To address our goals of developing plants which respond to pest damage with effective innate defense mechanisms, we tested whether the highly infestation-induced gene pot167 and its homolog pop3 are insecticidal using expression of the recombinant genes in tobacco with PVX. We have shown that this gene is highly expressed by infestation in poplar, but its potential as a defensive gene has never been examined. We are currently transiently over-expressing these genes in tobacco using potato virus X. We will test the effect on insect development using bioassays of the recombinant PVX expressing plants. We have successfully expressed the pot167 promoter with the marker gene ß-glucuronidase (gus) in Arabidopsis and have shown that it is inducible by infestation. However, we were unable to produce viable Arabidopsis plants containing the pot167 promoter fused to an insecticidal cry gene. Considering this outcome and the fact that we will not continue work on Colorado potato beetle, we have not attempted transformation of tomato or potato with the pot167gus or cry construct.
Identification of maize genes affected by infestation of southern corn rootworm (CRW). Approximately 58,000 maize genes were examined by ARS researchers in Beltsville, Maryland, and researchers at the University of Alberta, Canada using microarray to determine whether they were differentially expressed upon infestation by CRW. 308 genes were induced in the root by infestation 2.7-22.7 fold. 237 maize genes in the root were repressed by CRW infestation. Since the maize genome has been sequenced, knowledge of the promoter regions of these genes is available and could be used to isolate CRW induced promoters for infestation-inducible expression of insecticidal genes. This will allow expression of the insecticidal gene in the infested root rather than the uninfested regions of the plant, which will produce maize with significantly less transgenic protein in the edible parts of the maize plant.
ARS scientists in Beltsville, Maryland, in collaboration with other ARS and university scientists, have made significant improvements in the methods used to determine what beneficial insect predators are eating what insect pests. Using molecular tools to determine food consumption patterns by beneficial predators requires collection of large numbers of insects, but since these methods are very sensitive, the methods used must assure that the predators are not contaminated with pest DNA during the sampling process, which could yield false positive detections. Findings indicate that mass collection methods can be accompanied by simple decontamination methods to obtain reliable information on biological control (feeding on pests) by insect predators. This will assist in determining which predators are most important in controlling agricultural pests.
Insight into predation consumption and digestion of prey and non-prey foods. ARS researchers (in Beltsville, Maryland, in collaboration with ARS researchers in Brookings, South Dakota) determined that larvae and adult generalist predators have variable ability to exploit non-prey foods, which are important for the survival and nutrition of many important natural enemies in agricultural systems. This is important to the conservation and augmentation of natural enemies to suppress major crop pests.
Dervinis, C., Frost, C., Lawrence, S.D., Novak, N.G., Davis, J. 2010. Cytokinin primes plant responses to wounding and reduces insect performance. Journal of Plant Growth Regulation. 29(3):289-296.
Greenstone, M.H., Szendrei, Z., Payton, M.E., Rowley, D.L., Coudron, T.A., Weber, D.C. 2010. Choosing natural enemies for conservation biological control: use of the prey detectability half-life to rank agroecosystem predators. Entomologia Experimentalis et Applicata. 126:97-107.
Lundgren, J.G., Weber, D.C. 2010. Changes in Digestive Rate of a Predatory Beetle over Its Larval Stage: Its Implications for Dietary Breadth. Journal of Insect Physiology. 56:431-437.
Jeffrey, S., Lawrence, S.D., Krell, P.J., Arif, B.M. 2010. A soluble form of P74 can act as a per os infectivity factor to the autographa californica multiple nucleopolyhedrovirus. Journal of General Virology. 91:915-918.
Szendrei, Z., Kramer, M.H., Weber, D.C. 2009. Habitat manipulation in potato affects Colorado potato beetle dispersal. Journal of Applied Entomology. 133:711-719.
Szendrei, Z., Greenstone, M.H., Payton, M.E., Weber, D.C. 2009. Molecular gut-content analysis of a predator assemblage reveals the effect of habitat manipulation on biological control in the field. Basic and Applied Ecology. 11:153-161.