2009 Annual Report
1a.Objectives (from AD-416)
Grasshoppers and other insect pests cause serious losses to rangeland and agricultural crops in the northern Great Plains. This project has two objectives:.
1)to understand grasshopper, locust and Mormon cricket interactions in order to develop ecologically-based management strategies, and.
2)to develop, implement and evaluate the impact of biological control for the wheat stem sawfly and sugar beet root maggot in annual cropping systems.
1b.Approach (from AD-416)
For grasshoppers, habitat management practices such as grazing and fire will be used to minimize variation in grasshopper populations around lower average densities. The reciprocal interactions among grasshoppers and plant communities will also be investigated. The efficacy of existing microbial agents for grasshoppers will be improved to make rangeland application practical. The environmental cues and behavioral interactions that drive Mormon cricket migratory bands will be investigated. Safe and effective natural enemies for the wheat stem sawfly will be developed and released. Sugar beet root maggot management will be developed that integrates microbial control with other control strategies.
Grasshoppers: New research was initiated in Colorado with researchers from USDA-ARS-Rangeland Resource Unit in Cheyenne, WY and the Shortgrass Steppe Long Term Ecological Research Site to examine grazing and fire effects on grasshopper population dynamics. New research was initiated to examine the effects of outbreak populations of summer grasshopper species on survival of nymph overwintering grasshoppers, which create periodic economic damage. Research was continued examining how winter soil temperatures and fall soil moisture affect grasshopper outbreaks, as they have been hypothesized to play an important role in northern latitudes.
Wheat Stem Sawfly: We have applied for, and received an APHIS PPQ permit to import the parasitoid Collyria from China, to continue studies to screen this potential agent in our quarantine facility in Sidney. Our goal will be to assess whether Collyria can complete development on wheat stem sawfly. We will additionally assess how it might interact (antagonistically or synergistically) with native parasitoids already present in the USA. Field collections of native parasitoids have been completed, and we hope to have Collyria shipped from China in late August.
Mormon crickets (Anabrus simplex) form large migratory bands that march over rangeland in the western United States in search of nutrients. We hypothesized that immune defenses are compromised in Mormon cricket bands due to nutrient limitations. Members of a migratory band in Utah preferred a protein diet, indicating a protein deficiency like that found in Idaho. In contrast, members of the Nevada band preferred the carbohydrate diet, and showed little interest in proteins. We determined that the difference in components of the immune system that are enhanced by the contrasting diets suggests that wound healing and fighting foreign invasion requires protein whereas encapsulation and antibacterial activity require carbohydrate fuels. In the general framework of ecological nutrition, insects may require a balanced diet to maximize defense against invasion.
Biological control of grasshoppers and Mormon crickets: ARS, APHIS PPQ and Utah State University continued evaluating a domestic Metarhizium anisopliae fungus (“DWR346”) for use against grasshoppers and Mormon crickets, and two new candidate strains of the fungus, “DWR356” and DWR203”. We produced several pounds of spores of each fungus for field trials. Samples of the lead candidate, DWR346, have been given to other ARS locations for evaluation against other insects. The strain is highly pathogenic for Lygus sp., Light Brown Apple Moth, Pink Bollworm adults and larvae; moderately pathogenic for sugarbeet root maggot.
There has been recent reawakening of interest in grasshopper-specific Bacillus thuringiensis strains. With discovery of two such strains in China. USDA ARS possesses 40,000+ B thuringiensis strains, many of which have not had their target activity characterized. NPARL has set up and validated a grasshopper bioassay for this purpose and begun initial screens.
NPARL scientists demonstrated that reducing populations of summer pest grasshopper species through manipulations of nymph-overwintering grasshoppers does not appear a promising management tactic. Nymph-overwintering grasshoppers periodically reach outbreak densities, but it is unknown if they impact the population dynamics of egg-overwintering grasshopper species, or if their herbivory reduces peak biomass production and causes economic damage. As a result, land managers and ranchers do not have the information needed to determine if grasshopper control is warranted during periods with high densities of nymph-overwintering grasshoppers. The results indicate that high densities of nymph overwintering grasshoppers would be required to reduce the survival of summer pest grasshopper species. Such high densities of nymph-overwintering grasshoppers would also result in a large reduction in grass biomass available for livestock. As a result, it does not appear feasible to manage populations of summer pest grasshopper species through manipulations of nymph-overwintering grasshopper densities. A better understanding of the processes leading to grasshopper outbreaks will allow ranchers and land managers to more cost-effectively and sustainably manage grasshopper populations, while reducing the use of pesticides.
Development of Superior Microbial Control Agents for Mormon cricket and Grasshopper Control: USDA ARS and APHIS PPQ are jointly searching for environmentally safe and effective microbial agents to manage outbreaks of Mormon crickets and grasshoppers in the Western United States. NPARL demonstrated in a second year of outdoor testing the superiority of a domestic fungus, Metarhizium DWR346, to both currently registered, commercial mycoinsecticides for Mormon cricket control and grasshopper control. These data, along with mass production evaluations made by NPARL, point toward the practical potential of this fungus. As a result USDA is closer to developing a satisfactory microbial control agent, to substitute for the broad-spectrum chemical insecticides currently in use on rangelands.
Branson, D.H. 2009. Influence of Individual Body Size on Reproductive Traits in Melanopline Grasshoppers (Orthoptera: Acrididae). Journal of Orthoptera Research. 17(2):259-263.
Rho, J.R., Srygley, R.B., Choe, J.C. 2009. Age of the Jeju pony (Equus caballus) at first reproduction: potential costs for foals and mothers that first reproduce early in life. Journal of Ethology. Journal of Ethology. 27(3):483-488.
Srygley, R.B., Dudley, R., Oliveira, E.G., Aizprua, R., Pelaez, N.Z., Riveros, A.J. 2010. El Niño and Dry Season Rainfall Influence Hostplant Phenology and an Annual Butterfly Migration from Neotropical Wet to Dry Forests. Global Change Biology. 16:936-945.
Jaronski, S., Jackson, M.A. 2008. Efficacy of Metarhizium anisopliae microsclerotial granules. Biocontrol Science and Technology. 18(8):849-863.
Solter, L.R., Gelernter, W.D. and Jaronski, S. 2009. Entomopathogens. In: Edited by W. Lamp, R. Berberet, L. Higley, and C. Baird. Handbook of Forage and Rangeland Insects. Entomological Society of America. pp. 146-153.