Location: Pest Management Research
2016 Annual Report
Objectives
Objective 1: Determine the role of rangeland insects, particularly grasshoppers and Mormon crickets, on rangeland ecosystem function and production. [NP304, Component 3, Problem Statements 3B1, 3B2]
Subobjective 1.A: Identify the impacts of grasshopper herbivory and drought on rangeland function and nutrient cycling.
Subobjective 1.B: Identify the competitive and predatory interactions between Mormon crickets and grasshoppers, their impacts on plant community composition and nutrient cycling on rangeland, and the effect of grasshopper abundance on Mormon cricket immunity to disease.
Objective 2: Identify climatic and biotic ecological drivers of pest population dynamics (such as wheat stem sawflies, grasshoppers, and Mormon crickets) in order to develop practical predictive models of when these key pests will exceed economic thresholds. [NP304, Component 3, Problem Statements 3A1, 3B1, 3B2]
Subobjective 2.A: Using long-term monitoring data, identify climatic and vegetation/landscape components that are associated with population shifts and variability of individual grasshopper species and grasshopper species diversity.
Subobjective 2.B: Determine whether Mormon crickets have annual, biennial, and plurennial populations, and identify cues that cause females to lay eggs that break diapause and hatch after one, two, or several winters.
Subobjective 2.C: Identify the role of moisture stress in breaking diapause and triggering Mormon cricket embryonic development.
Subobjective 2.D: Identify climatic correlates of wheat stem sawfly and parasitoid wasp abundance and quantify the effects of precipitation on pest pressure, biological control and crop yield.
Objective 3: Design sustainable approaches (e.g. roadside and conservation plantings, landscape diversification, rangeland fire, and grazing management) to manage key crop and rangeland insects, such as wheat stem sawfly, grasshoppers, and their natural enemies. [NP304, Component 3, Problem Statements 3A2, 3B2]
Subobjective 3.A: Identify components of native vegetation that provide sugar resources for beneficial natural enemies, and assess the potential influence of these resources on natural enemy longevity and biological control.
Subobjective 3.B: Identify components of rangeland management practices that can be used to sustainably manage grasshopper populations.
Objective 4: Develop microbial control agents as tools for control of key rangeland and wheat pests [NP304, Component 3, Problem Statement 3A2, 3B2]
Subobjective 4.A: Develop microbial control agents for grasshoppers and Mormon crickets.
Subobjective 4.B: Determine the biological significance of endophytic Beauveria affecting wheat stem sawfly.
Approach
Grasshoppers, Mormon crickets and wheat stem sawfly are key constraints on rangeland and crop productivity. Grasshoppers and Mormon crickets consume ~$1.5 billion of forage annually and wheat stem sawfly causes ~$250-350 million in crop damage annually. Current control strategies for these major pests are inadequate, costly and/or result in unacceptable environmental impacts due to the historical reliance on broad spectrum insecticides. The goal of this proposed project is to acquire the knowledge needed to develop innovative, environmentally sound and sustainable management alternatives for control of these pests which currently lack sustainable control measures. To achieve this end, we will pursue research to broaden our ecological foundation, enhance prevention of pest outbreaks, and develop microbial intervention tools. We will develop a sound understanding of pest impacts on rangeland function and determine climatic and biotic drivers that cause these pervasive Great Plains pests to exceed economic thresholds. We will design sustainable habitat and landscape approaches to manage these pests and their natural enemies. We will develop microbial control agents to provide critically needed alternatives to pesticide-based control. Pursuing research along these themes of ecology, prevention and intervention will provide the foundational knowledge necessary to achieve the ultimate goal of developing ecologically-based and economically practical management strategies that reduce economic impacts and promote food security, while decreasing environmental impacts of control measures. We will communicate our results through on-going relationships with land management agencies, farmers and ranchers, academic societies, industry and state extension services.
Progress Report
Wheat stem sawfly: Controlling wheat stem sawfly with fungi. Attempts to make Beauveria/Metarhizium fungi establish inside live wheat plants were successful although there was considerable variation among the 15 wheat varieties and 5 strains of fungi. Foliar spray was the most successful way to get the fungi to grow inside the wheat. Key fungus isolates are highly infectious for sawfly larvae that live inside wheat stems.
Carried out the second year of a common garden experiment to assess the performance of wheat stem sawfly larvae and associated parasitoids on common native and introduced grass species. Finished processing samples from year 1, and are now carrying out year 2, of a large precipitation manipulation experiment to assess drought effects on wheat stem sawfly infestations and the efficacy of their native parasitoids.
Grasshoppers: Long-term grasshopper sampling continued at 25 sites, with the goal of better predicting grasshopper outbreaks since detailed long-term data is highly uncommon. Initiated new collaborative USDA/NIFA funded research examining if a diverse grasshopper community is beneficial to rangeland functioning. New collaborative research examining how grasshopper communities respond to oil pad restoration and their impact on grazing systems was initiated in the Bakken oil field in Western ND. Expanded collaborative research examined how removal of the weedy tree Russian olive, followed by conversion into grasslands, affects grasshoppers and other insects, with results transferred to land managers.
A fungus bait for grasshoppers showed successful efficacy in lab and outdoor testing, with optimal spore loading on bait, and bait applications rates identified.
Alfalfa weevil: Completed 8th year sampling alfalfa weevils in the Yellowstone River Valley, and quantified larval parasitism (8 sites). Designed and coordinated a collaboration with researchers in MT, SD, WY to carry out a cross-state survey for parasitoids that attack adult alfalfa weevils. Preliminary rearing results suggest that although we surveyed counties where the parasitoids were recovered in the 1980’s they are no longer present in these areas.
Mormon crickets: Conventionally Mormon crickets are thought to require a single winter to hatch, but a population at high elevation (8000 feet) in the Bighorn Mountains of Wyoming is reported to require two summers to develop. ARS researchers at Sidney, MT investigated whether photoperiod could serve as a cue to delay embryonic development to the second summer. Twenty mating pairs were setup in a long-day photoperiod (15:9 h, corresponding to mid-summer in the Bighorn Mountains), and 20 others in a short-day photoperiod (12:12 h, corresponding to summer’s end). The photoperiod did not affect whether the eggs developed directly in the first summer or delayed their development until a later year.
Accomplishments
1. Landscape design as a tool to reduce pest outbreak duration and increase system stability in alfalfa. Alfalfa weevil is a major pest of alfalfa nationwide, and currently there are limited options for sustainable (non-chemical) approaches to manage this pest in the Great Plains. ARS researchers at Sidney, Montana demonstrated that larger alfalfa fields had higher average alfalfa weevil densities, and were more likely to sustain economic infestations of weevils following an outbreak year than smaller fields. At the same time, more alfalfa acreage in the landscapes surrounding individual fields was associated with both increased stability in attack by biocontrol parasitoids, and reduced pest densities and outbreak duration. The results suggest that designing agricultural systems such that individual fields are smaller and more evenly spread across the landscape would reduce weevil impacts, and stabilize biological control.
2. Grasshoppers frequently reach outbreak densities that can cause economic damage to the livestock grazing industry. Weather can impact grasshopper population dynamics, but our ability to predict the impacts of drought on grasshopper outbreaks needed by mangers is lacking. ARS researchers at Sidney, Montana examined the impact of competition and drought on performance of an economic pest grasshopper species. Despite much greater than normal late summer precipitation, grass biomass, grasshopper body size and grasshopper reproduction were all strongly affected by the drought treatment. This indicates that early summer drought could strongly negatively influence populations of this grasshopper, even when late summer precipitation is above average, thus reducing the need to actively manage existing outbreaks, and thus lowering the amount of pesticide use across large rangelands.
3. Parasitoid digger wasps prefer female Mormon crickets to males and may drive migration of Mormon crickets away from natal sites. By radio-tracking Mormon crickets in a migratory band, ARS researchers at Sidney, Montana found that predation by parasitoid digger wasps was heavy with 25% of the Mormon crickets paralyzed and drug underground to provision the wasps’ nests in a single day. Avoidance of wasp predation explains in part the migration of Mormon crickets away from natal sites, but the ability of wasps to encounter Mormon cricket bands and their strong preference for female Mormon crickets (6:1 over males) to provision their offspring make the wasps particularly effective at controlling Mormon cricket populations. Preferential predation on females results in a decline in the number of Mormon cricket eggs laid that is twice as fast as when predators are unbiased in their selection of the sexes.
Currently seeking a minority graduate student for internship in lab. Unsuccessful at present.
Review Publications
Branson, D.H., Vermeire, L.T. 2016. Grasshopper responses to fire and postfire grazing in the northern Great Plains vary among species. Rangeland Ecology and Management. 169(2):144-149. doi:10.1016/j.rama.2015.10.005.
Rand, T.A., Morrill, W.L., Runyon, J.B., Hoelmer, K.A., Shanower, T.G., Littlefield, J.L., Weaver, D.K. 2015. Assessing phenological synchrony between the Chinese sawfly, Cephus fumipennis, its egg-larval parasitoid, Collyria catoptron, and the North American sawfly, Cephus cinctus: Implications for biological control. The Canadian Entomologist. 148(4):482-492. doi:10.4039/tce.2015.64.
Mogren, C.L., Rand, T.A., Lundgren, J.G. 2016. The effects of crop intensification on the diversity of native pollinator communities. Environmental Entomology, 45(4), 865–872. doi: 10.1093/ee/nvw066.
Srygley, R.B., Lorch, P.D. 2016. Loss of safety in numbers and a novel driver of mass migration: radiotelemetry reveals heavy predation on a band of Mormon crickets. Royal Society Open Science. 3(5):160113. doi:10.1098/rsos.160113.
Rand, T.A., Waters, D.K., Shanower, T.G. 2015. Preliminary evaluation of the parasitoid wasp, Collyria catoptron, as a potential biological control agent against the wheat stem sawfly, Cephus cinctus, in North America. Biocontrol Science and Technology. 26(1):61-71. doi:10.1080/09583157.2015.1076377.
Lundgren, J.G., Mcdonald, T., Rand, T.A., Fausti, S. 2015. Spatial and numerical relationships of arthropod communities associated with key pests of maize. Journal of Applied Entomology. 139:446-456.
Basset, Y., Barrios, H., Segar, S., Srygley, R.B., Aiello, A., Warren, A.D., Delgado, F., Coronado, J., Lezcano, J., Arizala, S., Rivera, M., Perez, F., Bobadilla, R., Lopez, Y., Ramirez, J.A. 2015. The butterflies of Barro Colorado Island: Local extinction rates since the 1930's. PLoS One. 10(8):e0136623. doi:10.1371/journal.pone.0136623.
Srygley, R.B. 2016. Diet drives the collective migrations and affects the immunity of Mormon crickets and locusts: A comparison of these potential superspreaders of disease. Integrative & Comparative Biology. 56(2):268-277. doi:10.1093/icb/icw035.
Srygley, R.B. 2016. Mormon crickets maximize nutrient intake at the expense of immunity. Physiological Entomology. 42(1):1-9. doi:10.1111/phen.12155.
