Location: Pest Management Research2013 Annual Report
1a. Objectives (from AD-416):
Objective 1: Clarify how grasshoppers influence interactions between exotic and native grassland plants and the sustainability of grazing systems. Objective 2: Define factors that influence grasshopper outbreaks and Mormon cricket migration to enhance predictions of when outbreaks and migration occur, and identify management techniques that impact population densities. Subobjective 2a: Define the impact climate conditions have on grasshopper and Mormon cricket egg survival to further understand population dynamics and outbreaks. Subobjective 2b: Examine the effectiveness and underlying mechanisms of grassland management practices, such as fire and livestock grazing, to sustainably manage grasshopper populations. Objective 3: Identify ecological factors underlying variability in populations of key crop insect pests and their natural enemies, and identify factors and/or management approaches that augment natural enemies and maximize control of key insect pests. Subobjective 3a: Quantify the effects of semi-natural habitat (grasslands) on grass feeding herbivore-parasitoid food web dynamics and pest pressure in small grains. Subobjective 3b: Determine the effects of landscape structure on the diversity and abundance of natural enemy communities associated with alfalfa pests and how this ultimately influences key interaction-based ecosystem services (i.e. biological control of pests by parasitoids, predators and pathogens). Objective 4: Define biological factors and mechanisms that regulate locomotion, reproduction, and immunity to enhance grasshopper and Mormon cricket management. Subobjective 4a: Identify intake target of Mormon crickets in last nymphal instar and first 8 days of adult life, during which reproductive and immune systems are maturing, and determine if dietary deficiencies alter the efficacy of fungal control. Subobjective 4b: Determine if dietary deficiencies exhibited by migratory Mormon crickets in the field alter their ability to escalate their immune responses. Objective 5: Develop commercializable microbial control agents and methods for their use in managing pest insects such as grasshoppers and Mormon crickets. Objective 6: Assess the suitability and potential effectiveness of classical biocontrol agents against wheat stem sawfly.
1b. Approach (from AD-416):
Insects are key constraints in crops and rangelands. Rangeland is a fundamental resource for the beef industry, with grasshoppers frequently affecting food security on all inhabited continents. Wheat and alfalfa rank as the third and fourth most important crops grown in the U.S. ARS stakeholders have identified grasshoppers and Mormon crickets in rangeland, and wheat stem sawfly and alfalfa weevil in cropping systems as high priority pests. Current control strategies for these pests are inadequate, costly and result in unacceptable environmental impacts. Pest management in the modern era has generally focused on suppressive tactics, primarily via chemical means. However, the increasing reliance on agrochemical inputs in modern agriculture has led to public concerns over safety and environmental impacts. Ecologically based pest management approaches attempt to address these concerns by moving beyond the chemical paradigm, to develop safer and more sustainable control. This project focuses on generating the biological and ecological knowledge necessary to achieve the ultimate goal of developing ecologically-based and economically practical management strategies that maintain pest populations at sub-economic levels via biological and cultural means. A sound understanding of insect pest ecology will form the basis for predicting when an insect will be a pest, understanding pest impacts, and determining whether prevention or intervention will be necessary and/or effective. Long-term sustainable solutions to pest problems will only be achieved by restructuring and managing agricultural and rangeland systems in innovative and novel ways that maximize built-in preventive strengths or negatively affect pest population dynamics. In situations where preventive strategies are overcome or consistently ineffective, developing novel biological intervention tools becomes paramount to provide critically needed alternatives to pesticide-based control. In order to increase predictability of grasshopper and Mormon cricket outbreaks and assess their ecological impacts, we will investigate responses to changing climate conditions, and evaluate the effects of grasshoppers on competition between exotic and native rangeland plants. We will also develop novel, preventive strategies that either work against pest fitness in rangeland or render cropping systems less vulnerable to pest problems via the augmentation of natural enemies. Finally, we will develop innovative ways to intervene and control pests when preventive barriers are overcome, including investigations of Mormon cricket and grasshopper susceptibility to pathogens to enhance the efficacy of these natural enemies, and to identify new biocontrol agents to expand the biological arsenal to disrupt growth of wheat stem sawfly, grasshopper, and Mormon cricket populations. This research will fundamentally expand the knowledge base necessary to develop effective, ecologically-based pest management solutions, promoting food security while decreasing energy inputs and environmental impacts. BSL-2, 11/12/2010.
3. Progress Report:
Grasshopper ecology: Collaborations with six universities were developed leading to three NSF and NIFA grant proposals. To understand the impact of grasshopper outbreaks on grassland ecosystems, data from collaborative research in three grassland ecosystems examining the effects of geography and grasshopper diversity on grassland ecosystem processes was analyzed and results presented at a national meeting. Initiated new research examining how often grasshopper predators can reduce rangeland forage damage and grasshopper outbreaks through effects on grasshoppers. Research was completed examining how severe drought affects overwintering egg survival. Mormon crickets: Migrating Mormon crickets can be deficient in either protein or carbohydrates, depending on the population. ARS scientists showed that these two nutritional deficiencies have distinct effects on enzymatic immunities that might lead to susceptibility to fungus or bacteria for population control. We produced protein-deprived Mormon crickets in the laboratory and tested their susceptibility to insect-killing fungi. Following inoculation by the fungus Beauveria bassiana, a registered microbial agent for grasshopper and Mormon cricket control, adults with limited access to protein but adequate carbohydrates were more likely to be killed and died more quickly than those with a balanced diet or those with limited access to carbohydrates. Wheat stem sawfly: We are processing wheat and grass stem samples from a 2012 wheat stem sawfly survey (40 sites) to examine the effects of agricultural intensification on wheat stem sawfly infestation and parasitism. We additionally determined rates of sawfly overwintering mortality for a demographic modeling study. We have completed our containment experiments assessing the suitability of Collyria catoptron as a potential biological control agent for wheat stem sawfly. Our results indicate it will not be an effective agent against sawfly due host incompatibility, difficulty in rearing the parasitoid in a contained environment, and relatively low levels of attack even on its native host in China. Alfalfa weevil: We have completed data analysis and published the first manuscript on environmental influences on the effectiveness of alfalfa weevil natural enemies (2009-2010 samples). We have completed processing our 2011-2012 alfalfa weevil/natural enemy survey samples, and recently completed our 5th year of monitoring for weevils/ parasitoids in 2013 (15 sties). Grasshopper biological control using fungi: Assessment of complete thermal profiles completed for 131 ARS Beauveria isolates from grasshoppers and 150 Metarhizium isolates from Utah State. Few isolates withstood effect of transient heat that mimicks grasshopper behavioral fever; the African/Australian Metarhizium acridum was superior to all domestic isolates. Forty Beauveria isolates were bioassayed, with several being as virulent as the M. acridum. Preliminary evaluation of spore production on grasshoppers was completed; about two-thirds of the isolates are not commercially practical. In bioassays, Yersinia entomophaga showed some promise as a grasshopper pathogen.
Jaronski, S. 2012. Microbial Control of Invertebrate Pests-Chapter 7. In : Sundh, I., Wilcks, A., and Goettel, M.S. Beneficial Microorganisms in Agriculture, Food and the Environment: Safety Assessment and Regulation. Oxfordshire, United Kingdom: CAB International. p. 72-95.