Location: Pest Management Research2017 Annual Report
1. Management of wheat stem sawfly using a fungus that grows into the plant. Wheat stem sawfly is the most important insect pest of wheat on the Northern Plains, extending now into the winter wheat of Nebraska and Kansas, with almost no effective control measures since it lives protected inside the plant. Researchers at ARS in Sidney, Montana indicated that the insect could be managed using a fungus that was unexpectedly discovered attacking the sawflies, by first getting the fungus to establish harmlessly in the wheat plant, where it will lay in wait for an invading sawfly larva, then infect and kill it. A patent application for use of this fungus to control wheat stem sawfly was submitted jointly with Montana State University. ARS is currently negotiating a license of the technology with a private U.S. company and creation of a cooperative research agreement to further develop this approach to a practical, commercial level. The invention could provide a major tool for managing this very important pest in wheat.
2. Extreme early summer drought may be required to strongly reduce grasshopper densities. Grasshopper outbreaks frequently lead to large scale chemical control efforts, but ranchers’ and land managers’ abilities to proactively manage grasshopper problems are constrained by an inability to predict population responses to weather variation. Drought timing could be more important than drought intensity in how it affects grasshopper populations, but it is poorly understood. ARS researchers in Sidney, Montana modified patterns of rainfall and grasshopper abundance to examine how drought timing affected rangeland production and grasshopper populations. Moderate early summer drought positively affected grasshopper survival by improving protein content of vegetation. Combined with previous work by ARS researchers in Sidney, Montana, the results indicate that extreme early summer drought conditions are likely required to strongly reduce forage availability and lead to lower grasshopper populations in the following year. The results confirm that a better understanding of the timing of drought is critical to allow managers to predict both the beginning and end of grasshopper outbreaks.
3. Mormon cricket egg banks contribute to pest outbreaks. Mormon crickets are a major pest of crops in the western USA that often form huge groups and march in search of food. Conventionally, Mormon crickets are thought to complete their life cycle annually. In a laboratory study, ARS researchers at Sidney, Montana were the first to discover that Mormon cricket eggs can remain in the soil and still hatch more than five years after being laid. Delayed hatching is more prevalent in high altitude populations than populations at low elevations, but all populations thus far examined exhibit the potential to bank some eggs for multiple years. This research informs farmers and pest managers that Mormon crickets may remain in the soil in a location and life stage for which current insecticidal practices may not be effective.
4. Using population models to inform biocontrol management of the wheat stem sawfly. Wheat stem sawfly is the most damaging insect pest of wheat in the northern Great Plains. The lack of information on which pest life stages should be targeted (egg or larva), and how many pest individuals need to be killed to get effective control, hampers the development of effective sustainable pest management approaches. ARS researchers at Sidney, Montana used mathematical population models to identify the most vulnerable sawfly life stages to be targeted by management. Models indicate that killing larvae in the overwintering stage will contribute most to sawfly population suppression, and that parasitism levels must exceed 60% to exert significant control. Results suggest that effective biological control management of sawfly will require adoption of farming practices to increase parasitoid numbers (such as additional flower resources nearby to feed sawfly enemies) and the development of new biological approaches to killing overwintering larvae (such as fungal pathogens). This model represents a critical first step in developing better targeted biological control management of wheat stem sawfly.
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Peralta, G., Frost, C.M., Didham, R.K., Rand, T.A., Tylianakis, J.M. 2017. Non-random food-web assembly at habitat edges increases connectivity and functional redundancy. Ecology. 98(4):995–1005. doi:10.1002/ecy.1656.
Keysor, C.R., Fernandez, E.K., Rangel, D.N., Foster, R.N., Jech, L.E., Reuter, K.C., Black, L.R., Jaronski, S., Flake, D.D., Evans, E.W., Roberts, D.W. 2017. Laboratory bioassays and field-cage trials of Metarhizium spp. isolates with field-collected Mormon crickets (Anabrus simplex). Biocontrol. 62(2):257–268. doi:10.1007/s10526-016-9782-8.
Frost, C.M., Peralta, G., Rand, T.A., Didham, R.K., Varsani, A., Tylianakis, J.M. 2016. Apparent competition drives community-wide parasitism rates and changes in host abundance across ecosystem boundaries. Nature Communications. 7:12644. doi:10.1038/ncomms12644.
Smith, C.D., Srygley, R.B., Healy, F., Swaminath, K., Mueller, U.G. 2017. Spatial structure of the Mormon cricket gut microbiome and its predicted contribution to nutrition and immune function. Frontiers in Microbiology. 8:801. doi:10.3389/fmicb.2017.00801.
Branson, D.H. 2017. Effects of altered seasonality of precipitation on grass production and grasshopper performance in a northern mixed prairie. Environmental Entomology. 46(3):589-59. doi:10.1093/ee/nvx053.
Prather, C.M., Strickland, M.S., Laws, A.N., Branson, D.H. 2017. Herbivore species identity and composition affect soil enzymatic activity through altered plant composition in a coastal tallgrass prairie. Soil Biology and Biochemistry. 112:277-280. doi:10.1016/j.soilbio.2017.05.013.
Jaronski, S., Mascarin, G.M. 2016. Mass production of fungal entomopathogens. In: Lacey, L.A., editor. Microbial Control of Insect and Mite Pests from Theory to Practice. Yakima, WA: IP Consulting International. p. 141-155. doi:10.1016/B978-0-12-803527-6.00009-3.
Branson, D.H. 2016. Drought impacts on competition in Phoetaliotes nebrascensis (Orthoptera Acrididae) in a northern mixed grassland. Environmental Entomology. 45(2):492-499. doi: 10.1093/ee/nvv225.
Rand, T.A. 2017. Assessing the role of generalist predators in the biological control of alfalfa weevil (Coleoptera: Curculionidae). The Canadian Entomologist. 149(4):525-533. doi:10.4039/tce.2017.9.
Cockrell, D.M., Griffin-Nolan, R.J., Rand, T.A., Altilmisani, A., Ode, P., Peairs, F. 2017. Host plants of the wheat stem sawfly (Hymenoptera: Cephidae). Environmental Entomology. doi:10.1093/ee/nvx104.
Rand, T.A., Richmond, C.E., Dougherty, E. 2017. Using matrix population models to inform biological control management of the wheat stem sawfly, Cephus cinctus. Biological Control. 109:27-36. doi:10.1016/j.biocontrol.2017.03.007.
Branson, D.H. 2017. Grasshopper species composition shifts following a severe rangeland grasshopper outbreak. Short Communication: Journal of Orthoptera Research. 26(1):7-10. doi:10.3897/jor.26.14542.