Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
Browse
2 results
Search Results
Item Natal origin, migratory patterns, and abundance of the army cutworm moth, Euxoa auxiliaris(Montana State University - Bozeman, College of Agriculture, 2022) Dittemore, Clare Mikaela; Chairperson, Graduate Committee: Robert K. D. Peterson; This is a manuscript style paper that includes co-authored chapters.The army cutworm moth, Euxoa auxiliaris, is a migratory noctuid that migrates from and returns to the Great Plains. At their Rocky Mountain summering range, it is an important food for the Greater Yellowstone Ecosystem (GYE) grizzly bears, Ursus arctos horribilis. However, a limited understanding of moth migratory patterns, abundance at summering ranges, and the associated vulnerability and variability of these populations, is a shortfall in agency grizzly bear conservation strategies. Therefore, the objectives of our study were to assess the natal origin of moths collected from two mountain ranges and within the Great Plains, characterize larval feeding habits of migrants collected from the Absaroka Range, and assess a monitoring protocol to determine moth abundance at a GYE aggregation site. Using stable isotopes, we estimated the natal origin of migrants collected from the Absaroka and Lewis Ranges, examined migratory patterns within the Great Plains, and assessed the larval feeding habits of migrants collected in the Absaroka Range during 2017-2021. To estimate abundance, we sampled the airspace with a radar stationed within 1 km of an aggregation site in the GYE during 2020 and 2021. There was strong evidence that moths collected in the Great Plains and both mountain ranges were migrating north-south, in addition to previously established east-west movement. Although their origins were varied, moths of the Absaroka Range had the highest probability of origin in Alberta and British Columbia, and moderate probability in Montana, Idaho, and Wyoming across all collection years. Lewis Range moths had the highest probability of origin almost exclusively within the lower third of Canada. As larvae, the moths collected from the Absaroka Range fed almost exclusively on C3 plants. We estimate that 5 million moths passed through our radar's sampling plane (160-750 m above ground level and 2600 m across) over the course of 20 hours (5 nights of movement). Overall, our findings suggest that army cutworm moths at aggregation sites are 'supplied' by various source locations, and thus insulated against regional declines within their natal origins. Radar should be used at moth aggregation sites to continue monitoring army cutworm moths.Item The effects of increasing crop diversity on populations of wheat stem sawfly (Cephus cinctus) and associated braconid parasitoids(Montana State University - Bozeman, College of Agriculture, 2019) Fischer, Benjamin Vernon; Chairperson, Graduate Committee: David K. WeaverWheat stem sawfly, Cephus cinctus (Norton) (WSS) is the most damaging pest of wheat in the Northern Great Plains. Insecticides are not widely used to control this insect, and cultural control methods provide inconsistent management of this pest. However, biological control by the parasitoids Bracon cephi (Gahan) and Bracon lissogaster Muesebeck has been shown to reduce damage caused by WSS. In addition, increased agroecosystem diversity has benefitted biological control agents in many other systems. Therefore, this study assessed the effect on populations of WSS and associated parasitoids by the inclusion of pulse and cover crops near wheat fields. Field trapping, dissection of postharvest crop residue, and rearing of insects out of crop residue were used to survey WSS and parasitoid populations in pairs of wheat fields throughout the major wheat producing regions of Montana. One wheat field in each pair was seeded next to a fallow field, and the other was seeded next to a field of either pulse or cover crop. Postharvest stem dissection samples show that wheat fields next to pulse or cover crops had a mean increase of 51 parasitoids per m 2 than wheat fields next to fallow. A corresponding 3% reduction in stem cutting was also observed in postharvest samples from wheat fields adjacent to flowering pulse or cover crops. Land-use data from CropScape TM were used as well to evaluate other land-use impacts around each wheat field such as wheat, fallow, grassland/pasture, flowering crops, and developed space. The regression equation Y = 18.96X + 6.08, where X = proportion of fallow land within 2 km of the wheat field and Y = square root of WSS abundance in a 7.5 m sample of crop residue from rows of wheat, can be used to predict WSS abundance in wheat fields. Replacing fallow fields with flowering pulse or cover crops in the Northern Great Plains may be an important integrated pest management tactic to reduce WSS damage. Cultural practices such as crop diversification are key to developing consistent biological control for WSS.