Theses and Dissertations at Montana State University (MSU)
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Item Evaluating alfalfa weevil (Hypera postica) resistance to mode of action group 3A pyrethroid insecticides in the western United States(Montana State University - Bozeman, College of Agriculture, 2023) Rodbell, Erika Adriana; Chairperson, Graduate Committee: Kevin Wanner; This is a manuscript style paper that includes co-authored chapters.Alfalfa weevil (Hypera postica Gellenhal [Coleoptera: Curculionidae]) is an insect pest of forage alfalfa (Medicago sativa L. [Fabales: Fabaceae]) in the western United States. Over the last half-century, insecticides have been the primary control tactic used by alfalfa producers. However, in 2015 numerous reports of pyrethroid insecticide (mode of action (MoA) 3A) failure to control alfalfa weevil populations were made. In 2019, Montana producers were reporting the same failures in their production systems. Therefore, research efforts in the Wanner Lab commenced in 2020 with the exclusive research goal of identifying pyrethroid resistant alfalfa weevil populations in the western United States. The focus of the research is four-fold. The first was to identify alfalfa weevil lambda-cyhalothrin resistance and susceptibility in Montana. The second was to identify lambda-cyhalothrin resistance and susceptibility in Arizona, California, Montana, Oregon, Washington, and Wyoming. The third was to identify if resistance to lambdacyhalothrin resulted in the loss of efficacy of other MoA 3A active ingredients. The fourth was to develop a case study addressing integrated resistance management recommendations for alfalfa weevil pyrethroid resistance mitigation. We conducted our research through contact bioassays, molecular genomics, and field trials, to corroborate our results and to identify if alfalfa weevil strain was a factor influencing our documented pattern of resistance. Cumulatively, our results suggest that alfalfa weevil lambda-cyhalothrin resistance is present in Arizona, California, Montana, Oregon, Washington, and Wyoming, and that susceptible populations remain in the western region. Our data further illustrate that regardless of alfalfa weevil strain, alfalfa weevils resistant to lambda-cyhalothrin will be resistant to other type II pyrethroid active ingredients and permethrin. A pattern seen in three distinct alfalfa production zones in the western United States (i.e., Arizona, Montana, and Washington), determined by both contact bioassays and field trials. In conclusion, our results illustrate a challenge that forage alfalfa production faces in the western United States and provides strategies that western forage alfalfa producers can employ to mitigate pyrethroid resistance from developing.Item Characterization and assessing fungicide sensitivity of Fusarium spp. causing root rot and wilt in lentils in the northern Great Plains(Montana State University - Bozeman, College of Agriculture, 2022) Bugingo, Collins; Chairperson, Graduate Committee: Mary Burrows; This is a manuscript style paper that includes co-authored chapters.Fusarium root rot and wilt are yield limiting diseases caused by Fusarium spp. in lentils globally. Seedborne Fusarium species and races of Fusarium oxysporum f. sp. lentis (Fol) have not been characterized. The sensitivity of commonly used fungicides on prevalent species is not fully known. In 2019 and 2020 commercial lentil fields were surveyed and seed lots collected from infected patches and further isolation, morphological and molecular characterization was conducted in the laboratory. Additional isolates and lentil seed were received from Washington, Montana, Idaho, North Dakota, southern Canada, and Spain for fungicide, seedborne Fusarium spp. and race-characterization of Fol respectively. In addition to assessing presence of seedborne Fusarium pathogens on the seed coat, the cotyledon and embryo were assessed for the presence of Fusarium spp. Fungicide sensitivity was assessed using mycelial assays and an additional spore assay for pyraclostrobin. A total of 84 seed lots from the Northern Great Plains (NGP) were assayed where a total of 486 and 228 Fusarium isolates were isolated in 2019 and 2020, respectively and all the representative isolates were virulent with a 1.5-4.5 root rot severity rating. Most isolates were found in the seed coat (57- 75%), cotyledon (19-23%) and embryo (6-20%) for the 2019 and 2020 isolates, respectively. F. oxysporum and F. acuminatum were all either sensitive or intermediately sensitive to prothioconazole and ipconazole. A total of 51 isolates were race-typed and 9 races identified whereby race 7 and 1 were the predominant at 53% and 16%, respectively. This study underscores the importance of understanding Fusarium spp. composition in lentil production, role of seedborne inoculum, fungicide efficacy in root rot/wilt management and race composition upon developing effective Integrated Pest Management (IPM) strategies.Item The composition of wireworm species in Montana wheat and barley fields and its effect on developing IPM programs(Montana State University - Bozeman, College of Agriculture, 2014) Morales-Rodriguez, Anuar; Chairperson, Graduate Committee: Kevin Wanner; Kevin W. Wanner was a co-author of the article, 'An evaluation of four different bait traps for sampling wireworms (Coleoptera: Elateridae) infesting cereal crops in Montana' submitted to the journal 'Journal of economic entomology' which is contained within this thesis.; Ruth P. O'Neill and Kevin W. Wanner were co-authors of the article, 'A survey of wireworm (Coleoptera: Elateridae) species infesting cereal crops in Montana' in the journal 'Pan-pacific entomologist' which is contained within this thesis.; Kevin W. Wanner was a co-author of the article, 'Determining the potential for cereal crop injury by wireworm species commonly found infesting cropland in Montana' submitted to the journal 'Canadian entomologist' which is contained within this thesis.; Kevin W. Wanner was a co-author of the article, 'Efficacy of thiamethoxam and fipronil, applied alone and in combination, to control Limonius californicus and Hypnoidus bicolor (Coleoptera: Elateridae)' in the journal 'Pest management science' which is contained within this thesis.; David Wichman and Kevin W. Wanner were co-authors of the article, 'Effects of cultural practices on wireworm populations and damage in cereal fields' submitted to the journal 'Crop sciences' which is contained within this thesis.Wireworms, the larvae of click beetles, are the most important soil-insect pest of small grain fields in Montana. Worldwide, there are about 9,300 species of elaterids in 400 different genera, and in North America 885 species in 60 genera have been identified. In Montana, 166 species were identified, among them, 21 species have been identified as possible pests in small grain fields and some are serious pests of a wide variety of crops. My research focused on three main objectives related to wireworm IPM: first, the identification of the species causing damage in the field and their geographic and seasonal distribution in Montana; second, establishing the potential of different baited traps to monitor pest wireworm populations; and third, evaluating chemical and cultural management alternatives. To complete the first objective a statewide wireworm survey was conducted for three years as well as an intense sampling of four cereal fields season for three consecutive years. To complete the second objective, the effectiveness of four baited traps were assessed: traditional pitfall compared to pot, stocking and canister type traps, in four cereal fields for three years. To complete the last objective, laboratory, greenhouse and field studies were conducted to evaluate new insecticides, crop injury, tillage practices and seeding density. 5,097 wireworms were collected from the four sites during 2010 - 2012 including four common species, Aeolus mellillus, Hypnoidus bicolor, Limonius californicus and L. infuscatus, and three minor species, Agriotes spp., Dalopius spp. and Selatosomus aeripennis. Peak wireworm activity at the soil surface was found to coincide with cereal crop germination and establishment. While all trap types can be used to detect wireworm activity and estimate population levels, pitfall and stocking were more efficient than pot and canister traps. Thiamethoxam does not kill wireworms but its ability to suppress wireworm populations in the field can be improved by the addition of fipronil. Increasing seeding density is one of the most common cultural recommendations for managing wireworms, but my studies did not support its benefit to higher crop yields. Significantly, species-specific crop injury and seasonal movement in the soil support the need for species-specific IPM research.