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Item Tritrophic responses to signaling formulations sprayed in wheat stem sawfly-infested field plots(Montana State University - Bozeman, College of Agriculture, 2019) Caron, Christopher G.; Chairperson, Graduate Committee: Scott PowellThe wheat stem sawfly (Cephus cinctus Norton) is an economically important pest of wheat in the Northern Great Plains of North America. Producers and researchers are continuing to search for an effective management strategy. A combination of management tactics, such as host-plant resistance and biocontrol, may be the best method to suppress wheat stem sawfly (WSS) populations. My study examines whether direct toxicity, induced host-plant resistance, or the manipulation of tritrophic interactions, can be achieved through the application of signaling molecules in WSS-infested plots. The overall objective was to assess whether signaling molecules could be incorporated as a management tactic for WSS. Field experiments assessed whether aqueous applications of methyl jasmonate (MeJA), methyl salicylate (MeSA), and Actigard? influence WSS fitness, host-plant fitness, or the recruitment of natural enemies. Treatments were applied in WSS-infested plots for 3 consecutive weeks in both 2017 and in a second experiment in 2018. Wheat samples were collected before harvest and processed to assess parameters of infestation and parasitism. Plant growth and yield parameters were also recorded. The field trials suggested that MeJA and Actigard? induced significant changes that can impact tritrophic interactions in winter wheat. No effect was observed from the applications of MeSA. WSS fitness parameters decreased with applications of MeJA. MeJA treated plots had decreased infestation (2017), decreased larval weight (2018), and increased neonate mortality (2018). Actigard? treated plots had decreased larval weight and increased recruitment of clerid beetles (Phyllobaenus dubius Wolcott) (2017). Treatments of MeJA decreased stem height and grain weight, while treatments of Actigard? decreased grain weight in 2017. Although many of these findings were not consistent for both growing seasons, this study demonstrates the potential for these signaling molecules to manipulate the interactions between the WSS, or its host plant, and associated natural enemies in winter wheat.Item Assessment of host selection behaviors and oviposition preferences of Cephus cinctus Norton (Hymenoptera: Cephidae) using wheat and smooth brome(Montana State University - Bozeman, College of Agriculture, 2020) Bhandari, Rekha; Chairperson, Graduate Committee: David K. Weaver and Tracy M. Sterling (co-chair)Wheat stem sawfly, Cephus cinctus Norton (WSS), is an important pest of cereal crops in Northern Great Plains. Smooth brome has historically been suggested as a potential trap crop around wheat fields in Montana. The objective of this study was to compare oviposition preference and selection behaviors of female WSS and measure subsequent larval survival in wheat and smooth brome stems. We compared infestation, parasitism and larval development of WSS using field transects in smooth brome and adjacent wheat fields. We found no clear difference in infestation between the two host plants. There was greater larval mortality and less tunneling in smooth brome stems compared to wheat at a site near Big Sandy, Montana. At a second site near Big Sandy, there was greater infestation in smooth brome compared to wheat, but there were more dead larvae and greater parasitism in smooth brome. In Y-tube olfactometer studies, WSS females were more attracted to volatiles emitted by smooth brome than wheat. In greenhouse trials, the observation of specific behaviors leading to oviposition indicated differences in duration of ovipositor insertion and in number of ovipositor insertions that favored greater oviposition in smooth brome, but only by emergence of the first awn of the inflorescence (Zadoks 49 growth stage). There were different numbers of eggs in smooth brome stems relative to wheat, with no difference in the proportion of infested stems in choice tests conducted for two days at Zadoks 49. In no-choice tests, there were differences in both infested stems and in the number of eggs in stems at Zadoks 49. We found significantly greater amounts of key behaviorally active compounds used by female WSS, like (Z)-3-hexenyl acetate and beta-ocimene, that were among the few differences in the amounts of volatile compounds collected from two plant species. The greater amount of these compounds leads to more eggs that subsequently experience greater larval mortality in young plants, resulting in fewer cut stems in mature plants. Our findings support the consideration of smooth brome for use in trap crops to improve integrated pest management strategies for WSS.Item Age-specific life table studies of potential strains or host races of Calophasia lunula (Lepidoptera: Noctuidae) (Hufn.) reared on Dalmation toadflax, Linaria genistifolia ssp. dalmatica (L.) Maire and Petitmengen, or yellow toadflax, Linaria vulgaris (Mill.)(Montana State University - Bozeman, College of Agriculture, 1995) Breitenfeldt, Todd AlanItem Determination of host races in three insect species attacking Dalmatian toadflax and yellow toadflax in North America(Montana State University - Bozeman, College of Agriculture, 1991) McDermott, Gregory James