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Item Quantifying tansy ragwort (Senecio jacobaea) population dynamics and recruitment in northwestern Montana(Montana State University - Bozeman, College of Agriculture, 2003) Trainor, Meghan AnnItem Molecular taxonomy, bionomics and host specificity of Longitarsus jacobaeae (Waterhouse) (Coleoptera: Chrysomelidae) : the Swiss population revisited(Montana State University - Bozeman, College of Agriculture, 2003) Puliafico, Kenneth Patrick; Chairperson, Graduate Committee: Jeffrey L. Littlefield.The ragwort flea beetle, Longitarsus jacobaeae (Waterhouse) (Coleoptera: Chrysomelidae) is considered to be the most important biological control agent for the suppression of tansy ragwort, Senecio jacobaea L. (Asteraceae) in the Pacific Northwest. A recent infestation of tansy ragwort in northwest Montana has rekindled the search for a cold adapted strain of the ragwort flea beetle. This study endeavored to determine the molecular taxonomy, host specificity, bionomics and life history of the Swiss strain. I found that populations of L jacobaeae from Switzerland are phenologically adapted to cold continental climates. Molecular techniques of species determination were applied to L. jacobaeae and three other species in the genus Longitarsus. Application of these techniques were able to discriminate between L. jacobaeae and its cryptic sister species L. flavicornis (Stephens). Five Swiss flea beetle populations and three Oregon populations were determined to be clustered together in the L. jacobaeae species. This is the first report of life history observations for naturally occurring populations of L. jacobaeae in Switzerland. Adult flea beetles emerge in early spring and immediately start oviposition by mid-July. Oviposition continued into November for captive beetles. Eggs enter a diapause phase and hatch in the spring after exposure to cold temperatures. Larvae initially feed in the leaves and then move to the root crowns in their second instar to complete their development. Pupation occurs in the soil after the third instar leaves the plant. Twelve plant species closely related to S. jacobaea were exposed to ragwort flea beetles in three host tests. In all three host tests, larval development was completed only in the usual host plant, S. jacobaea. Limited larval feeding was observed in the cut foliage host test on three non-target species, S. eremophilus, S. flaccidus, and S. triangularis, however all the larvae tested died during development. Very slight damage to no-target plants was observed in host tests utilizing whole potted plants in the greenhouse. An. open field host test in Switzerland revealed no substantial attack on non-target plants and no larval development. Eight previously untested North American plant species were found unacceptable hosts to L jacobaeae.Item The population dynamics of tansy ragwort (Senecio jacobaea) in Northwestern Montana(Montana State University - Bozeman, College of Agriculture, 2006) Bauer, Brad David; Chairperson, Graduate Committee: Bruce D. Maxwell.Following the Little Wolf wildfire of 1994 in northwestern Montana, tansy ragwort (Senecio jacobaea) was classified as a state noxious weed. This project aimed to help prioritize the management of populations of tansy ragwort through an understanding of the biotic and abiotic factors influencing the species. Using field collected data and by constructing a prediction model, we found that the most important variables to predict the presence of tansy ragwort were distance from the main road, slope, cosine of aspect, and several remotely sensed LANDSAT ETM+ bands. Most of the predicted occurrences of tansy ragwort were within the boundary of the wildfire. The life stage and density of tansy ragwort plants in 94 plots in several environments created by the wildfire were used to project the population growth rate after seven to eleven years following the wildfire. Using the relative invasiveness (probability ë > 1.0) of populations to prioritize environments for management, the burned and salvaged logged population had the highest probability of being invasive with probability ë > 1.0 between 0.31 and 0.24. The burned but not logged had a probability ë > 1.0 between 0.20 to 0.10 and the non-burned meadow had a probability ë > 1.0 between 0.01 and 0.00. Additionally, as the native plant populations recovered, the population growth rate and rosette survival declined. Following a field study of the role of slashpiles in the establishment of tansy ragwort we found the highest maximum percent emergence of tansy ragwort seedlings in the low severity burn and non-burned disturbed environment of the slashpiles. The low survival of emerged seedlings and the low projected growth rates for the surviving plants indicated that the dynamics responsible for a large increase in tansy ragwort density did not occur within our slashpiles after two years. With the addition of biological control agents to populations of tansy ragwort, the seed predator fly did not negatively affect the relative invasiveness of tansy ragwort. However, the addition of a foliage herbivore to a limited number of populations reduced the relative invasiveness of these populations.