Modeling Basal Sprout Production in Vector-Borne Tree Disease

The introduction of non-native pests that vector disease and kill trees poses a serious threat to native tree populations. Mathematical models of vector-borne tree disease can investigate the impact of certain pathogen and host characteristics on disease dynamics and provide a framework for evaluating management strategies that mitigate the effects of introduced vector-borne disease. This is especially useful for characteristics with impacts that are difficult to measure empirically. In this dissertation, I investigate the impact of basal sprout production in trees infected by an introduced vector-borne disease that is vectored by a non-native bark or ambrosia beetles (e.g. laurel wilt, dutch elm disease, among others). Basal sprouts are shoots or sprouts that grow from the root system of an existing tree, and the production of basal sprouts is commonly induced in response to vascular wilt disease. I develop a series of mathematical, epidemiological models that incorporate basal sprout production and secondary infection via vertical transmission. We interpret these models to study the effect of basal sprout production on the ecological and epidemiological outcomes, both locally and spatially, of the introduction of vector-borne disease into a novel environment. Results suggest that when secondary infection is low, the production of basal sprouts decreases the likelihood of local extinction of the host population, but simultaneously increases the likelihood of endemic disease or future waves of epidemic disease. I also provide a framework for evaluating the utility of basal sprout-centered management of vector-borne disease in a variety of disease and management contexts. This theoretical work provides a set of initial models and a basis upon which future field studies and more tailored models can be developed, together helping to protect trees as novel pathogens and introductions into new areas continue to threaten tree populations.