Lining up at the buffet: How water stress and host choice interact within intensified landscapes

As agricultural systems become intensified and less diverse, the risks of pest and pathogen outbreaks increase. Generalists with many hosts are most difficult to control, as continual immigration from non-crop hosts decreases management efficacy. Weedy hosts are also reservoirs for pathogens and are more susceptible to water stress, which influences interactions with insect vectors and their pathogens. I used an economically important system in the Pacific Northwest to understand the effects of climate on the movement, host choice, and oviposition of a vector insect. The potato psyllid (Bactericera cockerelli Šulc) feeds on solanaceous plants and is the primary vector of Candidatus Liberibacter solanacearum, which causes zebra chip disease. We analyzed four years of sampling data to examine overall movement trends, then tested how water stress and host identity affect host use in a common garden experiment. The experiment used potato (Solanum tuberosum), and two weed species that have been identified as common B. cockerelli hosts- bittersweet nightshade (Solanum dulcamara) and goji berry (Lycium barbarum). We found that movement of potato psyllids into potato fields correlates with non-crop host senescence due to water stress and the connectivity between monocrop fields also leads to decreased barriers of movement once the pests leave their overwintering hosts. We also found that water stress interacts with host choice to affect oviposition and egg survival. Thus, both climate and landscape configuration should be taken into account when considering the effects of non-crop hosts on management.