Resource tracking by an invasive stink bug in a highly heterogeneous environment
Introduced species are a major component of global environmental change, and introduced herbivorous arthropods are among the most ecologically and economically damaging. Predicting where and when herbivorous pests will be found and potentially do damage is further complicated when those pests have highly generalized diets. The brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae), feeds on over one hundred plant species and is a severe pest on many high-value crops. In this study, we investigate patterns of host use over space and through time for H. halys in diverse woody plant nurseries. Because these herbivores are so generalized in their feeding, we hypothesized that their abundances would be elevated at nursery edges, especially where the adjacent habitat also contained potential host plants. Within nurseries, we hypothesized that the highest abundances would be on fruiting trees when and where mature fruit was available. In a three year field survey, we recorded the number of H. halys egg masses, nymphs, and adults on nursery trees at the edges and centers of production fields. We correlated abundance patterns with the availability of fruits on trees and then conducted a season-long fruit removal experiment to isolate the importance of fruits for each life stage.
In our multi-year field survey, H. halys exhibited a pronounced edge effect, with higher abundances of nymphs and adults at field edges compared to field centers; in fact, adult abundances dropped off within the first 5 m into production fields. Overall, H. halys abundances were highest on trees adjacent to soybean fields, which present a high-quality resource for stink bugs. Within nursery fields and across diverse cultivars, we found a strong relationship between H. halys abundance and the presence of mature fruits. Within trees, nymphs and adults were found more often on fruits than on other parts of the tree as fruits matured. Over time, H. halys adults tracked fruiting resources as they became available during the season, with peak abundances coinciding with peak fruiting periods. Furthermore, in a season-long experiment, H. halys nymphs and adults were far more abundant on trees with fruits compared to trees from which fruits were removed. Together, our field surveys and fruit-removal experiment demonstrate that H. halys effectively tracks resources as they become available in heterogeneous environments. These findings may provide insight for potential management options targeted at common forest and landscape trees at key times in the seasonal development of H. halys populations.