Invasive herbivorous insects can cause massive ecological and economic problems in regions favorable to their survival and reproduction. Predicting the impacts of invading generalist herbivores is complicated by their broad host range. Halyomorpha halys (Hemiptera: Pentatomidae), the brown marmorated stink bug, is a highly polyphagous pest of both high value crops and native vegetation. Although it uses scores of plants as hosts, its abundance and oviposition patterns are far from uniform across these plants. Our research on H. halys in mid-Atlantic nurseries has discovered clear relationships between the abundance of H. halys and fruiting bodies, habitat edges, plant origin, and plant abundance. Factors governing oviposition constraints, however, are unclear, given that a taxonomically broad set of plants have been found suitable for oviposition. Furthermore, whether H. halys actually damages nursery plants has yet to be evaluated. Here, we present results from a series of experiments that aim to quantify oviposition constraints and plant damage. To evaluate whether leaf size governs oviposition, we experimentally manipulated leaf size in the lab and used threshold leaf sizes from this experiment to understand oviposition data from a multiyear field study. To assess damage, we performed a series of field caging studies.
Results/Conclusions
In our laboratory study, we found a minimum size threshold for successful oviposition. This size threshold was directly related to egg mass size. Specifically, narrow leaf sections were avoided by gravid females, whereas leaf sections larger than the average egg mass width (7.5 mm) were used. Field data corroborate the important physical constraint of leaf size: narrow-leafed trees were rarely used for oviposition in our multiyear field survey. This result helps explain why, in a previous study, gymnosperms were underrepresented in patterns of host plant use. Our damage studies demonstrate that although H. halys can reach moderately high abundances in nurseries, little damage is evident on these plants. We found little aesthetic damage, little evidence for impacts of caged adults on plant growth, and no evidence for the transmission of pathogenic fungi. Although direct damage to nursery plants is lacking, nurseries and other diverse and heterogeneous habitats may be very important for the regional population dynamics of this herbivore.