Climate affects the outbreaks of a forest defoliator indirectly through its tree hosts

Spatial variation in climate is known to affect the survival and reproduction of herbivorous forest insects and tree-species compositions, but the importance of indirect effects of climate on outbreaks of forest insects through its effects on forest composition is unclear. This data was compiled to examine the direct and indirect effects of climate, water capacity of the soil, host tree density, and non-host density on the spatial extent of Lymantria dispar outbreaks in the Eastern USA over a period of 44 years (1975-2018). Host species were subdivided into four taxonomic and ecologically distinct groups: red oaks (Lobatae), white oaks (Lepidobalanus), other preferred hosts, and intermediate (less preferred) hosts. The data offer quantitative evidence that geographic variation in climate can indirectly affect outbreaks of a forest insect through its effects on tree species composition.