Local and landscape drivers of Cucurbita herbivory on the Southern High Plains

Herbivory is a major driver of crop losses in agroecosystems where dense monocultures favor herbivorous insects, particularly those who specialize on crops. Yet, levels of herbivory are not uniform within or among regional cropping systems, and determining factors that drive herbivory variation is a crucial step in supporting appropriate pest control methods. Crops in the genus Cucurbita host a suite of specialized co-evolved herbivores that inflict significant damage in the humid continental climates of the midwestern and northeastern United States. However, much less is known about cultivated Cucurbita herbivory within semi-arid climates. In this study we surveyed plants and arthropod communities and collected landscape and agronomic data for 20 pumpkin fields in the Southern High Plains Region of Texas during the 2021 growing season. We used a generalized linear mixed models and confirmatory path analysis to examine the local and landscape factors driving pumpkin herbivory and insect dynamics. We found that though herbivory increased throughout the growing season, overall damage levels remained low at < 10%. Neither the abundance nor diversity of specialized herbivores within fields influenced herbivory. However, fields with greater weed plant diversity had significantly lower levels of herbivory. We found lower abundances of specialized cucumber beetles (Family: Chrysomelidae) with greater proportion pumpkin within 100m, indicating a resource dilution effect in our study landscape. Further examination of cucumber beetle movement could clarify if the annual recolonization process among rotated pumpkin fields contributes to this dilution effect.