Response of cucumber beetles and their natural enemies to pest management practices, land use and abiotic factors in watermelon

Cucumber beetles are major pests of watermelon production in the Midwest. They are commonly controlled by scheduled insecticide treatments that disrupt natural enemies, pollinators, and their ecosystem services. We evaluated the effects of integrated versus conventional pest management practices, agricultural land use (at 200, 500, and 1000 m), and abiotic factors (precipitation, temperature, and soil moisture) on cucumber beetles and representative natural enemy taxa. Nine linear mixed models per taxon were compared and the best fit determined using AIC criteria. Striped cucumber beetles (Acalymma vittatum) significantly increased under IPM practices, but along with spotted cucumber beetles (Diabrotica undecimpunctata), were negatively influenced by landscapes with a high percentage of natural areas at 500 and 200 m, respectively. Lycosid spiders were significantly more abundant under IPM practices, while linyphiid spiders were significantly less abundant with a high percentage of natural areas at 1000 m. Carabid beetles in the tribes, Bembidini and Harpalini, significantly increased with agricultural land use at 500 m, while Pterostichini significantly increased only under IPM practices. Coccinellid abundance significantly decreased with agricultural land use at 500 m. Additionally, we evaluated tachinid parasitism in cucumber beetles and found no significant difference between pest management practices or year, but significant differences between locations where the highest parasitism rates were in sites surrounded by more natural areas. Our results show how the factors driving pest and natural enemy taxa abundance can vary, and ultimately determine the best management practices to protect natural enemies and conserve their ecosystem services in cucurbit production.