Pest management practices disrupt spider communities in watermelon production

Commercial watermelon (Citrullus lanatus) production in the Midwest typically relies on insecticides applied on a calendar basis to manage insect pests, particularly striped and spotted cucumber beetles (Acalymma vittatum Fabricius and Diabrotica undecimpunctata howardi Barber, respectively). Common cucumber beetle predators include spiders (Araneae) found on the soil surface and plants in watermelon fields. However, these generalist predators are usually at risk from pest management practices used without regard to economic thresholds. Our study compared the effect of different pest management strategies on spider predators used as response variable under two treatments: 1) watermelons treated with neonicotinoids at planting time and pyrethroid sprays applied on a calendar basis surrounded by corn with neonicotinoid treated seeds (Conventional Pest Management - CPM), or 2) watermelons treated with pyrethroid sprays only when economic thresholds were reached (i.e., 5 striped cucumber beetles/plant) surrounded by corn with untreated seeds (Integrated Pest Management - IPM). Spider community was significantly higher in IPM compared to CPM fields during both years of the study. All most all the spiders found in this study consisted of species in the families Lycosidae and Linyphiidae corresponding to guilds of wandering and web-builders, respectively. The excessive use of insecticides as a pest management strategy can diminish spider abundance and reduce the availability of natural pest control in watermelon production.