Using the Environmental Impact Quotient (EIQ) to quantify the impact of pesticide use on natural enemy guilds in organic and conventionally-managed agroecosystems

The use of pesticides can have non-target impacts on predatory arthropods that provide valuable biocontrol services. Determining which pesticides pose the greatest threat to these organisms is important for making informed integrated pest management decisions. The Environmental Impact Quotient (EIQ) is a model created to determine the holistic effect of commonly used pesticides on the environment based on farm worker and consumer safety, as well as ecological impacts. This project aims to assess the efficacy of the EIQ in reflecting the impact of pesticide use on natural enemies in sweet corn (Zea mays) and summer squash (Cucurbita pepo).  These two vegetable crops typically experience significant damage by key pests, often resulting in a need for frequent pesticide application to avoid significant yield losses. Data were collected during the summer of 2013 on produce farms across northeastern Ohio, comprising a mixture of conventional, organic, and transitional management strategies.  Pitfall traps and yellow sticky card traps were deployed for one-week intervals at three times throughout the growing season to sample the ground-dwelling and above-ground predators, respectively. EIQ values were calculated using information on pesticide usage collected through grower surveys. Generalized linear mixed model analysis shows a negative correlation between EIQ and the abundance of both hover flies (Syrphidae) and ground-dwelling spiders (Araneae), and a positive correlation between the abundance of ants (Formicidae), long-legged flies (Dolichopodidae), and soldier beetles (Cantharidae), suggesting that the EIQ may not be suitable for determining the impact of pesticides on the natural enemy guild as a whole.