Chronic Exposure to Herbicides and Herbicide Residues Influences the Weight and Feeding Behavior of the Wolf Spider Pardosa milvina

Tyler Gross, Rachel Morehouse, Joe'l Morris, Sara Nicola, Kevin Rainey, Aaron Romano and Jordan Washko (Matthew Persons) Susquehanna University, Department of Biology, 514 University Avenue, Selinsgrove, PA 17870

Herbicides or their residues may impact feeding behavior and growth rates of beneficial predators in agricultural systems and subsequently compromise integrated pest management efficacy. We measured feeding behavior and weight changes of juvenile Pardosa milvina wolf spiders when exposed to soil with field-relevant concentrations of one of six commonly used herbicides: atrazine, S-metolachlor, mesotrione, glyphosate, 2,4-D, and dicamba. We also tested a combined mixture of all six herbicides and a distilled water control. Spiders were housed individually in containers with topsoil previously sprayed with a recommended herbicide dosage or water control group. To test for herbicide residue effects, we reared spiders under herbicides exposed to three soil aging treatments: freshly applied herbicides, herbicide-sprayed soil aged for 69 days under room-temperature laboratory conditions (indoor aged) or aged for 69 days in a greenhouse with variable temperature, humidity, light exposure, and evaporative cycling (outdoor aged) (n=40, N=960 across 24 treatments).  Spiders were maintained on treated substrates for 48 days. Individual spiders from each herbicide treatment were standardized for hunger then presented a cricket weekly after initial treatment exposure. We found significant differences in weight change as well as lunge and prey capture latency for spiders across herbicide and soil aging treatments as well as significant interactions between soil age and herbicide treatment. Mesotrione alone had particularly large effects on feeding and weight gain. Some herbicides significantly increased lunge latency and prey capture latency relative to the control and some decreased the molting frequency of spiders. Fresh and indoor-aged soil had similar effects while outdoor-aged soil dampened most herbicide effects indicating photodegradation and/or temperature degradation of herbicides over the 69-day period. Our results show that some herbicides significantly impair feeding and growth rates in this agriculturally abundant predator with some effects detectable even with greenhouse-aged herbicide residues.  

Additional Abstract Information

Presenters: Tyler Gross, Rachel Morehouse, Joe'l Morris, Sara Nicola, Kevin Rainey, Aaron Romano, Jordan Washko

Institution: Susquehanna University

Type: Poster

Subject: Ecology

Status: Approved

Time and Location

Session: Poster 5
Date/Time: Tue 12:30pm-1:30pm
Session Number: 4098