Presenter Information

William WardFollow

Faculty Advisor

Dr. Matthew Persons

Start Date

28-4-2020 12:00 AM

End Date

28-4-2020 12:00 AM

Description

Herbicide use in crop systems has increased dramatically over the last fifty years yet the effects of chronic exposure to these chemicals on beneficial non-target arthropods have been poorly tested. We tested the lethal effects of field-relevant dosages of five commonly used herbicides on the economically important wolf spider, Pardosa milvina. Tested herbicides included atrazine, S-metolachlor, rimsulfuron, mesotrione, glyphosate, a mixture of all five herbicides, and a distilled water control. Spiders were housed individually in containers with topsoil previously sprayed with a recommended herbicide dosage or a water control. Tested spiders were collected from two nearby fields; one field was kept under continuous crop rotation for over twenty years and sprayed with various combinations of all of these herbicides (“conventional field) while the other site had no pesticide application for the last 12 years but was maintained under alfalfa cultivation (“no herbicide field”). Adult male and female spiders from each plot were exposed to the seven herbicide treatments (N=1,214, n= 43 spiders across 28 treatments). Spiders were maintained on these soil substrates for 52 days, fed weekly, and checked for mortality daily. We found significant herbicide treatment effects, with mesotrione being particularly lethal to wolf spiders while atrazine and S-metolachlor had modest, but significantly higher survival than the control group. We also found significant differences and treatment interactions by sex and collecting site. In general, male spiders showed significantly shorter survival and spiders from the pesticide-free site had longer survival than spiders collected from a field maintained under constant crop rotation. The mesotrione-treated spiders had significantly poorer survival than even the combined herbicide treatment suggesting a complex antagonistic interaction of some of these herbicides on wolf spider survival. Given that species of Pardosa are found on six continents and occur at high densities in most agricultural systems, use of mesotrione may be particularly counterproductive in systems that rely on integrated pest management and biocontrol using generalist arthropod predators.

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Apr 28th, 12:00 AM Apr 28th, 12:00 AM

Lethal Effects of Common Herbicides on an Agriculturally Important Wolf Spider (Pardosa milvina)

Herbicide use in crop systems has increased dramatically over the last fifty years yet the effects of chronic exposure to these chemicals on beneficial non-target arthropods have been poorly tested. We tested the lethal effects of field-relevant dosages of five commonly used herbicides on the economically important wolf spider, Pardosa milvina. Tested herbicides included atrazine, S-metolachlor, rimsulfuron, mesotrione, glyphosate, a mixture of all five herbicides, and a distilled water control. Spiders were housed individually in containers with topsoil previously sprayed with a recommended herbicide dosage or a water control. Tested spiders were collected from two nearby fields; one field was kept under continuous crop rotation for over twenty years and sprayed with various combinations of all of these herbicides (“conventional field) while the other site had no pesticide application for the last 12 years but was maintained under alfalfa cultivation (“no herbicide field”). Adult male and female spiders from each plot were exposed to the seven herbicide treatments (N=1,214, n= 43 spiders across 28 treatments). Spiders were maintained on these soil substrates for 52 days, fed weekly, and checked for mortality daily. We found significant herbicide treatment effects, with mesotrione being particularly lethal to wolf spiders while atrazine and S-metolachlor had modest, but significantly higher survival than the control group. We also found significant differences and treatment interactions by sex and collecting site. In general, male spiders showed significantly shorter survival and spiders from the pesticide-free site had longer survival than spiders collected from a field maintained under constant crop rotation. The mesotrione-treated spiders had significantly poorer survival than even the combined herbicide treatment suggesting a complex antagonistic interaction of some of these herbicides on wolf spider survival. Given that species of Pardosa are found on six continents and occur at high densities in most agricultural systems, use of mesotrione may be particularly counterproductive in systems that rely on integrated pest management and biocontrol using generalist arthropod predators.

 

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