Faculty Advisor

Dr. Matthew Persons

Start Date

April 2021

End Date

April 2021

Description

We tested the sub-lethal effects of six commonly applied herbicides on juveniles of the agriculturally abundant wolf spider Pardosa milvina. We compared spider toxicological effects from herbicides that were freshly applied to soil, aged for 69 days indoors at room temperature, or aged for 69 days in a greenhouse with variable temperature, humidity, light, and evaporative water cycling. Field-collected juvenile P. milvina were exposed to one of eight herbicide treatments (atrazine, glyphosate, mesotrione, Smetolachlor, 2,4-D, dicamba, a combination of all six herbicides, or a distilled water control; N = 960, n = 40, across 24 treatments) and maintained for 49 days on the treated soil substrate. We recorded prey capture behavior, weight change, and growth rate across treatments. Mesotrione had particularly significant negative effects on feeding and weight gain. Mesotrione impaired prey capture latency and led to weight loss. We found significantly decreased molting frequency of spiders in the 2,4-D, S-metolachlor, glyphosate, and dicamba treatments relative to the control but this effect was not present in the greenhouse-aged soil treatments. Fresh and indoor-aged soil had similar effects while greenhouse-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.

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Apr 27th, 12:00 AM Apr 27th, 12:00 AM

Sub-Lethal Effects of Herbicides on the Wolf Spider Pardosa milvina

We tested the sub-lethal effects of six commonly applied herbicides on juveniles of the agriculturally abundant wolf spider Pardosa milvina. We compared spider toxicological effects from herbicides that were freshly applied to soil, aged for 69 days indoors at room temperature, or aged for 69 days in a greenhouse with variable temperature, humidity, light, and evaporative water cycling. Field-collected juvenile P. milvina were exposed to one of eight herbicide treatments (atrazine, glyphosate, mesotrione, Smetolachlor, 2,4-D, dicamba, a combination of all six herbicides, or a distilled water control; N = 960, n = 40, across 24 treatments) and maintained for 49 days on the treated soil substrate. We recorded prey capture behavior, weight change, and growth rate across treatments. Mesotrione had particularly significant negative effects on feeding and weight gain. Mesotrione impaired prey capture latency and led to weight loss. We found significantly decreased molting frequency of spiders in the 2,4-D, S-metolachlor, glyphosate, and dicamba treatments relative to the control but this effect was not present in the greenhouse-aged soil treatments. Fresh and indoor-aged soil had similar effects while greenhouse-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.

 

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