Disruption of the chemical communication of the European agrobiont ground-dwelling spider Pardosa agrestis by pesticides

Lycosid spiders are among the most abundant and diverse insectivores occurring in all agroecosystems. Certain pest management practices, such as the application of pesticides, can disrupt their role in insect pest control. Therefore, understanding the effects of pesticides, including sublethal effects, is essential for the assessment of chemical effects on beneficial arthropods. We investigated the sexual chemical communication of the beneficial agrobiont spider Pardosa agrestis and its disruption by two widely used pesticides, the glyphosate-based herbicide Roundup and the pyrethroid-based insecticide Nurelle D. A two-choice olfactometer and Y-maze were used to study the effectiveness of female airborne and dragline pheromone cues and the disruptive effect of the pesticides. Males of P.agrestis did not locate females via airborne cues, but were very receptive to female dragline silk and male dragline silk. When both female dragline silk and male dragline silk were provided at the same time, the males preferred female silk. Pesticide treatments significantly affected the male ability to follow female cues deposited on dragline silk. The 3-h residues of both Roundup and Nurelle D significantly disrupted the male ability to follow female cues deposited on dragline silk. Treatment by 48-h residues significantly disrupted the male ability only in the case of Nurelle D. Our results demonstrate that pesticides reduce the ability of male spiders to search for a mate due to the disruption of the male's ability to detect the silk cues of the female.