- Spiders are abundant predators within agricultural ecosystems and can significantly reduce pest populations, bringing significant economic benefits.
- Surfactants are a common component of pesticides.
Two chemicals used as co-formulants in pesticides have been found to reduce the predatory behaviour of the wolf spider Pardosa agrestis, an insect predator found within agricultural landscapes. A third co-formulant was found not to affect the predatory behaviour of females and increased the prey behaviour of male spiders. This is the first time that pesticide additives have been shown to alter the predatory activity of a potential biological control agent of crop pests.
Sublethal effect of agronomical surfactants on the spider Pardosa agrestis, ScienceDirect, Volume 213, Pages 84–89, June 2016.
Wolf Spider by Thomas.
In addition to their active ingredients, pesticides contain also additives – surfactants. Use of surfactants has been increasing over the past decade, but their effects on non-target organisms, especially natural enemies of pests, have been studied only very rarely.
The effect of three common agrochemical surfactants on the foraging behavior of the wolf spider Pardosa agrestis was studied in the laboratory. Differences in short-term, long-term, and overall cumulative predatory activities were investigated.
We found that surfactant treatment significantly affected short-term predatory activity but had no effect on long-term predatory activity. The surfactants also significantly influenced the cumulative number of killed prey. We also found the sex-specific increase in cumulative kills after surfactants treatment.
This is the first study showing that pesticide additives have a sublethal effect that can weaken the predatory activity of a potential biological control agent. More studies on the effects of surfactants are needed to understand how they affect beneficial organisms in agroecosystems.