Effect of some plant essential oils on the orientation and predation capacity of the predatory spider Pardosa pesudoannulata

Abstract

Abstract Investigating the potential side-effects of plant essential oils to natural enemies is necessary before applying them in the field to control insect pests. In the present laboratory study, the attractancy/repellency of two plant oils to the spider Pardosa pseudoannulata was evaluated using a paired choice method. An individual spider was allowed to choose between the odors of essential oils extracted from Piper nigrum, Litsea cubeba, or their mixture and the control within 10 min. The predation deterrent was evaluated by observing the predation of caged spiders supplied with 20 nymphs or adults of Nephotettix cincticeps pre-treated with essential oils in 24 h. Results revealed that P. nigrum and L. cubeba oil had no significant influence on the orientation of the predator in all tested concentrations. However, the mixture of P. nigrum and L. cubeba triggered significant attraction to P. pseudoannulata at 100 and 1000 ppm. Significant reduction of predation was observed with increasing concentration of the mixture and P. nigrum alone. The predation rate in the L. cubeba assay was not significantly different among the tested concentrations. In all cases, predation was higher on nymphs than on adult stages. We did not observe any interaction effect between the life stages and concentrations. To our knowledge, this is the first study discussing the potential influence of plant essential oils on orientation and predation of P. pseudoannulata. Based on these results, some essential oils and their combinations may influence the orientation of P. pseudoannulata and might affect its predation capacity. Further field studies are needed, but these findings suggest caution regarding the selection and application of plant extracts used for biological control in rice fields.