A drought-tolerant Neoseiulus idaeus (Acari: Phytoseiidae) strain as a potential control agent of two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

The two-spotted spider mite Tetranychus urticae Koch is a key pest of many crops worldwide and is mainly controlled using acaricides. To mitigate the undesired impacts of acaricides (e.g., evolution of resistance and resurgence of secondary pests), phytoseiid mites are often used as a biological control alternative. Control of this pest is a more serious issue in arid regions which favor the development of spider mite populations and limit the efficacy of phytoseiids. The phytoseiid mite Neoseiulus idaeus Denmark & Muma is commonly found in semiarid regions of South America in association with tetranychid mites. Thus, we used laboratory assays to compare the predation and oviposition performance of a drought-tolerant strain of N. idaeus with those of a commercial species, Neoseiulus californicus (McGregor), which is used to control tetranychids. Furthermore, we compared the effectiveness of the drought-tolerant strain of N. idaeus with a common acaricide for control of T. urticae on cowpea plants under semiarid conditions. Drought-tolerant N. idaeus had a higher predation rate than N. californicus (17.50 +/- 0.28 T. urticae eggs/female/day vs. 15.90 +/- 0.19) and similar oviposition performance (3.52 +/- 0.07 vs. 3.30 +/- 0.06 eggs/female/day). Additionally, N. idaeus was able to control the pest population at a relatively low density on cowpea, exhibiting efficacy similar to that of a phenylthiourea acaricide. The practical implications of our results for biological control of T. urticae in semiarid regions are discussed.