The effects of microemulsion formulations of some botanical acaricides on life table parameters of Amblyseius swirskii (Acari: Phytoseiidae)

Abstract

The microemulsion formulations of essential oils, including orange oil, neem oil, and a terpenoid blend, have demonstrated high efficacy in controlling Tetranychus urticae (Koch) (Acari: Tetranychidae), causing significant mortality and reducing egg-laying, while also enhancing their persistence. Besides using bio-acaricides, biological control agents also show promise for T. urticae control in IPM programs. However, their compatibility with the effective predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) remains unstudied. The current study evaluated the lethal effects of the microemulsion formulations of essential oils and the microbial-derived substance milbemectin (used as a positive control) at different exposure times on eggplant leaves. To evaluate their relative fitness on A. swirskii, biological observations were conducted on A. swirskii exposed after the 168-hour waiting period, which is determined safe for the essential oil formulations under controlled conditions (16-hour light/8-hour dark photoperiod at 27 +/- 1 degrees C and 70 +/- 5% humidity). The results showed that the development time of the offspring was not significantly affected by the essential oil formulations or milbemectin when compared to the control group. The longevity of A. swirskii females were not significantly shortened by essential oil formulations (21-24 days), while it was significantly reduced on leaves treated with milbemectin (8 days). While the mean fecundity and oviposition days were not significantly affected by essential oil formulations, no oviposition was observed on leaves treated with milbemectin. Based on the two-sex life table analysis, the net reproductive rate (R0=7, 8, 8 offspring), the intrinsic rate of increase (r=0.139, 0.149, 0.139 d-1), and the finite rate of increase (lambda=1.15, 1.16, 1.15 d-1) and the mean generation time (T =14, 14, 15 d) for A. swirskii treated with orange oil, neem oil, and terpenoid blend, respectively, were statistically similar to those observed in the control group (R0=7 offspring, r= 0.124 d-1, lambda= 1.13 d-1; T= 15). These findings indicate that the essential oil formulations can be effectively integrated into pest management programs involving the release of A. swirskii following a 168-hour waiting period.