Lethal and side effects of the acaricides spirodiclofen and spiromesifen on the two-spotted spider mite, Tetranychus urticae Koch, and its predatory mite, Neoseiulus californicus McGregor (Acari: Phytoseiidae)

The acute toxicity of the acaricides spirodiclofen and spiromesifen to eggs and adult females of the two-spotted spider mite, Tetranychus urticae Koch, was evaluated in laboratory at 27 ± 2°C temperature, 70 ± 5% relative humidity (RH), and 16/8 L/D photoperiodic conditions. The residual effects of these miticides on adult females were also assessed. In these assays, eggs and female mites were treated with five different concentrations of the two acaricides: spirodiclofen (0.21, 0.41, 0.83, 1.63, and 3.26 mg/L) and (0.79, 3.78, 18.11, 86.87, and 416 mg/L), spiromesifen (0.02, 0.06, 0.18, 0.53, and 1.56 mg/L) (0.39, 4.07, 10.10, 51.27, and 260 mg/L) for egg and female adult respectively. LC50 and LC90 of the chemicals were measured and the obtained data was analysed by probit analysis. The LC50 value of spirodiclofen against egg and adult of T.urticae were 0.86, 11.95 and for spiromesifen were 0.10, 5.95 ppm respectively. Also the effects of the two acaricide residues on mortality rate of female spider mites and its predatory mite, Neoseiulus californicus McGregor, were investigated at LC90 levelfollowing 0, 1, 3, 7, 10 and 14 days’ of treatment. at The results showed that the mortality of mites increased significantly with increasing acaricide concentrations. Generally, both acaricides, especially spiromesifen, proved to be highly toxic to eggs, moderately to adult females, and slightly to predatory female mites. After seven days of treatment, mortality in mites caused by spirodiclofen and spiromesifen were 86.6% and 70%, and after two weeks, were 46.6% and 51.6%, respectively. After two weeks of treatment, acaricides had gained efficient control against two-spotted spider mites and did not have a significant negative effect on the population of N. californicus. The results suggest that both spirodiclofen and spiromesifen could be successfully used for an IPM programme acco pany with the biological control agent, N. californicus.