Sub-lethal and lethal effects of Datura stramonium L. leaf extracts on the European red mite Panonychus ulmi (Koch) (Acari: Tetranychidae) and its predator, Stethorus gilvifrons (Muls.) (Col.: Coccinellidae)

Abstract

Ethanol extracts obtained from the leaf of the thorn apple (Datura stramonium L.) (Solanaceae) were examined for lethal and repellent properties against adults of the European red mite Panonychus ulmi (Koch) (Acari: Tetranychidae) and its predator Stethorus gilvifrons (Muls.) (Col.: Coccinellidae) under laboratory conditions. The Petri leaf disc-spray tower method was used. The results showed that D. stramonium leaf extracts were lethal to both the mite and its predator. Furthermore, an increase in the dose of leaf extract caused a significant increase in the death rates of both P. ulmi and S. gilvifrons adults. Probit analysis and parameter estimation showed that the LC50 values of leaf extract were 7097.5 and 1853.9 mg/l at 24 h residual activity for spider mite and ladybird adults, respectively. The mite and ladybird mortality rates associated with the extract were higher at 48 h than at 24 h, with LC50 values of 2013 and 1030 mg/l, respectively. However, the LC90 values of the extract were lower for ladybirds than for spider mites at both 24 and 48 h. According to Pearson’s chi-squared test, both spider mite and ladybird adults showed strong aversions to apple leaf surfaces sprayed with sub-lethal doses of the extract (from 13.72 to 1058.0 mg/l). Moreover, an odour test using a two-choice olfactometer demonstrated that ladybird adults prefer fresh air to the extract odour. These results suggest that D. stramonium extract can be used effectively as a safer phytopesticidal product for the management of P. ulmi in both organic and inorganic apple production, but it is not suitable for use in integrated pest management strategies due to its toxic and repellent effects against S. gilvifrons.