Selectivity of aqueous and alcoholic extracts of Calotropis procera on the predator Euborellia annulipes

Abstract

Extracts from plants, such as giant milkweed (Calotropis procera Aiton, 1811), have been employed in pest management due to their insecticidal potential and safety for humans and animals. However, applying these products in crops may lead to a reduction in natural enemies, such as the earwig (Euborellia annulipes Lucas, 1847), an important ally in biological control. Thus, there is a need to test whether the extract of C. procera affects the survival and biological parameters of E. annulipes. This study aimed to evaluate the effects of aqueous and alcoholic extracts of C. procera at different concentrations on the survival and morphological aspects of the predator E. annulipes. The study was conducted in the Invertebrate Laboratory of the Department of Biosciences at the Center for Agricultural Sciences, Federal University of Paraíba, Campus II, Areia, PB, Brazil, under controlled conditions. Concentrations of 5, 10, 15, and 20% of aqueous and alcoholic extracts from C. procera leaves were tested with topical application on nymphs and adults of E. annulipes. Insect survival, instar duration, body size, and head capsule length were evaluated. Under laboratory conditions, the aqueous extract of C. procera is harmless to E. annulipes; the alcoholic extract is harmless at concentrations of 5, 10, and 15% and moderately toxic at 20%. The alcoholic extract decreases, while the aqueous extract increases, the duration of instars in E. annulipes. Higher concentrations of the alcoholic extract reduce predator size and head capsule length.