Citrus essential oils control the cassava green mite, Mononychellus tanajoa, and induce higher predatory responses by the lacewing Ceraeochrysa caligata

Abstract

Plant essential oils and their active compounds are recognized as sustainable tools for the management of arthropod pests. Here, the chemical composition of essential oils obtained from different Citrus scions was characterized (i.e., sweet oranges ‘Kona’ and ‘Pera CNPMF-D6’; acid lime ‘Persian lime 58’ and mandarin ‘Piemonte’), and it was evaluated whether these oils could be used to control Mononychellus tanajoa (Acari: Tetranychidae), a key pest of cassava crop. In addition, it was assessed whether exposure to acid lime oil alters the predatory ability of the generalist predator Ceraeochrysa caligata (Neuroptera: Chrysopidae). Predatory bioassays were conducted at two prey densities (i.e., 25 and 50 mites in an arena of 7.1 cm2) immediately after exposure to essential oil and over three consecutive days. Sabinene and linalool were main components in oranges and mandarin oils, while limonene made up more than half of acid lime oil. Based on their LC50 values, all the essential oils and the limonene isomers equally controlled M. tanajoa. However, mites exposed to the LC25 or LC50 of acid lime essential oil exhibited reduced survival rates compared to control. In comparison, exposure to the LC80 of acid lime essential oil caused low mortality (i.e., 20.4 ± 5%) of C. caligata larvae. Moreover, C. caligata larvae that survived exposure to LC50 and faced prey scarcity exhibited higher predatory ability immediately after exposure. Overall, this study demonstrates that the essential oils of these Citrus scions could be successfully integrated into management programs for M. tanajoa.