Evaluation of plant extracts for the management of citrus leafminer, Phyllocnistis citrella (Lepidoptera: Gracillariidae)

Abstract

Citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) is a major pest of citrus, which feeds on almost all citrus cultivars, and some related Rutaceae spp. We evaluated the efficacy of aqueous and alcoholic extracts of selected plant species (Azadirachta indica A. Juss, Musa acuminate Colla, Eucalyptus camaldulensis (Dehn.), Mentha arvensis L., Datura stramonium L., Citrullus colocynthis (L.) and Citrus limon (L.) against P. citrella larvae by two different application methods; leaf dip and topical applications. Highest P. citrella mortality was observed in the aqueous (61.17%) and alcoholic (58.3%) extracts of A. indica compared to rest of the plant extracts after 24 hours of exposure. Among two treatment application methods, higher P. citrella mortality was obtained in the topical application of A. indica extract than leaf dip application. Furthermore, the LC₅₀ value of A. indica aqueous extracts was 6.8% in leaf dip bioassay as well as 4.55% in topical application which was lower compared to all other extracts. Musa acuminate and C. limon extracts (aqueous and alcoholic) was found least effective against P. citrella larvae. When combined efficacy of plant extracts with abamectin was evaluated, the aqueous and alcoholic extract of A. indica combination treatments provided highest mortality (62.25% and 66.25% respectively) than the rest of the treatments. Our findings indicate that A. indica extract has potential to be tested as a botanical insecticide for the management of P. citrella larvae as a stand-alone (for organic growers) or in an integrated approach with abamectin. It would not only reduce the input cost of the growers, but also help to reduce negative impacts of the synthetic chemical insecticides.