Use of Oils and Plant Extracts to Control Diaphorina citri Kuwayama on Mexican Lime in the Dry Tropic of Mexico

The Asian citrus psyllid (ACP; Diaphorina citri) is the most important pest affecting Mexican lime (Citrus aurantifolia) in the dry tropics of Mexico, and is the vector of huanglongbing disease. Its control is based on synthetic insecticides. The search for sustainable and effective alternatives is a priority in the management of ACP. In this study, the effect of different kinds of oils and plant extracts were evaluated to control ACP nymphs in Colima, Mexico. The tests were conducted on mature Mexican lime trees and nursery plants infested with the pest. One foliar application of each treatment was done to tagged 5-7 d shoots. Paraffinic oil (99% of unsulfonated residues) at 1, 2, and 3%, reduced the ACP population between 77 to 98% as compared with the untreated control. Different paraffinic oils, cooking oils, and citrus oil maintained a low infestation of ACP compared to the control. Also, neem, garlic, and onion extracts showed a significant reduction of ACP nymphs. Jatropha curcas seed oil had a good effectiveness. No signs of phytotoxicity were observed with any of the oils applied during the winter, but in the summer fitotoxicity signs were observed with cooking oils. These results indicate that oils and plant extracts can be included in a program of ACP control in Mexican lime to reduce the use of synthetic insecticides (organophosphates), which are having resistance problems with D. citri.