Interference of plant fixed oils on predation and reproduction of Neoseiulus baraki (Acari: Phytoseiidae) feeding on Aceria guerreronis (Acari: Eriophyidae)

Abstract

The coconut mite, Aceria guerreronis (Acari: Eriophyidae), is a major pest in coconut plantations in America, Africa and Asia. The management of this pest usually relies on scheduled applications of synthetic pesticides. Recent research demonstrated that degummed soybean and cottonseed oils may potentially control the mite. Although these fixed oils have considerable selectivity for predatory mites, little is known about their sublethal effects on these key natural enemies. This study aimed to assess whether degummed soybean and cottonseed oils modify the functional and numerical responses of Neoseiulus baraki (Acari: Phytoseiidae), a predatory mite frequently associated with A. guerreronis. The exposure of N. baraki to the dosage required to kill 99% of the population (LC99) of the plant oils, estimated for A. guerreronis, changed the functional response of the predator from type III to type II. Attack rate and the change in consumption were not influenced by the fixed oils. However, handling time and consumption peak were adversely affected by the exposure of the predator to degummed soybean oil. Additionally, exposure to this oil reduced N. baraki female oviposition. Our results suggest that degummed soybean oil can be more detrimental to the control of A. guerreronis exerted by N. baraki. Although both oils altered the curve of the functional response, the predator could consume high proportions of A. guerreronis, mainly at low prey densities.