Past, present, and future: Biological control of spider mites on California-grown avocados

Abstract

Oligonychus perseae Tuttle, Baker and Abatiello (Acari: Tetranychidae) is a foliar pest of avocado, Persea americana Miller (Lauraceae), and both species are native to Mexico. Damaging O. perseae populations can occur in areas of the world where the Hass cultivar is grown commercially, including California (USA), Costa Rica, Spain and Israel. In California, the efficacy of biological control agents, including well studied predators such as Euseius hibisci (Chant) and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), for management of O. perseae populations in commercial orchards, is limited. This situation differs from the successful biological control of introduced heterospecifc tetranychids on California avocados during previous decades. Using California avocados as a model system, potential key factors responsible for the limitations of O. perseae biological control are discussed. One key factor that accounts for the prevalence of O. perseae infestations in California is the increasing distribution of avocado cultivars that are highly susceptible to O. perseae. Other attributes contributing to cultivar susceptibility could potentially include the limited searching ability of predators for O. perseae. Additionally, some life history traits of phytoseiids that have been used to target O. perseae populations likely restrict their utility as effective biological control agents of this pest. Future research directions for improving O. perseae biological control strategies are discussed. Among these is the prospect of using members of the family Stigmaeidae that occur naturally on avocado but whose potential as biological control agents has not been well studied.