Oligonychus perseae Tuttle, Baker and Abattiello (Acari: Tetranchidae) is a foliar spider mite pest of avocados, Persea americana Miller (Lauraceae), and both are native to Mexico. In California, O. perseae can cause significant premature defoliation to Hass avocados which is most important commercial avocado cultivar in the world market. Recent work form Israel has shown that extensive foliar injury caused by populations of O. perseae on Hass foliage can translate into fruit yield reduction. Consequently, there is warranted concern over the damage from O. peseae populations in other Hass producing areas such as Spain, Israel, and Costa Rica, but also within its home range in Mexico.
In California, great effort has been placed in developing and implementing an integrated pest management program for O. perseae, but improvements are still needed for effective control of this pest in commercial Hass orchards. In particular, the success of releases of commercially-available phytoseiids as part of an inoculation biological control program has been limited, the role of resident phytoseiids for control of O. perseae is not well understood, and effective research-based sampling plans to monitor the activity of O. perseae and resident phytoseiids are not available. Consequently, the motivation for conducting the work presented in the five chapters of this dissertation was to address these limitations.
The first chapter provides insight into the trophic interactions between O. perseae and natural enemies in California Hass avocados. This information can be used to improve the current biological control program of O. perseae in California and potentially other avocado systems where this spider mite occurs. The second chapter examines the limitations of the current sampling guidelines recommended for assessing O. perseae densities. The third chapter focuses on the development and validation of a binomial sampling plan for O. perseae that minimizes the counting effort and could be used by pest control advisers to monitor levels of this pest in commercial orchards. The fourth chapter compares the performance of enumerative and binomial sampling plans to monitor populations of resident phytoseiids that feed on O. perseae. Finally, the fifth chapter examines the role of resident phytoseiid populations in controlling field populations of O. perseae over a 10-year period.