Oligonychus perseae (Acari: Tetranychidae) Population Responses to Cultural Control attempts in an Avocado Orchard
Populations of Oligonychus perseae Tuttle, Baker and Abbatiello (Acari: Tetranychidae) were monitored for 37 weeks in an avocado (Persea americana Miller) orchard in Fallbrook California, USA. Three cultural control methods were tested to reduce vertical recolonization of avocado trees by O. perseae. Control methods examined were: (1) Tanglefoot® barriers on tree trunks. (2) Removal of ground cover and leaf litter under tree canopies, and (3) Tanglefoot ® barriers combined with ground cover removal. All treatments were compared to control trees that were not subjected to any of the preceding cultural practices. No significant differences in O. perseae populations or O. perseae -induced leaf damage were found among trees receiving different treatments. However, aerial dispersal activity of O. perseae was found to increase as O. perseae populations on monitored avocado trees increased, suggesting that populations could have been augmented as new immigrants arrived from unmonitored avocado trees or other miscellaneous host plants. The phytoseiids Galendromus helveolus (Chant) and G. annectens (De Leon), Amblyseius similoides Buchelos and Pritchard, Euseius hibisci (Chant), and Neoseiulus californicus (McGregor) were also monitored during this study. Natural enemy numbers were not adversely affected by cultural control attempts targeting O. perseae. Aerial applications of abamectin with NR 415 oil for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) had an adverse effect on Galendromus spp., which are important predators of O. perseae in avocado orchards.