Comparison of Scirtothrips Perseae (thysanoptera: Thripidae) Infestation Levels on Avocado Fruit and Leaves

Avocado fruit can be severely damaged by Scirtothrips perseae (Thysanoptera: Thripidae) in southern California. Scirtothrips perseae is found on leaves and fruit, but its prevalence on one versus the other substrate has not been documented. In this study, the occurrence and infestation levels of S. perseae on avocado leaves and fruit during late spring and summer were compared at three sites in Ventura and Santa Barbara Counties, California, from 19982000. In all sites and years, adult and larval S. perseae were more abundant on young leaves than on small fruit from early to mid June. After leaves matured and hardened with increasing temperatures from late June through August, overall S. perseae populations generally declined. However, populations became proportionally higher on fruit than on leaves compared with earlier in the season. This usually resulted in equal numbers on the two substrates and sometimes in higher numbers on fruit late in the season. The change in relative S. perseae abundance on leaves and fruit between preand post-leaf hardening indicates control efforts need to be made shortly before leaves harden and become unsuitable for S. perseae feeding and oviposition or shortly after the first thrips move onto fruit.