Phenology of arthropod pests and associated natural predators on avocado leaves, fruit, and in leaf litter in southern California

Abundance of Scirtothrips perseae Nakahara (Thysanoptera: Thripidae), Oligo nychus perseae Tuttle, Baker & Abbatiello (Acari Tetranychidae), predators, and associations among their population trends on avocado leaves and fruit were determined in three untreated avocado orchards in Ventura and Santa B arbara Counties, CA, from 1998 to 2000. Objectives were to understand pest- predator dynamics and to assess which predators have potential as biologica l control agents. Numbers of S. perseae and predators from leaf litter/soil were also determined in one orchard from 1998 to 2000. On leaves, O. perse ae was the most abundant pest, followed by S. parseue, and Oligonychus puni ciae (Hirst) (Acad: Tetranychidae). Phytoseiid mites and spiders were the m ost abundant predators. The predatory thrips Franklinothrips orizabensis Jo hansen and Aevlothrips kuwanaii Moulton (Thysanoptera: Aeolothripidae) were also relatively abundant compared with at least 13 other species of predat ors on leaves. On immature avocado fruit, S. perseae was the most abundant pest and phytoseiid mites, F arizabensis, and A. kuwanaii were the three mo st abundant predators. No consistent positive associations between pests an d predators were seen on leaves, but F. orizabensis, A. kuwanaii, and phyto seiid numbers on fruit and S. perseae numbers on fruit were positively and significantly associated in all three orchards. In addition, there were sig nificant positive associations between S. perseae and predatory thrips popu lations from leaf litter in two of the 3 yr. These pest-predator interactio ns may play a role in developing new control strategies and the importance of these relationships needs to be experimentally investigated.