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), Oligonychus 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 Barbara Counties, CA, from 1998 to 2000. Objectives were to understand pest-predator dynamics and to assess which predators have potential as biological 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. perseae was the most abundant pest, followed by S. perseae, and Oligonychus puniciae (Hirst) (Acari: Tetranychidae). Phytoseiid mites and spiders were the most abundant predators. The predatory thrips Franklinothrips orizabensis Johansen and Aeolothrips kuwanaii Moulton (Thysanoptera: Aeolothripidae) were also relatively abundant compared with at least 13 other species of predators on leaves. On immature avocado fruit, S. perseae was the most abundant pest and phytoseiid mites, F. orizabensis, and A. kuwanaii were the three most abundant predators. No consistent positive associations between pests and predators were seen on leaves, but F. orizabensis, A. kuwanaii, and phytoseiid numbers on fruit and S. perseae numbers on fruit were positively and significantly associated in all three orchards. In addition, there were significant positive associations between S. perseae and predatory thrips populations from leaf litter in two of the 3 yr. These pest-predator interactions may play a role in developing new control strategies and the importance of these relationships needs to be experimentally investigated.