Natural Enemies Associated with Avocado Thrips in Ventura County Avocado Groves: Results of a pilot study and year one of a three-year survey

Fourteen avocado groves were surveyed by leaf samples, beat samples and sticky cards to assess avocado thrips (AT) and natural enemies (NE) populations in avocado trees in 2003. In the groves, the presence of NE and AT between January and September was only slightly affected by a single abamectin treatment, with Chrysopa sp. being the only NE significantly impacted. In untreated groves, considerable differences between NE populations were found. Leptothrips mali were the most abundant predatory thrips in beat samples and arachnids the most abundant NE. On sticky cards, Aeolothrips fasciatus were most abundant, followed by the Coleoptera, while Ceranisus menes and Franklinothrips orizabensis were equally abundant in untreated groves. Distance from the coast did not affect L. mali or Aeolothips, but impacted C. menes (more abundant near the coast) and F. orizabensis (more abundant inland). The presence of groundcover (dead, dying, mowed and living) increased the number of parasitoids and spiders recorded in beat samples and increased the numbers of Leptothrips mcconnelli and predaceous Coleoptera. F. orizabensis and C. menes numbers on sticky cards declined when >70% of the orchard floor was covered. When only living ground cover is considered, parasitoids numbers in beat samples and A. fasciatus numbers on sticky cards increased with >70% living ground cover, while C. menes was more abundant where living ground cover did not exceed 70% and F. orizabensis were most abundant where 11-70% of the orchard floor was living ground cover. The presence of flowering plants on the orchard floor had no significant effect on NE observed in beat samples or on sticky cards. Trends indicated higher numbers of L. mali and Orius sp. in beat samples in orchards where between 1-10% flowering plants were present on the orchard floor, while lower numbers of F. orizabensis were found on sticky cards in these orchards. C. menes numbers were not impacted by the presence of flowers in the ground cover. Most results of this survey are descriptive and need replication before conclusions or generalizations can be made. Data from future seasons will allow for temporal analyses which will be necessary to fully understand the NE complex in avocado orchards.