Yael Argov - Israel Cohen Institute for Biological Control, Plant Production and Marketing Board, Citrus Division, POB 80, Bet Dagan 50250, Israel

Moshe Coll - Department of Entomology, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel

To improve the biological control of persea mite (Oligonychus perseae) in Israeli avocado orchards we evaluated two approaches: (1) Augmentative inundative releases in commercial orchards of Neoseiulus californicus, an exotic spider mite predator, and (2) Conservation of Euseius scutalis, the prevalent indigenous phytoseiid predator found in avocado orchards, by pollen provisioning. The latter was done at three spatial scales; leaf discs, seedlings and trees. Neoseiulus californicus releases led to a significant reduction in persea mite population densities. Nonetheless, most of the recovered predators consisted of E. scutalis. The leaf disc experiment showed that E. scutalis can significantly reduce persea mite populations even though it cannot penetrate or tear the mite nests. The seedling experiments demonstrated that E. scutalis can suppress persea mite when pollen is available and provisioning maize pollen substantially increased E. scutalis populations. Field trials revealed that conservation of E. scutalis using Rhodes grass (Chloris gayana) as a windborne pollen provisioning cover crop (WPPCC) was highly effective, compared to repeated artificial pollen applications. Densities of phytoseiid populations were significantly higher on trees adjacent to the Rhodes grass patches than on distant trees, whereas persea mite populations on trees adjacent to these patches were consistently lower. In this study, we show that the use of Rhodes grass as a WPPCC for conservation of E. scutalis is both effective and sustainable. While our results indicate that E. scutalis has potential for mite control, future studies are needed to demonstrate the efficacy of this approach in commercial orchards.