Biocontrol of persea mite, Oligonychus perseae, with an exotic spider mite predator and an indigenous pollen feeder Yonatan Maoz a,c , Shira Gal a , Yael Argov b , Moshe Coll c , Eric Palevsky a,⇑ a Department of Entomology, Institute of Plant Protection, Volcani, Agricultural Research Organization (ARO), Newe-Ya’ar Research Center, POB 1021, Ramat Yishay 30095, Israel b Israel Cohen Institute for Biological Control, Plant Production and Marketing Board, Citrus Division, POB 80, Bet Dagan 50250, Israel c Department of Entomology, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel article info Article history: Received 2 November 2010 Accepted 19 July 2011 Available online 23 July 2011 Keywords: Avocado Euseius scutalis Neoseiulus californicus Oligonychus perseae Cover crop Pollen Alternative food abstract 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 indig- enous 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 demon- strated 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 demon- strate the efficacy of this approach in commercial orchards. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction The persea mite Oligonychus perseae Tuttle, Baker and Abbati- ello, a pest of avocado, was discovered in Israel in 2001 and is presently established in most of the avocado growing areas in the country. The mite spins densely woven nests along the veins on the lower side of leaves. Feeding damage by the persea mite on the leaf surface produces circular necrotic spots (Aponte and McMurtry, 1997b) and high mite densities can cause substantial economic losses (Maoz et al., 2011). Acaricides are presently the only tool available to Israeli growers to prevent persea mite damage. Until the arrival of this pest, Israeli avocado growers have managed to avoid pesticide treatments by implementing classical biological control and augmentative releases of indigenous natural enemies (Swirski et al., 2002). To continue to maintain this pesticide-free agro-ecosystem, efficient biocontrol agents for the persea mite need to be identified, conserved and if needed, augmented. Following the introduction of persea mite to California in the early 1990’s, phytoseiid predators (Acari: Phytoseiidae) with a preference for spider mites (McMurtry and Croft, 1997) were sought out and evaluated (Hoddle et al., 1999, 2000; Kerguelen and Hoddle, 1999). Two phytoseiid predators, Neoseiulus californi- cus (McGregor) and Galendromus helveolus (Chant), were identified and release rates were established. Types III and IV phytoseiid species can develop on mites, small insects, pollen and fungal spores (McMurtry and Croft, 1997). While spider mites may be just as suitable as pollen for the popu- lation development for certain species (Bounfour and McMurtry, 1987), copious webbing may prevent the predators from reaching their prey, rendering the latter a suboptimal food source. Still McMurtry (1992) maintained that generalist phytoseiids could be considered effective spider mite control agents, provided that alternate food sources, such as pollen, are available. Provisioning of pollen could allow generalist predators to persist even when prey is absent or scarce (Overmeer, 1985; Rosen and Huffaker, 1049-9644/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.biocontrol.2011.07.014 ⇑ Corresponding author. Fax: +972 4 9836936. E-mail addresses: yael@jaffa.co.il (Y. Argov), coll@agri.huji.ac.il (M. Coll), palevsky@volcani.agri.gov.il (E. Palevsky). Biological Control 59 (2011) 147–157 Contents lists available at ScienceDirect Biological Control journal homepage: www.elsevier.com/locate/ybcon