Oligonychus perseae (Acari: Tetranychiidae)
The persea mite, Oligonychus perseae Tuttle, Baker and Abbatiello (previously miss identified as Oligonychus peruvianus [McGregor]) is native to Mexico and invaded Costa Rica (in 1974), California (1990), Israel (2001), Spain (2004) and Florida (2007). Persea mites are found in avocado orchards year round and avocado varieties vary significantly in their susceptibility to infestation (Kerguelen and Hoddle, 2000). Mites prefer to live on mature leaves, and in California, populations begin to build in April-June, peak in July-August, and crash in September-October (Kerguelen and Hoddle 1999a,b; Hoddle et al., 2000). In Israel, the mite was found for the first time in October 2001 (Swirski et al. 2002) and has since become a serious pest of avocado there. In Israel an additional peak of infestation appeared in October-November (Maoz et al. 2011). In Florida the mite was detected in 2007 with few additional detections thereafter. However, so far no economically damaging populations have been observed.
Part of plant damaged: Leaves
Mites live, feed, and breed on the undersides of avocado leaves in small colonies within the protection of circular silken nests (Aponte and McMurtry 1997a). Characteristic circular necrotic spots result from feeding (see Hoddle 2010a for color photos of O. perseae, its natural enemies, and damage). Once necrotic feeding damage on the undersides of leaves approaches ~10% (or around 100 mites per leaf), trees begin to drop leaves (Kerguelen and Hoddle, 1999; Hoddle et al. 2000).
Monitoring and action levels
Maoz et al.(2011) recommended that scouts adopt an action threshold of 50-100 mites per leaf in Israel, but cautioned that more research is needed to refine the action threshold. Hernandez et al. (2000) suggested the removal of fallen foliage infested with mites from the ground below infested trees as a cultural control method. However, this tactic is not efficacious (Takano-Lee and Hoddle, 2002). According to Hernandez et al. (2000) no known prey-specific predators of the persea mite have been reported in Mexico. Consequently, research into the management of the persea mite has focused along three major avenues: (1) biocontrol with commercially-available predatory mites, (2) enhancement of naturally-occurring predator populations via resource subsidies, and (3) pesticides.
Field tests screening of six species of predatory mite species (Hoddle et al. 1999) indicated Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) could provide control equivalent to pesticide applications (Hoddle et al., 1999; Kerguelen and Hoddle, 1999). However, the cost was 13-14 times more expensive than pesticides (Hoddle et al. 2000a). A modified mist blower was shown to be very effective at delivering predators to avocado trees (Takano-Lee and Hoddle 2001) but this application technology was not sufficiently efficient to reduce costs associated with predator introductions. Generalist predator populations do build in response to increasing O. perseae populations, but control is often inadequate (Yee et al. 2001a).
In Spain, an omnivorous phytoseiid mite, Eusieus stipulatus (Athias-Henriot) can be enhanced in avocado orchards via the artificial provision of pollen from deliberately planted maize plants. Increased populations of E. stipulatus were correlated with lower persea mite populations (González-Fernández et al., 2009). Additionally, airborne pollen from surrounding olive groves was also correlated with increased populations of E. stipulatus in avocado orchards. Subsequent laboratory experiments indicated olive pollen was suitable for E. stipulatus development (González-Fernández et al., 2009). In Israel, Euseius scutalis (Athias-Henriot) previously described as Euseius rubini (Swirski and Amitai) demonstrated was effective reducing mite populations. Eusieus scutalis will respond positively to resource subsidization via windblown pollen from patches of Rhodes grass or artificial application with an electrostatic sprayer, with the former being more beneficial for predator mite population growth (Maoz et al., 2009).Field surveys concluded that pollen subsidization generally promoted higher predator populations which were correlated with lower pest densities but this was not significantly different from control treatments that did not receive pollen (Maoz et al., 2009). Signficant practical and economic challenges confront the use of pollen for enhancing predator populations in avocado orchards.
In California, the standard industry control practice for the persea mite is the application of abamectin combined with a horticultural oil in summer. This product is also used against avocado thrips, Scirtothrips perseae Nakahara, in the spring to control populations of this pest. Consequently, pest populations in avocado orchards can be exposed to two abamectin applications per year. Abamectin applications have a very long period of activity against targeted avocado pests, ~10-12 weeks (Morse et al., 2000) and resistance development is a concern (Humeres and Morse, 2005). To combat this potential problem in California, pesticide rotation programs to manage resistance development are encouraged. In Mexico, use of hot-pepper extracts failed to provide significant mite control (Reyes et al., 1995), and the best chemical control was obtained with organophosphates and poorest control was observed with sulfur applications (Andrade, 1988). Martinez (1989) has suggested that the persea mite has developed resistance to organophosphates in the states of Morelos, and Michoacan in Mexico.
Kerguelen, V. and Hoddle. M. S. (2000) Comparison of the susceptibility of several cultivars of avocado to the persea mite, Oligonychus perseae (Acari: Tetranychidae). Scientia Horticulturae 84: 101-114.
Kerguelen, V. and Hoddle, M.S. (1999a). Measuring mite feeding damage on avocado leaves with automated image analysis software. Florida Entomologist 82, 119-122.
Swirski, E., Wysoki, M., and Izhar, Y.(2002) Subtropical Fruit Pests in Israel. Fruit Board of Israel (Production and Marketing). 285pp (In Hebrew)
Aponte, O. and McMurtry J. (1997a.) Damage on ‘Hass’ avocado leaves, webbing, and nesting behavior of Oligonychus perseae (Acari: Tetranychidae). Experimental and Applied Acarology 21, 265-272.
Hernandez, H.G., Johansen, R., Gazca, L., Equihua, A., Salinas, A., Estrada, E., Duran, F., and Yalle, A. (2000) Plagas del aguacate. In Teliz, D (ed) El aguacate y su manejo integrado.Ediciones Mundi-Prensa, Mexico DF pp. 117-136.
Maoz, Y., Gal, S, Zilberstein, M., Izhar, Y., Alchnatis, V., Coll, M., and Palevsky, E. (2011) Determining an economic injury level for persea mite Oligonychus perseae, a new pest of avocado in Israel. Entomologia Experimentalis et Applicata.138, 110-116.
Hoddle, M.S. Robinson, L.and Virzi. J. (2000a) Biological control of Oligonychus perseae on avocado: III. Evaluating the efficacy of varying release rates and release frequency of Neoseiulus californicus (Acari: Phytoseiidae). International Journal of Acarology 26, 203-214.
Takano-Lee, M. and Hoddle, M. S. 2001. Biological control of Oligonychus perseae (Acari: Tetranychidae) on avocado: IV. Evaluating the efficacy of a modified mistblower to mechanically dispense Neoseiulus californicus (Acari: Phytoseiidae). International Journal of Acarology 27, 157-169
Yee, W., Phillips, P.A. Rogers, J.L. and Faber, B.A.(2001a) Phenology of arthropod pests and associated natural predators on avocado leaves, fruit, and in leaf litter in southern California. Environmental Entomology 30, 892-898.
González-Fernández, J.J., F. de la Peña, J.I. Hormaza, J.R. Boyero, J.M. Vela, E. Wong, M.M. Trigo and. Montserrat, M (2009) Alternative food improves the combined effect of an omnivore and a predator on biological pest control. A case study in avocado orchards. Bulletin of Entomological Research 99, 433-444.
Maoz, Y., Gal., S. , Abrahams, J. , Gan-Mor, S., Coll, M. , and Palevsky, E.. (2009). Pollen provisioning enhances Eusieus scutalis (Phytoseiidae) populations and improves conrol of Oligonychus perseae (Tetranychidae). In: Proceedings of the 3rd International Symposium on the Biological Control of Arthropods, Christchurch New Zealand, Feb 8-13, 2009. Editors: P.G. Mason, D.R Gillespie, and C. Vincent, pp. 339-346. USDA Forest Service Publication FHTET-2008-06. 636 pp. (MISSING 2010 REF, IN THE TEXT IS 2010 and 2011 only, the bellow ref. Probably in text suppose to be 2009
Morse, J.G., M.S. Hoddle, and Urena, A.A. (2000). Persea mite pesticide efficacy trial. California Avocado Society Yearbook 84, 127-137.
Humeres, E.C. and Morse,. J.G. (2005) Baseline susceptibility of persea mite (Acari: Tetranychidae) to abamectin and milbemectin in avocado groves in Southern California. Experimental and Applied Acarology 36, 51-59.
Reyes, J.C., Rubi, M, Aguilar, J. (1995) Manejo organico en el cultivo del aguacate. Memorias Fundacion Salvador Sanchez Colin, CICTAMEX, Coatepec Harinas, Mexico pp. 29-37.
Andrade G., S. (1988) Control quimico de la arana cristalina Oligonychus perseae, Tutle, Baker and Abatiello en el cultivo del aguacatero. Tesis. Universidad Michoacana de San Nicolas Hidalgo, Uruapan, Michoacan, Mexico.
Martinez, B. R. (1989). El cultivo del aguacate en Mexico, sus problemas fitosanitarios, soluciones y perspectivas. Fruticultura de Michoacan. 2, 7-13.