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Can Exotic Phytoseiids Disrupt Pest Control in Stable Cropping
Systems?
Eric Palevsky
Dept. Entomology, Newe-Ya'ar Research Center, Agricultural Research Organization (ARO),
Ministry of Agriculture, P.O. Box 1021, Ramat Yishay 30095, Israel.
email: [email protected]
Abstract: Exotic phytoseiid species (Acari: Mesostigmata: Phytoseiidae) have been moved from
continent to continent in protected and perennial agricultural systems. In protected cropping systems,
specialized and generalist species have been used argumentatively both curatively and prophylactically.
In contrast in perennial crops inoculative releases, with the aim of establishing the natural enemy, were
performed. Here we focus on the question: Can the establishment of exotic phytoseiids disrupt pest
control? To answer this question, we review the efficacy of biological control efforts with phytoseiids in
several case studies, where exotic and indigenous species were used against pests on indigenous host
plants and some crops that were historically or recently introduced. Related factors affecting predator
establishment, such as intraguild predation and pesticide effects are discussed, as well as the potential
negative effects of exotic species releases on biological control and their impact on the indigenous natural
fauna. On citrus, apple, grape and cassava exotic phytoseiids have enhanced biological control without
negatively affecting indigenous species of natural enemies, except for the case of Euseius stipulatus
(Athias-Henriot) on citrus that displaced Euseius hibisci (Chant) in a limited region of coastal California,
USA, the latter considered to be an inferior biocontrol agent of Panonychus citri Koch.
Key words: Phytoseiidae, biocontrol agents, invasive species, exotic species.
Below we summarize a series of introductions of exotic phytoseiid predators for pest control, and
their outcome with respect to establishment and displacement of indigenous species.
Following the discovery of the Spider mite Oligonychus punicae on Avocado in California
augmentative releases of 3 native and 6 introduced phytoseiids were conducted with no
significant effect on pest control, but evidently due to the resident indigenous intraguild predator
E. hibisci (McMurtry et al., 1984). In a follow up study, 6 species collected from avocado
orchards in Mexico and Central America were introduced. Here too the result was negative, none
of the introduced species established, again apparently due to the overwhelming presence of E.
hibisci (McMurtry, 1989).
For the control of Tetranychus urticae and Panonychus ulmi in deciduous crops in
Australia two phytoseiid species were released. Typhlodromus pyri established and controlled P.
ulmi in grapes. An azinphos-methyl resistant (AMR) strain of Galendromus occidentalis
established and provided satisfactory T. urticae control in peaches. However, when azinphosmethyl treatments ceased the AMR predator was replaced by resident E. victoriensis.
Interestingly, there was no evidence of harmful effects on native fauna, possibly because the
exotic predators did not colonize the native flora (James, 2001).
For P. citri control in California, 20 species were introduced from South America,
Mediterranean, South Africa, Asia and Australia (McMurtry, 1989). Only E. stipulatus
established extensively in coastal southern California, displacing E. hibisci and subsequently
providing more effective P. citri control. New records showed E. stipulatus dispersal in
California, northward and host plant listings have expanded from citrus to avocado, cherimoya,
raspberry and grape.
Of the many exotic phytoseiid candidates released for cassava green mite (CGM)
Mononychellus tanajoa control on cassava in Africa only the two species Typhlodromalus aripo
and Amblydromalus manihoti established. T. aripo, a slow-developing plant-feeding species,
became a continent-wide control success, colonizing an area of over 400.000 km2 (Yaninek and
Hanna, 2003). No negative effects in the abundance of native phytoseiids were detected and
there is evidence of ‘facilitation’ of the exotics on the abundance of two native phytoseiids
(Zannou et al., 2007).
In summary despite large scale releases of specialized, generalist and plant feeding
phytoseiids, and the establishment of key species, no cases have been documented that have
showed any negative effects on biocontrol and/or native fauna. Based on our review (Palevsky et
al., 2013) and many studies that were not cited therein, I question whether there is any scientific
evidence to support the restriction of movement of phytoseiid species from continent to
continent. Accordingly I question the validity of lab studies conducted for the registration of
exotic phytoseiids, such as those aimed at evaluating intraguild predation, survival at low
temperatures, and or non-target effects, as non of these parameters have ever been shown to
identify phytoseiid species that have had any detrimental effects.
References
James, D.G., 2001: History and perspectives of biological mite control in Australian horticulture
using exotic and native phytoseiids. In: Halliday, Walter, Proctor, Norton, Colloff (Eds.),
Acarology: Proceedings of the 10th International Congress. CSIRO, Melbourne, pp. 436443.
McMurtry, J.A., 1989: Utilizing natural enemies to control pest mites on citrus and avocado in
California, USA. In: Channabasavanna, Viraktamath (Eds.), International Conference of
Acarology. Oxford and I.B.H., New Delhi, pp. 325-336.
McMurtry, J.A., Johnson, H.G. & Badii, M.H., 1984: Experiments to determine effects of
predator releases on populations of Oligonychus punicae (Acarina: Tetranychidae) on
avocado in California. Entomophaga 29: 11-19.
Palevsky, E., Gerson, U. & Zhang, Z.Q., 2013: Can exotic phytoseiids be considered ‘benevolent
invaders’ in perennial cropping systems? Exp Appl Acarol 59: 11-26.
Yaninek, J.S. & Hanna, R., 2003: Cassava green mite in Africa - a unique example of successful
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