Zetzellia mali Ewing
Taxonomic placing: Acari, Prostigmata, Raphignathoidea, Stigmaeidae.
Geographic distribution: North America, Europe, Middle East and, Iran.
Host plants: Many fruit trees, especially apples.
Morphology: Body yellow to orange red, about 0.4 mm in length. Prodorsal sclerite reticulated, with 3 pairs of setae, Opisthosomal sclerite also reticulated and bears 5 pairs of setae. Postocular bodies only slightly larger than eyes.
Life history: Zetzellia mali is mainly a predator of eggs and immature stages of various eriophyids but also of spider mite eggs and even of its own eggs, locating these prey only through random encounters. At 21ºC a generation requires about 3 weeks. Females overwinter, sometimes in large groups, within cracks or crevices on tree twigs or bark, or under the empty scales of Diaspididae, often near concentrations of their prey. They emerge in spring and raise 3-4 generations during summer, at times dispersed by winds. During fall in cooler regions they move to overwintering sites, some remaining active on leaves in autumn. The distribution of Z. mali on apple trees depends on that of their prey, especially the apple rust mite. Its ability to feed on various eggs (including its own), and to withstand periods of starvation (about 3 weeks), enables it to survive in orchards longer then other co-occurring predators, such as Phytoseiidae. It is resistant to organophosphates and some other insecticides and tolerant to many fungicides.
Economic importance: Zetzellia mali is an effective predator of Bryobia rubrioculus in Turkey. In North American apple orchards it preys on eggs and immature stages of Panonychus ulmi and on active stages of A. schlechtendali. Predation on the latter is enhanced by high nitrogen levels and is influenced by the specific cultivar on which the interaction takes place. Zetzellia mali may also prey on the eggs of co-occurring phytoseiids. In Italy the predator is considered to be important in controlling A. schlechtendali. Zetzellia mali is usually unable to reduce large populations of pest mites. However, early in the season, or in orchards where pest numbers had been reduced by other means, this predator can keep pest populations for long periods at low levels. It may also hinder or displace the phytoseiid Typhlodromus pyri Scheuten when co-occurring in apple orchards.
References
Clements, D.R. and Harmsen, R. 1992. Stigmaeid-phytoseiid interactions and the impact of natural enemy complexes on plant inhabiting mites. Experimental & Applied Acarology 14: 327-341.
Croft, B.A. 1994. Biological control of apple mites by a phytoseiid mite complex and Zetzellia mali (Acari: Stigmaeidae): long-term effects and impact of azinphosmethyl on colonization by Amblyseius andersoni (Acari: Phytoseiidae). Environmental Entomology 23: 1317-1325.
Croft, B. A. and Slone, D. H. 1997. Equilibrium densities of European red mite (Acari: Tetranychidae) after exposure to three levels of predaceous mite diversity on apple. Environmental Entomology 26: 391-399.
Dogan, S. 2007. Checklist of raphignathoid mites (Acari: Raphignathoidea) of Turkey. Zootaxa 1454: 1–26.
Jamali, M.A., Kamali, A., Saboori, A. and Nowzari, J. 2001. Biology of Zettzellia mali (Ewing) (Acari: Stigmaeidae) in Karaj, Iran. Systematic and Applied Acarology 6: 55-60.
Kasap, I. and Çobanoğlu, S. 2006. Population dynamics of Bryobia rubrioculus Scheuten (Acari: Tetranychidae) and its predators in sprayed and unsprayed apple orchards in Van. Türkiye Entomoloji Dergisi 30: 89-98.
Rahmani, H., Fathipour, Y. and Kamali, K. 2010. Spatial distribution and seasonal activity of Panonychus ulmi (Acari: Tetranychidae) and its predator Zetzellia mali (Acari: Stigmaeidae) in apple orchards of Zanjan, Iran. Journal of Agricultural Science and Technology 12: 155-165.
Rasmy, A. H.; Zaher, M. A. and Abou-Awad, B. A. 1972. Mites associated with deciduous fruit trees in UAR. Zeitung angewandte Entomologie 70: 179-183.
Strapazzon, A., and Monta, L.D. 1988. Role and distribution of Amblyseius andersoni Chant and Zetzellia mali Ewing in apple orchards infested by Aculus schlechtendali Nalepa. Redia 71: 39–54.
Walde, S.J., Hardman, J.M. and Magagula, C.N. 1997. Direct and indirect species interactions influencing within-season dynamics of apple rust mite, Aculus schlechtendali (Acari: Eriophyidae). Experimental & Applied Acarology 21: 587-614.
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