Aceria tosichella (Keifer)
(Earlier sometimes identified as Aceria tulipae (Keifer)).
Aceria tosichella is now believed to consist of several host- specialist and generalist lineages, which may represent different species. These lineages (temporarily designated TM-1 to TM-8) differ in their ability to accept hosts and to transmit viruses. Such genetic diversity may result from their ability to infest many wheat cultivars and Poaceaeous weeds, especially in the Middle East.
Common name: Wheat curl mite.
Taxonomic placing: Acari, Prostigmata, Eriophyoidea, Eriophyidae.
Geographical distribution: Apparently world-wide, wherever Poaceae (Gramineae) grow.
Morphology: The body of the adult mite is 170-250 microns in length, whitish, and 8-rayed empodium on leg I, a small lobe over the gnathosoma, prodorsal shield with longitudinal median line restricted to its posterior half.
Host plants: More than 100 Poaceaeous plants, especially wheat (Triticum aestivum L.).
Life cycle: The mite completes a life cycle in 7–13 days at 20 and 27ºC, respectively. A female deposits up to 25 eggs, which are usually placed within sheltered plant structures, and thus difficult to detect. They initially feed on the wheat leaves, then move onto other parts, later also colonizing the head as it emerges. As the hosts begin to dry, the mites are dispersed by mild winds. In cooler regions, during the absence of crop plants, the mites survive on Poaceaeous volunteer plants. Methods for rearing A. tosichella in the laboratory on wheat blades are available. Off-host they can survive for about 4 days at 10°C and 95% RH.
Economic importance: Aceria tosichella is a major pest of the world’s grain industry, capable of reducing wheat yields by about one third. Mite feeding reduces leaf chlorophyll and it may become whitish and its cell walls collapse. Infestations and damage are more severe when the plants are under drought. In addition the mites vector several major viruses (like Wheat streak mosaic virus (WSMV)), which further reduce yields. Immature mites acquire WSMV after feeding for 30 min, and may transmit the virus for at least 7 days.
Horticultural methods: In cooler regions, the removal of volunteer wheat (or other Poaceaeous hosts) by mechanical means or herbicides.
Plant resistance: This is the main strategy used to reduce pest damage, and it can be combined with resistance to the viruses vectored by the mite. Resistant cultivars can be identified by placing single and groups of mites on susceptible wheat varieties and checking for the characteristic leaf rolling and folding.
Chemical control: Avermectins reduced mite numbers by about 80% in Egypt.
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Chuang, W.-P. (and 6 co-authors). 2017. Wheat genotypes with combined resistance to wheat curl mite, wheat streak mosaic virus, wheat mosaic virus, and triticum mosaic virus. Journal of Economic Entomology 110: 711–718.
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