Seasonal prevalence and susceptibility to agrochemicals of Tyrophagus similis (Acari: Acaridae) in spinach buds and agricultural soil under greenhouse conditions |
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Authors: | Shikoh Kasuga and Hiroshi Amano |
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Institution: | (1) Laboratory of Applied Entomology and Zoology, Faculty of Horticulture, Chiba University, Matsudo, Chiba 271-8510, Japan;(2) Present address: Laboratory of Entomology, Department of Fruit Vegetables, National Institute of Vegetable and Tea Science, Kusawa 360, Ano, Mie 514-2392, Japan |
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Abstract: | Seasonal prevalence of Tyrophagus similis was investigated from 1997 to 1998 in two spinach greenhouses in central Japan. Susceptibility of T. similis to agrochemicals was also tested in the laboratory. Tyrophagus similis density in the soil was low during the high temperature period from May to August. The density rapidly increased in late
autumn and remained at a high level during the cool season from December to February. The number further increased in April
and then rapidly decreased in May. The high temperatures in the greenhouses from spring to early autumn are considered the
main causes of population decrease. Mites on spinach buds increased the number after those on and in the soil increased. Mites
attacked spinach buds mostly in late autumn and early spring. Dichlorvos did not reduce the number of mites in either greenhouse
even though it was highly toxic under laboratory condition. This discrepancy suggests that the mites in both the soil and
spinach buds had little direct contact with the chemicals. These data suggest that once crop damage by mites is detected,
it is usually too late to use chemicals, and that mites that live in the buds are protected from agrochemicals.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Agrochemicals Pest management Population dynamics Seasonal prevalence Spinach Tyrophagus similis |
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