Seasonal incidence and source of the panicle rice mite, Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) in paddy fields of Central Vietnam

The panicle rice mite, Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) is the most important and destructive mite species attacking rice crop in Vietnam. Field surveys were carried out in Thua Thien Hue province, Central Vietnam during 2021-22 to investigate the seasonal incidence of S. spinki on commonly used rice varieties and the importance of ratoon rice plants and weeds found on paddy fields as possible sources of S. spinki to infest rice plants in next crop seasons. The panicle rice mites were recorded at all growth stages of investigated rice varieties grown during summer-autumn and winter-spring rice seasons. Incidences of S. spinki were more during the summer-autumn season than during the winter-spring season. Among the seven investigated rice varieties, TH5 and HAPHAT3 recorded higher infestation by S. spinki. Ratoon rice plants in the fallow season (Sept.-Dec.) were survival habitats and maintenance of the panicle rice mite between the two rice seasons. Seven weed species, including Echinochloa crus-galli (L.) Beauv., Fimbristylis sp., Eleocharis sp. and Eschaemum rugosum Salisb. were found as alternative hosts and important sources of infestation of S. spinki. Therefore, the removal of ratoon and weed plants during the crop-free seasons is good field practice in integrated pest management for S. spinki in Central Vietnam.