Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) -: A yield reducing mite of rice crops in West Bengal, India

The rice mite, Steneotarsonemus spinki Smiley (Acari: Tarsonemidae), was observed for the first time as a serious pest of rice crops in West Bengal. Susceptibility and tolerance level of twelve most commonly grown rice cultivars were evaluated against the mite during the wet season of 2002-2003. Damage, visible on leaf sheaths and on grain as brownish patches, led to an increase in chaffy grain and loss of yield. None of the cultivars were found to be resistant, however, the rice cultivars MTU-7029 (83.33 mites/sheath) and IR-64 (160.00 mites/sheath) were recorded as 'tolerant' and IR-36 (570.00 mites/sheath) and IET-4094 (496.67 mites/sheath) were recorded as 'susceptible.' Among the characters studied, only chaffy grain and grain yield had significant positive or negative correlation, respectively, with the occurrence of the mite.