Abstract
West Bengal is one of the main rice producing Indian states, where about 14 million t are produced in 6.2 million ha. In recent years, the rice sheath mite, Steneotarsonemus spinki Smiley, has been one of the most destructive mite pests of this crop in the Bengal Basin, especially in the wet season. It colonizes the leaf sheath, causing chaffy and sterile grains and brownish patches on the affected plant parts.An experiment was conducted to study the impact of five different dates of transplanting (at seven day intervals) of rice cultivar IET-4786 on mite density and crop yield. The study was conducted from July to November 2007 in Kalyani, West Bengal. Rice sheath mite population increased gradually, reaching the maximum level on September 25 on plants of the first three planting dates, and on October 5, on plants of the last two planting dates. The result revealed that peak incidence of mite occurred at the ripening stage of the first three planting dates, but significantly higher number of mite population and damage symptoms in all plants were observed in the last two planting dates, at the panicle emerging to flowering stage. Poor yield was obtained from plants of the last planting date, which could be due to the sheath mite attack.