Impact of organic-inorganic nutrients combination in rice on the occurrence of Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) in West Bengal, India

Rice sheath mite, Steneotarsonemus spinki Smiley (Acari: Tarsonemidae), was observed to pose a serious threat to the rice cultivation under Bengal Basin of West Bengal, India during wet season. The mite appeared during tillering to panicle emergence with a maximum population encountered during early ripening stage of the crop causing characteristic brownish specks on the leaf sheath and on the grains resulting poor yield particularly in case of susceptible rice cultivars, IET-4786, IR-36, IET-4094 and many others high yielding varieties. Field experiment was carried out in a randomized complete block design with 11 treatments, comprising different organicinorganic nutrients combination. The result of the experiment reveals that the mite population significantly varied among different treatments with a maximum mite population colonized (930 mites/ leaf sheath) in chemical fertilized plots and a minimum recorded (108 mites/leaf sheath) in leaf manure of Gliricidia sepium (Jacq.) treated plots. However, maximum seed yield (fresh rough grain) was obtained from chemical fertilizer treated plots (8.23 t/ha) followed by combined application of mustard cake, Gliricidia leaf manure and chemical fertilizers (7.37 t/ha) treated plots and the minimum yield was recorded from control plots (4.60 t/ha).