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Acaricidal activity of essential oils obtained from pepper (Piper nigrum Linn.), lemon grass (Cymbopogon citratus (Dc.ex Nees)) and citronella grass (Cymbopogon nardus Rendle.) against mushroom mite (Luciaphorus perniciosus Rack.)on mushroom cubes was evaluated.Essential oils at various concentrations of 0 (2.5% Tween-20 in water), 10, 20, 30, 40 and50 μl/L air were placed respectivelyinto 35 L fumigation chamber.The fumigation time was 24 hrs and mortalities of mites were observed in3 and7days after treatment.The result presented that essential oils of pepper, lemon grass and citronella grass were highly toxic to the L.perniciosus, remarkably at1 0 μl/L air, more than 70and 90% mite mortalities were found at 3 and 7 days, respectively.The effect of those essential oils on mushroom (Lentinus polychrous Le'v) was conducted by evaluating their growth inhibition rates.Essential oils at the concentrations of 0% (2% Tween-20) and 1.5% were tested bypaper disc diffusion on PDA.It was found that essential oil of pepper did not inhibit the growth of L.polychrous,comparatively similar result was found in the control.Field application was also investigated by direct spray of pepper essential oil at50% inTween-20 for 15 cc / L water in mushroom farm at the l stand 2nd week after blooming period.The results presented that it could completely control the mushroom mite within4 weeks.