author(s)
Tanmoy Mandal and Sunil Kr. Ghosh

abstract
Som plant (Machilus bombycina King) is an important plant in agroforestry system. Localized cottage industries are involved with this plant like sericulture industry (muga silk worm cultivation). Leaves of som plants are major food of muga silk worm (Antherea assama). The plant is susceptible to mite pest (Tetranychus sp.) causes heavy damage to tender leaves. Higher mite population was recorded during 46^th to 51^st standard week, during 3^rd week of November to 3^rd week of December and peak population (6.06/3 leaves) was recorded on 46^th standard week that is on 3^rd week of November. Correlation studies revealed that mite population had a significant negative correlation with temperature and non-significant positive correlation with relative humidity. Water extracts of tobacco leaf was found most effective against mite providing 40.51% suppression, closely followed by methanol extracts of Spilanthes (39.06% suppression). Methanol extracts of Garlic bulb and Polygonum gave moderate results, recording about 38.10% and 37.78% mite suppression respectively. Synthetic insecticides contaminate plant leaves with the toxic chemicals. Plant extracts are of biological origin having low or no hazardous effect on health and environment and so can be incorporated in organic cultivation.