EFFECTIVENESS OF ESSENTIAL OILS OF MEDICINAL PLANTS AGAINST STORED PRODUCT MITE, SUIDASIA PONTIFICA OUDEMANS

Abstract

Acaricidal activity of essential oils obtained from 28 selected medicinal plants against stored product mite, Suidasia pontifica Oudemans, was investigated using the dry film method. The bioassay was conducted in a glass tube, 0.4 cm in diameter, 3 cm long covered with fine nylon mesh on both ends. In preliminary tests, 1.0% (53 µg cm-2) of various essential oils and 95% ethanol used as control were evaluated. Each glass tube was treated internally with 20 µl essential oils. Observations were made at 24 h after treatment and the number of dead mites was recorded. At the dose of 1.0%, essential oils of clove (Syzygium aromaticum), cinnamon (Cinnamomum bejolghota), myrtle grass (Acorus calamus), betel vine (Piper betle), and turmeric (Curcuma longa) were highly toxic to S. pontifica with more than 70% mite mortality observed at 24 h. Dry film effect of essential oils at various concentrations (0, 0.05, 0.1, 0.5, 1.0 and 1.5% equaling to 0, 2.65, 5.3, 26.5, 53 and 79.5 µg cm-2, respectively) resulting in mite mortality observed at 24 h was used to establish LD50 values. Based upon 24 h LD50 values, the essential oil of cinnamon (fresh leaf) was the most toxic to the mite with high activity at 24.05 µg cm-2, followed by essential oils of clove (dried bud), myrtle grass, cinnamon (dried bark), clove (fresh leaf), turmeric and betel vine at 24.28, 28.34, 30.89, 33.67, 38.09 and 41.76 µg cm-2, respectively.