Biology and Seasonal Abundance of Rice Leaf Mite, Oligonychus oryzae

摘要

An investigation on the biology and seasonal abundance of the rice leaf mite, Oligonychus oryzae Hirst was carried out by conducting lab and a field experiments. Egg, larval, protonymphal and duetronymphal periods lasted for 3-5 days, 1-2 days, 1-2 days and 1-2 days, respectively. Adult longevity of female and male varied from 7-8 days and 5-6 days, respectively. Unmated males lived for 9 days. Among the seven species of monocot weed plants, the highest population of mite was recorded in Chloris barbata (2.80/leaf) and Saccharum sp. (2.46/leaf). The lowest number of 0.43 eggs per leaf was recorded in February sowing and the high number of eggs was noticed in March, May and August sowings. Nymph and adult mite populations were high in April sowing. The lowest number of 0.12 nymph and 0.17 adult per leaf was observed in November and June sowing, respectively. Rice mite preferred 35 to 49 days old seedlings of rice. Very young stage and old stage plants did not support higher population of rice mite.