Impact of Mechanical Defoliation and Detillering on Rice Yield

Experiments were conducted in rice fields during kharif 1994 and 1995 to understand the insect crop relationship and the reaction of plants to injury by insect pests. Mechanical defoliation and detillering of Basmati rice plants was carried out in field at different levels and at different days after transplanting (DAT) and its effect on crop yield was recorded. 25% defoliation or 10% detillering of plants on 15 and 30 DAT did not affect rice yields. 25% defoliation at 45 DAT caused yield loss compared to the control. 50% defoliation at 15, 30 or 45 DAT caused yield loss of 7.0%, 18.7% and 45.2% respectively compared to the yield in control. Similarly, 10% detillering at 45 DAT caused 5.7% less yield than the control while 20% detillering at 30 or 45 DAT caused 5.7% and 15.3% yield loss compared to the control respectively. The results from these studies indicated that damage to rice plant in early crop growth stage may not be considered as alarming to justify pesticide application since plant showed compensatory mechanism due to such injury.