Yield loss in rice caused by the caseworm Nymphula depunctalis Guenee (Lepidoptera: Pyralidae).
Economic injury levels for Nymphula depunctalis [Parapoynx stagnalis] on rice plants of the cultivar IR 36 of different ages (5-30 days after transplanting) were determined in screenhouse and field tests in the Philippines. The economic injury levels were based on number of larvae per hill, percentage of leaves cut for case-making and percentage of leaf area scraped by larval feeding. Although the extent of plant damage at a given level of larval infestation varied according to the age of the plant attacked, an economic injury level of 1 larva/hill and 3 in. leaves cut or leaf area scraped is suggested. A grain yield loss of about 500 kg/ha or 10% occurred when there were approximately 10 larvae/hill, 30% of the leaves were cut or 25% of the leaf area was scraped during the first month after transplanting.