Diaphania indicaSaunders larvae feed on cucumber leaves, almost defoliating plants when populations are high. Using insecticide treatments, population levels of caterpillars were manipulated in cucumber plantings. Carbaryl, dimethoate andBacillus thuringiensiswere effective in reducing caterpillar populations. Regression analysis of yield of cucumbers onD. indicapopulations per leaf showed that yield loss was approximately 10% whenD. indicapopulations reached one per leaf. Yield loss could not be detected below this level. Yield loss increased linearly as populations increased above 1 per leaf. Moderate populations ofThrips palmiKarny, up to 80 thrips per leaf, in one of the three trials had no significant effect on yield.