When is a rice insect a pest: Yield loss and the green revolution

Abstract

As land area to expand rice production is limited most increases in crop production in Asia must come from increasing yields on farms already under production. Insect pests are among the most important biological constraints limiting yield potential of modern rices but the extent of damage depends on how vigorous the crop is growing as well as the number of biotic and abiotic stresses affecting the crop that season. Yield loss data is useful for farmers, extension workers, researchers, and policy makers. A number of methods to estimate losses are available and more than one should be used. As accurate crop loss assessments are expensive to obtain for a nation on a regular basis, estimates are only available for limited areas of countries. Insect pest resistance exists for epidemic pests but not for chronic pests, the insect pest group that causes greater losses every year. Modern high tillering rices have greater capacity than traditional rices for compensation from insect pest damage and that capacity is enhanced by agronomic practices thus integrated pest management should be thought of within the context of crop management. For making better control decisions farmers need to assess the compensatory status of the crop and severity of crop stress acting on it. Due to crop compensation capacity, farmers need not correct all stresses to obtain high yields thus can combat the easiest or least expensive constraints and let the crop compensate for the rest. lf nations are to get a handle on the extent of losses, farmers will need to be involved in the data gathering.