Yellow Stem Borer
Feeding damage near the growing point causes deadheart and dead tillers at the vegetative stages and whiteheads (whitish unfilled panicles) at the reproductive stages. After hatching the larvae bore into the leaf sheath and feed on the inner surface of the stem wall in the direction of the stem. Tiny holes, frass and fecal matter can be observed on the damaged stems and tillers. The larvae can move from one internode to another. Frequent larval feeding does not cause visible symptoms because the plant compensate for the damage by producing extra tillers. This costs energy and in the end yield. The adults do not feed and live for four to ten days.
The yellow stem borer is a pest of deepwater rice. It is found in aquatic environments where there is continuous flooding. Second instar larvae enclose themselves in body leaf wrappings to make tubes and detach themselves from the leaf and falls onto the water surface. They then attach themselves to the tiller and bore into the stem. High nitrogenous field favors population buildup. Fields planted later favors more damage by the insect pests that have built up in fields that have been planted earlier. Stubble that remains in the field can harbor stem borer larvae and or pupae.
Cutting the leaf-top before transplanting reduces the carry-over of eggs from the seedbed to the field. Raising the level of irrigation water submerges the eggs deposited on the lower parts of the plant and also helps to control the populations.
Always consider an integrated approach with preventive measures together with biological treatments if available. Soak the roots of the seedlings in 0.02 per cent chlorpyriphos for 12-14 hrs before transplanting to give protection from the attack of stem borer up to 30 days. Pheromone traps may significantly decimate stem borer populations.