Cnaphalocrocis medinalis

Cnaphalocrocis medinalis, the rice leafroller, is a species of moth of the Crambidae family. It is found in south-east Asia, including Hong Kong, Sri Lanka, Taiwan, Thailand and most of Australia.

The wingspan is about 16 mm.

The larvae are considered a pest on Zea mays, Oryza sativa and Triticum, Saccharum and Sorghum species.

The moth is very active, bright yellow or straw in colour with two distinct wavy lines in the fore wing and one wavy distinct line in the hind wing. It has a wing span of 15mm. Eggs are laid singly or in groups arranged in longitudinal rows on the undersurface of the leaves which are scaly white in color. Fecundity is about 56 eggs. Incubation period is 4–8 days. We find 5–6 larval instars, larval period is about 22–23 days. It pupates with in the infested leaf fold for a period of 6–7 days. The fully grown caterpillar is green in color and is 16.5mm long. The total life cycle completed in about 5 weeks.

All the stages of the crop is attacked by this pest. On hatching the newly hatched caterpillar cut the leaf edges and folds the leaf. When young seedlings are attacked it folds 3–4 adjacent plant leaves and scrapes the green matter so that the infested leaves appear white. A single caterpillar damages several leaves. The attacked plants dry up and it reduces the vigour of the plant. Ultimately the yield gets reduced. The yield loss may vary up to 10–50 per cent. It is more problematic at boot leaf stage.