Common name: Rice leaffolder
Scientific name: Cnaphalocrocis medinalis, Marasmia patnalis, M. exigua
Synonyms: Rice leafroller, Grass leafroller
Rice, maize, sorghum, wheat, oats, coconut, barley, banana, tobacco, millet, and sugarcane
Commonly found in Asia
The larvae feed on the unopened leaves of young plants. Feeding damage includes folded leaves (rolled leaves) and the removal of leaf tissue leaving longitudinal and transparent whitish streaks. The folded leaves have a tubular design where the larvae hide to feed. Sometimes, the tips are fastened to the basal part of the leaf with silk strands. The larva connects the two edges of the leaf by the silken threads it produces. It swings its head back and forth between opposite margins of the leaf while its anal and abdominal prolegs hold the leaf surface. The silken threads contract when dried producing a folded leaf in about 15 minutes. The larva stays in the folded leaf to feed. A single larva always occupies one tubular fold. After some time, it transfers to another leaf to fold and feed. Heavily infested fields show many folded leaves and a scorched appearance of leaf blades. Feeding reduces the productive leaf area that affects plant growth (Heong; Escalada; editors, 1997: p. 10; Pathak; Khan, 1994: p. 89; Shepard; Barrion; Litsinger, 1995: p. 228).
Eggs are jelly-like, transparent, and ovoid with irregular upper surfaces. Eggs are laid singly or in groups along the midrib of young leaves. Hatching occurs within about 5 days.
Larvae are yellow, turn yellowish-green with brown heads as they mature, and are about 12-25 mm long. Each larva can make 2-4 folded leaves. Before pupation, it makes silken threads and forms a cocoon to cover itself.
Pupae are light brown to bright brown and turn reddish-brown when they are about to become adults. A pupa is about 9-12 mm long and is found inside the rolled leaf. The pupal period is about 6-10 days.
Adults usually emerge in the evening. They mate 2-3 days after emergence. Females lay eggs at night. A female lays about 250 eggs in her lifetime (IRRI, 2001).
Cnaphalocrocis medinalis moth is yellow brown in color. While resting, the body shape is like that of an equal-sided triangle. It has a group of thick black hairs in the midcosta.
Marasmia patnalis moth has an incomplete third band that connects the middle bands. The forewings are pale yellow with a grayish marginal band.
Marasmia exigua moth has three or four complete bands on its wings.