One of the rice’s most damaging insect pests is the rice leaf folder or roller. It is common in most rice-growing areas. Cnaphalocrosis medinalis is the scientific name for this insect, which belongs to the Pyralidae family of the Lepidoptera order. When these insects are larvae, they cause injury.
They cause damage by rolling the leaves and decreasing the surface available for photosynthesis. The leaf folder caterpillars wrap a rice leaf around them and connect the leaf borders with silk strands. While hiding inside the folded leaf, photosynthesis is restricted. The caterpillar eats by scraping the surface tissue of the leaf.
Leaf Folder management in Paddy
The life cycle of the Leaf Folder or Leaf Roller
Eggs, larvae, pupa, and adults are the usual stages that make up the life cycle of a leaf folder or leaf roller. The leaf folder has a life cycle of around one and a half months (egg – 5 days, larvae – 25 days, pupa – 7 days, and adult moth – 10 days).
Factors favoring population increase of Leaf Folder or Leaf Roller in the field
During the wet seasons, more abundant. When the temperature is between 25 and 29 °C, the humidity is above 80%, and the field is shaded. They are most often found in shady locations. The caterpillars may remain alive between rice fields by consuming the weeds around the bunds. The moth is stimulated to grow and reproduce by the high amounts of new growth produced by high nitrogen fertilizer.
Identification characters of Leaf Rolder or Leaf Roller in Rice field
- Egg: A flat, oval-shaped object that is a yellowish-white color. Oval-shaped eggs that are 0.90 mm in length and 0.39 mm in width. Duration of incubation: 4–7 days.
- Larva: Greenish, transparent larvae with rounded laterals and a quick apical prothoracic defense. The larval stage lasts 15–27 days. The lifespan is 26–42 days.
- Pupa: Pupals last between seven and ten days.
- Adult: Moth has yellowish-brownish wings, a black band around the edge, and several dark wavy streaks in the center. Golden or orange-brown zigzag patterns can be seen on the wings of adult moths.
Damage symptoms of Leaf Folder or Leaf Roller in the Rice field
- The larval stage of the insect is the most damaging.
- The larvae fold the leaves longitudinally and use silk to bind the borders together.
- They feed on the green mesophyll inside the folded section of the leaf.
- Scraping the leaves is how the larvae eat.
- Larvae in the first and second instars feed inside slightly folded regions.
- In the late second instar, the larvae coil up the entire leaf.
- After eating, a larva can harm numerous leaves by migrating from one to another.
- Feeding diminishes the photosynthetic area of the leaves, causing vegetative growth and production to suffer.