The rice leaf folder, Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae) was earlier considered a minor pest in many Asian countries. However, it assumed major pest status since the 1980s causing serious economic loss in case of severe infestation coinciding with susceptible crop growth stages (maximum tillering to booting). The shift in pest status is mainly attributed to changes in crop management practices such as cultivation of high yielding varieties, adoption of higher plant density, planting either too early or too late, higher N fertilizer use and increased insecticide applications for pest control adversely affecting natural enemies of leaf folder. The pest undergoes two to three generations on rice crop. The first brood on rice is initiated mainly through immigrating adults while the second and third broods develop within the crop and are the most damaging .
Recognize the problem
Leaf folders are caterpillars of a moth. The caterpillars roll leaves around their bodies and feed inside the tube. The feeding creates a see-through whitish area on the leaf.
The caterpillars are yellow to green. Heavily infested fields appear scorched and have many folded leaves.
The rice leaf folder is a common pest and can be found in all rice growth stages. The most damaging stage is during tillering as this can reduce the yield of the crop.
The caterpillars can survive between rice crops by feeding on weeds around the bunds. High nitrogen fertilizer creates lots of new rice plant growth which encourages the moth to grow and multiply. The life cycle of a leaf folder is about 1.5 months (egg- 5 days, larva- 25 days, pupa- 7 days and adult moth- 10 days).
- Encourage predators such as spiders, parasitic wasps, predatory beetles, frogs and dragon flies
- Use thorn wood on the leaves during hot weather to chase insects away
- Rice crops can usually recover from early damage when enough water and fertilizer are applied
- If infestations are high (>50%) during tillering, insecticide sprays may be helpful
- Apply insecticides such as alpha-cypermethrin, Abamectin 2% or Cartap hydrochloride to kill the larvae
Note: excessive insecticide use can promote the build-up of other crop pests such as the Brown Planthopper. Follow the manufacturer’s recommendations on the label.
When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.