Rice Leafroller

  • Symptoms

  • Trigger

  • Biological Control

  • Chemical Control

  • Preventive Measures

Rice Leafroller

Cnaphalocrocis medinalis

Insect


In a Nutshell

  • Caterpillars fold a rice leaf around themselves with silk strands.
  • Longitudinal whitish and transparent streaks appear on the blade.
  • Presence of disc-shaped ovoid eggs or of fecal matter are also signs of infection.

Hosts

Rice

Symptoms

Also called leaffolder. The adult moths are about the length of your fingernail and have brownish zig-zag lines on the wings. Eggs are usually laid at the tip of the leaf. Caterpillars fold a rice leaf around themselves and attach the leaf margins together with silk strands. They then feed inside the tubular folded leaf creating longitudinal whitish and transparent streaks on the blade. Sometimes, leaves are folded from tip to basal part. Presence of disc-shaped ovoid eggs laid singly or of fecal matter are also signs of infection.

Trigger

Rice leaffolders occur in all rice environments and are more abundant during the rainy seasons. High humidity, shady areas of the field, and the presence of grassy weeds from rice fields and surrounding borders favor the development of the pest. Expanded rice areas with irrigation systems, multiple rice cropping and insecticide-induced resurgences are important factors in the insect’s abundance. Heavy use of fertilizer encourages rapid multiplication of the insect. In tropical rice areas, they are active year-round, whereas in temperate countries they are active from May to October. Optimum temperature and humidity are 25-29°C and 80%, respectively. The young and green rice plants are more severely infested.

Biological Control

Make use of light traps to attract and collect adults. Also the protection and release of natural enemies, like egg parasitoid wasps (Trichogrammatidae), spiders, predatory beetles, frogs and dragon flies or entomopathogenic fungi and viruses provides helpful. Spread of neem leaves randomly in the field deters adults from laying eggs.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. If infestations are high (>50%) during tillering, insecticide sprays based on the active ingredients chlorpyriphos, chlorantraniliprole, indoxacarb, azadirachtin, gamma- or lamda-cyhalothrin or flubendiamide are helpful, particularly if leaf folder is severe at booting stage. Care should be taken not to use chemicals causing resurgence of the insect.

Preventive Measures

Resistant varieties to prevent outbreaks.,Alternate rice with a different crop or fallow period.,Remove grassy weeds from fields and borders.,Reduce density of planting.,Minimize the use of fertilizers.,Avoid ratooning to long as this favors the disease.,Flood and plow fields after harvest to remove crop residues.