- Rice

Rice Rice

Yellow Stem Borer

Insect

Scirpophaga incertulas


In a Nutshell

  • Dead - hearts or dead tillers due to boring activities.
  • Tiny holes on stems and tillers.
  • Frass or fecal matters inside damaged stems.
  • Oval patches of eggs near the tip of leaf blade.

Symptoms

Feeding damage at the base of the plant or along the central stem causes dead tillers at the vegetative stages ('deadhearts') and whitish unfilled panicles ('whiteheads') at the reproductive stages. After hatching, the larvae bore into the leaf sheath and feed on the inner surface of the stem. Tiny holes, frass and fecal matter can be observed on the damaged plant tissues. The larvae can move from one internode to another. During the vegetative stage, larval feeding may not cause visible symptoms because the plant compensates for the damage by producing extra tillers. But, this costs energy and ultimately yield will be affected.

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Hosts

Trigger

The damage is caused by the larvae of the yellow stem borer, Scirpophaga incertulas, a pest of deepwater rice. It is found in plants or leaf-over stubbles in aquatic environments where there is continuous flooding. Young larvae wrap part of a leaf around their body and detach themselves from the plant, falling onto the water surface. They then attach themselves to the base of a new plant and bore into the stem. High nitrogenous field are highly favorable. Fields planted later in the season also favor the insect, whose population has built up in fields that have been planted earlier. As a comparison, the pest can cause about 20% yield loss in early planted rice, and 80% in late-planted crops.

Organic Control

Natural predators and parasitoids are numerous and include several species of ants, beetles, grasshoppers, flies, wasps, nematodes, mites, earwigs, birdsdragonflies, damselflies and spiders. Five to six releases of the egg parasitoid Trichogramma japonicum (100,000/ha) starting from 15 days after planting can be planned. Treatments include the application of products containing bacteria and fungi that affect the larvae (before it penetrate the stem). Neem extracts, bacillus thuringiensis can also be used for that purpose.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Preventive chemical treatment include the soaking of the roots of the seedlings in 0.02 chlorpyriphos for 12-14 hrs before transplanting (30 days protection). Apply the following insecticides based on fipronil, chlorpyrifos or chlorantraniliprole either as granules or spray once the threshold is reached (25-30 male moths/trap/week). Do not use broad-spectrum insecticides to fight pests.

Preventive Measures

  • Cultivate varieties that are resistant to this pest (e.g.
  • TKM 6, IR 20, IR 36).
  • Plant early in the season to avoid the worst damage.
  • Before transplanting, cut the leaf-top to reduce carry-over of eggs.
  • Avoid planting seedlings too close to each other.
  • Monitor the seedbeds and fields regularly.
  • Handpick and destroy egg masses in seedbeds and during transplanting.
  • Use pheromone traps or mass traps from 15 days after transplanting (3/acre or 8/acre, respectively).
  • Control weeds and volunteer plants in and around the field.
  • Pull out and destroy affected plants.
  • Apply the fertilizers in split applications during the season.
  • Raise level of irrigation water periodically to kill the eggs.
  • Apply nitrogenous fertilizers and manure moderately.
  • Harvest the crops at ground level to remove the larvae in stubble.
  • Remove stubbles, plant debris and destroy them after harvest.
  • Plow and flood the field after harvest to drown remaining larvae.

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