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Plantwise Factsheets for Farmers

Rice stem borer

Scirpophaga incertulas
Vietnam

Recognize the problem

Rice stem borers (RSB) can be present in all rice growing areas. During tillering, the typical damage symptom is deadheart, while in flowering stage, it causes whitehead. The larvae also produce tiny holes on the stem and deposit faeces within it, which is seen when the stem is cut open. The adult RSB is 1-1.5cm long and white, with one tiny black dot on each wing.

Eggs are laid in a cluster of about 200 white or brown eggs, similar in size to soybean seeds. These are laid on leaves and are covered with a yellow cottony layer, about 5 mm wide. Larvae are creamy white and between 2mm and 20mm long.

Background

After hatching, larvae are spread by wind. They enter rice stems, then live and feed inside the stem. A larva can consume 3-4 stems and move from plant to plant. The larvae move downwards in the stem and pupate in the lower part for 7-10 days, after which an adult emerges. The adult is more active at night and normally shelters within the plant tillers during the day.

Management

  • If possible, plant early to avoid peaks of larval stage
  • After harvesting, ploughing rice stubble into the soil to kill larvae and pupae and avoid leaving unwanted ratoons
  • Remove alternative hosts of the insect such as weeds
  • Crop rotation with non-host crops
  • Cultural measures: For stems/stalks with deadhearts, cut at the base, and remove from the field. Destroy the larva or burn the stalk. Remove egg masses manually in the nursery and field.
  • Monitoring: Observe the field every 7 days and count the number of deadhearts per 10 plants and whiteheads per 10 plants
  • Where planting time could be adjusted, apply chemicals if more than 10% deadhearts during tillering or more than 5% whitehead during flowering are observed.
  • Where planting time could not be adjusted, apply chemicals slightly earlier
  • Chemicals: use chemicals containing one of these active ingredients: abamectin (e.g. Voliam Targo 063SC), chlorpyrifos or fipronil

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.

The recommendations in this factsheet are relevant to: Vietnam

Authors: Nguyen Huu Khanh, Dao Thi Hang, Dang Thi Luong, Bui Thi Minh Hao

©CAB International. Published under a CC-BY-SA 4.0 licence.

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