YELLOW STEM BORER

  • Eggs: The eggs are creamy white, oval, and flattened. They are laid in masses and are covered with buff-colored hair

Occurrence

The yellow stem borer is a prevalent pest in tropical wetland rice areas, especially in lowland and deep-water environments. This pest targets rice crops at all growth stages. Eggs, laid in clusters averaging about 80, are typically found on the upper half of leaf surfaces and are covered by tan scales. They hatch within 5–10 days, and the larvae bore into the leaf sheath, causing yellowish-white patches. As they grow, larvae penetrate the stem, leading to “dead hearts” (drying central shoots) during the vegetative stage or “whiteheads” (empty panicles) at the reproductive stage. Fully grown larvae measure about 20 mm and are pale yellow or greenish-yellow with brown heads. Pupation occurs in hollow stems, with larvae sometimes submerged in deep-water rice fields.

During dry seasons or when rice is not cultivated, larvae become dormant, often residing in stubble below the soil. The mortality rate during dormancy can be high due to environmental factors, stubble destruction, or predation. Female moths are pale yellow or light brown with a black spot on each forewing, while males are smaller, grey or light brown, and have two rows of spots at the forewing tips. They disperse in various forms: as eggs on seedlings, larvae on silken threads carried by wind, pupae in harvested stems, or adults flying at night. High nitrogen levels and late planting favor pest outbreaks, while stubble left in fields provides a habitat for the larvae and pupae.

Impact

Stem borers can harm rice plants at any growth stage. They feed on tillers, causing dead hearts during the vegetative phase and whiteheads during the reproductive phase

Identification

Small holes on stems and tillers

Whiteheads in the reproductive stage with empty or unfilled panicles

Presence of frass inside damaged stems.

Dead tillers (dead hearts) that detach easily from the base during the vegetative stage.

Dead hearts and whiteheads may resemble damage caused by other pests or diseases like rats, neck blast, or black bug infestations. To confirm stem borer damage, inspect crops for these signs and dissect stems to find larvae or pupae.

Solutions

  • Use resistant rice varieties (consult local agricultural resources for recommendations).
  • Handpick and destroy egg masses during seedbed preparation and transplanting.
  • Periodically raise irrigation levels to submerge eggs laid on lower plant sections.
  • Trim leaves before transplanting to reduce egg transfer.
  • Synchronize planting times, harvest crops at ground level, and remove stubble to eliminate larval habitats.
  • Employ light traps (1 per hectare) and pheromone traps (5 per acre).
  • Release the egg parasitoid Trichogramma japonicum (2 cc/acre, three times weekly).
  • Apply nitrogen fertilizers in recommended splits.
  • Consider specific pesticide applications such as Mortel SC, Mortel GR, Ambivi, and Corato at suggested rates.