The yellow stem borer of rice yellow stem borer,(Scirpophaga Incertulas) is a species of moth of the family Crambidae. Stem borers can destroy rice at any stage of the plant from seedling to maturity. It is polyphagous and prefers sugarcane to rice. Stem borer has many species among them six species attack the rice. It was described by Francis Walker in 1863. It is found in Afghanistan, Nepal, north-eastern India, Sri Lanka. Yellow stem borer damage can lead to about 20% yield loss in early planted rice crops, and 80% in late planted crops. It causes dead heart or drying of the central tiller during the vegetative stage and whiteheads, where the emerging panicles are whitish and unfilled or empty in the reproductive stage. They occur in all rice-growing areas, and can locally reach relatively high densities in some years.

Identification

Egg :

Eggs are creamy white, flattened, oval and laid in a mass that is covered with buff-coloured hairs. They are laid mostly near the tip of the leaves. The egg period is 5-8 days.

 

Larva :

Pale yellow with a dark brown head having a prothoracic shield. The larval period is 28 to 30 days.

Pupa :

White silken cocoon. Pupation takes place inside the rice stem, straw or stubble. The Pupal period is 8 to 10 days.

Female moth :Adult :

Has bright yellowish-brown with a black spot at the centre of the fore wings and a tuft of yellow hairs at the anal region.

Male moth :

Smaller with pale yellow forewings without black spots.

Symptom of Damage :

Feeding damage at the base of the plant or along the central stem causes dead tillers at the vegetative stages (‘dead hearts’) 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 faecal 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.

Nature of Damage :

In the vegetative phase, the central shoot dies off turning yellow in colour (dead heart). In the ear bearing stage, the ear head appears completely chaffy and white in colour (white ear head). Both come out easily when pulled up and show indication of feeding injuries at the base.

Management Strategies :    

Cultural Methods:

  • The field should necessarily be scouted during the vulnerable crop growth stages for early detection of dead hearts and a white ear.
  • Removal and proper disposal of stubbles will keep the borer population low in the next
  • Grow resistant varieties
  • Apply the fertilizers in split applications during the season.
  • Raise the level of irrigation water periodically to kill the eggs.
  • Apply nitrogenous fertilizers and manure moderately.
  • Clip the tip of the seedlings before transplanting to eliminate egg masses.
  • Collect and destroy the egg masses.
  • Avoid close planting and continuous water stagnation at early stages.
  • Pull out and destroy the affected tillers.
  • Harvest the crop up to the ground level and disturb the stubbles with plough immediately after the harvest to keep the borer population low in the next

Chemical Methods:

  • ETL : 2 egg masses/m2 (or) 10% dead heart at vegetative stage (or) 2% White ear at Flowering stage.
  • When natural enemies of stem borers are present, the application of chemical measures can be delayed or dispensed with.
  • The newly hatched borer larvae must be flit with 2 rounds of quinalphos or phosphamidon at 1000ml/ha at 7 days interval.
  • Spray any one of the following based on ETLs :Monocrotophos 36 SL 1000 ml/ha (or) Quinalphos 25 EC 1000 ml/ha (or) Phosphamidon 40 SL 600 ml/ha (or) Profenophos 50 EC 1000 ml/ha.
  • Applications of Chlorantraniliprole at 40 g.a.i./ha were found to be efficacious against S. incertulas.

Biological Methods:

  • Release of egg parasitoid Trichogramma japonicum thrice at weekly interval starting 28 days after transplanting @ 5 ccs (1 lakh egg parasitoids)/ha/release. Followed by the release of Trichogramma japonicum at 35 and 42 DAT.
  • Apply Bacillus thuringiensis var kurstaki at 2.5 kg/ha to reduce the oviposition by the stem borer.
  • Release the egg cards in the field during morning hours. Tie the egg cards under the leaf surface facing outside.
  • Avoid spraying of chemicals on three days before and up to to seven days after field release of egg cards.

Natural enemies :Natural enemies and predators:

Tetrastichus schoenobii – Wasp

Telomomous rowani – Wasp

Stenobracon nicevillei – Braconidae

Cotesia flavipes – Braconidae

Agriocnemis pygmaea – Damselfly

Predators :

Lycosa pseudoannulata – Spider predator

Metioche vittaticollis – Cricket

Trap Methods:

  • Set up one light trap/5 ha to attract and kill the moths.
  • Set up bird perches to encourage bird predators.
  • Use sex pheromone trap for the control of rice stem borer.
  • Monitor through pheromone traps (@ 10 to 12/ha) for timely control measures. Change the lure at 15-20 days intervals.