Pest:Rice stem borer

Scirpophaga incertulas Pyraustidae.

The adult moth can be identified with the presence of a black spot on each orange yellow forewing.The spot is distinct in the case of females and indistinct in male.Eggs are laid in batches covered with straw coloured hairs.Eggs hatch in 5-10 days.The emerging caterpillars from the eggs get distributed to the surrounding plants,bites its way in to the rice stem.Pupation takes place inside the larval tunnel.

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Symptoms

  • All stages of the crop are infested by the insect.The caterpillar grows by feeding on the internal tissues of the stem. In the vegetative phase the central shoot dries off turning yellow in colour causing “dead heart”.
  • In the ear bearing stage the ear-head appears completely chaffy and white in colour causing “white ear head” .
  • Both dead heart and white ear head come out easily while pulled up.
  • Generally high borer infestation is seen in rice during October- January and low infestation in crops planted from June to October.
  • The infestation is negatively correlated with rain fall and minimum temperature and positively with maximum temperature.

Procedure for Observation

Randomly mark 4 sq.meter plots in 0.4 Ha .Record the total number of stem borer egg masses/moth per sq. meter and percentage of dead heart/white heads and work out the average.

ETL

  • Nursery stage- One moth or one egg mass per meter square.
  • Planting to pre tillering – 10 % dead heart or one egg mass or one moth per sq. meter.
  • Mid tillering : 10 % dead heart or one moth or one egg mass per sq. meter.
  • Panicle initiation to booting: One egg mass or one moth per sq. meter.
  • Flowering and after. : Two percent white head.

    • Control Measures

  • Kanchana, Aruna, Dhanu, IR 20 varieties show resistance/tolerance to rice stem borer.
  • Field sanitation by incorporation of stubbles immediately after harvest will help to destroy the stages of insects like caterpillars and pupae.
  • Collect egg masses of stem borers and keep it in perforated poly bags. Parasite will emerge out from the parasitized egg masses. These can be released back to the fields.
  • Use sex pheromones. This can be utilized for monitoring as well as for direct control through mass trapping of male moths.
  • Mass trapping of stem borer by installing pheromone traps at the rate of 20 numbers per Ha can effectively reduce stem borer damage.
  • The egg parasitoids Trichogramma japonicum is effective against rice stem borer. For this, egg cards (Trichocards) have to be installed in the field at the rate of 5 cc per Ha starting from the first week of transplanting.
  • Presence of moths in the field in large numbers can be taken up as criteria for installing egg cards.
  • In areas where stem borer occurs as a serious pest in all seasons, apply any one of the following insecticides keeping water at minimum level. Cartap hydrochloride (Cartox 4 G -25 Kg/Ha ,Cartox 50 SP -1 kg/ha) Flubendiamide (Takumi 20 WDG-125 g/Ha, Fame 480 SC -50 ml/Ha) Intoxacarb (Avaunt 15.8 Sc -200 ml/Ha, Hindoxa 15.8.SC- 200ml/Ha) Spinosad (Tracer 45 SC -100 ml/Ha,Spinstor 45 SC- 100 ml/Ha) Carbosulfan (Marshal 6 G-16.67 Kg/Ha) Quinalphos (Quinalphos 25 SC-1000 ml/Ha,Ekalux 25 SC -1000 ml/Ha) Carbaryl (Sevin 50 WP -1.5-2.kg/Ha,Carbaryl 50WDP- 1.5- 2 kg/Ha )