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Life cycle of Yellow stem borer Scirpophaga incertulas Wlk
1.Yellow stem borer (YSB), Scirpophaga incertulas (Walker)
- This species is prevalent in many states across the country.
- It is a serious pest in all the rice ecosystems, particularly in deep water rices.
- The forewing of the female YSB moth is ochreous yellow to whitish with a black spot in the middle.
- It has a wingspan of 24-36 mm.
- Its abdomen is wide anal tufts are pale ochreous.
- The adult male is smaller than female.
- The forewings are gray or light brown in color and have two rows of black spots at the tip.
- Sometimes the males are whitish yellow and spots on the forewing are not very clear.
- Variation in the intensity of colour in the forewing and the size of the moth has also been observed.
- Adults mate only once and up to 150 eggs are laid per female.
- Each female lays 1-3 egg masses.
- Egg masses are usually laid on leaf tips but they are also laid on the base of the stems.
- The size of the egg mass also varies with the brood.
- The egg mass of YSB is covered with pale ochreous (buff coloured) hairs from the anal tufts of the female.
- Individual eggs are white, oval and flattened.
- Egg period varies from 5-9 days and the newly hatched larvae disperse through silken threads and bore into the plant.
- The first instar YSB larva is about 1.5 mm long.
- A full-grown larva is pale yellow to yellowish green with brown head and prothoracic shield and measures 20 mm.
- It feeds within the plant for more than 30 days and undergoes 5 -7 moults.
- Usually only one larva is found in a tiller.
- The number of moults and larval duration depends on the prevailing temperature.
- Larval diapause is a common phenomenon.
- The YSB pupa is whitish to pale yellowish green and measures about 12 mm long.
- It is enclosed in a white silk cocoon.
- Fresh cocoon is pale brown and turns dark brown with age.
- The pupal period ranges from 6 -10 days.
Rice stem borers in India- species composition and distribution. Technical Bulletin No. XX,Directorate of Rice Research, Rajendranagar, Hyderabad - 500 030, A.P., India.
FIELD MANAGEMENT OF INSECT PESTS OF RICE - A READY RECKONER. TECHNICAL BULLETIN NO.46, DIRECTORATE OF RICE RESEARCH, RAJENDRANAGAR