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Yellow stem borer

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Yellow stem borer (YSB), Scirpophaga incertulas (Walker)

Distribution: 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.
Description: 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.
Biology: 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
Host plants: Though considered predominantly as a monophagous pest, YSB has also been reported from wild rices {Oryza spp.), Cyperus, Cyanodon dactylon and Leptochloa panicoides.

File Courtesy: 
DRR Technical Bulletin No. 59/2011, Rice stem borers in India: species composition and distribution
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