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1. White stem borer (WSB)
There is no clarity regarding the taxonomic identity of the white stem borer species reported on rice in India. Two species reported in the literature relevant to rice are described below:
a. White rice borer, Scirpophaga nivella (Fabricius)
Distribution: White stem borer has been reported as rice pest from Kerala, Tamil Nadu, Orissa and Punjab.
Description: Wing span 14-40 mm; fore- and hind wings white with upper side of forewing sometimes yellow brown. Anal tufts are ochreous yellow in female.
Biology: The biology of this species has been studied only in the laboratory (Kamani and Vyas, 1985). The durations for different stages of the life cycle reported are 7.97 days for egg stage, 2.13, 4.63, 5.23, 5.85 and 6.42 days for the first, second, third, fourth and fifth larval instars respectively. The pre pupal and pupal periods reported are 1.45 and 11.80 days respectively. The life span of male adult is 3.63 days while that of female is 3.44 days.
Host plants: Cyperus spp, Saccharum officinarum, S. spontaneurn, S.arundinaceum, Eleocharis sp, Cyanodon dactylon and Oryza australiensis have been reported as alternate hosts of this insect in India.
b. White stem borer, Scirpophaga innotata (Walker)
Description: The moth resembles YSB, but is white in colour without black spot on forewing. The upper side of forewing is pale ochreous or white in both sexes, without any markings; Labial palpi is about twice the diameter of eye. Hind wings are with the frenulum spine double in female. Anal tufts whitish in female. Hind wings are white in colour. The larva is also similar to that of YSB but white in colour. S. innotata is a monophagous pest.
Biology: All information on biology of S. innotata is from Indonesia. Eggs are laid in clusters of 70-260, usually on the underside of young leaves and covered with a tuft of hairs. Incubation period is 4-9 days. The young larva penetrates the leaf sheath and goes down into the stem. It is milky white and grows to a length of 25mm. The larval period varies from 19- 31 days. Pupae are soft bodied, pale and whiter than YSB pupae. Pupal period is completed in 7-11 day:
DRR Technical Bulletin No. 59/2011, Rice stem borers in India: species composition and distribution