Factors influencing yellow stemborer damage to transplanted rice
1987
Pena, N.B.
Effect of egg mass density on the incidence of deadhearts and whiteheads in uncovered and covered plots was studied using IR62. Regardless of egg mass density used, no significant differences were observed on percent deadhearts and whiteheads in uncaged and caged plots. However, it was observed that percent deadhearts and whiteheads were higher in uncaged than in the caged plots. A decrease in grain yield was observed in an increasing egg mass density. However, crop age did not affect grain yield in uncaged and caged plots. Ninety-two percent of the egg mass and 47.02% of the eggs were parasitized, hence egg parasitism was considered the most important mortality factor of the immature stages. Also, the mirid bug, Cytorhinus lividipennis and wolf spider, Lycosa pseudoannulata contributed to the mortality of yellow stemborer (YSB) egg masses and larvae. No definite pattern was observed on the oviposition preference of YSB. High percent deadhearts and whiteheads were observed on traditional varieties. Grain yield was higher on modern and traditional varieties. Use of insecticide, Cypermethrin did not affect the natural enemy population. It did not affect the egg parasites wherein a high percent parasitism of egg masses was observed. However, the number of egg masses that were preyed upon was low. Predation studies showed that C. longipennis is an efficient predator of YSB egg masses. Its rate of predation increases with an increase in prey density. The early instars were observed to feed on the plant parts and its own exuviae.
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