Effects of silica in resistant and susceptible rice varieties on Nilaparvata lugens (Stal.) and its natural enemy Cyrtorhinus lividipennis Reuter
1994
Chaiyawat, P.
Significantly more silica was found in all varieties grown in culture solution with silica. Silica uptake by plants was greatest at levels between 100 ppm and 200 ppm. In general, silica content was higher in leaves than leafsheaths in 45-day old and 65-day old rice. The silica level in the hydroponic solution did not adversely affect survival of BPH nymphs in all varieties at the seedling stage (14 days old). However, on the older plants (45 days old) the adverse effect of silica was noticeable in TN1 and IR22 on the 16th day after confinement of BPH. The effects were detected as early as 4 days on the resistant 45-day old IR72 and Mudgo plants. On 14-day old plants, silica did not significantly affect BPH survival and development except on the resistant IR72 variety. However, silica prolonged the nymphal period of BPH on all varieties. On 45 day old plants, adverse effects of silica were detected for the following parameters: survival, number of adults that developed, population growth index, nymphal period, and fecundity. Silica level in the culture solution did not affect the amount of honeydew excreted by BPH adults. The role of silica appeared to be indirect or in association with other resistance factor(s) as suggested by the more pronounced adverse effects on the resistant IR72. The adverse physiological effects caused by silica apparently synergized with other resistance factors in the rice plants
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