Abstract
The effect of damage to the leaf sheath caused by oviposition of the white-backed planthopper on the vegetative growth of rice paddy was studied in 1989 and 1990. Release levels were changed from 0 to 8 adult females per hill. The number of tillers, top dry weight and leaf area index (LAI) were reduced at the end of the experiment periods in the release plots. The same reduction was observed in non-sprayed plots after immigration. Growth differences among the plots were reduced towards the reproductive stage. A non-contact, non-destructive method for estimating the top dry weight and the LAI using a portable spectroradiometer was tried in 1990. Changes in the spectral reflectivity in the near-infrared range were useful for measuring the recovery of the top dry weight and the LAI when the LAI was less than 5.
