GROWTH AND YIELD ANALYSIS OF RICE PLANTS INFESTED WITH LONG-DISTANCE MIGRATORY RICE PLANTHOPPERS .3. QUANTITATIVE-EVALUATION OF VEGETATIVE GROWTH OF RICE PLANTS INFESTED WITH WHITE-BACKED PLANTHOPPER, SOGATELLA-FURCIFERA HORVATH (HOMOPTERA, DELPHACIDAE)

The effect of feeding by the white-backed planthopper (WBPH) nymphs were assessed by infesting rice plants in a pot with 0 to 200 nymphs per plant. Rice plants at the active tillering and panicle initiation stages were used. WBPH were allowed to feed during the nymphal period and were removed after 11-12 days. The dry weight of the insect, leaf area, and shoot dry weight as well as the photosynthetic rate and leaf color index were decreased by feeding of the nymphs. The proportion of bracypterous females and the dry weight of individual bracypterous females decreased with increasing WBPH density at the active tillering stage. However, at the panicle initiation stage the proportion of bracypterous female was low regardless of the density. The leaf weight ratio and leaf allocation ratio increased with increasing infestation. A linear relationship was observed between the total dry weight of WBPH and loss of shoot dry weight. WBPH nymph feeding reduced the shoot dry weight by about 400% more than the total dry matter removed by insect feeding. WBPH feeding had a direct effect on biomass production by removing phloem sap, and an indirect effect by reducing the photosynthetic rate and other physiological processes.