Rice germplasm comprising 66 lines/varieties was evaluated under field conditions for two wet seasons against a yellow stemborer, leaffolder and whitebacked planthopper (WBPH) at the vegetative and panicle initiation crop stages. Glasshouse screening of germplasm for WBPH resistance was done at the seedling stage. At the vegetative stage, over the 2 years, 18 lines/varieties showed leaffolder damage from 6.21 ± 0.33 to 9.99 ± 4.07%, while at the panicle initiation stage, six lines/varieties showed damage from 8.77 ± 1.25 to 12.25 ± 4.67%. A highly significant correlation between flag leaf width and per cent infested leaves at the vegetative (r = 0.88) and panicle initiation (r = 0.79) stages was recorded. No significant correlation was observed between plant height and leaffolder infestation at the vegetative stage; however, it was significant at the panicle initiation stage (r = 0.37). The dead heart (DH) damage at the vegetative stage over the years was less than 1% in six lines/varieties, while at the panicle initiation stage, seven lines/varieties showed whitehead (WH) damage ranging from 1.29 to 1.92%. A highly significant correlation was observed between plant height and per cent DH and WH at the vegetative (r = 0.73) and panicle initiation stages (r = 0.81). Such a relationship was not observed between leaf width and stemborer infestation at both stages. Two lines, viz. IR 59 547-235-3-3 and SPR 85 163-5-1-2-4, were resistant to the WBPH under glasshouse screening, whereas 20 lines were moderately resistant and the remaining lines were susceptible.

The effect of some rice varieties on the biology of the stalk-eyed fly Diopsis thoracica West was investigated. The rice varieties affected the developmental period from egg laying to adult emergence, the sex ratio, percentage survival, adult weights on emergence, ovary development and the rate of tiller damage by a single larva. The rice varieties OS6 and Tos 4121 were consistently the most unfavourable in terms of insect growth; but were the most susceptible in terms of damage. Thus varietal susceptibility to damage by the insect seemed to be different from varietal suitability for its growth.