Effects of Changes in Density of Rice Skipper Parnara guttata guttata (Lepidoptera: Hesperiidae) Larvae on the Quantity and Quality of Late-Transplanted Forage Rice Crops

We investigated the effects of changes in the density of rice skipper Parnara guttata guttata Bremer et Grey larvae in paddy fields on the damage caused during the cultivation of forage rice for whole-crop silage. Young instar larvae were released in mesh cages on late-transplanted rice plants. The larvae were reared in the cages until the pupal stage. After removal of the insects, rice plants at the yellow ripening stage were harvested and dried, and the number of panicles and dry weight of panicles and straw were measured. The total digestible nutrients content of the rice plants was also estimated. Dry matter weight decreased with increasing larval density on the rice plants, whereas total digestible nutrients content did not decrease significantly. Thus, P. guttata guttata may cause quantitative damage to forage rice, but the qualitative damage it causes is relatively small.