Abstract
Cartap concentrations in rice plant treated with soluble powder, dust and granular formulations were measured, and the toxic effect to the rice leafroller on rice plant examined. The initial concentrations of cartap in the leaf blade of the plant treated with soluble powder and dust were 49 and 5.7ppm respectively; only one tenth of these initial concentrations remained 7 days after application. In submerged application of the granule, cartap concentration in the leaf blade reached a maximum of 1.5ppm 3 days after application, and then slowly decreased. LD50 values for cartap applied topically decreased from 61μg/g to 19μg/g from 2nd larval instar stage to 5th one. In the leaf dipping method, however, LC50 values for 1st to 5th instar larvae ranged from 0.45 to 4.4ppm. In the root dipping method, LC50 values were 0.51ppm for 1st instar, and 8.0ppm for 5th instar larvae. Terms of exceeding the LC50 levels for 1st and 5th instar larvae in cartap concentration in the leaf blade were 29 and 8 days for soluble powder, 19 and 1 days for dust, and 18 and 0 days for granule application, respectively. The feeding amount of each instar larva without cartap ranged from 0.18 to 0.24cm2/mg/day. When larvae ate leaf blade which had been dipped in cartap solution of several concentrations, there was a high negative correlation between mortality and feeding amount rate.
