Abstract
To determine the optimum time for chemical control, I investigated the infestation and damage of citrus fruits by Scirtothrips dorsalis Hood in four experimental plots where insecticide was applied at different times. The peak days of adult immigration into citrus orchards from the 2nd to the 7th generation were predicted by real-time calculation of the total effective temperature in 2000, 2001, and 2002. The four experimental plots were set up as follows: insecticides were applied at 6.6±1.5 days before the peak days, at 1.0±1.7 days before the peak days, at 5.2±2.1 days after the peak days; no insecticides were applied to one plot, which was considered the control plot. In the two plots where the insecticides were applied at 6.6 or 1.0 days before the peak days, the density of S. dorsalis and the rate of damage caused to the fruits were significantly lower than those in the control plot. However, in the plot where insecticides were applied at 5.2 days after the peak days, the density of adults temporally increased and the rate of damage caused to the fruits were higher than in those in the above two plots.
