Abstract
This study was conducted in a Quercus serrata forest in 2008 and in a Q. crispula forest in 2009. Each forest was divided into an equal number of non-sprayed and sprayed trees. The sprayed trees were sprayed with 1.6% fenitrothion on the trunk surface lower than 6 m above ground level just after the initial attack of Platypus quercivorus adults and again three weeks later. The number of attacks was not increased after the first spraying in infested trees. Therefore, the spraying just after the initial attack prevented subsequent attacks. Secondly, the percentage of newly infested trees among the non-sprayed trees was 81.1% and 95.7% in the Q. serrata and Q. crispula forests, respectively, but was controlled to 2.8% and 18.5%, respectively, by spraying. The attack density in the sprayed trees tended to drop. These results suggest that spraying of 1.6% fenitrothion twice has a high control effect on boring throughout the period of occurrence of P. quercivorus adults.
