1966 Volume 35 Issue 4 Pages 361-366
The environmental conditions of citrus orchards infested by citrus flat-headed borer, Agrilus auriventris, which is one of the most destructive insect pests of the citrus, were studied during the time of outbreak in Nagasaki Prefecture, 1961-1963.
Two hundred and twelve orchards including 5, 551 citrus trees under the various degree of infestation by the borer were surveyed. The degree of infestation and some environmental factors such as the age of trees, species or variety of citrus, climatic conditions, methods of management and the infestation of gammosis were examined in each orchard.
This insect attacked older trees than younger one, especially more than 50 years old. In Satsuma orange, the percentage of infested trees were not so much, but the attacked trees fell into dye frequently. On the other hand, Natsudaidai and other species of orange and lime trees were more parasitized than Satsuma Orange. But the percentage of dead trees were not so much.
In the orchards, which were suffered by cold weather, draught or abnormal defoliation, the more severe damages by citrus flat-headed borer were observed.
The positive correlation between the infestation of gammosis and the damage of flat-headed borer was recognized. But the gammosis was not assumed as the necessity for infestation of borer.