About Japanese oak withering prevention

Since oak wilt was confirmed in the city, a project to prevent oak wilt is being implemented to prevent rapid expansion.

Oak wilt is an infectious disease of trees that causes the death of oaks, oaks, and oaks caused by oak fungi carried by oak bark beetles (hereafter referred to as "casinaga"). In particular, it causes collective withering of Quercus crispula and Quercus serrata.
It is said that oak trees with a diameter of 10 cm or less are difficult to breed, and the larger the diameter tree, the better the breeding efficiency. In recent years, due to the discontinuation of tree renewal in satoyama, oak trees have become larger in diameter, and the number of forests and forests suitable for breeding of cassava has increased, which is one of the factors that caused nationwide damage. mentioned as one.

From June to July, new imagoes of cassia moth fly to healthy trees for spawning. Aggregation pheromones released by males intensively penetrate a large number of moths. Spawning also takes place within the pore.
As the oak fungus carried by the female enters the tree, the tree loses its ability to conduct water from around July to September, and the leaves begin to turn red and wither, and then die rapidly in 1 to 2 weeks ( It may not dry out).
The larvae of the longhorn moth grow by feeding on the yeast grown in the hole, and fly to new healthy trees around June of the following year.

The oak wilt has the following characteristics.

1. oaks such as Quercus crispula and konara oak;
2. Leaves quickly turn reddish brown and wither from June to September
3. There are many small holes with a diameter of 1.4 to 1.9 mm that were pierced by the longhorn moth.
4. There is a large amount of frass near the root

Until now, no oak wilt damage could be confirmed, but in August 2020, oak wilt was confirmed in the trees in the city park. Damage has also been confirmed in privately owned forests, such as the natural environment conservation area located south of Inagi Station.

The damage status (as of October 2020) on land managed by the city, such as parks and green spaces, is as follows.

• park green space

6 in Inagi Central Park, 71 in Shiroyama Park, 4 in Hirao Neighborhood Park, 1 in Daimaru Nature Park, 28 in Yatoyama Green Space

• others

31 forests of Inagi Fureai
Total 141

Measures for trees damaged by oak wilt can be roughly divided into the following methods.

1. How to harvest and properly dispose of
2. How to inject pesticides into standing trees
3. A method of covering trees with a sheet, etc. to prevent the escape of the longhorn moth

Since it is not suitable to leave dead trees that have a high risk of falling trees in parks and green spaces that are frequently visited by people, the basic policy is to cut them down and dispose of them appropriately.