About oak blight control

Since oak wilt has been confirmed in the city, an oak wilt prevention project is being carried out to prevent the disease from spreading rapidly.

Oak wilt is an infectious disease of trees that causes the death of oaks, Chinese oaks, and oaks, caused by the oak fungus transmitted by the oak bark beetle (hereinafter referred to as oak beetle). In particular, it causes collective death of Quercus and Quercus oaks, and the mortality rate is high and the damage tends to spread to surrounding areas.
It is said that oaks with a diameter of less than 10 centimeters are difficult to reproduce, and the larger the diameter, the better the reproduction efficiency. In recent years, trees in satoyama areas have not been regenerated, leading to large-diameter oaks, and an increase in forests and stands suitable for oak moth breeding, which is one of the factors that caused the damage nationwide. It is listed as one.

From June to July, new adult oak moths fly to healthy trees to lay eggs. A large number of oak moths penetrate intensively due to the aggregation pheromone released by the male. Also, spawning takes place within the hole.
When the oak fungus carried by the female enters the tree, the tree loses its water circulation function from July to September, and the leaves begin to turn red and wither, and rapidly wither within one to two weeks ( It may not dry out).
Cassinaga larvae feed on yeast grown in the tunnel and grow, then fly to new, healthy trees around June of the following year.

Oak wither has the following characteristics:

1. These include oaks such as Mizunara and Konara, and chestnuts and oaks such as Quercus glauca and Castanopsis sieboldii.
2. From June to September, the leaves rapidly turn reddish brown and die.
3. There are many small holes measuring 1.4 to 1.9 mm in diameter, which were made by the oak leafminer.
4. There is a large amount of frass near the base

Until now, no damage from oak wilt had been confirmed, but in August 2020, oak wilt was confirmed on trees in a city park. Damage has also been confirmed in privately owned forests, such as in the nature 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 areas, is as follows.

• park green space

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

• others

Inagi Fureai no Mori 31 trees
Total 141 pieces

There are two main ways to deal with trees damaged by oak wilt:

1. How to harvest and properly dispose of trees
2. How to inject insecticide while the tree is still standing
3. How to cover trees with sheets to prevent oak moths from escaping

In city-managed land such as parks and green spaces with a lot of foot traffic, leaving dead trees that are at high risk of falling is not appropriate, so the basic policy is to cut them down and dispose of them appropriately.