Ash Flower Gall
Green ash, white ash
What you will see:
- Ball-like irregular masses
- Current years galls are green early in the season
- Old galls are reddish-brown
- Gall masses persist for up to two years
- Mites begin feeding on the male flower clusters of ash
- Mite feeding initiates gall formation of flower tissue
- Female mites then lay eggs in the developing galls
- Mites are too small to be seen with the unaided eye
- Female mites spend the winter under bud scales or bark
- Galls do not harm the health of infested trees
- Once a gall starts growing it will continue to form even if the mite dies
- Increase acceptance of galls by consumers
- Galls create additional visual structure in winter
- Add color in late season
Additional Ash Flower Gall Information:
Green and brown clusters hanging from branches of ash trees are perfectly common. The majority of ash trees are dioecious. The tree has all male flowers or all female flowers. In spring, a tiny eriophyid mite feeds on the male ash flowers. This results in ash flower gall mites, which are too small to be seen without a magnifying glass.
In response to the mites who are feeding on it, the ash tree will grow tissue around them. This causes the flowers to enlarge and stay on the tree for up to two years, instead of dropping off after the first spring. The galls are green to start, but later turn brown as growing season develops. Research proves that these galls do not harm the vitality of the tree, but they are not very attractive. In rare situations, the weight of the galls will cause the branch to strain.
These tiny mites – which are only about 2/100 of an inch long – spend all winter beneath flower buds and begin feeding and laying eggs in flowers in spring. The mites then stimulate plant tissue growth around the insects creating the gall. In the fall, fertilized females move to the bark of the tree and beneath the bud scales in winter.
If you see round, green ½ to 1" tumor growths on flowers, it is likely these insects. You may even see some leaf distortion. In late summer, the galls turn dark brown and become woody. They will stay on the tree for up to two growth seasons. They are extremely noticeable in the fall when the leaves drop.