I have several (around half a dozen) growths like this on the tree in our garden, should I be worried ? Is my tree going to on its last legs (roots?) in no time ?
The growths look like this on the inside (one of them was much less dense, more eaten away, and had some kind of grub living in it).
Being somewhat botanically challenged I’ve no idea what kind of tree it is, it’s leaves look like this(and have some kind of acorn in them, so maybe Oak ?). This is in the San Francisco Bay Area in Northern California.
Some sort of gall insect. Probably a wasp. The females lays eggs under the bark and injects a chemical to cause the gall to begin to grow., the juveniles hatch and start eating the gall and release the same chemical.
It’s unsightly and makes the plant less thrify, but unless every single branch is affected it’s not fatal.
You can probably cure it by cutting of any small galls as they appear (they take months to get to the size you’ve got). If you’re real worried then apply a systemic insecticide every week for three weeks, then once/month during the growing season. I suggest Confidor.
