We have three birch trees that are 6 to 7 years old. They are beautiful, but something is happening to them this year that we haven't seen before. The bark is splitting quite deeply and there are piles of soft, brown droppings all over the yard underneath the trees (those green fuzzy things that were on the tree before). Is this a normal progression or is something wrong?

The leaves and limbs looked fine this fall – possibly a little droopy, but that may be the weather. I did notice a lot of ants on the tree, so I sprayed a ring around the trunk, 3 to 4 feet off the ground, then a light spray from there down.

Those are my favorite trees and I sure don't want to lose them. Hope you can give us some advice.

– Kim Robb, Sacramento

Your tree is probably a European white birch (Betula pendula), according to the UC master gardeners. As these trees mature, the bark on the main trunk and limbs becomes white but is marked with deep, black clefts.

This is the splitting you are seeing. The brown droppings are shattered seed pods – catkins – which were the "green fuzzy things" you observed on the trees earlier in the season.

This is a normal process and not cause for concern.

Now for the ants. They're climbing the tree to feed on the honeydew produced by another insect, most likely aphids.

Try blasting them off the tree with water from a garden hose, if possible. (The aphids won't survive the impact.) That eliminates the ants' food source – and the ant issue.

Another ant deterrent is to apply Tanglefoot to some tape or fabric wrapped around the trunk of the tree. This product will lose its stickiness over time and will have to be replaced as needed.

GARDEN QUESTIONS?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.

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