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Garden Q&A: The bubbling pine and the gall of forsythia

Slime flux is a fairly harmless response to surface bacteria in the wound of a tree. - Original Credit: For The Baltimore Sun
Slime flux is a fairly harmless response to surface bacteria in the wound of a tree. - Original Credit: For The Baltimore Sun(Ellen Nibali / HANDOUT)

While walking today, I noticed white foam at the base of this pine tree. It’s just like bubble bath bubbles! It this tree in danger of dying and falling into the road?

This looks like one of the many manifestations of slime flux. Slime flux is caused by a surface bacteria that enters and feeds in a small bark crack or tiny wound. Gasses produced by the bacteria build up and push out sap. Seeping sap most often appears as a constantly wet area on the trunk. Other times the sap looks whitish or beige. It can ferment and have an alcoholic odor, attracting insects.

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In your photo, the gases are blowing bubbles. With enough pressure, the tree can even “whistle” — quite startling if you happen to be walking by. No treatment is recommended for slime flux. It’s fairly benign.

As always, prevent unnecessary injuries to trees, e.g. mulch to keep mowers at bay. (Mulch should never be in contact with a trunk and only 3” deep max.)

Looking for my forsythia to burst into bloom, I see that every single stem has hard, bumpy balls about an inch round. Is this a problem?

Stem galls on forsythia were diagnosed previously as Phomopsis, a fungal disease. It is known now to be a bacterial disease called Pseudomonas savastanoi. The name change does not change management of the galls, which encircle branches and cause dieback.

Since flowering occurs at tips, yes, this is a problem. All you can do is prune back each branch to healthy wood.

To prevent spreading the disease, do this during dry periods and disinfect your pruning shears between cuts. Alcohols wipes may be easiest to use. Dispose of diseased branches in the trash; do not compost. Though pruning away all galls may mean virtually eliminating the plant, forsythia are so tough they should grow back eventually.

If you do not want to wait, consider replanting with an early-blooming native shrub.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.

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