bumps on tree trunk
Can you tell me what these bumps could be? They have been becoming more and more dense, though the tree seems healthy otherwise. Is there anything we should do about this? The tree is in the backyard of a brownstone in Manhattan.
New York County New York
Can you send photos of the tree and the bumps? That would help us identify the problem.
These bumps appear to be soft scale insects and the white flecks around them are related to the scale infestation.There are thousands of types of scale insects and the type will depend partly upon the type of tree.They multiply quickly. When removed, they leave a little mark where they have been feeding on your plant.
These look a lot like European fruit tree scale but regardless of type, the life cycle is similar. The large bumps are adult, female scale insects with armor built around them that will protect them from most chemical treatments. During the warm months, crawlers hatch and venture out to feed (in some scales as far as to the leaves and soft tips of the plant where they may create a honeydew sap). Some time later, (in European fruit scale, when weather cools again) they return to the stems and trunk to complete their life cycle. Those are the white spots you see on the stem.
The scale insects can reduce your plant's vigor and even cause die back of twigs and branches. The most effective time to treat them is when they are in the unprotected crawler stage, though picking the mature scale off by hand is an effective step in the process that can help limit future infestation.
Here is an excellent fact sheet on scale from the Missouri Botanical Gardens that includes a run down of the possible treatments. And here is more information on European fruit scale so you can make a closer examination of your tree to see if its a match.
Good luck with your tree.