white oak insect problem

Asked September 26, 2015, 2:04 PM EDT

Our 10-year-old white oak has fuzzy, puffy "balls" on the bottoms of leaves, some as large as an inch in diameter. They are light brown in color and the leaf from the point of the "balls" to the outer edge turns yellow, then brown. In addition to these growths, other parts of the leaves have small black dots that become increasingly bigger as the days pass. The parasitic growth and subsequent death of the leaf seems very fast. It seems that much of the tree is affected now, and I'm wondering if the browning of the needles of 30-year-old blue spruce next to it reflect a spreading problem. The pictures of mites/worms on-line don't seem to match anything I'm seeing. Do you have any ideas of what we are dealing with? We really don't want to lose these trees.

Ramsey County Minnesota oaks oak pests oak galls

3 Responses

It sounds like lots of things are going on here, with your trees. In order to ease your mind about some of them, let's start with the photo.

This (these) are galls that are the tree's tissue response to some small insects - usually tiny wasps. They do not present any health problem to your trees. Here is some information about them:
http://www.ipm.iastate.edu/ipm/hortnews/2010/8-25/oakgalls.html

The browning leaves are probably Anthracnose - a very common fungal infection that shows up in wet weather (which we've had a Lot of lately). but just to make sure, take a look at this link to see if something else, more serious could be going on. If you think that there is something else, please send some high quality photos of the whole tree and the affected leaves so we can take another look.
http://www.extension.umn.edu/environment/trees-woodlands/oak-wilt-or-anthracnose/
http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/oak-diseases

Finally - there are no insects or diseases that oaks and spruce share. If your spruce are showing lots of brown needles, this may be another matter, entirely. If you are concerned please send some good close-ups of the affected branches/needles, and the whole tree so that we can narrow down the possibilities.

I hope this is helpful. Please contact AaE again if you have further questions.




Thank you. Your response was very helpful. The first website you referenced showed clearly that we have woolly oak leaf galls, and it is good to know that problem isn't as devastating as oak wilt. When the affected leaves fall from the tree, will the galls affect the soil?

No, not at all, but it's a good idea to rake up fallen leaves because they may also contain the anthracnose fungal spores that will re-infect the tree next year.