Many homeowners have asked “What has happened to my trees this year?” Most notable is the browning of white pine and spruce as well as maple trees that did not leaf out last spring.
Last fall there was not enough rain late to leave the roots of many trees, especially those in sandy soils, with enough moisture to keep the needles or new branches hydrated through the winter. Add to that a very cold winter. Especially hard hit were trees that were recently transplanted.
Now that the trees have been treated to a relatively wet summer, you can tell if the damage was permanent and if they may eventually recover. Spruce and pine should have formed buds and new needles at the tips of the affected branches by now. While the tree will look rather bare in the middle, eventually new needles and branches will grow to cover the bare branches on the inside of the tree.
Evergreens, especially blue and white spruce, are very susceptible to fungal diseases. The most common is rhizosphaera needle cast disease. You can tell this disease by the way it starts at the bottom of the tree and works its way up the branches, turning the needles brown.
Sometimes if the infection is minor, you can trim off the bottom branches. In my experience I have ended up removing the tree several years later.
Deciduous trees are another matter. While a dead branch or two can be pruned out, trees that have dead tops will not recover to be a shapely tree. The test to find out if the limb is truly dead is to scrape a small portion of the branch with your thumbnail. If you see green, the limb is still alive. If the bark peels away easily and is brown, the branch is dead and will not recover.
If you are planting new trees this year or have recently planted trees, there are recommendations to promote the health of the tree and avoid weed competition. After planting, place mulch five feet around the tree, 5 inches deep and 5 inches away from the trunk. This retains moisture, minimizes frost injury and eliminates weed competition. Water well until freeze-up
To make matters worse, there were many reports of hail damage when trees were just leafing out this spring in Beltrami County. Unless a tree is totally stripped, many will form new buds and leaf out enough to survive. They may have a rather bedraggled look this year but will usually do just fine next year.
Leaf fall in the spring or summer, especially in a wet year can also be the result of a disease called anthracnose. The leaves affected by this fungus are usually deformed and have dark spots or blotches. The disease especially affects white oak, ash and maple. This is not a serious problem and the tree will sometimes send out new leaves or wait until next year.
Those of you with apple trees should be on the lookout for apple scab this year. The fungal disease is identified as round, olive green spots that eventually turn brown and get bigger. While fungicides will control the disease, timing of application is important.
There are numerous resources to identify tree diseases and pests in Minnesota. A good place to start is the Minnesota DNR website under Tree Planting and Care at www.dnr.state.mn.us/treecare/index.html. The University of Minnesota Extension has a Tree Diseases section in Yard and Garden that is very useful as well.
Click on "Yard and Garden at the University of Minnesota Extension website, www.extension.umn.edu, for gardening information. Local Master Gardeners will respond to your questions via voicemail. Call (218) 444-7916, leaving your name, number and question. You can also find us on Facebook.