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Green trees
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Scott Schwieder is a Rochester resident who has overseen a diversity of civil engineering projects over the decades and is currently a certified Minnesota Department of Natural Resources tree inspector. Scott Schwieder has an extensive knowledge of trees in Minnesota and the diseases that can affect them.
For apple and crab apple trees, one major concern is the fungus-caused apple scab, which causes leaves to become covered with black and dark green spots and to fall prematurely. Typically occurring in spring, the condition can persist when conditions remain moist. To avoid this, many horticulturists plant disease-resistant varieties of crabapple trees.
Another fungal leaf-spot disease is anthracnose, which can impact ash and white oak trees when spring weather is unusually wet and cool. The fungus results in dead leaf tissue and leaf wilting, and the premature falling of leaves. Fortunately, anthracnose does not usually progress beyond the cosmetic stage and pose a serious threat to the tree itself.
A more serious fungal disease is cytospora canker, which impacts the inner bark layer of Colorado spruce and results in branch and stem cankers. These cankers can grow larger and ultimately encircle a branch, at which point its needles will turn brown and the branch will die.
