Summer 2009 - Fungus Weather

By: Anthony C. Arnoldi, Board Certified Master Arborist WI-0102B

Summer 2009 Newsletter in Adobe PDF format We’ve had it again: the kind of weather that delayed summer and put a damper on many outdoor activities this spring. It made the mood a little bit more somber, and was prevalent for the first part of the 2009 growing season.

Fungi love this weather, and evidence of this fact is everywhere to be seen. We all know that familiar fungi like mold and mildew do best in cool, moist environments. It is the same with the fungi that bother trees. There are many kinds of fungi causing problems on a variety of tree species.

A large group of fungi form leafspots or lesions on broadleaf trees. These lesions start when spores land on wet or moist leaves in spring and are too small to be seen at first. Over time, the fungus grows into bigger and bigger spots, feeding on the leaf tissue. Eventually, the leaf may fall off as result of accumulated damage. If many leaves fall off early in the growing season, it is more weakening to the tree than if the leaves fall off later because the food-making season is cut short. One of the most dramatic leafspot diseases this spring has been anthracnose on ash. It causes a dramatic but short-lived leaf fall right after they leaf out. Another example is anthracnose and tar spot fungi causing black spots on maple leaves. Include apple scab on crabapples and rust on hawthorns. There are many others as well, but not all leafspots require action. If many leaves are made to fall early in consecutive years, then treatment may be indicated. Apple scab and rust are good examples of this.

Other fungi form leafspots on evergreen needles. They are known as needlecasts and cause browning on pines and spruce. If heavy, these fungi can affect both beauty and health and are more routinely controlled. This group of fungi has greatly increased its infection presence over the last few years and we have had to treat many evergreens! Another fungus of pines is Diplodia tip blight. It infects growing shoots (“candles”) at the same time as the leafspot diseases. It can kill progressively more of the branch over the years if weather favorable to fungi continues or if the tree is weak and unable to resist the fungus effectively.

Another important group of fungi are known as root rots or root collar rots. These attack the root system and lower trunk. They also have increased in the last several years as trees weakened by previous years of drought encounter wet soils. Alternating too dry, then wet conditions favor this disease. Sudden tree death is often attributable to these fungi.

Fungus issues are generally more challenging to control than insect outbreaks, so staying on top of the situation and providing consistent care are necessary for success. You can count on Wachtel Tree Science to provide the best and up to date care for every situation. Call your Certified Arborist to assess your trees to see if treatment is advised and for the best management plan.

© Copyright 2009 – Wachtel Tree Science & Service, Inc.

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