We’ve had it again. The kind of weather that delayed summer, put a damper on many outdoor activities this spring, and made the mood a little bit more somber. Cool, wet weather has been prevalent for the first half of the 2013 growing season.
Many fungi form leafspots or lesions on the leaves of deciduous 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 a bigger and bigger spot, feeding on the leaf tissue as a parasite. Eventually, the leaf may fall off as a result of accumulated damage. Examples of leafspot diseases this spring are anthracnose on ash, oak, maples, sycamore and several other species; tar spot fungi causing black spots on maple leaves; apple scab on crabapples and rust on hawthorns. There are many others as well. Not all leafspot diseases require action. If many leaves fall early in consecutive years, then treatment may be needed. Apple scab and rust are good examples of this.
The weather this year has enabled fungi like apple scab fungus to have an extremely long infection time and even sprayed trees are dropping leaves. The spray program still
enables many more leaves to make it through to fall so that some food can be made and some aesthetics can be preserved for the year. Treatments prevent the scab from becoming a serious health concern.
Other fungi form leafspots on evergreen needles. These are called needlecasts and cause browning and needle loss on spruce and pine. With heavy infections, these fungi can reduce both the beauty and the health and are more routinely controlled. Needlecasts have greatly increased their infection rate over the last few years and we have had to treat many evergreens! Spruce trees, in particular, have been struggling with needlecast (Rhizosphaera) and drought for years and many really show the wear. Numerous trees that have had consistent and uninterrupted care for several years have been able to prevail and slowly add replacement needles. But the toll on the needles has been unrelenting.
Experience has shown that patience is needed in order to preserve spruces. And the trees may not regain the density they once had, but they can still provide much needed evergreen accents to our landscapes. Gratefully, the wet spring has given some relief to the many years of accumulated drought.
previous years of drought encounter wet soils. Alternating too dry, then too wet soils 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.