Every spring, the first time we get the right combination of temperature and rain, the eastern red cedars “bloom” with the spore producing structures of cedar-apple rust galls. YESTERDAY WAS THE DAY! And this year, the phenomenon seems especially spectacular, with some trees that look like they are completely covered with fluorescent orange jelly. Not surprising, considering how the wet weather last summer caused severe infestations of the disease on the alternate host, apple trees, where the spores that infect the cedars originate.
More explanation of the disease and photos of the apple trees can be found at July 15, 2009 article.
A client in Collegeville asked me to look at her apple trees, which appeared unhealthy as the leaves were turning color and dropping off.
Viewed up close, the leaves display the orange colored lesions typical of cedar apple rust.
Nearby, at the property line, is an Eastern red cedar tree that is completely infested with cedar apple rust galls.
This is an interesting disease because it has a two year life cycle – spores (aeciospores) released in summer from the fungal fruiting bodies on the apple leaves travel through the air and when they land on Eastern red cedar or another susceptible juniper infect that host and produce galls that, in the spring, produce spores (basidiospores) that, in turn, infect leaves of nearby apple trees. To see the fruiting galls on juniper in spring (an incredible sight!) scroll to the April 21 entry in this column.
I also noticed evidence of a canker fungus disease (possibly Botrosphaeria) and fireblight, a disease caused by a bacteria – Erwinia amylovora – both causing injury and death of branches.
If my client can convince her neighbor to remove the cedar tree (it is not a nice tree, either location or health-wise_ her apple trees will probably have much less leaf-spot problems in future years.
This winter we will do maintenance pruning on the apple trees, including removing the dead wood. This should reduce the problem with the Botrosphaeria and Erwinia diseases.
This morning as the rain was clearing out, I went to a clients property in Collegeville to quote some pruning work. While there I noticed an eastern red cedar tree that was just beginning to “bloom” with the reproducing stages of cedar apple rust.
This common disease has a very interesting lifecycle : the fungus that grows as a leaf spot disease on apple trees produces spores which, when carried by the wind are deposited on cedars or other species of juniper, grow to form galls on the juniper twigs. Then, after a spring rain when the temperature is suitable, the galls erupt into a brilliant orange jelly-like substance that is the spore producing stage on cedars. This reproducing stage occurs magically fast after the rain, then only lasts a few days. Spores from this fruiting body then infect the leaves of apple trees to complete the 2-stage lifecycle.
Galls just starting to expand