Anthracnose is a disease caused by fungi.  Tiny fungal spores, borne by wind, land on moistened leaves and begin another cycle of their life.  Symptoms of Anthracnose include irregular patches of dead, brown leaf tissue.  Extreme infestations can appear as a failure to leaf out in spring.

In Utah, Anthracnose is not usually considered a serious disease, because spring moisture disappears by the end of May.  This year (2005), however, our cool wet spring has allowed this disease to infest many susceptible trees severely.

Susceptible trees include Sycamore, Oak, Ash, and Maple.  In our office, we have seen mostly the sycamore and oak tree leaves, but recently a boxelder tree (a member of the Maple family) was also brought in for diagnosis.

Treatment of fungal infestations are not curative.  Instead, the anti-fungal materials must be sprayed onto the plant foliage before the spores light on their surfaces.  Presence of the anti-fungal material will prevent the spore from infesting the leaf tissue. 

Hopefully, before long, the spring rains will end.  Decreased moisture will allow new leaves to emerge uninfested.  Over the summer, leaves will photosynthesize enough energy to compensate for the damage we see now.

Removing the fallen leaves can help decrease the amount of anthracnose fungal spores laying around your trees.  These leaves should be hot-composted or taken to the landfill compost piles.

More information about Anthracnose can be viewed at the USU Extension Plant Pathology website, http://extension.usu.edu/plants