Right now a terrible disease is spreading through eastern North America killing Flowering Dogwoods, one of our most beautiful and treasured native tree species. The disease is caused by Dogwood Anthracnose Fungus, and the picture at the right shows the disease's symptoms.
Note the dark brown spots (dead tissue) surrounded by yellowness. In the disease's later stages the leaves are often red, as during the fall. The fungus kills by releasing a substance that breaks down the dogwoods' tissues into something the fungus can absorb and use for its own purposes. The fungus also releases toxins that kill tissue outright, and can spread into the stem to infect new limbs and cause cankers. There are two main types of anthracnose fungus on dogwoods. One is a species of Discula, to which science hasn't yet given a scientific name.. The other, more deadly, fungus is called Discula destructiva. Since this disease is so important, there is plenty on the Web about it. To visit one of the best sites, which has a good section on identifying fungi by looking at their DNA, click here.