Top 10 Tree Diseases (and What You Can Do About Them)

3 / 10

Canker Diseases

A variety of canker diseases affect trees, including Cytospora canker on pine, poplars, spruce and willows. Canker diseases result when a fungal or bacterial pathogen enters bark or sapwood through a wound. Eventually the tree’s vascular system becomes blocked and nutrients cannot flow. Depending on where the canker is, this blockage can cause branches to die. If it’s wrapped around the trunk, the entire tree may die.

Trees that are stressed — from environmental factors, animal browsing, mechanical injury, etc. — are most susceptible. Preventive measures include growing trees suited to the available space and conditions, avoiding injury to bark, proper maintenance and winter protection, and removing any branches affected by canker. Sterilize pruning tools between cuts with a 10 percent bleach solution.

4 / 10

Cedar-Apple Rust

As the name implies, cedar-apple rust is a fungus that requires two hosts to complete its life cycle: cedar (Juniperus spp.) and apple and crab apple (Malus spp.). A related fungus, cedar-hawthorn rust, infects hawthorn trees.

The fungus spends its first year on the cedar. The following spring, spores are carried by wind and infect the second host, usually located within several hundred feet but sometimes up to a mile away.

The disease causes bright yellow-orange spots on leaves and fruit, and swollen fruiting bodies on stunted twigs. Leaves and fruit may drop prematurely. One cultural control is to plant a variety with resistance to cedar-apple rust (check with your local cooperative extension for recommendations). Or spray a fungicide in spring before symptoms develop. Several applications are needed.

5 / 10

Diplodia Tip Blight

Blight can affect many different tree species, but this disease is common on stressed conifers, particularly Austrian pine. New growth is stunted, turns yellow and then brown, eventually dying. Trees under stress are more prone to diplodia tip blight, so keep them mulched and watered, especially during dry periods. Remove and destroy infected cones and tips, as well as dead or dying branches, disinfecting pruning tools between cuts with rubbing alcohol or a 10 percent bleach solution. Fungicides are applied three times in spring: when buds first break, when new shoots (called candles) are half emerged and again when they are fully developed.

ncG1vNJzZmivp6x7p63MoqOyoJGjsbq5wKdlnKedZLmqv9Noq6udlWKxqr%2FEmqqeq12Wu6V51qGYrWWkpHqlu44%3D