There are many diseases that can damage or kill the trees in your backyard, including phytophthora root rot, also called phytophthora dieback. Here are four things gardeners need to know about phytophthora root rot.
What causes phytophthora root rot?
Phytophthora root rot is caused by phytophthora, a type of mold. This mold is widespread and can be found in the soil. You could introduce this mold to your backyard when you bring home a new tree or shrub from a garden center, but the mold could also already be present. As a water mold, phytophthora thrives in poorly-drained soil and will affect trees that grow in such soil.
What are the signs of this disease?
If your trees have phytophtora root rot, you may notice some or all of the following signs:
Red to brown cankers that ooze sap;
Sudden browning of leaves;
Gradual leaf loss;
Brown or gray spots on leaves;
Beetle activity on the affected tree.
A number of different trees and shrubs can be affected by these symptoms, so it's important to inspect your plants regularly. Common trees like maple, beech, ash, oak, willow or fir trees are susceptible. Some types of shrubs, like rhododendrons, roses and lilacs, may also be affected.
How can you treat infected trees?
There is no chemical or treatment that can completely get rid of phytophtora mold. Once a tree is infected with this mold, the mold will always be present. However, there are treatments that you can perform to keep the mold under control and reduce the impact the mold have on your tree.
Phosphite, a type of salt that comes from phosphoric acid, can be applied to infected trees. This salt is diluted with water before use and can be easily obtained from nurseries or garden centers. The resulting solution can be injected into larger trees that have a diameter of 10 to 14 centimeters at the height of your chest. Smaller trees or shrubs should have their leaves sprayed with phosphite instead.
The injection method will protect an infected tree for up to five years, while spraying gives up to two years of protection. Remember to repeat the treatment at the appropriate time to ensure that your tree stays healthy.
It's also important to correct any drainage problems that may be present in your yard. Poorly-draining soil provides a good habitat for molds, so make sure that your soil drains well to avoid encouraging their growth.
If you're worried that one of your trees has phytophthora root rot, contact a tree service for help keeping the mold under control.