How to Manage Root Rot in Fruit, Nut, and Landscape Trees

Many fruit, nut, and landscape trees can succumb to root rot caused by three types of fungi and a group of water molds (that used to be considered fungi); these include the fungi Armillaria, Phymatotrichum, and Xylaria and the water mold Phytophthora.

The trees show varying symptoms from these different diseases.

However, in all cases, there is a distressing tendency for the trees to be so weak that they lean or even break near the soil line.

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There is no easy cure for any of these diseases. Trying to prevent them is your best bet. So read on to learn about these disturbing diseases, so you know what to look for.

Phytophthora species have such a strong preference for moist soils that they are known as water molds. The infamous species Phytophthora infestans caused the Irish potato famine in the late 1800s and the death of one million Irish.

Despite this term, they are now classed in a separate kingdom (the oomycetes) and are no longer considered fungi. However, they act like them!

A large number of these organisms cause root rot on a huge array of plants. However, in trees and shrubs, the species primarily responsible for root rot is Phytophthora cactorum.

While you might expect this type of root rot to only be a problem in moist areas, vegetation in dry areas can also be susceptible. Irrigation can result in wet soils and increase the susceptibility  to this type of root rot.

These organisms have two types of spores. Oospores are thick-walled spores that can lurk in the soil for a long time and strike when conditions are moist. Other types