Gardening Question From Sue:

I live in the Arizona desert. I have 25 mature California Pepper trees. This summer one died. The root ball had white laced fungus. Now another tree is dying. This tree sat close to the dead tree. My question is. Does the fungus in the ground spread to the other trees? If so how far apart can they be to not catch the fungus? I also have eucalyptus trees nearby. I have over 120 trees. I don’t want to loose them.

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Answer From Pat:

I am not familiar with the common name “white laced fungus”. Perhaps you are referring to Phymatotrichopsis omnivora? This type of root rot and others, can kill ornamental trees in desert areas. Yes it is spread from tree to tree, usually by monsoon rains during hot summer months. Since spores are carried in the air and by other means, I do not know if it would be possible to say how far apart trees should be in order to avoid contracting this fungus. If this is the disease affecting your trees, usually a white mat shows on top of the soil suddenly overnight, seemingly by magic after rain. Later this mat may go brown. Hot weather and rain can cause and bring on this and other fungus diseases affecting trees and other plants.

I suggest you contact the University of Arizona Agricultural Extension for advice and ask if application of a fungicide might help save your trees and if so, which one. You might also contact the Master Gardeners’ Hot Line in your area for help with this problem. One of the best ways to avoid dealing with problems such as fungi of ornamental landscape plants is to concentrate on growing plants native to desert areas that are immune to exotic fungus diseases and to use arbors and pergolas and other shade structures to provide wanted shade. A few citrus varieties have been developed that are resistant to root rots.

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