Hi Ccarroll,

I believe what the gardener was referring to is Sooty Canker, a fungal pathogen that affects stressed plants and usually invades the host at sites of pruning, sunburn, freeze damage, etc. The fungal spores can be transmitted from plant to plant on tools or can be airborne.

This disease is not new. Healthy plants are rarely affected. Take care to maintain optimum plant health by watering properly, not overpruning, avoiding freeze damage (if possible) and disinfecting tools.

Your tree (citrus?) may or may not have Sooty Canker. To be sure I've included a link to the U of A Extension Plant Pathology web site. You can also take samples or send photos to the U of A Cooperative Extension office in Phoenix.

Here is a link that might be useful: Diseases of Citrus in Arizona

Thanks! I'm sure I mis-heard the gardener, since we use the wrod "city" more than "sooty." And thank you for the link!