Q: I just moved to the Tucson area and in the front yard is a very large mesquite tree that has not been trimmed much over the years.
It appears that a couple large branches may have broken in the past and subsequently the branches were cut off with a saw. They are leaking a blackish tar substance on the ground that made me think its slime flux. However there is no odor to it.
Any thoughts what this might be and if anything can be done to stop it from leaking? Otherwise the tree looks healthy.
A:Β You are correct. Wetwood or slime flux is caused by the infection of sapwood by several types of bacteria and is a problem with mature mesquites.
The disease-causing microorganisms are found in the soil and probably gain entry through above or below the soil line wounds or pruning cuts. After several years, affected areas will exhibit a water-soaked appearance (wetwood). Although some wounds produce no odor, the wound may produce gas resulting from the bacteria (and possibly yeasts) that force out a foul smelling liquid from cracks and wounds. The liquid is dark brown to black in color. Infected trees live many years and slime flux is more of a nuisance that requires periodically a strong, hard stream of water to prevent staining of patios and cars. There is no cure for this disease. Seriously infected branches may need removal if they present a safety hazard. The old remedy of placing drainage tubes into the infected areas is not recommended and may in fact, present more entry sites for the disease.
Peter L. Warren is the urban horticulture agent for the University of Arizona Pima County Cooperative Extension. Send questions to plwarren@cals.arizona.edu
