October 15

1 - Tree replacement is the ultimate solution to incurable slime flux disease, but often not an urgent matter. Prune dead branches before dormancy so you can more easily identify the dead branches.

Q. We have a globe willow that is sick. There is a very foul-smelling odor coming from the trunk. Beetles are gathering there and feeding off of that foam. We spray it with pressurized water, only to find it the next day in the same condition. Also, aphids are a big problem for this tree as well. We also have a Spanish Broom with many dried branches. When is a good time to prune these off?

A. Your globe willow probably has a disease called "slime flux disease" also known as "wet wood disease". This disease is due to a bacterial infection of the heartwood. It is incurable, but does not usually kill a tree quickly. However, it does cause oozing (fluxing) of the sap which ferments when it reaches the yeasts and fungi on the bark. The fermentation process results in the unpleasant smells. Washing it off is one line of defense, scrubbing with 10 percent chlorine bleach (1 part bleach to 9 parts water) will give a little longer time without the odors. During the winter and during dry periods, the fluxing may slow somewhat. In time, it will cause death of branches and the tree will not look good. Removal of the tree and replacing it with another kind of tree is the long-term solution to the problem. Aphids can be treated in a number of ways. They are sensitive to a number of insecticides, but can be managed without pesticides. A strong jet of water can wash them from the tree. They will attempt to climb back, but while climbing, they are not feeding and damaging the tree. In addition, if they are present (climbing up the tree or on the leaves) they attract a number of biological predators (lacewings, hover flies, lady bird beetles, etc.) that feed on the aphids and ultimately reduce their population to a bearable level. Washing the aphids out with water does not harm the predator insects and helps minimize the damage caused by aphids while waiting for the predators to build up their populations. If you cannot reach the highest branches in the tree, you will still have a significant impact on the aphids. If you have a power washer, you may be able to reach most of the twigs and leaves on even tall trees. The dead Spanish broom branches can be removed now. It is easier to see them when the other branches have leaves. Cut the dead branches as near the ground as possible. This is true for other trees and shrubs that were damaged by last winter's cold weather or the drought this spring and summer.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

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