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Armillaria

Q: We discovered an irrigation head had broken right at the base of this palm. Do you think the extra water could have caused the palm to die?

Q:  I have a whole bunch of mushrooms growing at the base of my sabal palm.  The palm has brown fronds, some appear to be dying.  We discovered an irrigation head had broken right at the base of this palm where the mushrooms are growing.  We do not know how long the water has been pooling as this site but we have removed broken head.  Do you think the extra water could have caused the palm to die?

A:  After seeing the palm directly it appears the mushrooms are Armillaria mushrooms.  These honey-colored, clustering mushrooms usually do not live for long periods of time so I was glad for an opportunity to photograph them before they disappeared.

Armillaria fungi are normally found in the soil and generally do not pose a problem for healthy, unstressed plants. The fungi attack about 700 species of plants, most of them woody ornamentals.  However, some herbaceous plants can be susceptible such as blackberry, flowering bulbs, potato, raspberry, and strawberry. Armillaria often causes problems on oaks and maples in the urban landscapes where compacted soil is common and improper maintenance procedures often occur.

Any plant exposed to stresses such as drought, flooding, poor soil conditions drainage, frost, repeated defoliation by insects or diseases, herbicide damage, or injury from weed eaters or lawn mowers are susceptible to attack. The loss of fine feeder roots from this disease deprives affected plants of sufficient nutrients and water, and often results in branch dieback.

There are no chemical applications to cure this disease. The best defense is to keep trees and shrubs from as many environmental stresses as we can control. I am confident the excessive water contributed to a root rot which placed the palm in a stressful situation. Once the palm became stressed the fungi took over.

The palm should be removed and destroyed as soon as possible.  Removal of some of the soil might be beneficial as well.  We discussed leaving the site bare and avoiding putting another plant in the site.  Another lesson learned it to consider checking irrigation systems on a regular basis. This would help avoid potential damage to the grass and plants in our landscapes.