Q: What can you tell me about the mushrooms growing out of one of my palm trees?
A: I have seen the mushrooms before at the bottom of deciduous trees, but it is most unusual to see them up one whole side of a palm. I sent the photo to the University of Florida just to be sure I was on target. Guess what? I was correct; the mushrooms are the fruiting bodies of Armillaria. Armillaria root rot is a disease that decays the root system of many common trees and shrubs. It is caused by several species of Armillaria, fungi that can be recognized by the clusters of yellow to honey-colored mushrooms that emerge during moist conditions. The disease is often lethal, and infected trees may have wilting branches, branch dieback, and stunted growth. Infected trees and shrubs should be removed and replaced with resistant species. In Florida, Armillaria tabescens is the most common pathogenic species and is primarily an opportunistic pathogen, but it may kill seemingly healthy trees and shrubs in both urban and natural areas, particularly when host species are stressed. As with many landscape disorders, the most appropriate management technique is the avoidance of infection. Maintain healthy trees by using proper pruning, fertilization, irrigation, and pest management practices. One should commit to planting a more diverse landscape because they tend to better withstand pests, diseases, and even severe weather events. Symptoms of Armillaria root rot often do not appear until 1–3 years after infection has taken place. Therefore, it is difficult, if not impossible, to save trees once they become infected. There are no fungicidal cures for Armillaria. Always disinfect pruning tools between plants to reduce the possibility of transmitting diseases. Some plants with only a small area of infected roots or root collar may be saved by exposing the area to aeration, drying the fungus, and halting growth. Because Armillaria spp. can live in dead stumps and roots for years, an infected tree or shrub should be completely removed, including the stump and major roots. Removal of other susceptible trees or shrubs near the infected plant may be necessary to prevent the disease from spreading over a large area. It is unfortunate for the palm as it will need to be removed, it will not be able to survive. http://edis.ifas.ufl.edu/ep478