Gardening: Discussing a widespread palm disease

Ganoderma butt rot is a widespread palm disease affecting trees all over Marco Island and the southeastern United States.

This disease has been found on about 40 or 50 species, but it is thought that all species are probably susceptible. The two palms which are affected by this disease the most, on Marco Island, are the queen palm and the areca palm. However, I have seen it on coconuts, sable palms and even on oak trees. Ganoderma mainly affects mature palms.

Symptoms begin as wilting and death of the oldest fronds, but gradually progresses up through the canopy until the bud is dead. One of the most easily recognizable symptoms of this disease is the fungal conk on the lower portion of the trunk near the soil line. These conks start out as small white lumps and quickly mature into brown woody brackets up to one foot across. These conks can release millions of spores which are capable of infecting dead palm wood or healthy palms some distance from these conks. While wounds on palm trunks increase the likelihood of infection they are not necessary for infection to occur.

Ganoderma can also be spread through the soil, living on dead palm roots and wood. It is important to remove infected trees from the landscape as soon as possible. Also, be careful to dig out the remaining stump after the tree is removed. Infected palms should never be chipped and used for mulch as this can transmit the disease to healthy palms. Any new conks should be removed quickly and regularly to prevent the production of spores which could spread to neighborhood trees.

It is common for ganoderma to infect clumping palms like the areca. When mature canes of these palms are removed, the dead stump is quickly invaded by ganoderma spores and then spreads to healthy living canes until the entire palm is affected and killed.

Prevention is the only control for root diseases. There are no effective treatments for curing established root disease in trees. Promoting overall tree vigor by properly fertilizing and watering is a good start. Avoid damaging roots by digging too close to palms or wounding lower trunks. When planting trees in areas where trees have previously succumbed to root disease, first remove old stumps and roots to reduce local fungus present. Then consider soil sterilization using chemicals or solar radiation. It is best to plant something other than another palm for that location.

Pruning tools also spread this disease and landscape maintenance personnel should be aware of this disease and its symptoms. Palms showing decline should be pruned last in the landscape to avoid spreading the disease to healthy trees. Pruning tools should be disinfected in a one to four dilution of bleach and water for a couple of minutes before trimming any healthy trees.

Unfortunately, this is not an option for professional tree trimming companies who trim hundreds of trees a day using a chainsaw. The small crooks and crevices of a chainsaw make cleaning it thoroughly after each job virtually impossible. It would be a good practice for professionals to have a “dirty” chainsaw that they use only on declining or diseased trees.

If you discover ganoderma on your palms it is best to remove them from the landscape as soon as possible since the disease can not only spread to your healthy trees but also to those of your neighbors. And that’s not very neighborly!

Eileen and Peter Ward have owned a landscape and lawn maintenance company for 35 years. Eileen can be reached at Gswdmarco@comcast.net or 239-394-1413.