Ganoderma on Palms Diagnostic Guide

Ganoderma zonatum

Ganoderma butt rot (Ganoderma zonatum) is a lethal disease of palms. Symptoms may include wilting and/or general decline. The disease often forms a conk, called a basidiocarp, on the trunk. However, many diseased palms do not produce conks prior to death.

Ganoderma is a white rot fungus that begins be degrading lignin followed by cellulose. Degrading internal lignin and cellulose within the palm affects water conducting parts of the plant, and predisposes the palm to trunk failure.

Trees at Risk

At least 65 species of palms throughout Florida, from Key West to Jacksonville to Pensacola. It is also known to occur in Georgia and South Carolina.

Signs of Ganoderma

Comparison of pygmy date palm sections that are either healthy (right) or diseased (left) with Ganoderma zonatum.

Signs of Damage

The conk is the most easily identifiable sign of this disease. The conk originates from fungal growth inside the palm trunk. The conk begins as a solid white mass which is soft to the touch. It will have an irregular to circular shape and is relatively flat on the trunk or stump. As the conk matures, a small shelf or bracket will start to form. The mature conk will have a shelf-like structure that is hard and appears to have a glazed reddish-brown top surface and a white undersurface.

Physical Appearance

Nutrient deficiency and root damage. Fruiting conk is a key distinguishing factor.

Signs of Ganoderma

Sabal palm with wilted and dessicated leaves due to Ganoderma zonatum infection.

Signs of Ganoderma

Beginning symptoms of Ganoderma butt rot

Treatment Strategy

Field diagnosis of the diseases and the host plant are usually sufficient. It is difficult to sample for this disease if no conk is present.

This disease affects healthy trees in diverse environments. There is no known control. Remove, bag, and dispose of conks to reduce the amount of spore production. Preventatively remove palms displaying conks as they pose a risk of failure.

Other Treatment Strategy

Monitor trees for crown symptoms and conks.

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