What Causes Brown Spotting on Canary Palm Trees?

Palm trees should always look lush and green.Palm Tree image by SISS-Solutions.com from Fotolia.com

Canary palm trees add beauty to landscaping and provide just the right amount of shade during the hot afternoons. These tress should always look lush, green, and full of leaves. Brown spots, however, indicate problems. By knowing what causes brown spotting, you can take steps to cure your sick tree.

Nutritional Needs

Palm trees need a lot of nutrients to grow successfully. According to the University of California's Master Gardener Nancy Gravender, Canary palm trees need nitrogen, potassium and magnesium in large quantities. Since boron, iron, magnesium, nitrogen, potassium and zinc are also needed, conventional fertilizers are not enough. A manifestation of undernourishment in Canary palms is necrotic spotting of the leaves. This is particularly true of potassium deficiency.

According to Gravender, frost damage can also cause brown spots on the mature fronds (or leaves). The tree itself may survive, but parts of the leaves will suffer frostbite and can die off. New leaves will eventually grow in to fill in the gaps left by the dead leaves, but only if the tree has not been killed by frost.

Fusarium Wilt is a disease caused by the Fusarium oxysporum fungus. According to the University of California's pest management program, this disease is lethal to Canary palms with no known cure. The first indication is brown spots on the fronds. The disease is spread easily by pruning tools such as chain saws, so it's best to wash and disinfect tools that have cut down a diseased tree.

Pink rot is caused by the fungus nalanthamala vermoeseni and is also deadly. It is a secondary invader. This means if the tree is weakened, it will invade. Otherwise, a normal, healthy tree will not contract it. The symptoms are rotting and spotting along the leaf bases and along the trunk. Pink spore masses can also form.

Sudden crown drop is another disease that affects Canary palms. While the causes have not been confirmed, the presence of the fungus Thielaviopsis paradoxa is prevalent. Internal trunk decay sets in first, so by the time brown spots develop and the crown drops, the tree is already dead. As the name suggests, sudden crown drop ends with the entire crown of the tree along with some of the upper trunk falling to the ground suddenly with little to no warning. There is no known cure for sudden crown drop.