Palm trees can develop leaf spots and leaf blights, caused by a number of fungal infections that manifest in similar symptoms. Young palm trees are particularly susceptible to these pathogens which first appear as small lesions that will grow in size, eventually killing off the palm leaves. If you notice signs of fungal infection on your palm tree, preventing it from spreading is key to saving your tree.
Stop any overhead irrigation and protect the trees from rainfall. Keeping leaves dry is integral to preventing leaf spot fungus.
Increase space between plants if growing them in a nursery. This will improve air circulation and inhibit fungal growth.
Remove and dispose of any leaves that are severely infected with leaf spots. In some situations, you will have to eliminate the tree itself.
Prevent leaf damage or injury to the plant. Stresses such as sunburn and too much water or fertilizer burn can make a fungal infection worse.
Apply a fungicide to prevent further infection on leaves that have not been infected; once a leaf spot appears, you cannot cure it. Prune away all diseased leaves before applying fungicide. Read the directions on the fungicide package and add the recommended amount along with the recommended amount of water to your sprayer. Spray the palm tree, making sure you cover both the upper and lower sides of the leaves. Use all of the fungicide that is inside the sprayer's tank.