Palm trees prove an ubiquitous presence in many regions of the United States, from Florida to southern California, Nevada to Texas and beyond. Gardeners and landscapers commonly use species of palm in a number of projects, from large municipal beautification projects to home lawn specimens. Two types of disease cause brown spots to appear on trees, leaf spots and bud rot. Sources recommend various tactics for dealing with instances of these diseases.
Several pathogens cause leaf spot diseases on palm trees. These diseases result in the presence of watery legions that turn grey, red, yellow, black or brown, depending on the pathogen causing the particular disease. As the disease spreads, more and more spots appear on leaves, eventually consuming them. The fungal spores causing these diseases, such as Annellophora, Bipolaris, Cercospora, Colletotrichum, Pseudocercospora, and Stigmina transmit easily via water or wind. Determining the exact pathogen causing leaf spots in a certain specimen requires scientific examination. Leaf spot diseases commonly affect juvenile trees rather than adult trees.
Leaf Spot Management
The most important management techniques for leaf spot diseases in palm include sanitation and controlling irrigation. Because fungal diseases spread through water, eliminating overhead irrigation prevents further dissemination of the disease. Keeping leaves dry also prevents the spread of leaf spotting diseases. Increasing air circulation also helps prevent the spread of the disease to nearby specimens and serves as a general preventive measure for fungal diseases. Severely pruning infected leaves removes the disease from the tree and prevents the spread. Fungicides kill leaf spot disease though should not be the sole method of diseases treatment.
Bud rot is another fungal disease caused by one of a number of pathogens, particularly those of the Phytophthora and Thielaviopsis genera. In Florida, the disease proves particularly prevalent in coconut palm species. Trees affected with bud rot display brown, sunken spots throughout the plant. Leaves wilt and wither, turning greyish brown and darkening in hue as they collapse. The disease typically affects the youngest parts of a plant first and may take as long as six months to appear on old growth.
Bud Rot Management
Bud rot spreads through water, like other fungal diseases, and proves worse with wet leaves. Avoiding overhead irrigation proves key in bud rot management. According to horticulturalists at Clemson University, palms affected with bud rot rarely recover. The most effective means of managing the disease entails removing and destroying infected plants. Fungicides such as copper hydroxide or copper salts of fatty acids can be used as a pre-emptive means of combating the disease.