Trees are a splendid feature to any landscape and are an important source of shade, shelter, and beauty. But like all living things, they can get sick and die. While not all diseases are easy to spot, understanding common tree diseases that occur during spring can help you keep your trees healthy and safe.
Anthracnose
Anthracnose is a fungal disease that typically targets young leaves and shoots. It can infect ash, maple, oak, and sycamore trees. It is not usually fatal to the tree, but leaves can be heavily infected and fall prematurely if the disease becomes severe. Leaves affected by anthracnose often develop irregular tan, brown, or black spots. They may be scattered over the entire leaf or confined to major leaf veins. Fruits can also become infected, especially tomatoes and papaya. These lesions look like target-like water-soaked areas that grow on the surface and sink into the fruit. When you spot a plant with anthracnose, treat it promptly. A fungicide spray such as Daconil(r) Fungicide Ready-to-Use or Concentrate can simplify treatment.
Leaf Spots
Leaf spots are caused by a variety of fungi. Some are very common, while others are specific to a certain species or variety of plant. The most obvious symptom of leaf spots are spots on the leaves that vary in size and color. Often the spots are brown, tan, or black in color. Concentric rings or dark margins may also be present. Rake up and destroy fallen leaves before the first snowfall to eliminate locations where spores can be carried back to your trees the following growing season. A tree affected early in the year may re-leaf and not be affected, but if defoliation occurs three or more years in a row, many established plants will suffer damage. Routine neem treatments will help catch any disease before it gets out of control.
Leaf Rust
Rust is caused by a group of fungal pathogens that show up as multiple orange, yellow or red spots on leaves and stems. They can be a serious problem for certain trees and shrubs. Infected plants may lose their leaves prematurely or have stunted growth. You can spot leaf rust by looking for small, round orange pustules that are surrounded by an orange dust. To prevent rust infection, water plants only when they need it and make sure to avoid soil splashing on the leaves when you water them. Overhead watering, especially from sprinkler systems, is a major source of infection. When the weather is warm and moist, rust fungus grows and spreads infective spores called urediospores through the wind. Urediospores are very light and can easily be carried by the wind to a different region or even across a field. This can lead to massive infections and crop losses.
Leaf Discoloration
Leaf discoloration can indicate a wide variety of plant diseases. It’s important to keep an eye out for this symptom as many of these fungal problems start early in the spring and continue into the summer season. Common symptoms of leaf discoloration include yellowing or browning of the central veins of leaves, particularly those of younger, actively growing plants. This is usually indicative of iron deficiency, but other nutrient deficiencies may also cause this symptom.