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5 Common Tree Diseases

leaves with spots possibly one of the common tree diseases

Like any living thing, trees are vulnerable to illness and disease. If you’re looking for tree disease treatment in Maryland, knowing how to identify common tree diseases is helpful. Even if your trees are healthy, learning about common tree illnesses can help you care for your plants and keep them in good condition. Here are five of the most common tree diseases.

1. Rust Diseases

Tree fungi cause rust diseases, and you can generally see their effects in late August. Hardwood species like oaks, birches, maples, cottonwood, and poplars are especially vulnerable to rust disease. Fruit-bearing trees like quince, crabapple, pear, and hawthorn may also be affected. Red cedars, like the Eastern red cedar, are also very rust-susceptible.

To identify these common tree illnesses, look for signs like twig galls or cankers on cedar trees. Infected twigs may have red-orange fungal spores. Fruit from infected trees may be cracked, rotted, and abnormally shaped.

Trees with rust diseases often lose their leaves by the middle of summer. This loss affects the trees’ growth and decreases their crop yield.
To treat rust diseases, remove any visible galls from trees before April. You can also plant susceptible fruit trees far apart, so a potential infection doesn’t spread.

2. Root Rot

A fungal infection causes this common tree disease. Root rot can affect trees planted in wet or infected soil or those with damaged stems or roots. Newer plants may get root rot if the decay is in the ground from previous infestations. Older plants can be affected if water drainage patterns change.

Forest trees, or trees planted in heavy, wet soil, are especially vulnerable to root rot. Their wood may become spongy and ooze with sap at the tree’s base. Other symptoms of root rot include:

  • Poor growth
  • Needle loss
  • Needles turning brown or light yellow
  • Discolored wood at the bottom of the stem
  • Dark brown threads at the bottom of the stem
  • Loosening and separation of dead lower bark

People can’t cure root rot, and they can’t extract the fungi from the soil. You can help prevent root rot by planting trees away from poorly drained soil, downspouts, and other areas where water collects.

3. Black Knot

Black knot stems from tree fungi that create galls and black swelling on trees and shrubs. The fungus releases spores from the galls and infects new branches in late spring and early summer, especially in damp weather. Black knot often affects fruit trees, like plum, cherry, flowering almond, apricot, and blackthorn.

In the first year of infection, trees develop brown swellings, which may be on the trunk or branches. These swellings surround the stem in the second year and form black galls. The tree’s surface may crack or split. A severe black knot infection can kill a tree if galls surround trunks or large limbs.

The easiest way to prevent this common tree illness is to prune any infected branches and stems in early spring.

4. Bacterial Leaf Scorch

When bacteria get inside plants’ vascular tissues, they can spread and cause this common tree disease, blocking water as it moves from the roots to the branches. Bacterial leaf scorch affects shade trees like elm, oak, maple, ginkgo, and sycamore.

Infected trees may develop irregular browning on their leaves each year in mid- to late summer. The browning may progress from lower to higher branches. Some tree species might have a yellow halo or “scorch” around them in infected areas.

While there are no treatments for bacterial leaf scorch, you can prune dead wood and infected branches.

5. Powdery Mildew

Powdery mildew is one of the most common tree illnesses. Caused by tree fungi, powdery mildew can be identified by white spots that look like patches of dust or talcum powder. This dust grows on the leaves, stems, shoot tips, and flower buds of infected trees.

Young plants that grow in the shade are most likely to get severe cases of powdery mildew. The mildew spreads during dry, warm days and humid, cool nights; fungi spread from plant to plant on air currents during the day and absorb moisture to grow at night. Fungi can infect a tree during the growing season, stay in the leaves through the winter, and move to new plants the following spring.

While powdery mildew probably won’t kill a tree, it may cause leaves and flowers to be distorted and discolored. The mildew blocks the plants from receiving light.

Many varieties of flowering trees are resistant to powdery mildew, so select mildew-resistant varieties when you’re planting. Make sure plants have plenty of space in areas with plenty of sunlight and air circulation.

Prestige Tree Experts: Help for Common Tree Diseases

The arborists at Prestige Tree Experts can diagnose and treat multiple common tree illnesses. We’ll also advise you on how to prevent tree diseases and keep your trees healthy and strong. We’ve protected Maryland trees for over a decade with our removal, trimming, and healthcare services. Don’t let diseases destroy your favorite trees—call the experts for high-quality treatment that helps your trees last for years. Contact Prestige Tree Experts at 240.673.2474 or online.

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