As the weather warms up in Northern Virginia, trees begin to awaken from their winter dormancy. At Green Horizon, we are well aware that this time of year also brings an increased risk of tree diseases. Here’s a quick guide to some common spring tree diseases in the region, their causes, consequences, and how we can help you manage them before they become destructive to your outdoor oasis!
Black Sooty Mold can affect many trees such as crape myrtles, maple, pine, elm, linden, and catalpa trees. It can also affect ornamental plants like azaleas, camellias, and gardenias. You may notice black trunks and branches and a sticky coating on the tree and surrounding areas. While sooty mold may not kill your trees, it is unsightly and indicates presence of sucking insects such as aphids, whiteflies, or scale. These insects damage trees by draining nutrients from leaves and twigs, and leaving behind honeydew which hosts fungi.
We could apply insecticide to control the insects that result in sooty mold but that has the unintended consequence of killing beneficial insects such as ladybugs and microscopic wasps. Best to use horticultural oil!
Scales are sap-sucking insects that have either armored shells or soft shells, and are only mobile for a brief period after they hatch. Once attached to a tree or leaf they stay there for the season and may appear as a “waxy bump.” Scales thrive on trees that are under stress!
How to control them? Best to ask for help from Green Horizon on this one! Conventional pesticides are undesirable for managing scales because their tough skin or waxy shell is impenetrable to foliar pesticide applications. Scales DO have several natural enemies such as ladybugs and microscopic wasps and use of a horticultural oil is the ideal treatment for scale.
Anthracnose is a fungal disease that affects many hardwood trees in Northern Virginia, particularly sycamore, dogwood (as in the image at the top of this post), oak, maple, ash, and walnut. You may notice leaf spotting, blighting and shriveling of leaves, brown papery lesions on leaves, purple or brown streaks on leaves, and significant premature leaf drop. Anthracnose is caused by fungal spores that thrive in cool, wet spring conditions.
While considered a cosmetic issue, severe cases can lead to thin canopies and weakened trees. For mature trees, pruning affected areas is necessary, as well as removal of fallen twigs and leaves. For younger trees, a fungicide treatment with a specialized chemical may be needed to prevent further infestation and protect the health of the tree. As always, maintaining tree health through proper watering, fertilizing and mulching is helpful.
Phytophthora Root Rot is a soil-borne fungal disease and affects a wide range of plants, including trees, shrubs, flowers, and vegetables. It causes a slow decline of trees and shrubs, especially new plantings, and you may first notice this in landscape beds affecting your azaleas, rhododendrons, and Japanese andromeda (Japonica.)
Root rot can occur year-round but it becomes apparent in spring as plants resume growth. You may notice yellowing of leaves and plants that seem to struggle. This fungus can be fatal to plants if left untreated! To treat and prevent, ensure proper drainage in landscaped areas, avoid overwatering, remove infected plants immediately, and because it is soil-borne, fungicides can be applied throughout summer.
Prevention Strategies for Spring Tree Diseases
- Maintain tree health through proper watering, fertilization, and pruning.
- Ensure good air circulation around trees by proper spacing and pruning.
- Water early in the day to allow leaves to dry thoroughly.
- Remove and dispose of infected plant material properly.
- Consider using preventive biofungicides as foliar sprays or soil applications.
- Regularly inspect trees for signs of disease, especially in spring.
By staying vigilant and implementing these preventive measures, you can help protect your trees from spring diseases and ensure a healthy, vibrant landscape throughout the year.
Contact us if you have any questions or concerns about your trees and shrubs! We are here to help you and your lawn.
