Dogwoods Might Need Help Overcoming Powdery Mildew
Q: What is this white powdery stuff I’m finding on the leaves of my dogwood?
A: We have had several samples and questions come into the office over the past couple of weeks dealing with white powdery growth on dogwood leaves.
Powdery mildew is a disease which is common on many ornamental trees and shrubs, including dogwoods. Powdery mildew is a powdery white to light gray-colored fungus that will grow on succulent stems, leaves, buds, and flowers. Young plants and new growth are usually more severely damaged than older plants, leaves, or branches. Parts of the plant that are severely infected will usually look distorted and stunted.
Powdery mildew usually occurs in the spring and autumn months during cool weather. Powdery mildew will also show up in shady, damp locations especially where plants are crowded and air circulation is poor. High humidity and rainy conditions (like we had in early May) are good environmental conditions for powdery mildew to occur.
The good news is there are several control measures that can be followed in order to prevent and treat powdery mildew. If you are getting ready to purchase a dogwood, you can immediately manage powdery mildew by purchasing a resistant variety and avoiding susceptible varieties. The level of resistance to powdery mildew varies for particular dogwoods. Location and environmental conditions can also affect the level of resistance in some dogwood varieties. Some dogwood varieties will have good to excellent resistance to powdery mildew, while others will be very susceptible. When shopping for dogwoods note the variety and check for the extent of resistance.
When pruning a dogwood, thin the canopy so that you allow good air circulation throughout the tree. Good air circulation will allow the leaf surface to dry out more quickly after a rain and will reduce wet surfaces for powdery mildew to show up on. Pruning out severely diseased portions of the plant will also help reduce the disease if only a few parts are infected.
If the disease is severe enough, there are some chemical control options available. For a fungicide spray to be effective it should start before the disease appears usually when the flower buds begin to open. A second spray should be made when the leaves are unfolding, a third spray about the last week in July and a fourth before leaf drop in the fall. Full coverage of the plant is necessary. Available fungicides to control powdery mildew on dogwoods and many other trees and shrubs include: myclobutanil (Eagle, Immunox), propiconazole (Banner), horticultural oil (do not apply when temperature is greater than 90°F) and copper-based fungicidies. When using any type of pesticide remember to read the label and follow directions.
For additional lawn and garden information contact the Wayne County Extension Master Gardener Volunteer Plant Clinic on Mondays and Wednesdays from 10 a.m. to 1 p.m. One can reach the Wayne County Extension Master Gardener Volunteer Plant Clinic by phone at 919-731-1433, e-mail at Master.Gardener@waynegov.com, or stopping by Room 100 of the Wayne County Extension Office (208 West Chestnut Street, Goldsboro).
Recommendations for the use of agricultural chemicals are included in this article as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this article does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical.
• Visit our website at https://wayne.ces.ncsu.edu/. Click on “Lawn & Garden” on left side of webpage.
• “Like” us on Facebook to receive timely garden tips, ask questions, and learn of upcoming gardening events. www.facebook.com/waynecountygardening
Upcoming Wayne County Extension Gardening Programs:
• Wayne County Gardening Kids Summer Camp. Do you have children who like to play outdoors in the garden? Wayne County Extension Master Gardener Volunteers are offering a four-day camp to explore the fascinating world of gardening. Children will learn how to grow plants, why soil is important, cool insects and honeybees that pollinate your garden, and fresh veggies they can grow at home. Participants will grow and care for their own plants during the camp and take them home on the last day along with a certificate for completing the camp.
- The camp will be held on Thursday July 9th, 16th, 23rd and 30th from 9 a.m. to noon at Wayne Co Cooperative Extension Office
- Camp age range is 8 to 11 years old
- Registration cost is $50
- The camp is held through the Wayne County 4-H Summer Camp program. Wayne County 4-H Summer Camp brochure can be found on our website at wayne.ces.ncsu.edu.
- To register, stop by the Wayne County Cooperative Extension Office (208 W. Chestnut Street, Goldsboro). Office is open Monday to Friday, 8 a.m. to 5 p.m.
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North Carolina Cooperative Extension
Wayne County Center
P. O. Box 68
Goldsboro, NC 27533