Dogwood anthracnose. Dogwood borer. Powdery mildew. You may have heard these scary terms, and they may have discouraged you from planting flowering dogwoods in the past. Yes, dogwoods have recently been under attack from some troublesome insect pests and diseases. The good news is that you can grow healthy dogwoods with a little know-how. This guide will show you the three simple keys to growing disease- and pest-free dogwoods in the home landscape. You’ll learn to:
• Know the symptoms of the most common dogwood problems
• Choose healthy trees
• Practice proper dogwood care
Common flowering dogwood pests and diseases
1 Dogwood anthracnose
This fungal disease can weaken and even kill a dogwood over time. The first symptom is small leaf spots with purple halos, which may expand to form larger tan blotches. Infected leaves will cling to the tree all winter instead of dropping in fall. Dogwood anthracnose may spread to the twigs, larger branches, and trunk, causing dieback. The lower branches will die first.
There are other leaf spot diseases which are merely cosmetic and cause no serious harm, so don’t assume the worst if you see a few spots. Also, dogwood anthracnose is much more common in the wild in cool, moist forests at high altitudes than it is in the typical home landscape, so the situation will not be as dire as it seems in most residential areas.
2 Dogwood borer
This insect is the larva of a moth which burrows into a branch or trunk of a dogwood and feeds under the bark, weakening the tree and sometimes killing it. Borers often gain entrance through a wound in the trunk, such as one caused by a lawnmower. One symptom to watch out for is leaves that start to turn red in summer. You may also see some dieback in the canopy, along with rough bark and frass (caterpillar droppings) at the borer’s point of entry.
3 Powdery mildew
This fungal disease appears as a white coating on dogwood leaves and buds, particularly on newer growth. In a heavy infestation, the leaves are distorted as soon as they emerge. However, powdery mildew isn’t a particularly serious disease, and the damage is mostly cosmetic.
GRowing healthy dogwoods
1 Buy from a reputable grower
Don’t bring disease home! Buying a healthy tree from a reputable nursery is always smarter than taking a chance with a tree from a cut-rate grower, and it’s especially important with trees that are vulnerable to serious diseases.
2 Water well
Dogwoods are finicky when it comes to watering. They require a “just right” amount of water, which can be difficult to provide as often as it’s needed. However, the payoff is worth it. Proper watering produces optimum root growth and a sturdy, healthy tree. Better yet, there’s a tool that makes watering simple. Our Elements® Watering System excels at providing trees with the perfect amount of water as they need it!
As always, we recommend Elements® Fertilizer (soluble or granular) for use on all trees and plants. These are the same products we use on the nursery to encourage a moderate growth rate that is best for the long-term health of your tree. High-nitrogen fertilizers used elsewhere produce a tree ready to be sold more quickly, but it is done at the expense of growth and health. This leaves trees open to disease.
4 Don’t use pesticides
We do apply preventive pesticides from time to time as required. We grow intensively, so pests are attracted to the large number of trees we grow. This is not at all like the conditions you have at home, and we do not recommend a preventative pesticide program for flowering dogwoods. Healthy trees defend themselves without use of costly chemicals. So, empower your tree with proper watering and fertilization instead!
5 Consider other varieties of dogwoods
Our native flowering dogwood is a magnificent tree, and some homeowners will settle for nothing else. However, there are many other beautiful dogwoods to choose from that are much more resistant to insects and disease. Kousa dogwoods, for instance, are very resistant to many of the problems that affect flowering dogwoods. Though they bloom later, they have equally gorgeous flowers, edible fruits, and colorful fall foliage. The Samaritan® Japanese Dogwood is an especially attractive form with variegated white and green foliage. Or, you might love one of the Rutgers hybrids from Rutgers University. These exciting new trees have excellent disease resistance as well. Stellar Pink® and Celestial® are two popular selections. We are particularly fond of the Starlight® Dogwood, which has large white flowers in late spring.
6 Plant with care
Proper care for any tree, especially flowering dogwoods, starts at planting. When planting:
• Choose a site that’s sunny in the morning (so foliage can dry out after being damp all night) and has good air circulation.
• Plant the rootball two inches higher than grade. This ensures good drainage.
• Fertilize your dogwood with Elements® fertilizer.
• Spread three to four inches of mulch around the tree (but don’t heap it up against the trunk).
Our number one goal is your success. For us, this means growing patiently and intelligently in a way that reduces tree stress, because stressed trees are predisposed to pests and diseases. This means growing a strong and healthy root system, even if it takes more time. After all, our growers have grown flowering dogwoods in containers for many years, and they’ve mastered the techniques required to produce healthy and vigorous trees!
If you’re concerned about your flowering dogwood, please do not hesitate to reach out to us. We’ll advise you and do what we can to get your tree healthy again!
Dogwood Anthracnose Image: Robert L. Anderson, USDA Forest Service, Bugwood.org
Dogwood Borer Image: James Solomon, USDA Forest Service, Bugwood.org
Powdery Mildew Image: John Hartman, University of Kentucky, Bugwood.org