Brown spots scattered across redbud leaves are very often the work of a common fungus, and the disease it causes is more of a cosmetic problem than a threat to the tree.1Lady Bird Johnson Wildflower Center. Brown spots on young redbuds in Lincoln TX The fungus attacks leaves, not the trunk or roots, and a redbud grows a fresh set of leaves every spring. Most of the work of controlling it is housekeeping around the tree, and spraying is rarely needed.
What Cercospora Leaf Spot Looks Like on Redbud
Cercospora leaf spot is caused by Cercospora fungi, and redbuds can be infected by more than one kind.2Oklahoma State University Extension. Anthracnose and Other Common Leaf Diseases of Deciduous Shade Trees The spots are brown, round to angular, and about 1/8 to 1/4 inch across, roughly pencil-eraser size or smaller.3Texas Plant Disease Handbook. Redbud Their color can range from gray to brown, and they often have a darker border.4Ask Extension. Redbud tree Many show a lighter halo around the edge.5Texas Plant Disease Handbook. Redbud They tend to appear first on the upper side of the leaf.6Lady Bird Johnson Wildflower Center. Brown spots on young redbuds in Lincoln TX
To inspect your tree, start with the lower, shadier branches, where leaves stay damp longest. Turn several leaves over and compare the top and bottom surfaces.
As a spot grows, its center turns tan and dead, and the fungus makes new spores there.7Purdue Plant Doctor. How to Identify and Treat Cercospora Leaf Spot on Redbud In damp weather the spots multiply and merge into larger brown patches. Heavily spotted leaves can turn brown.8Ask Extension. Redbud tree Badly affected trees may drop leaves earlier than normal in late summer or fall.9Texas Plant Disease Handbook. Redbud A tree with bare branches in fall is not necessarily dying.
Redbud leaves can show brown marks from other causes. Leaf scorch from hot, dry wind or drought usually browns the leaf edges and tips rather than making separate spots. Other fungal diseases and insect damage can also leave spots or holes, so the leaf spot is a likely suspect but not a certain one from a glance.
Wilting, dying branches or cracked bark point to a different problem. A local extension office can confirm the cause from a sample of leaves.
Is Cercospora Leaf Spot Harmful to Your Redbud
The disease is rarely serious, so most trees need no chemical treatment.10Lady Bird Johnson Wildflower Center. Brown spots on young redbuds in Lincoln TX The damage is limited to the leaves and to early leaf drop.11Texas Plant Disease Handbook. Redbud There is a caveat. In a trial of many redbud varieties, the worst-affected ones showed heavy spotting and early leaf loss, and survival differed among varieties.12Plant Disease Management Reports. Survival and reaction of redbud cultivars to Cercospora leaf spot in Central Alabama A susceptible tree hit hard year after year deserves more attention than one with a few spots.
Early leaf drop usually isn’t fatal because leaves that fall in late summer have already done most of the season’s food-making. The tree pushes out a full new set of leaves the next spring. The real concern is repetition: several years of heavy early leaf loss can drain stored energy, especially if drought or poor soil is also stressing the tree.
Young or newly planted redbuds are a different case. Small trees have fewer leaves to spare, so heavy spotting matters more. They are also easier to inspect, clean up under and treat. Watering well at the roots during dry spells helps them recover.
How the Fungus Survives and Spreads
The fungus survives the winter in fallen leaves from trees infected the season before.13Purdue Plant Doctor. How to Identify and Treat Cercospora Leaf Spot on Redbud Spores that land on new leaves infect them when the leaves are wet or the air is very humid.14Purdue Plant Doctor. How to Identify and Treat Cercospora Leaf Spot on Redbud In related Cercospora disease on other plants, infection needed leaf wetness or humidity above 95%.15PubMed. Factors affecting the onset of cercospora leaf spot epidemics in sugar beet and establishment of disease-monitoring thresholds Spores made in older spots are then splashed by water onto healthy leaves, spreading the disease.16Purdue Plant Doctor. How to Identify and Treat Cercospora Leaf Spot on Redbud Rainy springs, overhead sprinklers and still, damp air all favor more spots.
Several conditions raise the risk. Sprinklers that spray the leaves keep them wet for hours. Crowded or shady spots dry slowly after rain or dew. Thick piles of old leaves under the tree keep the fungus close, and lower branches near the ground get splashed most.
Cleanup and Watering Steps That Control Leaf Spot
Cleaning up is one of the best ways to treat leaf spot, because it removes the fungus that would survive the winter.17Ask Extension. Redbud tree Rake up fallen leaves and put them in the trash.18Ask Extension. Redbud tree Remove low-hanging spotted leaves and prune damaged parts.19Ask Extension. Redbud tree Clean garden tools after use.20Ask Extension. Redbud tree Bag or trash the leaves instead of mulching them under the tree, since mulching leaves the fungus in place.
Composting is a common mistake. A casual backyard pile may not get hot enough to kill the fungus, and spreading that compost back under trees can return spores. Trashing infected leaves is the safer choice.
Keeping leaves dry stops new infections. Water the tree at its base, since wet leaves encourage fungal disease.21Springfield News-Leader. Master gardener shares tips for redbud spots and pruning yew trees If you have a sprinkler system, make sure it isn’t spraying the tree’s foliage.22Ask Extension. Redbud tree
A soaker hose or a slow hose trickle at the root zone waters without wetting leaves. Water in the morning so any splashed leaves dry quickly. Mulch around the base also reduces soil splashing onto low leaves.
When and How to Use a Copper Fungicide
Fungicide is not normally needed, but a copper spray such as Liquid Copper can be used in severe cases or to improve the tree’s look.23Lady Bird Johnson Wildflower Center. Brown spots on young redbuds in Lincoln TX It is a backup to cleanup, not a replacement for it.24Springfield News-Leader. Master gardener shares tips for redbud spots and pruning yew trees
Timing makes the spray work:
- Spray first when you notice leaf spots.25Lady Bird Johnson Wildflower Center. Brown spots on young redbuds in Lincoln TX
- Spray again about 14 to 20 days later.26Lady Bird Johnson Wildflower Center. Brown spots on young redbuds in Lincoln TX
- The next spring, spray again shortly after the buds open to keep the disease from carrying over.27Lady Bird Johnson Wildflower Center – Ask Mr. Smarty Plants. Brown spots on young redbuds in Lincoln TX
A copper spray works as a protectant: it shields healthy leaves from new infection. It does not erase spots already on the leaves, so those will stay. Spraying late in the season, once most leaves are already spotted, gains little because the damage is done. Coverage matters, so wet both the top and underside of the leaves.
Read the product label first and follow it for mixing rate and for the protective gear it calls for. Choose a calm, dry day so the spray stays on the leaves instead of drifting or washing off. A mature redbud may be taller than a home sprayer can reach, and in that case hiring an arborist is a sensible option.
Redbud Varieties Less Likely to Get Leaf Spot
Redbud varieties differ greatly in how much leaf spot they get.28Plant Disease Management Reports. Survival and reaction of redbud cultivars to Cercospora leaf spot in Central Alabama In one field trial, Ace of Hearts, Pink Heartbreaker, Oklahoma and Traveler showed no leaf spot.29Plant Disease Management Reports. Survival and reaction of redbud cultivars to Cercospora leaf spot in Central Alabama The Rising Sun, Floating Clouds, Alba (a Chinese redbud) and Don Egolf had the most damage.30Plant Disease Management Reports. Survival and reaction of redbud cultivars to Cercospora leaf spot in Central Alabama Tennessee Pink also had heavy spotting.31Plant Disease Management Reports. Survival and reaction of redbud cultivars to Cercospora leaf spot in Central Alabama If you are replacing a tree or adding one in a humid area, choosing a resistant variety can spare you the yearly cleanup.
When buying, look at the plant tag for the variety name, because “redbud” alone doesn’t tell you how it will fare. Ask the nursery whether a given variety holds up to leaf spot in your area. The results came from a trial in one region, so performance in your yard may differ, and even a resistant variety still benefits from good watering and cleanup.
Some of the showiest varieties, with unusual leaf color, were among the hardest hit in the trial, so appearance and resistance can pull in different directions. Planting in a sunny, airy spot lowers the risk for any variety, because leaves dry faster there.