Black spot is the disease Georgia rose growers fight most, because warm, wet summers suit that fungus better than any other. Powdery mildew arrives in spring and fall, and downy mildew follows cool, soggy spells. Rose rosette, the one with no cure, is present in the state. Each disease follows its own kind of weather. Growing roses in Georgia goes easier once you know which disease belongs to which month.
Which rose diseases Georgia’s climate brings
Four fungal diseases cause most of the trouble on roses here, and each one tracks a different kind of weather. A fifth, rose rosette, is a virus and gets its own section further down.
What does black spot look like?
Black spot makes round, dark spots with feathery, fringed edges on the upper side of the leaf. The tissue around each spot turns yellow, and the leaf drops. The fungus needs leaves that stay wet for several hours, and a hot, rainy summer with heavy dew supplies that night after night. Spores splash up from fallen leaves and infected canes onto fresh growth. A bad case can strip a bush bare by late summer, which leaves it with little to store for winter. Rake up and discard fallen leaves all season, because they carry the spores. Cercospora leaf spot looks much like black spot, loves the same heat, and gets the same treatment.
How does powdery mildew show up?
Powdery mildew is a white, dusty coating on new leaves, buds and young stems. Affected leaves curl and turn purplish. Unlike most leaf fungi, it does not need wet leaves. It does best where days are warm, nights are cool and the air stays humid, which describes spring and fall in the Piedmont. A rose crowded against a fence or packed into a bed holds humid air longest and gets hit first.
Is downy mildew a problem for roses?
Downy mildew is the least common of the four, but it moves fast. It favors cool, wet, cloudy weather. It shows up as purplish-red to brown patches with angular edges, and leaves can drop within days. On a damp morning, a gray fuzz may show on the underside of the leaf. Growers often mistake it for black spot, and a wrong guess means the wrong fix.
Some roses shrug off these fungi far better than others. The ones that do are listed in Roses That Hold Up in Georgia.
When each one shows up here
Atlanta is the reference point for the dates below. By the NOAA NCEI 1991-2020 climate normals (station USW00013874), the last spring freeze falls between March 11 and March 29, and the first fall freeze between November 13 and December 1. Those are ranges, since the 30 to 70 percent probability band is wide. Atlanta is also an urban heat island. North Georgia and the mountains freeze several weeks earlier in fall, and the coastal plain runs milder, so shift everything below accordingly.
| Months | Disease | What you see first |
|---|---|---|
| March to April | Downy mildew, in cool wet spells | Purplish-red patches on new leaves |
| April to May | Powdery mildew | White dusting on new shoots and buds |
| Late April to June | Black spot begins | Dark spots on the lowest leaves |
| June to September | Black spot, cercospora | Yellowing and leaf drop from the bottom up |
| October to November | Powdery mildew, downy mildew in cool wet spells | White film on late flushes, blotchy leaves |
What shows up first in spring?
Roses leaf out as the freeze risk passes in March. Cool, damp stretches in that window can bring downy mildew on the first soft growth. By April, warm days and chilly nights let powdery mildew settle on tender shoots. Most growers see the first black spots between late April and May, almost always on the lowest leaves, where rain splash lands first.
What changes in summer and fall?
Black spot spreads upward through June, July and August whenever afternoon storms keep leaves wet. Peak summer heat slows powdery mildew, though shady, crowded plants can still carry it. As nights cool in October, mildew returns on the fall flush of growth, and black spot slows. Spores overwinter on canes and leaf litter, so winter cleanup counts. Timing the cut is covered in When to Prune Roses in Georgia.
What this changes about spacing and watering
Every one of these fungi needs either wet leaves or still, humid air around them. Spacing and watering take away both, and no spray does the same work.
How far apart should roses be planted for airflow?
Give hybrid teas and floribundas generous room between plants. Shrub roses want more room, and large shrub roses and climbers do better with the most space. Keep some space between a rose and any wall or fence, so wind can pass behind it. Morning sun helps, because it burns off dew early. Aim for plenty of direct light, with the morning hours included.
Open the center of the bush when you prune, so air moves through the canes. A layer of mulch also helps. It keeps soil from splashing onto lower leaves, and soil splash is how many spores climb the plant.
What time of day should you water roses?
Water in the early morning. Leaves then dry within an hour or two. Evening watering leaves foliage damp all night, which is exactly the condition black spot needs. Run a drip line or soaker hose along the base of the plant and skip overhead sprinklers. If a sprinkler is your only option, run it at dawn and keep it brief. Roses want steady water from rain and irrigation combined, delivered in a deep soak rather than daily sprinkles.
Fungicide sprays protect healthy leaves but do not cure spots that have already formed. They have to go on before infection, and the label sets the schedule. Your county Extension office can tell you what is approved and when to start.
Rose rosette: the one that means digging the plant up
Rose rosette is present in Georgia. A virus causes it, and a microscopic mite carries it from plant to plant on the wind. Wild multiflora rose along fence lines and roadsides is a common source. No spray, pruning cut or soil treatment cures it. The plant has to come out, roots and all.
How do you recognize rose rosette?
Look for a witches’ broom, a dense tangle of short shoots bunched at the end of a cane. The new growth is red or deep purple and stays that way. Healthy roses also push red growth in spring, but it fades to green within a couple of weeks. Rosette canes are unusually thick and soft and carry far more thorns than normal. Leaves come in small, crinkled and misshapen, and flowers open deformed or not at all. Symptoms may show on one cane first, but the virus moves through the whole plant.
What do you do with an infected plant?
Cutting off the affected cane does not save the rose. The virus stays in the plant, and an infected rose usually declines over a few years. Meanwhile it can pass the disease to its neighbors. Dig out the whole plant, roots included. Leftover roots can resprout and carry the virus. Bag the plant and put it in the trash. Do not compost it. If you can, remove any wild multiflora rose nearby too. Report suspected cases to your county Extension office, because early reports help track where the disease is moving.
Checking this against your own county
Georgia runs from the mountains to the coast, and disease timing shifts with elevation and distance from the coast. University of Georgia Extension has an office for your county, and its agents know which diseases are active locally. They can identify what is on a leaf and confirm or rule out rose rosette. Take a cutting to your county Extension office that shows both healthy and affected growth. Seal it in a dry bag and carry it in soon after cutting, before it wilts.
Common questions
Will black spot kill a rose?
Rarely, and not directly. Repeated defoliation weakens the plant, so it makes less food and enters winter in poor shape. Pick off spotted leaves, clean up fallen ones, and keep the foliage dry. Most roses push out new leaves once conditions improve.
Does mildew mean I’m watering too much?
Not usually. Powdery mildew spreads in humid air, even when leaves are dry. Poor airflow and shade matter more than how much you water, so check spacing and sun before changing your watering routine.
Is red new growth always rose rosette?
No. Healthy roses push out red or bronze leaves in spring, and they turn green as they mature. Rosette growth stays red or purple and comes with thick canes, heavy thorning and a bunched, broom-like shape. If you are unsure, have the county Extension office look at it.
Can I plant a new rose where a diseased one came out?
After black spot or mildew, yes. Replace the top layer of mulch and clear every fallen leaf first. After rose rosette, dig out every root you can find before replanting. Keep an eye on the new plant for red, distorted growth, and remove any wild multiflora rose within reach.