Spot Anthracnose on Dogwood

A spray will not un-spot this year’s bracts, because those pinpricks started when the flower buds opened in the rain, so rake the fallen leaves and spotted bracts tonight and wait for bud break if last year’s show was ugly on a young tree. Spot anthracnose is the fungus Elsinoë corni. People still say Elsinoë leaf spot, then it is this disease. It waits out winter on last year’s twigs and fruit, then splashes onto opening bracts and young leaves when spring stays wet.

On flowering dogwood the first useful sign is a tiny round spot with a reddish-purple border and a tan or almost white center, often first on the white bracts people call petals. The spots are all about the same pinhead-to-eighth-inch size. Later the centers fall out, so the leaf looks shot-holed, and a badly spotted bract can pucker or drop. The twigs stay alive. Hanging gray leaves and a dying branch are dogwood anthracnose, a different fungus. A white film in summer is powdery mildew.

Skip the bottle on spotted bracts. Rake the leaves

Once a bract is spotted, that tissue is already infected, so a bottle now cannot rewind the white. The useful job this season is to cut next spring’s splash, because the fungus spends winter on twigs and leftover fruit as well as in the litter. Rake spotted bracts and fallen leaves, then bag them or put them in household trash. Do not spread that litter back under the same flowering dogwood as mulch. A cold pile under the canopy still wets up and shoots spores when April rains. Raking is not a one-year erase, because the fungus also waits on the shoots, so you still look again at bud break.

Thin a crowded canopy so leaves dry after rain, and water the root zone with a soaker, not a sprinkler on the bracts, because this fungus needs wet tissue as the buds open. In a dry bloom week you may see almost nothing. In a wet April the same tree can look peppered. A flowering dogwood in hot sun with spotted bracts is still this fungus, not a reason to panic about the shade-loving anthracnose that girdles wood.

Skip a routine spray. Severity follows the rain, so a calendar bottle every spring is not the home-yard job. If last year was ugly on a young specimen you mean to keep, a labeled protectant has to start at bud break, when the flower buds first show color, and keep going until the leaves are fully expanded, on the label interval, shorter when the week stays wet. Chlorothalonil, mancozeb, copper, and thiophanate-methyl are the names extension actually uses. Read the current label for dogwood. A spray in May on already-spotted bracts does not un-spot them. Skip the brand aisle as the plan. Neem and a kitchen baking-soda mix are leftover; they do not replace raking.

1. Confirm. Tiny spots, all about the same size, with a purple ring and a tan or pale center, first on the white bracts. Twigs on that shoot still have live buds. Hanging gray leaves, or a white film, are different jobs.
2. Rake spotted bracts and fallen leaves. Bag them. Do not mulch them back under this dogwood.
3. Water the soil, not the bracts, and open the canopy so new leaves dry after rain.
4. Skip the bottle unless last year was ugly on a young tree you still want clean bracts. Then a labeled protectant starts at bud break, not on tissue that is already spotted.

Tiny purple-border pinpricks on the bracts, then shot holes

Look at the white bracts while the tree is in bloom, because that is when this fungus shows first and the spots are easiest to tell from later leaf blotches. Each spot is tiny and round, usually from a pinhead up to about an eighth of an inch on the bract, with a reddish-purple border and a dusty yellow, tan, or almost white center. The spots stay about the same size as each other, which is the useful tell. Leaves pick up the same rings as they expand, often even smaller, and young leaves can show a yellow halo that fades as the leaf hardens.

As the spots age, the dead centers often drop out, so the leaf looks shot-holed or ragged. Badly spotted bracts wrinkle and can drop, and a heavily infected flower bud may never open. Green shoots and the berries can pick up elongated purple-margin marks, still without killing the wood. If the bloom week stayed dry, you may see almost no bract spotting, and then the leaves are usually milder too, because the same wet spell drives both.

Hanging blighted leaves and dying twigs are a different anthracnose

Hanging gray or brown leaves that stay stuck on the tips, irregular tan blotches that run along a vein, and a twig that dies back into a sunken canker are dogwood anthracnose, the fungus Discula destructiva. That disease moves from the leaf into the wood and can kill a flowering dogwood. This spot fungus does not. Do not prune the canopy for pinhead bract spots, and do not run that Discula cut-and-spray calendar on a tree whose only mark is these small rings. See that disease if a lower branch is dying and blighted leaves still hang.

A dusty white coat on the leaf, or leaves that twist and bronze in summer without hanging gray tissue, is powdery mildew. Do not copy a mildew sulfur program onto peppered bracts. Larger angular spots that show up in late summer, with the canopy still full, are Septoria leaf spot or Cercospora leaf spot. Those are later cosmetics. Rake those leaves too, and do not treat them as this April bract job. Even browning of the leaf edge after a hot, windy week, with no purple rings, is drought scorch. Flowering dogwood is shallow-rooted, so water the roots. A sunken, leaking patch at the soil line is crown canker from a wound at the flare, not this bract fungus walking down the trunk.

These spots do not kill the tree

This fungus spoils the bloom in a wet spring, and it can pucker leaves and drop a few early, but it does not girdle a branch and it does not take the tree down. A flowering dogwood that looks peppered in April still sets next year’s buds on the same wood. The spotted bract will not turn white again, so pick the fallen ones for next year rather than waiting for a miracle spray. Live with a year of ugly flowers if you already missed bud break. Spend the effort on the rake, then look again when the flower buds swell.

What comes back is the wet bloom, because the fungus waits on the twigs as well as in the litter, and not every spring is wet enough to pepper the bracts. One clean-up week does not end it. Keep raking through the next few falls. Kousa dogwood can pick up the same tiny rings, and it is still a cosmetic mark, not a reason to replace the tree. Cherokee Chief, Cherokee Brave, and Cherokee Sunset are names garden centers actually stock as less spotted; they are not a promise, and a wet April can still mark them. Do not take the tree out for ugly bracts. Replace it only if the wood is dying from something else, because hanging blight and a chocolate-brown canker are the other anthracnose.

Related reading

• Dogwood anthracnose — hanging blighted leaves and twig cankers, not pinhead bract spots.
• Powdery mildew — a white film in summer, not purple rings on the bracts.
• Septoria leaf spot — later angular spots, not this April bract job.
• How to grow dogwood — siting, soil, and water for the tree, not this bract fungus.