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Cercospora Leaf Spot

Cercospora Leaf Spot

Cercospora species

Fungalalso: Cercospora

A common fungal leaf spot that speckles the foliage of beets, Swiss chard, and many other crops with small gray-centered spots ringed in reddish-purple. In warm, humid weather it can spread fast and brown out the leaves, cutting both the look and the yield of leafy and root crops. Wet foliage and crowded plantings feed it.

🔎 How to spot it

Look for many small, round spots, up to a quarter inch across, with ash-gray or tan centers and distinct reddish-purple to brown borders, scattered over the leaves. As spots multiply they merge and whole leaves brown, wither, and die, usually starting on the older, lower leaves. With a hand lens the gray centers may show tiny dark specks.

🥀 Damage it causes

Heavy spotting kills leaf tissue and can collapse the whole canopy of beets, chard, and greens, which both reduces the harvest of the leaves and starves developing roots so they stay small. On crops grown for their greens the spotted, browning foliage is directly unmarketable.

🔬 What causes it

Cercospora leaf spot is caused by Cercospora fungi, which overwinter on infected crop debris and on related weeds and can come in on seed. Spores spread by wind, splashing rain, and overhead watering. The disease is favored by warm, humid weather, roughly 75 to 85 F with wet foliage, so it tends to build through the warm, wet middle of the season.

🛡️ Prevent it

Rotate beets, chard, and related crops to a new spot on a two to three year cycle and clean up crop debris at season end. Space plants for airflow, water at the base rather than overhead, and avoid working among wet plants. Start with clean or treated seed and choose resistant varieties where they are offered.

🧯 If it is already here

Pick off and destroy the first spotted leaves and keep the foliage as dry as possible. On a valued crop, an approved organic fungicide such as copper, applied early and repeated per the label, can slow its spread. Remove and destroy heavily infected plants and all debris at the end of the season so spores do not carry over.

💡 Good to know

The gray center ringed in reddish-purple is the signature that separates Cercospora from other leaf spots. Because it overwinters on debris and nearby weeds, cleanup and rotation matter as much as anything you spray. It is most aggressive in the warm, humid part of summer, easing as conditions dry.

🌱 Plants it affects

277 plants in the library can be affected by this problem

African MarigoldAgapanthusAgeratumAji Amarillo PepperAlice du Pont MandevillaAmethyst Falls WisteriaAnaheim PepperAnemoneAngelique TulipAngeloniaAnnabelle Smooth HydrangeaAnnual VincaApeldoorn TulipApril Tryst CamelliaArizona Sun Blanket FlowerArugula🥕Atomic Red CarrotAugust Beauty GardeniaAutumn Joy SedumBachelor's ButtonBanana PepperBarbara Karst BougainvilleaBecky Shasta DaisyBee BalmBenarys Giant ZinniaBengal Tiger Canna🥬Bibb Lettuce🥬Black Seeded Simpson LettuceBlack-Eyed PeaBlack-eyed Susan VineBlood OrangeBloomsdale SpinachBlue Bird DelphiniumBlue Bird Rose of SharonBlue Fescue🥕Bolero CarrotBrunneraBull's Blood BeetBurning BushButtercrunch LettuceButterfly Blue Pincushion FlowerButterfly Marguerite DaisyButterfly WeedCafe au Lait DahliaCaladiumCalendulaCalibrachoaCalifornia Giant ZinniaCalifornia PoppyCampanulaCardinal FlowerCarolina GeraniumCarolina JessamineCarolina Reaper PepperCascara SagradaCayenne PepperChantenay CarrotChicoryChioggia BeetCleyeraClimbing HydrangeaClimbing Prairie RoseCocktail Vodka BegoniaColeusCollard GreensCoral Drift Groundcover RoseCornelian CherryCosmic Purple CarrotCosmosCreeping PhloxCrimson Cherry RhubarbCubanelle PepperCupani Sweet PeaCylindra BeetDandelionDanvers CarrotDavid Garden PhloxDelft Blue HyacinthDenim n Lace Russian SageDetroit Dark Red BeetDiabolo NinebarkDragon CarrotDusty MillerDutch Master DaffodilEarly Amethyst BeautyberryEastern Red ColumbineEndiveEndless Summer HydrangeaEnglish LavenderEnglish Shelling PeaEvening PrimroseEvergreen HuckleberryFanal AstilbeFeather Reed GrassField PeaFireworks GoldenrodFlamingo Feather CelosiaFlower Record CrocusFountain GrassFoxglove

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.