Kale with little black spots on stems and leaves

(There are many fungi within the Alternaria genus; check out what some of them can do to oranges and broccoli.)

Whatever it is, she said, the trouble likely started back in the field, when the leaves were wet for long periods of time and water pooled along the stems. Moisture is just what thirsty microbes need to do their dirty work. 

As cases of Alternaria advance in kale, you typically see a yellow ring around the black spots. Scientists call them chlorotic halos; “chlorotic” because they’re failing to produce the chlorophyll that normally makes the leaves and stems green. The yellowing effect can be traced to toxins the pathogen releases as it breaks down the leaf, Smart said. As Alternaria continues to ravage the kale, the lesions will expand into spots with target-like concentric rings, according to a University of Massachusetts Amherst fact sheet. The centers often turn brown and crack or fall away. 

How can the rest of the kale still look fine if it’s sick?

“The symptoms appear to be local lesions (localized to one area) and not moving throughout the plant,” Smart wrote to me after I sent these images. “Plants really start to look bad when you have a root problem and the whole plant wilts, or if there is a pathogen inside the plant clogging up the veins. These spots appear to come from pathogens in the air or in rain-splashed water that are landing on the leaf.” 

Why does some kale have fungal black spots?

Alternaria fungi tend to release their spores during warm, humid periods. Their spores can spread via wind, water, insects, farm equipment and workers moving through fields. Spores can also show up on or even inside seeds.  

Alternaria fungi that specialize in kale also enjoy its brassica cousins, like broccoli and cauliflower. Once the fungus settles on a tasty plant, it enjoys cool, wet weather. This is a perfect match for fall in New England and parts of the Mid-Atlantic, which is all consistent with where and when the kale featured in this post was harvested. 

I just ate some kale with black spots! Am I going to get sick?

It’s very unlikely you’ll come down with a food-borne illness after eating kale flecked with black spots. If you were to get sick from kale, it would probably be from invisible-to-the-naked-eye contamination from a human pathogen like salmonella. Such illness-causing contamination is rare and the contaminated produce can look perfectly fine. 

That said, some fungi, like Alternaria, can deposit toxins in food (it’s how they break the food down so they can consume it). The toxins are usually targeted at the plant but some potentially could affect people, particularly with enough exposure over time. Additionally, people with serious allergies to airborne mold may be sensitive to any Alternaria spores they manage to inhale. So, while consuming the black dots is unlikely to cause immediate illness and may never negatively affect you, we recommend against it (as well as any other unexpected fungus you find on your food). Also? With all those fungal juices they’re releasing into the kale, those areas might taste off.  

But again, the areas that still look good, are still fine. 

“It’s sad to see on such beautiful kale,” Smart wrote. 

Thanks to reader Kai R. of Arlington, Va. for sharing images of her kale for this post!