I was slicing cherry tomatoes for a salad yesterday until I came across a couple of tomatoes with black spots on their skin. The first question that popped in my mind was, “Are these even safe to eat?”
So I put my knife down, opened my laptop, and started researching on the Internet. Let’s just say it turned out that I wasn’t the only one asking.
Here’s what I found.
Are tomatoes with black spots safe to eat?
Black spots can appear on the skin of your tomatoes because of anthracnose, a plant disease caused by fungi that emerge in warm temperatures and wet weather. The tomatoes are safe to eat as long as cut out the affected areas.
The fungi survive winter by growing in dead twigs and fallen leaves. Rainy weather creates ideal conditions for their spores to spread.
The term that farmers and other folks in agriculture use to describe the plant disease caused by this type of fungi is anthracnose, also known as Colletotrichum coccodes in Latin.
The dark spots on tomatoes are actually dead cells. This is why the skin of the tomatoes under these dark spots is usually soft and unlively and can oftentimes appear as sunken-in.
Anthracnose can infect green and ripe tomatoes, typically in warm temperatures, usually above 80°F (27°C), and wet weather, especially in several days of consecutive rain.
“Growth of C. coccodes is most rapid at 80°F, although the fungus can cause infections over a wide range of temperatures (55°-95°F).” says a 1987 paper by Helene Dillard, who is now dean of the College of Agricultural and Environmental Sciences at UC Davis.
“Wet weather promotes disease development, and splashing water in the form of rain or overhead irrigation favors the spread of the disease.”Dillard (1987), Tomato Anthracnose Fact Sheet
The dark spots caused by anthracnose are not easy to identify on green tomatoes straight away but develop relatively quickly as the fruit ripens.
“As the spots grow, they can coalesce and bigger areas develop,” writes Gretchen Voyle, Horticulture Educator at Michigan State University (MSU), on the institution’s website.
“On ripe fruit, a spot or lesion can develop in five to six days.”
The good news for home cooks is that, as long as you cut out and throw away the affected areas of the tomato, it is generally safe to eat tomatoes infected with anthracnose.
The more you cook, the more tomatoes infected by anthracnose you will come across—especially if those tomatoes are grown locally and organically in wet weather conditions.
Before cutting out the areas with black spots on my cherry tomatoes, I sliced them in two and made a photo of those of you who are curious how they looked on the inside:
I’m not an agriculture expert, but it looked to me as if the two cherry tomatoes in my fridge were fairly early into their anthracnose infection.