[vc_row][vc_column width=”1/1″][vc_column_text]I love beets and chard, and I have tried to grow them with varying success. This year, I planted Early Wonder Beets and Bright Lights Swiss Chard that I started using Winter Sowing, which you can read about here.
Sadly, even though the beets are growing like crazy, some of them seem to with Cercospora beticola (see photo below). C. beticola is a fungus that causes small circular spots on beets, Swiss Chard, sugar beet, and spinach.
According to the University of Massachusetts at Amherst:
Symptoms occur as numerous, initially small circular leaf spots. Spots have a pale brown to off-white center with a red margin. Lesions expand in size, coalesce, turn gray as the fungus sporulates, and can result in extensive loss of foliage. Leaves at the center of the plant are often less severely affected. The pathogen produces sclerotia or stromata which can be seen with a hand lens as small, black dots in the center of lesions. Lesions may also occur on petioles, flower bracts, seed pods, and seeds. Leaf symptoms are similar to those caused by Beet Phoma (Phoma betae), except that the phoma will have more obvious tiny fruiting bodies in the lesions and can also affect the roots.
As you can see below, my beets have only purple spots. Most of the photos that I have seen on the web have brown spots. But, there have been a couple of photos with purple spots. I suppose, since the beets have so much red/purple pigment in them, the pigment tends to turn the spots purple to some extent. I’m not sure if the spots on my beets would turn brown, or not. I suppose that time would tell, but I plan to yank the infected beets out ASAP (i.e., tomorrow).[/vc_column_text][vcex_spacing size=”30px”][vc_single_image image=”6821″ border_color=”grey” img_link_target=”_self” alignment=”center”][vcex_spacing size=”30px”][vc_column_text]Upon conducting a little research, I have found that Cercospora beticola can live in the soil for up to two years, and that it is also found in crop residues, on saved seed and on host weeds (i.e., things related to beets, chard and spinach). The infection can be spread by crop residues, insects, rain splash, wind, and the like. It grows well in high relative humidity and temperatures between 75-85˚ F, and boy have we had a lot of that lately.
There are some other beet diseases that can look similar to C. beticola. Pseudomonas syringae pv. aptata is the most notable (bacterial leaf spot) is the most notable, and may be difficult to distinguish from C. beticola. The University of Minnesota has a terrific color handout comparing Cercospora versus
bacterial leaf spots on sugar beet, and which shows the differences between the two infections. And here is another handout from the University of Nebraska.
I couldn’t find many treatments for leaf spot (C. beticola), though this is a big problem in sugar beet cultivation. Though there are some chemical treatments, such as copper sulfate anti-fungals, there are resistant strains of C. beticola. Thus, cleanliness and crop rotation with non-host crops (not in the Chenopodium family) on a schedule of two to three years seems to be one of the best treatments. Avoiding water splash, over-crowding and keeping a tight control of bugs also helps a lot.
I tried to find out if it was dangerous to eat beets infected with C. beticola, but I couldn’t find any mention of it, other than a heavy infection can make the crop look unappetizing. So, you will have to decide for yourself if it is OK to eat leaves infected with C. beticola or not.
On a side note, all of this talk of sugar beets reminds me of growing up on Grand Forks, North Dakota. We lived in a house on the crest of the flood plain of the Red River. Across the river from our house, there was a farm that raised sugar beets and potatoes. There may have been another crop in there, but I can’t remember for sure. However, the sugar beets were certainly rotated with the potatoes. After the sugar beets were harvested, you would see enormous piles of them at the Crystal Sugar factory. It was kind of remarkable, because sugar beets are huge, and the piles looked like they were made of huge, dirty white rocks. You can see a picture of that here.
Here are a few more useful resources, if you are interested in beets.
- A list of Beet Diseases (click here) from Wikipedia;
- A discussion of beet diseases (click here), pests and propagation from Plant Village; and
- A discussion of a wide variety of veggie diseases (click here), including beets, from the Department of Agriculture and Food of Western Australia.
If you have had problems with beet infections, I would be interested to know how to solved the problem.
Happy gardening! :D[/vc_column_text][vcex_spacing size=”30px”][/vc_column][/vc_row]