What's on my cabbage?

Asked May 27, 2020, 2:45 PM EDT

For several years we have raised Chinese cabbage with great success. This year we planted a trial bed of Merlot Chinese Cabbage (without great success!) Last week when I went to harvest in our hoop house, I found that the outer leaves of several Merlot Cabbages had discoloration. This bed is next to a bed of regular green Chinese cabbage and none of them were affected. I quickly harvested the Merlot heads, disposing of the outer leaves. The inside heads were okay, and the taste was good. Is this a type of fungus on the Merlots?

Alpena County Michigan

3 Responses

Hello,

Looking at the affected areas, I don't see anything fuzzy in the yellow that would suggest spores are being produced. The pattern and shape of the yellowed areas isn't symptomatic for any brassica disease. Was it last week the first time you noticed these symptoms? Had there been any discoloration previously?

I think this looks abiotic. Could these leaves have been impacted by the frost/freeze events we had earlier in the month? Different varieties have different cold tolerances. Is there anything about the placement of the bed that comes from that might cause differences in plant nutrition or sun exposure?

If anything comes to mind, let me know.

Thanks for your response. I AM happy that it does not appear to be a fungus. An added thought, however: the week before I had sprayed with Bee-Safe that claims to help control insects, mites, and fungus. The spray comes out a rather yellow hue, like the leaf spots. Could these be caused by my over-spraying these particular plants?

You said this was in a hoophouse? Was it hot and humid when you sprayed? Sometimes spray residues, including those of organic products, can damage foliage on a hot day. It looks like Bee-Safe does have oils in it, and oils can cause plant damage if the weather conditions are right. This page has some info on this: https://extension.umd.edu/hgic/topics/fertilizer-or-pesticide-burn-vegetables