This has appeared on the leaves of my 4 tomatillo plants in the past couple of days. I have a feeling it is something nasty... Front view ( photo / image / picture from Kiasmum's Garden ) Back view ( photo / image / picture from Kiasmum's Garden ) Nothing else is touched so far.
Karin, I don't think you need to over worry. It looks like the cells erupted after a good rain and a lot of heat. Not 100% sure, but I think it is a physical stress that is causing the problem. you can pick off those leaves (since they are ugly and practically useless anyhow) and see if this gets better.
Thank you Carolyn,perhaps they don't like being in the greenhouse as I'm waiting for a window in the weather (and my back) to get them outside. Fingers crossed.
