Euphorbias and their mildew

The Euphorbia meloformis in the foreground had a little bout of mildew, which left scars, called corking

@kansuze was surprised when I told her that her Euphorbia had probably been attacked by mildew but it is a common complaint with Euphorbia, and almost impossible to get rid of. The only way to keep it mostly under control is to keep the plants in full sun, so that the skins are tougher and to make sure that there is good airflow around the plants. I found that colder or rainy weather, even is the soil wasn't watered, or moving plants, which subjects them to stress, is enough to set up a bout of mildew. In general, it doesn't seem to kill the plants, just leaves them with ugly scars and damages flowers.

I think that this is Euhopbia pentops, but I'm not sure. The mildew can be seen on the flower stalks.

There are a couple of ways to treat the mildew either copper spray of an antifungal suitable for roses seems to work, I also used cinnamon powder on the plant in the first picture. I opted to treat the flowers with a dusting of cinnamon too. It's necessary to always rotate treatments instead of using a single one, because fungi easily become resistant to a single treatment if you use it constantly. Prevention is better than cure although the mildew will probably be back f the weather turns rainy.