Euphorbia robbiae turns black
I'm trying to understand why my euphorbia starts out very robust and lush in the spring, but then some areas begin to turn black mid-season. I first noticed it last year or the year before and removed plants that were affected, and replaced with ones that were growing well. Is it something in the soil that can spread to other areas, and if so, what and how would I treat it. Thanks!
Montgomery County Maryland
Since this has happened for two years, yet the plants continue to return in the spring, it sounds like Southern blight. Here is our webpage about it and how to manage it: https://extension.umd.edu/hgic/southern-blight-flowersgroundcovers
Keep in mind that the little round balls of sclerotia are very tiny and though they start out white, they are very hard to see once they turn brown.