Most welcome CH. If the black substance appears to be building up ----- such as forming layers and if it appears to be taking out/destroying portions of the leaf, then Ray's suggestion of a copper treatment could put a stop to whatever it is. And if the spread just so-happens to continue ......... then cutting could be then be necessary to do (- mentioned by E.S.).
And also could ask the seller if they were aware of those particular features. All behind you on this one! Nice orchid!
|