Question
I have about 8 Jades in my bow window & various other plants the big jade is about 25yrs old. Overnight it seems like they are covered in big black spots & leaves are dropping off quickly. What is it? Could it spread 2 other plants & is there a cure?

Answer
Hi Val,

As a precaution, segregate the healthy plants from the one showing these symptoms.  

A couple of questions, what do the black spots look like, are they watery? Do they have any kind of oily nature?  Is there any stickiness on the leaves or areas surrounding the plants?  Can you see any small round-to-oval "discs" on the leaves or stems?

There is a condition called sooty mold which appears as black spots on the leaves of plants infested with scale insects.  Sooty mold can have an oily texture to it, but the black spots do not look "wet". They may appear to be dusty or dirty.  Leaf drop is a common symptom in an advanced scale infestation.  Examine the plant very, very closely for these small flat discs (1/8 inch, 3-5 mm).  If you find them, then you need to remove them.  The adults (the actual hard disc is a shell that covers the insect) are fixed and can be removed with a little elbow grease and some soapy water.  It may not be easy with a large plant or heavy infestation.  The juveniles are mobile, and they appears as small white flecks.  They can be treated with a swab and some 70% isopropyl (rubbing) alcohol.  They can be found just about anywhere in the juvenile stage, but sometimes they will be found in the small crotches of branches.

If you can, send a close-up picture of the black lesions to:
[email protected]

All the best!