I bought 3 black knight echeveria’s a while ago. Being a complete novice, I had no clue when the mealy bugs began to feed on them. Despite my efforts late in the infection to combat the mealy bugs, the plants’ leaves all fell off and I purchased 3 new repotted echeverias in September. They’ve been doing well, until a few weeks ago. One of the echeveria’s is looking quite small compared to the other two. I came back from a vacation today and noticed about 3 leaves from the larger two were wilting and came off quite easily. I meticulously studied the plants for a sign of infection. NO LUCK! All I noticed was that they have a few little black holes on the bottom of a few leaves and that they look wilted. Can you suggest what to do?
It’s cold in Vancouver, BC (in fact it snowed about 1 week ago) so they’ve been inside all winter. I’ve kept them in a room that gets at least 3-5 hours of sunlight, WHEN IT’S SUNNY. The room is colder and they are right next to a glass door. I water them maybe 1/4 c. every 2-3 weeks. Except, when I noticed it looked like they were wilting I watered them a little more. The soil doesn’t feel wet, rather, slightly damp. The water is able to drain if they are too wet.
I’m at wits end and need some advice. Thanks. I’ve attached some photos.
My first guess is the smooth polished pebbles are staying wet under the leaves and causing fungal infections. As a rule of thumb we do not use smooth rock as a mulch or decorative top-dressing since the surface tension of water loves to cling to smooth round pebbles and stay wet forever. This gives a place for mold spores to “hatch” and start eating the leaves. Try to find black lava rock or a nice crushed black gravel which is rough and faster drying to use under the rosettes. You can keep the polished black rock on the exposed surface, but don’t let the leaves touch it. It should help keep them from staying too wet. Also during the winter water them well, but only about once a month. They should dry out completely between watering’s. It is OK if they look a little thirsty during the winter since they are basically asleep.
You can treat the plants with 1% Neem Oil solution to help fight off any infection they currently have. Just don’t spray and have in bright sun right away, treat, put somewhere shady for a day or two and then move back to the sun.