It looks like calcium deposits on plant leaves, outside

Asked June 19, 2015, 2:30 PM EDT

Can you help me identify what pest I have? The plant leaves have a white, gritty, slightly tacky residue, looks like a calcium deposit, but is only on random leaves. It is only a small group or cluster of this residue on each leaf, so at first I thought it was cigarette ashes. There are no exit holes, curling, or browning of the leaves, and I don't see any bugs at all, underside or top, e.g., no whiteflies or aphids, but I did find a small cluster of raised black bumps on one leaf. Full disclosure, it's an indoor ornamental fig (ficus) I move to a covered porch in the summer. I have also found cobwebs on some of my other plants on the porch, true spider cobwebs not mealybug webs, although I don't know if the two are related. I was thinking of trying a DIY 'natural' pest control recipe, dish soap and cooking oil or the like, but I want to double check with you if that would be effective since I'm not sure what I have. Thank you kindly! Nancy

Baltimore Maryland houseplants pest control ficus

3 Responses

Is there a sticky residue on any of the leaves?
Can you use your fingernail to dislodge the bumps?
It sounds like you may have scale insects, which suck plant juices. They don't look like what we'd normally expect an insect to look like, because they spend most of their lives settled in one spot and you don't see their bodies, which are under cover.
You could try scraping the bumps off, spraying it good with the hose and then monitoring carefully. Scale can be a stubborn problem though, and you could also go to a nursery and get a granular insecticide labeled for houseplants with the active ingredient imidacloprid. It is a systemic that you water in and it goes into the plant. Follow label instructions carefully.
Spiders and their webbing are natural and great outdoors. They will not harm your plant.
cm

Yes and yes. Thank you, I'll start with cleaning the leaves and also make it a point to start with a systemic insecticide as you describe. Much appreciated!

Yes and yes. Thank you, I'll start with cleaning the leaves and also make it a point to start with a systemic insecticide as you describe. Much appreciated!