Plant Doctor Archive

Scale-like creatures on bromeliad

Question A BROMELIAD I acquired recently has what appear to be small black scales on the undersides of the lower leaves. Are they scales and if so what should I do about them?

Answer  ALTHOUGH they do look like tiny scale insects, these black spots on the sample you sent are actually the excretions of small flies known as cecids and phorids. While they don’t harm plants, these flies seem to like to occasionally deposit their droppings on them.

You can remove the spots by simply washing them off with soapy water or just scraping them with your fingernails.

Cecid and phorid flies tend to breed in damp shady parts of the garden. They’re not a pest of plants apart from the occasional deposit on the leaves — I’ve even known them to leave their marks on plastic pots and walls of greenhouses.

Weekend Gardener, Issue 162, 2005, Page 24