A: You have been visited by leafrollers! These caterpillars do a lot of damage to cannas and the vinca groundcovers, especially vinca major, in a very short period of time. The good news is that your ground cover should be just fine. Here’s how to get it back to normal.
Start by shearing the vinca major to within a few inches of the ground with a hedge trimmer, if it’s been badly hit. This won’t hurt it, but will let the plant get on with making nice, fresh growth. Then spray the area with a systemically absorbed pesticide – we usually recommend Bonide Systemic Insect Control (acephate), but several other pesticides will help as well. Anything that will kill most caterpillars will work.
(As a note: hedge trimmer, please, not a line trimmer or a lawn mower. Weed-eater style trimmers will beat things half to death, and mowers can get tangled.)
Lightly fertilize the area, and give it a bit more water than usual until you start to get healthy new growth. The beds will recover.
Burton specializes in diagnosing and solving plant problems. If you have a question for Burton, please email him at firstname.lastname@example.org and include photos showing the problem.