Hydrangea Cane Borer
Q: For a number of years I’ve had a problem with some sort of borer getting into the stems of my hydrangeas. What can I do to get rid of them?
A: There are any number of cane boring insect larvae, some of which affect hydrangea. Insecticides don’t offer much control. The best therapy is to cut a cane successively lower until you find the spot where damage stops. The borer is above that point. Collect all of your clippings and put them in the garbage. It may take a couple of years but regularly removing the grubs will result in a lower population.