Using Treated Leaves As Vegetable Garden Mulch – Is It Safe?

Q: I use Bayer Protect and Feed on oak trees to control the caterpillars. I collect the leaves to mulch my vegetable garden. How long does it take for the chemicals to break down and is it safe to use them in a vegetable garden?

A: “Safe” is a loaded word but we do know that imidacloprid is recommended by experts for controlling wooly adelgids in hemlock trees. Researchers say it takes a year for the insecticide to be fully distributed in a tree but once in place, it kills the needle-feeding insects for five years. Thus your oak tree may have the chemical in the leaves for at least a couple of years. But keep in mind that imidacloprid is frequently used as a seedling drench on vegetable plants that gardeners commonly buy. So I can’t say it’s “safe”, but based on scientific research I would feel comfortable eating vegetables mulched with your oak leaves.