Can Bacteria Breakdown Pesticides and Herbicides?

Read the labels and follow the manufacturer’s advice.

In general the answer is yes. Almost all domestic pesticides and herbicides can be broken down in a compost heap. The hotter the heap and the longer the material spends in the heap or unit, the less likely for the possibility of problems to occur. Today's chemicals are designed and tested to ensure they have no long-term residual effect on soil or the environment.

Some chemicals are designed to kill fungi and bacteria (e.g. bleach, fungicides) and are lethal on application, but rapidly lose effectiveness over time. If you pour neat bleach or leftover fungicide onto your heap, it will kill 99% of the bacteria. However after a few days, the bleach will be salt (NaCl) and the bacteria will start to re-colonise the heap.