I didn't worry about pesticides in leaves until this year. Mostly people didn't treat the actual trees with anything but now they do since the Spotted Lantern Fly came to town.

It was originally discovered in Reading PA and now it is spreading across PA. Maple trees are their favorite and this year my Silver Maple trunk was covered with them as in THOUSANDS of them.

People are using soil drenches of chemicals like Sevin as a systemic poison so I will no longer use leaves from other people.

I fear that all of this poison is going to end up in the water table. As a former beekeeper I was contacted by Penn State University asking for a sample of my honey. They are now finding pesticide residue even in organic honey. The Spotted Lantern Fly secretes a honeydew which attracts the bees and they get exposed to the poison too and bring it back to the hive. It's awful.

Years ago on Garden Web there was a thread about why nothing can be safe to compost. No matter what organic matter was named, someone could come up for a potential reason why it was unsafe. Several years ago the head of our local community gardens used such claims to not use municipal compost. Pesticides and herbicides are now primarily manufactured to have a shorter half life. Many are such that heat of composting neutralizes them.

Martin

I found a study while browsing around, it is from 1996 in New Jersey and at that time the contaminants in leaves were mostly due to contamination with soil during the raking and bagging process.
https://sustainable-farming.rutgers.edu ... Leaves.pdf
Systemic pesticides is a different story. I'm told that they can persist several years, and I was concerned about putting lemon rinds in my compost because unless they are organic (not always available here) they are likely to be treated. I discovered a couple of years ago that I have halictid bees here that overwinter or nest in my compost piles where the herb straw and structure is ideal for them. So I would hate to put a poison in there that might harm them. How to compost the doubtful material so that chemicals are destroyed is another question, worth exploring. It's true that heat destroys and time and microbes also help, but it depends on the chemical as well as the composting method and local conditions (how hot), and then you may be able to reckon, how long should I compost certain things to be sure that residues are gone.