Q.Is it safe for me to mulch my vegetable garden with grass clippings that have been treated with Prodiamine and Lesco Three-way Her
bicide? In the past I have mulched with my lawn grass clippings but now that we treat the yard through a company called Organic Turf I wonder if the grass is safe to use. I always would wait till after rain and dispose of the first mowed clippings. No one seems to know the answer.

Certified GKH Gardening Expert
The reason no one knows is because the school of thought varies. I researched several extension publications on mulching with grass treated with herbicides and the answer ranged from wait one week to wait at least four weeks to not using it on or near sensitive vegetable such as tomatoes.
I would err on the side of caution and not use treated grass to mulch in the vegetable garden. Why take the chance?
You can always use it to mulch around trees, annuals and perennials, just avoid the vegetable garden.
http://cesantaclara.ucanr.edu/files/238922.pdf
https://hgic.clemson.edu/factsheet/controlling-weeds-by-cultivating-mulching/