Is Preet a safe pre-emergent weed killer?
Queen Anne's County Maryland
We do recommend Preen broad-leaf pre-emergent, but you must read and follow the label directions.
Preen is a brand rather than a single product. One of the active ingredients commonly found in Preen products is trifluralin.
Here is an EPA fact sheet on trifluralin: https://www.epa.gov/sites/production/files/2016-09/documents/trifluralin.pdf
You can also contact the National Pesticide Information Center (NPIC) at 800-858-7378 for help.
Thank you. Do you know of any adverse effects on bees or other helpful insects?
Whatever formulation you end up using, read the label for the active ingredient and impacts on non-target species.
Then call the National Pesticide Info Center listed above and ask them.