Hi Karen,

I am Heather Houk the ag/horticulture specialist for La Plata County Extension. I would love to know a few more details. I am curious why you think it might be contaminated with Grazon? Have you checked with the rancher where you got the manure? 
I had to do a quick refresher on Grazon herbicides and because it specifically targets broadleaf plants and trees, I would have been more suspicious if your squash and cucumber plants were dying. 

I agree that emptying the soil is a last resort, and we can find other solutions if herbicide is suspected. I am curious about the age of the manure. Had it been composted for at least 1 year before you added it to your beds and if not, did you put it in and let it rest for 2+ months before starting to plant? I ask because there are a few things going on with manure when it is too fresh. One is that it can 'burn' plants because it is too high in urea and nitrites and the second issue is if it is too fresh the nitrogen can still be locked up for several months.

Nitrogen is our best friend for root development and those early growth stages for our plants and tomatoes and peppers are particularly sensitive to too much nitrogen. 

Send me an email at <personal data hidden> to reach me directly or call my office at 970.382.6464 if you want to talk instead of typing.

We can figure this out together, I am sure of it,
Heather