For those feeding/using grains or hay products. All pesticides have a withdrawal rate where nothing can be harvested in that window.
Many herbicides have some carryover as well. One of the worst is
Picloram (commonly sold under the trade names Tordon and Grazon) which has a half life of 1-4 years. It is used a lot on fields where hay is harvested.
The following is part of an article about
Picloram and two other like herbicides.
***
"Minute concentrations of picloram, clopyralid and aminopyralid, as low as 1 ppb (parts per billion), can be lethal to sensitive garden plants such as peas, beans, lettuce, spinach, tomatoes and potatoes.
Most pesticides, including herbicides, break down quickly in the composting process. Picloram, Clopyralid and Aminopyralid do not. These chemicals are
- Easily absorbed by plants.
- Remain chemically stable and intact in both live and dead plants.
- Do not breakdown substantially in animal digestive tracts so contaminate manure, urine and bedding with residues.
- Breakdown very slowly in composts and soils with an estimated half life of 1 - 2 years.
- Affect sensitive crops at very low concentrations - 1-3 ppb.
The only way to handle this potential threat is to keep materials contaminated with picloram, clopyralid and aminopyralid out of your garden in the first place.
When you're talking to a farmer supplying hay, straw or manure asking about picloram, clopyralid and aminopyralid is probably not enough. You'll need to ask about specific trade names of the herbicides.
These herbicides are sold under the following trade names.
- Picloram - sold as Tordon, Access, Surmount, Grazon, and Pathway.
- Clopyralid - sold as Curtail, Confront, Clopyr AG, Lontrel, Stinger, Millennium Ultra, Millenium Ultra Plus, Reclaim, Redeem, Transline.
- Aminopyralid - sold as Milestone, Forefront, Pharaoh, Banish." ***
If you have any doubt about the safe use of composted hay, try planting a few peas before using it on your garden. Legumes are very susceptible to damage from some of these herbicides. If they grow well your hay is most likely safe to use on you garden veggies.