Risks of Using 2,4-D-Treated Hay as Mulch or Compost: Tomato Sensitivity and Variable Breakdown

Q: Is it safe to use hay, as mulch and in compost, treated with 2-4-D?

I can't say it's "safe" in all situations. 2,4-D half-life is 7-60 days depending on water or soil application. Soil microbes break it down. However, several plants, especially tomatoes, are extremely sensitive to tiny amounts in mulch. Too risky for vegetable garden or flower beds. Might be landscape places where it's okay, but better not to use at all.