Q: What is the half-life in soil of 2,4-D? How can I tell if it is the culprit for damage to my tomatoes?
A: 2,4-D is a common component of broadleaf weedkillers. According to material from Canada, the half-life is 10 days and the effect on plants is cupping, puckering and strapping of leaves.
For a complete overview of many pesticides and their properties and effects see
Herbicide Mode of Action Categories