Q: We have three half-barrels we have used for years to plant annuals. We want to plant turnip greens in them this fall. We have used Orthene in them to control fire ants. Is the soil contaminated? May we plant edibles in the barrels?

A: Orthene is a mobile insecticide. This means it is washed out of soil rather than clinging to soil particles. In addition, its half-life is only three days.

Half-life is the period of time it takes for one-half of the amount of pesticide in the soil to degrade. Each half-life that passes reduces the amount of pesticide present in the soil by one-half, i.e. one to one-half, one-half to one-fourth, one-fourth to one-eighth, etc.