I would suggest you use a mulch of wood chips around edible plants as a weed block rather than a pre emergent such as Preen due to the fruit touching the ground and picking up debris sprinkled on the soil. Another weed blocking tip is to cut up lengths of old carpet or cardboard to place between rows and raised beds to keep weed seeds from sprouting. All plants need sunlight so blocking the light prevents weeds. Keep growing, Marianne Binetti