Q: Is it appropriate to apply a pre-emergent to pine straw beds to control winter and summer weeds?
A: I suppose you could do it, but why? Pre-emergent chemicals must be dissolved into a layer of soil in order to control weed seeds. If seeds are in the soil under the mulch, the chemical would wash through and help to control them. But if the mulch is thick enough and appropriately placed, no weeds will germinate anyway. I typically see weeds at the edge of a pine straw mulched area, not in the middle.