Timing pre-emergence herbicides on overseeded fairways

Pre–emerge herbicides such as Dimension (dithiopyr) and Barricade (prodiamine), when applied prior to overseeding, can knock fall and winter Poa annua populations back by 70% or more. But timing is tricky. If you apply too early in the summer, the products will no longer be active in the fall when poa begins to germinate (these herbicides are active for somewhere between 2 and 4 months, depending on rate, soil type, etc.). But if you apply too close to overseeding, some…