Crabgrass is starting to breakthrough in hotspots next to walks and drives, southern exposures, and in thin turf. Though many are quick to question the effectiveness of the specific preemergence herbicide used last spring, the vast majority of the breakthrough is due to weather, environment, or application techniques. Our research plots this year are showing equivalent control from most of the preemergence herbicides to date and almost all are treatments are starting to breakthrough under our difficult conditions (1” mowing height, no fertilizer, high crabgrass pressures, and irrigation). Simple observations reveal that none of the products are providing dramatically better or dramatically worse control compared to the others. This reaffirming that most preemergence failures are due to factors other than the herbicide. Though these factors are difficult to quantify exactly, some factors include:
Though crabgrass has 3-5 tillers or more, rescue applications with quinclorac-containing products will still be effective now. Be sure to read the label for the specific product, include a methylated seed oil (don't substitute other surfactants), apply to non-stressed turf, and avoid applying on fine fescue. A second application may be needed for most effective control.
Send corrections, suggestions, and comments to biehlj@purdue.edu