Pre-Emergent Season Begins for the Northern ZoneThe North has finally broken out of the deep freeze. While it is early in their growing season, it is not too early to be putting down pre-emergents.
Crabgrass is an annual grassy weed. Of the 3 major annual grasses, i.e. crabgrass, foxtail and goosegrass, it germinates first. Crabgrass requires several environmental conditions for germination to occur. First it requires light, next it needs a soil temperature of at least 55° F for 3-5 days and also requires moisture. Of all of the annual grasses, crabgrass is most affected by a thick actively growing lawn. By mowing tall, you prevent light from reaching the soil and the crabgrass seed.
Crabgrass can be controlled chemically either by the use of a pre-emergent chemical, prior to the plant emerging or post-emergently, once it has developed leaves and can be seen above the turf canopy.
Get the Most Out of Your Pre-Emergent TreatmentFor a pre-emergent to be effective, it needs to be applied to the soil prior to the germination of the seed. Once the crabgrass seed has germinated, the pre-emergent is absorbed by the young plant and either the root or shoot is prevented from developing and the plant dies. If the seed does not germinate, pre-emergents do not affect it. There are two major pre-emergents available to the turfgrass manager. They are Prodiamine and Dithiopyr.
Both of these chemicals provide excellent pre-emergent control of crabgrass, but Dithiopyr will also provide post-emergent control of the young 3-5 leaf crabgrass plant. If the plant gets larger than that, a true post-emergent herbicide such as quinclorac will be required.
Remember, that the best control of crabgrass is a thick actively growing turf!