According to Michigan State’s growing degree days (GDD) tracker, most of southern New England has entered the optimal time for preemergence crabgrass control. This is about two weeks earlier than last year, but still a somewhat normal time. Courses at low elevations south of New York City, Pittsburgh and Cleveland should have already made an initial application.
The question I get most often regarding preemergence herbicide applications is whether it is best to apply once or make split applications. While I lean toward making split applications, I also understand that time, equipment and labor are limited for many courses so this isn’t always an option. If you can only make one application, wait until you are comfortably inside the window for optimal timing. Making a singular application too early means products could lose efficacy later in the season, when you still need that herbicide barrier. Also, make sure to apply the full label rate of your chosen herbicide to maximize residual control.
If you can make split applications, you extend efficacy by getting some herbicide into the soil early, then follow that up with more product a few weeks later to extend control. I think this is the best way to hedge against variable spring weather and improve application uniformity and distribution. If you can slightly change the angle of the two applications, you safeguard against misses and improve overall coverage, whereas a miss with a single application leaves a gap in the herbicide barrier.
Spring preemergence applications are important. We often say in golf that it is cheaper and more efficient to control diseases, weeds and insects preventatively rather than curatively. Regardless of whether you make a single application or split applications, getting the barrier set at the appropriate time will control most weeds, helping you have a successful season.
Northeast Region Agronomists:
Darin Bevard, senior director, Championship Agronomy – dbevard@usga.org
Elliott L. Dowling, regional director, East Region – edowling@usga.org
Brian Gietka, agronomist – bgietka@usga.org