Crabgrass explosion in the future?

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Every now and then I like to take out the turf crystal ball to see what may be lurking in the future. This spring the weather may have created the perfect storm for a crabgrass outbreak this summer. Temperatures have been cool with soil temperatures throughout much of May hovering between 50ºF and 60ºF at zero to two inches depth. Any significant rainfall has been lacking, which likely further delayed crabgrass germination. Eighty to 90 percent of crabgrass germination occurs when adequate moisture is present and soil temperatures are between 60ºF and 70ºF at zero to two inches depth. Neither of these requirements for crabgrass germination has been consistently met during May.

Instead of the spring being the time when the turfgrass recovered from any previous injuries and filled in the thin spots with aggressive growth, this year the turf has basically stood still and in some cases has probably even thinned due to the lack of rain. When there are thin spots in the turf, there is an opportunity for weeds to encroach. There’s a nice rain system developing across Michigan today, and if the rain actually hits the ground this time and warm temperatures follow, don’t be surprised to see crabgrass emerge. Preemergence application timing for crabgrass is usually between April 15 and May 15. Most lawn care companies will err on the early side because of the reliable medium and long-residual products available. Long residual preemergence products (Dimension and Barricade) provide eight to 10 weeks of control and should be fine if crabgrass germination tails off by mid-June. Timing is somewhat more critical for medium residual products (Team Pro and Pendulum) that typically last six to eight weeks. Even professional applications and homeowners that properly timed their preemergence applications based on soil temperatures may have breaks in control this year. Although trying to accurately predict weed germination is probably as difficult as predicting long range weather forecasts, don’t be surprised if 2008 is one of those banner crabgrass years.

See MSU Extension bulletin E0002 “Crabgrass Control in Home Lawns” for specific management and herbicide recommendations.

Dr. Frank’s work is funded in part by MSU‘s AgBioResearch.

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