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Preemergence Control of Crabgrass 1994-1999

Clark Throssell and Dan Weisenberger

Objective

Our objective was to show the historical performance of commonly used preemergence herbicides to control crabgrass.

Rationale

The level of crabgrass control provided by a given preemergence herbicide varies from year to year. Why this variability in crabgrass control occurs is not completely known. It is important for professional turf managers to recognize that crabgrass control provided by a preemergence herbicide will vary from year to year and site to site.

How It Was Done

Commonly used preemergence herbicides were applied to Kentucky bluegrass turf prior to crabgrass seed germination. Percent cover by crabgrass was determined by visual rating in late Aug to early Sep each year.

Results

• The crabgrass population varied widely from year to year as indicated by the percent cover by crabgrass in the untreated check (Table 1). The exact reasons for this are not known.
• All the preemergence herbicides at the rates applied generally provided acceptable or better crabgrass control.
• On sites with a very high crabgrass population preemergence herbicide performance is not as effective as on sites with a low crabgrass population.
• On sites with a very high crabgrass population split applications of preemergence herbicides provide much less crabgrass cover than a single application when the same total of ai/A was applied.

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