Table of Contents

Postemergence Control of Crabgrass

Clark Throssell and Dan Weisenberger

Objective

Our objective was to determine effectiveness of commercially available and experimental postemergence herbicides for crabgrass control.

Rationale

Postemergence control of crabgrass offers an option to turf managers that choose not to use preemergence herbicides for crabgrass control and on turf sites where all crabgrass plants were not controlled by the preemergence herbicide that was applied.

How It Was Done

A stand of Kentucky bluegrass turf at the Agronomy Research Center, that has a known history of crabgrass invasion, was selected as the site for this experiment. The turf was mowed twice each week at a height of 2 inches with clippings returned. No fertilizer was applied during the course of the experiment and the turf was irrigated to prevent any sign of drought stress. The initial date of herbicide application was 2 July and split (sequential) applications, where specified, were made on 17 July 1997. All herbicide treatments were applied using a three nozzle hand held boom in 2 gals. of water per 1,000 sq. ft. Data collected were phytotoxicity to the Kentucky bluegrass turf and visual ratings of percent of the plot covered by crabgrass on 17 and 25 July and 25 Aug 1997.

Results

• None of the treatments caused unacceptable phytotoxicity damage to the Kentucky bluegrass turf.
• Crabgrass cover in the untreated check was 36.7%. This indicates a substantial crabgrass population was present on the site.
• On this test site, any treatment providing 10% or less crabgrass cover on 25 Aug 1997 was deemed acceptable. Several treatments provided acceptable or better postemergence control of crabgrass (Table 10).
• Some treatments that would normally be expected to provide good postemergence control of crabgrass were not completely effective in 1997. The most likely explanation for this was crabgrass seed continued to germinate after the application of the postemergence herbicide. Generally, in central Indiana crabgrass seed germinates over a 10 week period beginning in late April and ending in early July. In 1997 crabgrass seed did not begin to germinate until late May and continued to germinate well into July. Since the initial application of these herbicides was 2 July and many have postemergence activity only, crabgrass seed germinating after the herbicide was applied was not controlled resulting in a relatively high percent of crabgrass cover on 25 Aug 1997 for some treatments.

BAS 514 34H 75WG is an experimental compound from BASF. It has been shown to have good postemergence activity on crabgrass and many broadleaf weeds. The commercialization status of BAS 514 34H is not known.

Table of Contents

Send corrections, suggestions, and comments to biehlj@purdue.edu