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Postemergence Broadleaf Weed Control

Clark Throssell and Dan Weisenberger

Objective

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

Rationale

Broadleaf weeds are a problem on many turf sites. Postemergence herbicides are often applied on these sites to control broadleaf weeds. It is important to continually examine new herbicides and new ways to use existing herbicides for their ability to control broadleaf weeds.

How It Was Done

A stand of Kentucky bluegrass turf, at the Agronomy Research Center, with a substantial population of dandelion, black medic and mouseear chickweed was selected as the site for this experiment. The site was mowed at 2 inches twice per week with clippings returned. No fertilizer was applied during the course of the experiment and irrigation was applied to prevent any sign of drought stress. The initial date of herbicide application was 5 June and split (sequential) applications, where specified, were made on 26 June 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 a visual rating of percent of plot area covered with broadleaf weeds on 20 June and 3 and 17 July 1997.

Results

• None of the treatments caused unacceptable phytotoxicity damage to the Kentucky bluegrass turf. Tank mix combinations of BAS 514 34H and Trimec Classic did cause phytotoxicity but the level of damage was considered acceptable.
• Broadleaf weed cover in the untreated check was 51.7% indicating this was a good site for this experiment.
• On this test site, any treatment providing 10% or less broadleaf weed cover on 17 July was deemed acceptable. Many of the treatments provided acceptable or better broadleaf weed control (Table 11).
• CGA 136872 at 10 grams/A plus Scoil applied as a split application, BAS 514 34H 75WG plus BAS 090 02 S at all rates, Trimec Classic at all rates, and all combinations of BAS 514 34H 75WG plus BAS 090 02 S plus Trimec Classic provided effective broadleaf weed control.
• BAS 514 34H is an experimental compound from BASF. It has been shown to have good postemergence activity on many broadleaf weeds and crabgrass. The commercialization status of BAS 514 34H is not known.
• BAS 090 02S is a surfactant from BASF and will not be labelled for commercial use.

CGA 136872 is a herbicide from CIBA and will not be labelled for use in turf. Scoil is a surfactant also from CIBA.

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