Suppression of Annual Bluegrass or Crabgrass

Seedbed establishment for fine turf can be extremely difficult, and is often considered an art form.
Suppression of Annual Bluegrass or Crabgrass - Articles


Photo: Bruce Ackley, The Ohio State University, Annual Bluegrass

Whether it is creating a seedbed for a new putting green or for a home lawn, several factors can make effective seedbed establishment difficult. Weeds, temperatures, sunlight, soil conditions, irrigation, and traffic can each make or break a favorable seedbed. Annual bluegrass and crabgrass are probably the two most problematic weeds to control in seedbeds. Most pre-emergent herbicides cannot be applied at the time of seeding, which can make control of these weeds difficult. Several new products have been thought to be effective at suppression of these two grasses in seedbeds, so this effect needed to be explored.

Two different experiments were created to evaluate the effect of various products on the control of annual bluegrass and crabgrass at seedbed establishment. Each provided researchers with valuable information on product effectiveness and their potential for use in alternative situations.

The first experiment was determined to examine the effect of Tenacity (mesotrione) and Tupersan (Siduron) on crabgrass suppression. Because of to the fact that crabgrass is a summer annual, seedbeds established in late Spring can be difficult, especially in areas that suffer heavy crabgrass pressure. Each of these products was applied on the same day as seeding in the spring. Kentucky bluegrass and perennial ryegrass were the two turf types evaluated, and were separately evaluated. The effect of these products on desirable seed germination were of importance, as well as crabgrass suppression. Both Tenacity and Tupersan were each sprayed just one time (at seeding) and twice (at seeding and four weeks later).

Over the course of eight weeks, the amount of desirable turf (Kentucky bluegrass or perennial ryegrass) were evaluated in comparison to the amount of crabgrass present. This experiment ultimately showed that two applications of Tenacity (first at 8 oz / acre and the second at 5 oz / acre) yielded up to 99 percent effectiveness in the suppression of crabgrass in a perennial ryegrass seedbed. One single application of Tenacity at the time of seeding did provide up to 50 percent suppression as well. This amount of suppression was not reached in Kentucky bluegrass plots, and is probably due to the extended germination period that Kentucky bluegrass has. Nevertheless, this product may be useful to turf managers establishing areas with perennial ryegrass.

The second two experiments examined the effect of Tenacity (mesotrione) and Prograss (ethofumesate) on the suppression of annual bluegrass in seedbeds prepared in early fall. Again, treatments included single and double applications of Tenacity (first at 8 oz / acre and the second at 5 oz/acre) and Prograss (first and second at 4 oz/1000 ft2). The first applications of these products were made at seeding and the second, two weeks later. One half of the study was seeded with perennial ryegrass, and one half was not seeded at all, allowing for maximum annual bluegrass germination.

Over the course of six weeks, the amount of annual bluegrass in each plot was evaluated on a percent cover basis. Plots that received two applications of Tenacity suppressed annual bluegrass up to 60 percent, while plots with only one application showed minimal suppression. Plots which received both one and two applications of Prograss resulted in up to 100 percent suppression. In fact, plots which received two applications of Prograss exhibited over 95 percent control though March of the following year! This information may be extremely useful to managers that renovate or reseed newly established areas.