Early preemergence materials were applied on April 27 and 'normal' preemergence materials were applied on May 25. The Lesco fertilizer formulation with Ronstar did not arrive until May 4. The early application of this material (treatment #3) was made on May 4. The 'normal' application was made with the other treatments on May 25. All applications were made before crabgrass germination and were 'watered in'. Granular materials were applied using 'shaker dispensers' to ensure uniform application. Sprayables were applied using a carbon dioxide backpack sprayer equipped with TeeJet #8006 nozzles at a spray pressure of 30-40 psi. Liquid formulations were mixed with water to a volume equivalent to 3 gal/1000 ft².

Crabgrass germination in the untreated controls was noted on July 11 but the plants were not large enough to assess. Crabgrass infestation data were taken beginning July 25 and ending on August 28 (Table 3). Populations were estimated as the percentage coverage per plot. These data were converted to express crabgrass control as compared with the untreated controls (Table 5). Turf quality was monitored throughout the season and data were taken weekly from May 9 through August 28 (Tables 1 and 2). Quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality. There was no phytotoxicity on the bluegrass.

Data were analyzed using the Statistical Analysis System (SAS Institute Inc., 1989-1996) and the Analysis of Variance (ANOVA) procedure. Treatment effects on weed populations and visual quality were tested using Fisher's Least Significant Difference (LSD) test.

Ronstar formulations with fertilizer improved turf quality as compared to the other treated and untreated turf in May and June (Tables 1 and 2). These differences were significant for all weeks except May 1 and June 6. After June 27, the nitrogen response was gone and turf quality was similar for all treated and untreated turf.

All herbicide formulations reduced crabgrass populations significantly as compared with the untreated control (Tables 3 and 4). Crabgrass control levels were similar in all treated plots except on August 28 when significant differences among the treatments were recorded. There was significantly less crabgrass in turf treated with either Lesco fertilizer + Ronstar or TADS 14596 as compared with Pendimethalin 60WDG and the untreated control. Mean population values were similar for all treatments and were significantly lower than the untreated control. The best numerical control was provided by Lesco fertilizer + Ronstar but this level was not different from that produced by the other herbicides.

Table 1. Turf quality of Kentucky bluegrass treated for the 2001 Aventis Preemergence Annual Grass Study (May 1-July 3).