This trial was conducted to evaluate the level of crabgrass control with several Pendulum formulations and compare Pendulum to other preemergence products. It was located at the Horticulture Research Station north of Ames, IA. The plot was established in 'common' Kentucky bluegrass with a history of crabgrass infestations. The soil was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with 3.0% organic matter, 112 ppm K, 6 ppm P, and a pH of 7.05. The experimental design was a randomized complete block. Three replications were conducted and individual plot size was 5 x 5 ft. Irrigation was used to supplement rainfall and to maintain the turf in good growing condition.

The commonly-used herbicides Dimension 1EC and Pendimethalin 60WDG were included for comparisons in this trial that included numerous experimental formulations and herbicide plus fertilizer materials (Table 1). Preemergent applications were made on April 27 before crabgrass germination and the sequential application of treatment 22 was made on June 29. Granular materials were applied to dry foliage 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. All preemergent materials were 'watered in'.

Turf quality data were taken weekly from May 9 through September 13 (Tables 1 and 2). Quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality. Crabgrass infestation data were taken beginning July 25 and ending on September 13 (Table 3). Crabgrass populations were estimated as the percentage area per plot covered by crabgrass. Crabgrass control was determined by converting the population data to percentage reductions as compared to the untreated control (Table 4). In addition, the study was evaluated for phytotoxicity data during the entire duration. Phytotoxicity was assessed using a 9 to 1 scale with 9 = no damage, 5 = uniform damage with some brown turf, and 1 = dead turf (Table 5).

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 turf quality were tested using Fisher's Least Significant Difference (LSD) test.

On May 9 through May 22, quality was significantly better for turf treated with the experimental formulations with a nitrogen component (treatments 10-18) than for turf treated with other herbicides and the control (Table 1). After June 1, the nitrogen response began to fade and by June 27 there were no quality differences among the treatments.

Crabgrass was first detected in the untreated turf on July 12 but was not large enough to be assessed until July 25. Crabgrass populations in treated turf were significantly lower than the untreated control through August 28 (Table 3). Mean reduction data show that all materials except BAS 656 (treatment 8) provided > 82% crabgrass control and fourteen materials resulted in > 90% control (Table 4). The preemergence application of an experimental from Gowan (treatment 21) was more effective in controlling crabgrass than the same level of the material in split applications (treatment 22).

Discoloration and burning of the leaf blades were observed on turf treated with BAS 656 (treatment 8). After June 1, the phytotoxic symptoms were no longer present and the turf had recovered to a quality level similar to the untreated controls (Table 5).

Table 1. Visual quality¹ of Kentucky bluegrass treated for the 2001 Preemergence Annual Grass study (data through July 11).