This study was designed to determine the efficacy of research formulations as compared with the commercially produced herbicide Triplet and the degree of tolerance of turf to these products. The trial was conducted at the Iowa State University Research Station in an established area of 'Ram 1' Kentucky bluegrass. The soil was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with 4.2% organic matter, 120 ppm K, 6 ppm P, and a pH of 6.85.

The experimental design was a randomized complete block. Individual plot size was 5 x 10 ft with three replications. An experimental Dissolve formulation, RDL 2000, was applied at 1.65 lb product/A and at 1.25 lb product/A in combination with a diflufenzopyr salt (DFFP) at three rates for a total of six treatments (Table 1). Triplet 49.7 at 3.5 pt product/A was included as the treated standard and an untreated control was also added.

Sprayables were diluted in water and applied at an equivalent rate of 3 gal water/1000 ft². The materials were applied on June 22 using a carbon dioxide backpack sprayer equipped with TeeJet #8006 flat fan nozzles at 30-35 psi. It was 75 degrees, sunny with a 10-15 mph SW wind. We had the materials on by 11:30 a.m. This date coincided with local lawn care broadleaf weed control applications.

Weed control data were taken weekly until eight weeks after treatment beginning June 27 and ending August 16. On June 27 and 30, herbicide effects were recorded as percentage of plants severely damaged and expected to die (Table 1). Damage was assessed using a percentage scale with 100 = dead plants, 50 = 50% mortality, and 0 = undamaged plants. Beginning on July 7, the number of weeds remaining in each individual plot was counted. Dandelion and white clover were the predominant weed species present. Dandelion plants were counted as the number in each plot (Table 2) and clover infestation was estimated as the percentage area per plot covered by clover (Table 4). Dandelion and clover data were converted to percentage reductions as compared with the untreated controls (Tables 3 and 5).

Black medic was present in most turf prior to treatment. Following treatment black medic was found in untreated turf but only a few individual plants were found in treated areas (Table 6). Oxalis also was present but the distribution was not uniform among the plots (Table 7). Black medic infestations were determined as percentage cover per plot and oxalis plants per plot were counted.

Visual turf quality and turf tolerance ratings were made weekly from June 25 through August 16 (Table 8). Turf quality was rated using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality.

Data were analyzed using 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.

All materials caused similar levels of damage to dandelion and clover on June 27 and June 30 (Table 1). By July 7, there were very few dandelions left in treated turf (Table 2). Dandelion numbers increased in August but the numbers were still significantly less than the untreated control. Dandelion control remained > 98% for all products through July 27 and the mean level of control was above 92% for all herbicides (Table 3).

By July 7, percentage clover cover was significantly reduced by all treatments but there were differences in clover cover among the treatments (Table 4). Some of the materials did not kill the clover as quickly as others but by July 27, clover populations were very low in all treated turf. Clover did not re-establish in any of the treated turf through August 16. Clover control was > 93% for all treatments from July 27 through August 16 (Table 5).

Except for a few plants in one treated plot, black medic populations did not survive the herbicide treatments (Table 6). Oxalis was present in some treated plots beginning on July 14 had moved into all treated plots by August 16.

Following treatment visual quality was similar in treated and untreated turf until July 7 (Table 8). On this date all treated turf had worse quality than the untreated control. By July 14, turf quality was similar in all treated and untreated turf.