Evaluations of the effects of Drive 75DF and Drive 0.43GR herbicides on newly seeded turfgrass were made as compared to the industry standard herbicide. The study was conducted at the Iowa State University Horticulture Research Station. Individual 5 x 5 ft plots in a prepared bare soil area were seeded with either 'Quantum Leap' Kentucky bluegrass, or 'Brightstar II' perennial ryegrass, or 'Penncross; creeping bentgrass. The soil in this area was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an 3.8% organic matter, pH of 6.5, 3 ppm P, and 77 ppm K. Three replications were performed.

There were multiple applications of some materials with the timing dependent on days before seeding and after emergence (Table 1). A control treated with starter fertilizer and an untreated control were included for each grass species.

Treatment with granular materials was made using cardboard cartons as 'shaker dispensers' to ensure uniform distribution of product. Liquid materials were diluted into 287 ml of water. This translates to an application rate of 3 gal/1000 ft². Sprayables were applied at 30-35 psi using a carbon dioxide backpack sprayer equipped with TeeJet #8006 flat fan nozzles.

Drive 75DF at 0.75 lb a.i./A was applied 7 days prior to seeding, at seeding, 14 days after emergence, and 28 days after emergence (Table 1). Emergence was defined as the date when approximately 50% germination had occurred. Drive 0.43GR with starter fertilizer was applied at seeding, 14 days after emergence, and 28 days after emergence. Seven days before seeding and at seeding treatments were made with Siduron 50WP.

The '7 days before seeding' treatments were made on June 3 and seeding was performed on June 10. Following seeding, there was a substantial rainfall (Table 6). On June 11, the plots were lightly raked and the 'at seeding' applications were made. The '14 days post-emergence' treatments were applied on July 8 and the '14 days post-emergence' on July 21. Twenty-four hours following herbicide treatments the plot was irrigated with 0.5 inch of water.

Turf quality ratings were taken weekly beginning June 30. Visual quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality (Table 2). The plot was surveyed for phytotoxicity when quality ratings were taken. Phytotoxicity was rated using a 9 to 1 scale with 9 = healthy turf and 1 = dead turf. Turf density data were recorded weekly from June 30 through September 14 (Table 3). Density was estimated as the percentage of area per plot covered by turf species. Weed population data were taken weekly from July 14 through September 14 (Table 4). Populations were estimated as the percentage of area per plot covered by weed species. Grass and broadleaf weed species data were combined because crabgrass was the predominate species with a small number of broadleaf species present. On September 7 and 14, determinations of percentage cover were made for crabgrass, spurge, and witchgrass (Table 5). Counts per plot were made for plantain and oxalis.

Data were analyzed with the Statistical Analysis system (SAS, Version 6.12) and the Analysis of Variance procedure (ANOVA). Treatment effects on turfgrass cover, weed cover, and turf quality were compared with Fisher's Least Significant Difference (LSD) test.

There were no phytotoxic symptoms observed following treatment. The quality of herbicide treated turf was similar to fertilized and untreated turf of all three grass species (Table 2).

In this study, Drive 75DF and Drive 0.43GR were applied at approximately four times the recommended rate for newly seeded areas. At the termination of this study, percentage cover of turf treated with the Drive formulations was at least 70% for creeping bentgrass and perennial ryegrass.

Percentage cover for Kentucky bluegrass was very low. Typically establishment of bluegrass in the spring is difficult but in this study, germination rates were especially low. Data before September 14, include percentage cover for all turf species present in the bluegrass plots. In most of these, creeping bentgrass from adjacent plots had moved in.

Data from September 14 do not reflect any differences in Kentucky bluegrass cover between the treated and untreated turf (Table 3). The cover figures from the preceding weeks suggest that other turf species 'invaded' the fertilized bluegrass plots at a much higher rate than the other plots. Percentage cover data for the treated and untreated bluegrass are similar for much of the duration of the study, excluding the data for the fertilized bluegrass.

Mean percentage turfgrass cover figures show that the Drive formulations did cause significant reductions in creeping bentgrass cover as compared with untreated, Siduron treated, and fertilized turf (Table 3). For four of the final five weeks of the study, however, there were no differences in treated bentgrass cover as compared with untreated and fertilized turf.

Mean percentage turfgrass cover figures for the entire study show that none of the treatments significantly reduced ryegrass cover (Table 3). On September 7 and 14, percentage ryegrass cover for herbicide treated turf was significantly higher than untreated turf.

Significant differences in percentage weed cover occurred for all three turf species during the study (Table 4). Drive 75DF and Drive 0.43GR provided excellent weed control in bluegrass, bentgrass, and ryegrass. In most cases, control with Drive 75DF in all turf species tested was better than with Drive 0.43GR and Siduron 50WP. Mean weed cover data show highly significant reductions in weed cover for all three turf species treated with Drive 75DF, Drive 0.43GR, and Siduron 50WP as compared with untreated and fertilized turf.

Crabgrass cover was significantly reduced in bluegrass, bentgrass, and ryegrass treated with either Drive 75DF, or Drive 0.43GR, or Siduron 50WP as compared with fertilized and untreated turf (Table 5). The level of crabgrass control was similar for the three herbicides in all turf species. Population distributions of plantain, spurge, oxalis and witchgrass were not widespread enough to show any significant differences due to treatment.

Table 1. Materials and application instructions for the 1999 Micro-Flo Drive Seeding Study.

'Seven days before seeding' applications were made on June 3. Seeding was done on June 10 'At seeding applications' were made on June 11. 'Fourteen days after emergence' applications were made on July 8 and 'twenty-eight days after emergence' on July 21.

²The figures for KB cover on Sept 14 include only the area per plot covered by KB and are not included in the mean.

³The means for KB cover include data through September 7.