1999 Iowa Turfgrass Research Report

The efficacy of Drive 75DF applied alone postemergently (POST) and in combination with other postemergence broadleaf herbicides was evaluated. This study was conducted at the Iowa State University Horticulture Research Station north of Ames, IA in 'common' Kentucky bluegrass with a dense population of red clover, white clover, dandelions, plantain, and other assorted broadleaf weed species. The soil in this plot was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with 4.45% organic matter, 26 ppm P, 257 ppm K, and a pH of 6.65. The experimental design was a randomized complete block. The individual plots were 5 x 10 ft with 3 replications.

There were eight treatments including an untreated control. Drive 75DF was applied at 0.25, 0.50, and 0.75 lb a.i./A (Table 1). Drive 75DF also was applied at these same rates as a tank mix with 2, 4-D Amine 4.1SL at 0.75 lb a.i./A. Trimec Classic 3.32EC at 1.5 lb a.i./A and an untreated control were included for comparisons. Methylated soy soil (MSO) was added to all treatments as a carrier at 1.0% V/V.

All materials were applied POST on June 5, 1998 after the broadleaf weeds were well established. Application was made at 30 psi with a carbon dioxide backpack sprayer equipped with Teejet® #8006 flat fan nozzles. The materials were diluted into 567 ml of water that translates to an application rate of 3 gal/1000 ft².

The study was checked for phytotoxicity and visual quality differences weekly beginning June 10 (Table 1). Visual quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality. Phytotoxicity was quantified using a 9 to 1 scale with 9 = no damage, 6 = moderate damage, and 1 = dead turf.

Weed control was evaluated for all broadleaf and grass species found. Dandelion and clover damage ratings were taken on June 10, 24, and 30 (Table 2). Damage was assessed using a 9 to 1 scale with 9 = no damage, 5 = plants 50% dead, 1 = dead plants. Dandelion counts were taken on July 8 and July 30 and these figures represent the number of dandelions per plot (Table 3). Because of the large numbers of small dandelion plants, percentage dandelion cover data were taken on July 15 and July 30 (Table 4). In plots with large numbers of dandelions, the number in a portion of the plot was counted and this number was then adjusted to represent the entire plot. Percentage clover cover data were taken on July 8, July 15, and July 30 (Table 5). Percentage cover data represent the area per plot covered by clover. Population assessments were made of all weed species in each plot on July 30 (Table 6). The number of crabgrass, spurge, plantain, purslane, and oxalis was counted per plot.

All data were analyzed with the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance (ANOVA) procedure. Treatment effects were compared with Fisher's Least Significant Difference (LSD) test.

No phytotoxic symptoms were found on any treated turf as compared with the untreated controls. None of the materials reduced the quality of the treated turf as compared with the untreated controls (Table 1).

Some materials were causing damage to dandelion and clover as early as 5 days after treatment on June 10 (Table 2). By June 24, all treated dandelion and clover were damaged and by June 30, dead clover was found in turf treated with Drive 75DF at 0.25, 0.50, and 0.75 lb a.i./A (treatments 5-7).

All materials significantly reduced dandelion counts (Table 3). Drive 75DF at 0.25, 0.50, and 0.75 lb a.i./A in tank mix with 2,4-D Amine 4.1SL and Drive 75DF at 0.75 lb a.i./A alone reduced dandelion populations Ñ 92.5% on July 8 and Ñ 86.2% on July 30 as compared with the untreated controls.

Percentage dandelion cover was significantly lower in all treated turf as compared with the untreated controls (Table 4). On July 15 and July 30, Drive 75DF plus 2,4-D Amine 4.1SL tank mixes and Drive 75DF alone at 0.50 and 0.75 lb a.i./A reduced dandelion cover by Ñ 90.0% as compared with the untreated controls.

All treatments significantly reduced percentage clover cover as compared with the untreated controls (Table 5). Cover was reduced at least 95.9% in all treated turf for July 8, July 15, and July 30 as compared with the untreated controls.

The distribution of spurge, plantain, purslane and oxalis were quite sporadic. Populations of these broadleaves were not significantly different in the treated and untreated controls (Table 6).

The distribution of crabgrass was more uniform and there was more crabgrass in all treated turf than in the untreated controls (Table 6). There were significantly more crabgrass plants in turf treated with Drive 75DF at 0.25 lb a.i./A plus 2,4-D Amine 4.1SL and Trimec Classic 3.32EC at 1.5 lb a.i./A than in the untreated controls. The small crabgrass numbers in the untreated turf can be explained by the competition from the large populations of clover and dandelion. In the treated turf, crabgrass moved into bare areas created where dandelion and clover were killed.

Table 1. Visual turf quality¹ of turf in the 1998 Postemergence Broadleaf Weed Control Study.

	Material2	Rate (lb a.i./A)	June 10	June 24	June 30	July 8	July 15	July 24	July 30
1.	Untreated control	N/A	9	7	7	7	7	7	7
2.	Drive 75DF	0.25	9	7	7	7	7	7	7
3.	Drive 75DF	0.50	9	7	7	7	7	7	7
4.	Drive 75DF	0.75	9	7	7	7	7	7	7
5.	Drive 75DF + 2,4-D Amine 4.1SL	0.25 0.75	9	7	7	7	7	7	7
6.	Drive 75DF + 2,4-D Amine 4.1SL	0.50 0.75	9	7	7	7	7	7	7
7.	Drive 75DF + 2,4-D Amine 4.1SL	0.75 0.75	9	7	7	7	7	7	7
8.	Trimec Classic 3.32EC	1.50	9	7	7	7	7	7	7
	LSD0.05		--	--	--	--	--	--	--

¹Visual quality was assessed using a 9 to 1 scale with 9 = best, 6 = lowest acceptable & 1 = worst quality.

²MSO was added to all treatments at 1.0% V/V. POST applications were made on June 5, 1998.

-- = means comparisons tests are not valid for these data.

Table 2. Dandelion and clover damage¹ following treatment for the 1998 Postemergence Broadleaf Weed Control Study.

			Dandelion damage				Clover damage
	Material2	Rate (lb a.i./A)	June 10	June 24	June 30		June 10	June 24	June 30
1.	Untreated control	N/A	9.0	9.0	9.0		9.0	9.0	9.0
2.	Drive 75DF	0.25	8.7	7.3	4.3		8.7	7.3	2.3
3.	Drive 75DF	0.50	9.0	8.0	4.7		8.3	5.0	2.0
4.	Drive 75DF	0.75	8.7	7.0	5.0		8.0	7.0	2.0
5.	Drive 75DF + 2,4-D Amine 4.1SL	0.25 0.75	9.0	7.0	3.3		8.3	7.0	1.0
6.	Drive 75DF + 2,4-D Amine 4.1SL	0.50 0.75	8.3	6.3	2.7		7.7	4.0	1.0
7.	Drive 75DF + 2,4-D Amine 4.1SL	0.75 0.75	8.7	7.0	2.0		8.0	7.0	1.0
8.	Trimec Classic 3.32EC	1.50	7.0	7.3	3.3		7.3	7.3	1.7
	LSD0.05		1.0	1.5	2.1		NS	2.5	1.7

¹Damage was assessed using a 9 to 1 scale with 9 = no damage, 5 = plants 50% dead, 1 = dead plants.

²MSO was added to all treatments at 1.0% V/V.

NS = means are not significantly different at the 0.05 level.

 

Table 3. Dandelion counts¹ and reductions in dandelion counts² following treatment for the 1998 Postemergence Broadleaf Weed Control Study.

			Dandelion counts				Count reductions
	Material3	Rate (lb a.i./A)	July 8	July 30	Mean		July 8	July 30	Mean
1.	Untreated control	N/A	476.7	210.0	343.3		0.0	0.0	0.0
2.	Drive 75DF	0.25	123.3	95.0	109.2		74.1	54.8	68.2
3.	Drive 75DF	0.50	74.3	65.0	69.7		84.4	69.0	79.7
4.	Drive 75DF	0.75	36.0	29.0	32.5		92.5	86.2	90.5
5.	Drive 75DF + 2,4-D Amine 4.1SL	0.25 0.75	6.3	8.3	7.3		98.7	96.0	97.9
6.	Drive 75DF + 2,4-D Amine 4.1SL	0.50 0.75	3.0	3.0	3.0		99.4	98.6	99.1
7.	Drive 75DF + 2,4-D Amine 4.1SL	0.75 0.75	1.7	1.0	1.3		99.7	99.5	99.6
8.	Trimec Classic 3.32EC	1.50	107.0	71.7	89.3		77.6	65.9	74.0
	LSD0.05		79.7	67.7	56.5		16.7	32.3	16.5

¹These figures represent the number of dandelions per plot. In plots with large populations, dandelion counts were estimated by counting the number of dandelions in a portion of the plot. Smaller counts in the untreated controls were recorded on July 30 than on July 15. This could be explained by the large increase in the percentage clover cover and the difficulty in finding dandelions in a dense clover cover.

²Reductions in dandelion counts are expressed as percentages of the untreated controls.

³MSO was added to all treatments at 1.0% V/V.

POST applications were made on June 5, 1998.

			Percentage dandelion cover				Cover reductions
	Material3	Rate (lb a.i./A)	July 15	July 30	Mean		July 15	July 30	Mean
			__________________________ % __________________________
1.	Untreated control	N/A	23.3	25.0	24.2		0.0	0.0	0.0
2.	Drive 75DF	0.25	6.7	6.7	6.7		71.4	73.3	72.5
3.	Drive 75DF	0.50	2.3	2.3	2.3		90.0	90.7	90.4
4.	Drive 75DF	0.75	0.7	2.3	1.5		97.1	90.7	93.8
5.	Drive 75DF + 2,4-D Amine 4.1SL	0.25 0.75	0.3	1.0	0.7		98.6	96.0	97.2
6.	Drive 75DF + 2,4-D Amine 4.1SL	0.50 0.75	0.3	0.7	0.5		98.6	97.3	97.9
7.	Drive 75DF + 2,4-D Amine 4.1SL	0.75 0.75	0.0	0.7	0.3		100.0	97.3	98.6
8.	Trimec Classic 3.32EC	1.50	5.3	4.0	4.7		77.1	84.0	80.7
	LSD0.05		4.0	4.5	4.0		17.1	17.9	16.4

¹Percentage dandelion cover was determined by estimating the area per plot covered by dandelions. These estimations were made to more accurately depict the dandelion populations in treated plots.

²Reductions in dandelion cover are expressed as percentages of the untreated controls.

³MSO was added to all treatments at 1.0% V/V.

POST applications were made on June 5, 1998.

 

Table 5. Percentage clover cover¹ and reductions in clover cover² following treatment for the BASF Postemergence Broadleaf Study.

			Percentage clover cover					Cover reductions
	Material3	Rate (lb a.i./A)	July 8	July 15	July 30	Mean		July 8	July 15	July 30	Mean
			___________________________ % ___________________________
1.	Untreated control	N/A	56.7	56.7	73.3	62.2		0.0	0.0	0.0	0.0
2.	Drive 75DF	0.25	2.3	2.0	2.3	2.2		95.9	96.5	96.8	96.4
3.	Drive 75DF	0.50	0.0	0.7	0.7	0.4		100.0	98.8	99.1	99.3
4.	Drive 75DF	0.75	0.7	0.0	0.3	0.3		98.8	100.0	99.5	99.5
5.	Drive 75DF + 2,4-D Amine 4.1SL	0.25 0.75	1.3	0.3	2.3	1.3		97.6	99.4	96.8	97.9
6.	Drive 75DF + 2,4-D Amine 4.1SL	0.50 0.75	0.3	0.0	0.3	0.2		99.4	100.0	99.5	99.6
7.	Drive 75DF + 2,4-D Amine 4.1SL	0.75 0.75	0.0	0.0	0.0	0.0		100.0	100.0	100.0	100.0
8.	Trimec Classic 3.32EC	1.50	1.7	2.0	0.7	1.4		97.1	96.5	99.1	97.7
	LSD0.05		6.9	12.5	7.1	8.0		12.2	22.1	9.7	12.9

¹Percentage clover cover was determined by estimating the area per plot covered by clover.

²Reductions in clover cover are expressed as percentages of the untreated controls.

³MSO was added to all treatments at 1.0% V/V.

POST applications were made on June 5, 1998.

	Material2	Rate (lb a.i./A)	Crabgrass	Spurge	Plantain	Purslane	Oxalis
1.	Untreated control	N/A	2.0	0.0	1.7	0.0	0.0
2.	Drive 75DF	0.25	4.3	1.3	0.3	0.0	0.0
3.	Drive 75DF	0.50	4.7	3.7	0.3	0.7	0.3
4.	Drive 75DF	0.75	3.3	2.7	0.3	0.0	0.3
5.	Drive 75DF + 2,4-D Amine 4.1SL	0.25 0.75	13.7	2.3	0.0	0.0	0.3
6.	Drive 75DF + 2,4-D Amine 4.1SL	0.50 0.75	7.3	2.3	0.0	0.3	0.3
7.	Drive 75DF + 2,4-D Amine 4.1SL	0.75 0.75	4.7	2.3	0.0	1.3	0.3
8.	Trimec Classic 3.32EC	1.50	12.3	0.7	0.0	0.3	0.0
	LSD0.05		7.4	NS	NS	NS	NS

¹ These figures represent the number of plants per plot.

²MSO was added to all treatments at 1.0% V/V.

NS = means are not significantly different at the 0.05 level. 

ISU Horticulture:Publications:1999 Turfgrass Report

College of Agriculture