The efficacy of experimental postemergence herbicides for the control of annual grass and broadleaf weed species in turf was evaluated in this study. It was conducted at the Iowa State University Horticulture Research Station north of Ames, IA in an area of 'common' Kentucky bluegrass. The soil was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with 3.4% organic matter, 38 ppm P, 145 ppm K, and a pH of 7.0. Turf mowing height was consistent with a high (home lawn) mowing regime of 2 to 3" for Kentucky bluegrass.
The experiment was arranged in a randomized complete block design. Individual plots were 5 x 5 ft with 3 replications. There were fourteen treatments including an untreated control (Table 1). Treatments were applied early postemergence (EARLY POST) when crabgrass was in the 1- to 4-leaf stage and mid-postemergence (MID POST) when crabgrass had 1 to 3 tillers. EARLY POST treatments included Dimension 1EC at 1.5 oz/1000 ft2, Acclaim Extra 0.57EW at 0.06 lb a.i./1000 ft2 and Preclaim 3.09EC at 1.5 and 2.0 lb a.i./1000 ft2 Preclaim 3.09EC also was applied MID POST at 2.0 and 3.0 lb a.i./1000 ft2. Bas514 50WP was applied MID POST at 0.55 oz/1000 ft. Experimental formulations L-0051, L-0260, L-0289, L-0259, an L-0261 were applied MID POST at 3.0 lb a.i./1000 ft2. In addition, L-0051 was applied MID POST at 4.0 lb a.i./1000 ft2.
Early postemergence applications were made on July 1, 1998 and the MID POST on July 14. Liquids were applied using a carbon dioxide backpack sprayer equipped with Teejetâ #8006 flat fan nozzles at 30 psi. The herbicides were diluted into 283 ml of water that translates to an application volume of 3 gal/1000 ft2.
Kentucky bluegrass phytotoxicity was evaluated weekly beginning July 9. Phytotoxicity was rated using a 9 to 1 scale with 9 = no damage, 6 = some symptoms and 1 = dead turf. Turf quality was determined weekly beginning July 9. Quality was rated visually using a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = worst quality.
Crabgrass damage was assessed on July 29, August 4, and August 11 by estimating the percentage living crabgrass per plot (Table 2). Damage was determined by estimating the amount of damage to the crabgrass plants within each plot using a 0 to 100% scale with 0 = no damage and 100% = dead plants. To assess crabgrass mortality, the percentage of area per plot covered by crabgrass was estimated on July 9, August 18, August 26, September 4, September 9, September 16, and September 21 using a 0 to 100% scale (Table 3). Percentage reductions in cover were calculated by comparing the cover in treated turf to the untreated controls (Table 4).
Broadleaf weed control was determined through population counts on July 21. The number of oxalis, spurge, and dandelion plants per plot was counted. Clover populations were determined by estimating the percentage of area per plot covered by clover (Table 5). In addition, because of the large numbers of small plants in some plots, percentage cover data also were taken for dandelion.
All data were analyzed using the Statistical Analysis System (SAS, version 6.12) and the Analysis of Variance (ANOVA) procedure. Differences among the means were examined with Fisher's Least Significant Difference (LSD) means separation test.
There was no bluegrass phytotoxicity detected following either the EARLY POST or MID POST applications. There was a slight yellow tint observed on bluegrass following treatment with Preclaim 3.09EC but this discoloration disappeared after 24 hours. There were no visual quality differences among the treated and untreated plots throughout the season.
On July 9, virtually all of the crabgrass was dead in turf treated with the EARLY POST materials (Table 3 and 4). The MID POST treatments began to cause damage on July 17, three days after application. Symptoms included curling of leaves, collapsed plants, and leaf discoloration. Two weeks after the MID POST applications, crabgrass plants were exhibiting a wide range of damage from slightly damaged to moderately damaged (Table 2). Damage was severe in most treated plots by August 11.
There were significant differences in percentage crabgrass cover for August 18 through September 21 (Table 3). All materials significantly reduced crabgrass cover as compared with the controls on August 18, September 4, and September 9 (Table 4). On August 18, there was at least 55% crabgrass cover reduction in turf treated with the MID POST materials as compared with the untreated controls. Turf treated with the EARLY POST materials had Ñ 93% reductions in crabgrass cover as compared with the controls on August 18. After September 9, some of the materials were no longer providing significant reductions in crabgrass cover as compared with the untreated controls. The EARLY POST materials (treatments 9-11 and 14), however, provided Ñ 81% reductions in crabgrass for the duration of the study.
The mean crabgrass reduction data show that all materials significantly reduced crabgrass cover as compared with the untreated controls. Mean reductions were > 50% for all materials. Two EARLY POST materials, Dimension 1EC at 1.5 oz/1000 ft2 and Preclaim 3.09EC at 2,0 lb a.i./A, provided reductions in crabgrass cover > 96%. The other EARLY POST materials (Preclaim 3.09EC at 1.5 lb a.i./A and Acclaim Extra 0.57EW at 0.06 lb a.i./A) and Preclaim 3.09EC at 2.0 and 3.0 lb a.i./A MID POST produced mean reductions > 86%.
This study did not produce any hard evidence concerning the efficacy of these materials for controlling broadleaf weeds. There were numerical differences in oxalis and spurge populations found in the treated and untreated turf but the differences were not statistically different (Table 5). Most treated turf contained more oxalis plants that the untreated controls. Clover was found only in turf treated with either the EARLY POST materials or Preclaim MID POST. These results can probably be attributed to the decrease in competition in turf where the crabgrass was killed.
Dandelion counts were significantly different but no product significantly reduced dandelion populations as compared with the untreated control (Table 5). The largest dandelion populations were found in treated turf where the removal of crabgrass had reduced competition as compared to the untreated turf.
Table 1. Materials used in the 1998 Postemergence Annual Weed Study.
|
|
|
lb/1000 ft2 |
|
|
|
Untreated control |
|
|
|
|
L-00511 |
3.00 |
|
|
|
L-00511 |
4.00 |
|
|
|
L-02601 |
3.00 |
|
|
|
L-02891 |
3.00 |
|
|
|
L-02591 |
3.00 |
|
|
|
L-02611 |
3.00 |
|
|
|
BAS514 50WP1 |
0.55 oz |
|
|
|
Dimension 1EC1 |
1.50 oz |
|
|
|
|
lb a.i./A |
|
|
|
Preclaim 3.09 EC2 |
1.50 |
|
|
|
Preclaim 3.09 EC2 |
2.00 |
|
|
|
Preclaim 3.09 EC2 |
2.00 |
|
|
|
Preclaim 3.09 EC2 |
3.00 |
|
|
|
Acclaim Extra 0.57EW1&2 |
0.06 |
|
These materials are being screened for LESCO1 and AgrEvo2.
Early post applications were made on July 1 when the crabgrass was in the 1 to 4 leaf stage
and mid post applications on July 14 when the crabgrass had 1 to 3 tillers.
Table 2. Percentage living crabgrass per plot1 in Kentucky bluegrass treated for the 1998 Postemergence Annual Weed Study.
|
|
Materials |
29 |
4 |
11 |
|
|
|
|
|
|||
|
|
Untreated control |
100.0 |
80.0 |
38.3 |
72.8 |
|
|
L-0051 |
45.0 |
41.7 |
25.0 |
37.2 |
|
|
L-0051 |
63.3 |
58.3 |
11.7 |
44.4 |
|
|
L-0260 |
76.7 |
58.3 |
18.3 |
51.1 |
|
|
L-0289 |
66.7 |
68.3 |
10.0 |
48.3 |
|
|
L-0259 |
85.0 |
68.3 |
16.7 |
56.7 |
|
|
L-0261 |
53.3 |
60.0 |
13.7 |
42.3 |
|
|
BAS514 50WP |
53.3 |
61.7 |
3.7 |
40.0 |
|
|
Dimension 1EC |
0.0 |
30.0 |
0.0 |
10.0 |
|
|
Preclaim 3.09 EC |
0.0 |
66.7 |
6.7 |
24.4 |
|
|
Preclaim 3.09 EC |
0.0 |
0.0 |
0.0 |
0.0 |
|
|
Preclaim 3.09 EC |
16.7 |
8.3 |
2.0 |
9.0 |
|
|
Preclaim 3.09 EC |
36.7 |
8.3 |
1.7 |
15.6 |
|
|
Acclaim Extra 0.57EW |
0.0 |
0.0 |
1.0 |
0.3 |
|
|
LSD0.05 |
42.2 |
48.0 |
17.3 |
28.2 |
1These figures represent the percentage of crabgrass per plot that was green and healthy.
Table 3. Percentage crabgrass cover1 in Kentucky bluegrass treated for the 1998 Postemergence Annual Weed Study.
|
|
Materials |
9 |
18 |
26 |
4 |
9 |
16 |
21 |
cover |
|
|
|
|
|||||||
|
|
Untreated control |
9.3 |
71.7 |
58.3 |
66.7 |
58.3 |
70.0 |
76.7 |
58.7 |
|
|
L-0051 |
12.0 |
32.0 |
33.7 |
32.0 |
23.3 |
35.0 |
41.7 |
30.0 |
|
|
L-0051 |
25.0 |
26.7 |
25.0 |
18.3 |
16.7 |
43.3 |
61.7 |
31.0 |
|
|
L-0260 |
13.7 |
31.7 |
31.7 |
7.0 |
12.0 |
43.3 |
43.3 |
26.1 |
|
|
L-0289 |
7.7 |
16.7 |
25.0 |
20.0 |
23.3 |
33.3 |
53.3 |
25.6 |
|
|
L-0259 |
11.7 |
16.7 |
18.3 |
25.3 |
25.0 |
35.0 |
55.0 |
26.7 |
|
|
L-0261 |
19.3 |
20.0 |
21.7 |
23.7 |
13.7 |
28.3 |
53.3 |
25.7 |
|
|
BAS514 50WP |
18.3 |
23.3 |
25.0 |
28.3 |
23.7 |
25.0 |
26.7 |
24.3 |
|
|
Dimension 1EC |
0.0 |
2.0 |
1.7 |
0.7 |
0.3 |
5.0 |
5.0 |
2.1 |
|
|
Preclaim 3.09 EC |
0.0 |
5.0 |
8.3 |
6.7 |
8.3 |
13.3 |
2.0 |
6.2 |
|
|
Preclaim 3.09 EC |
0.0 |
0.7 |
2.0 |
0.3 |
0.3 |
3.3 |
3.7 |
1.5 |
|
|
Preclaim 3.09 EC |
17.3 |
3.7 |
8.3 |
8.7 |
6.7 |
1.7 |
16.7 |
9.0 |
|
|
Preclaim 3.09 EC |
32.3 |
3.3 |
3.7 |
3.7 |
5.3 |
10.0 |
5.0 |
9.0 |
|
|
Acclaim Extra 0.57EW |
0.3 |
2.0 |
5.3 |
5.0 |
8.3 |
13.3 |
20.0 |
7.8 |
|
|
LSD0.05 |
|
27.2 |
27.9 |
29.8 |
27.0 |
32.4 |
43.1 |
26.8 |
1These figures represent the area per plot covered by crabgrass.
EARLY POST applications were made on July 1 and MID POST applications on July 14.
Table 4. Percentage crabgrass cover reductions1 in Kentucky bluegrass treated for the 1998 Postemergence Annual Weed Study.
|
|
Materials |
9 |
18 |
26 |
4 |
9 |
16 |
21 |
reduction2 |
|
|
|
|
|||||||
|
|
Untreated control |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
|
L-0051 |
0.0 |
55.4 |
42.3 |
52.0 |
60.0 |
50.0 |
45.7 |
50.8 |
|
|
L-0051 |
0.0 |
62.8 |
57.1 |
72.5 |
71.4 |
38.1 |
19.6 |
52.3 |
|
|
L-0260 |
0.0 |
55.8 |
45.7 |
89.5 |
79.4 |
38.1 |
43.5 |
57.9 |
|
|
L-0289 |
17.9 |
76.7 |
57.1 |
70.0 |
60.0 |
52.4 |
30.4 |
57.2 |
|
|
L-0259 |
0.0 |
76.7 |
68.6 |
62.0 |
57.1 |
50.0 |
28.3 |
56.3 |
|
|
L-0261 |
0.0 |
72.1 |
62.9 |
64.5 |
76.6 |
59.5 |
30.4 |
60.0 |
|
|
BAS514 50WP |
0.0 |
67.4 |
57.1 |
57.5 |
59.4 |
64.3 |
65.2 |
62.1 |
|
|
Dimension 1EC |
100.0 |
97.2 |
97.1 |
99.0 |
99.4 |
92.9 |
93.5 |
96.4 |
|
|
Preclaim 3.09 EC |
100.0 |
93.0 |
85.7 |
90.0 |
85.7 |
81.0 |
97.4 |
89.4 |
|
|
Preclaim 3.09 EC |
100.0 |
99.1 |
96.6 |
99.5 |
99.4 |
95.2 |
95.2 |
97.5 |
|
|
Preclaim 3.09 EC |
0.0 |
94.9 |
85.7 |
87.0 |
88.6 |
97.6 |
78.3 |
88.6 |
|
|
Preclaim 3.09 EC |
0.0 |
95.3 |
93.7 |
94.5 |
90.9 |
85.7 |
93.5 |
92.3 |
|
|
Acclaim Extra 0.57EW |
96.4 |
97.2 |
90.9 |
92.5 |
85.7 |
81.0 |
73.9 |
86.8 |
|
|
LSD0.05 |
|
37.9 |
47.9 |
44.6 |
46.2 |
46.3 |
56.2 |
42.7 |
1These figures represent reductions in crabgrass cover in treated turf as compared with the untreated control.
2Mean reductions include data from August 18 through September 21. Mean reductions for the EARLY POST treatments (trts 9-11 and 14) include values from July 9 through September 21.
EARLY POST applications were made on July 1 and MID POST applications on July 14.
NS = means are not significantly different at the 0.05 level.
Table 5. Broadleaf weed species populations1 on September 21 in Kentucky bluegrass treated for the 1998 Postemergence Annual Weed Study.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Untreated control |
1.7 |
|
2.3 |
|
16.0 |
6.7 |
|
0.0 |
|
|
L-0051 |
7.3 |
|
3.7 |
|
13.3 |
5.0 |
|
0.0 |
|
|
L-0051 |
13.3 |
|
0.0 |
|
7.0 |
3.7 |
|
0.0 |
|
|
L-0260 |
3.3 |
|
0.3 |
|
13.3 |
8.3 |
|
0.0 |
|
|
L-0289 |
12.3 |
|
0.7 |
|
15.7 |
8.3 |
|
0.0 |
|
|
L-0259 |
4.7 |
|
1.0 |
|
7.0 |
3.7 |
|
0.0 |
|
|
L-0261 |
7.0 |
|
1.0 |
|
10.0 |
3.7 |
|
0.0 |
|
|
BAS514 50WP |
2.7 |
|
0.3 |
|
13.7 |
6.7 |
|
0.0 |
|
|
Dimension 1EC |
7.3 |
|
2.0 |
|
31.3 |
20.0 |
|
1.7 |
|
|
Preclaim 3.09 EC |
1.0 |
|
0.3 |
|
32.3 |
18.3 |
|
8.3 |
|
|
Preclaim 3.09 EC |
3.0 |
|
2.0 |
|
19.3 |
11.7 |
|
5.0 |
|
|
Preclaim 3.09 EC |
2.3 |
|
1.3 |
|
12.3 |
7.0 |
|
0.3 |
|
|
Preclaim 3.09 EC |
1.7 |
|
0.7 |
|
28.7 |
20.0 |
|
5.0 |
|
|
Acclaim Extra 0.57EW |
7.3 |
|
5.7 |
|
31.3 |
21.7 |
|
10.0 |
|
|
LSD0.05 |
|
|
|
|
16.0 |
|
|
|
1Count data represent the number of Oxalis, Spurge, and Dandelion per plot. Percentage cover data represent the area per plot covered by Dandelion and Clover.
Early post applications were made on July 1 when the crabgrass was in the 1-to 4-leaf stage
and mid post applications on July 14 when the crabgrass had 1 to 3 tillers.
NS = means are not significantly
different at the 0.05 level.
 |
ISU Horticulture:Publications:1999 Turfgrass Report | College of Agriculture |