LCO Weed Control Study
Barbara R. Bingaman, Melissa C. McDade, and Nick E. Christians
This study was designed to evaluate full season weed control with Drive 75DF delayed lawn care (LCO) programs compared to standard LCO programs. It was conducted at the Iowa State University Horticulture Research Station at Ames, IA in an established area of 'Park' Kentucky bluegrass. The soil in this area was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with 3.9% organic matter, 3.5 ppm P, 116 ppm K, and a pH of 7.3.
The study was arranged as a randomized complete block with three replications. Individual plot size was 10 x 5 ft with treatments randomly assigned within replications. There were four treatments with combinations of pre- (PRE), early post (EPOST), post (POST), late postemergent (LPOST) applications, and an untreated control (Table 1). One treatment combination included Pendimethalin 60WDG applied at the label rate PRE and Trimec Classic 3.32EC at 1.5 lb a.i./A applied POST and LPOST. Drive 75DF at 0.75 lb a.i./A was applied EPOST in a tank mix with Pendimethalin 60WDG at 2/3 label rate and was applied LPOST with 2,4-D Amine 4.1SL at 0.75 lb a.i./A. The fourth treatment was a tank mix of Drive 75DF at 0.75 lb a.i./A plus 2, 4-D Amine 4.1SL at 0.75 lb a.i./A applied EPOST and LPOST. Methylated soy soil (MSO) was added to all treatments as a carrier at 1.0% V/V.
Preemergent applications were made May 6, 1998 before crabgrass germination. Early post applications were made as delayed LCO pre- postemergent treatments on June 16. Postemergence applications were made following standard POST broadleaf timing schedules on July 14. Late postemergence treatments were applied as standard LPOST broadleaf materials on September 1, 1998.
The products were applied at 30 psi using a carbon dioxide backpack sprayer equipped with Teejet® #8006 flat fan nozzles. The materials were mixed into 567 ml water that translates to an application volume of 3 gal/1000 ft2.
Turf quality and phytotoxicity were assessed from May 13 through October 1 (Tables 2 - 4). Turf quality was estimated by making visual rankings 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 injury, 6 = moderate damage, and 1 = dead turf. Dandelion and clover damage were determined on June 30, July 7, and July 23 following the EPOST and POST applications (Table 5). Damage was estimated using a 9 to 1 scale with 9 = no damage, 6 = 50% dead, 1 = 100% dead. Damage symptoms included collapsed, discolored, and curled leaves. Percentage cover data were taken for dandelion (Tables 6 - 7), clover (Tables 8 - 9), and crabgrass (Tables 10 - 11) from July 15 through October 1. These data represent the percentage of area per plot covered by each weed species.
All data were analyzed using the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance Procedure (ANOVA). Differences among means were compared with Fisher's Least Significant Difference (LSD) Test.
The only significant differences in turf quality were observed on July 15, one day after the POST applications (Tables 2 - 4). There were numerical differences in quality on June 24 (8 days after the EPOST applications), on August 18, on September 16 (15 days after the LPOST applications), and on September 23. No phytotoxicity was detected.
On June 30 (15 days after the EPOST materials were applied), Drive 75DF plus either Pendimethalin 60WDG or 2,4-D Amine 4.1SL was causing severe levels of damage to dandelion and clover (Table 5). By July 15, the Drive 75DF tank mixes had reduced the percentage dandelion cover to æ 1.0% and the clover cover to æ 0.3% as compared to 16.7% dandelion cover and 6.7% clover cover in the untreated controls (Tables 6 - 8). On July 23, seven days after the POST treatments, the pendimethalin 60WDG tank mix was causing severe damage to the dandelion and clover and by July 29, the percentage cover for both species was significantly reduced as compared with the untreated controls. After July 29, all of the herbicides provided significant reductions in dandelion and clover populations as compared with the untreated controls (Tables 6 - 9).
Crabgrass was first detected in the untreated turf on July 15 and in the treated turf on July 23 (Tables 10 - 11). Crabgrass populations in the treated turf were reduced as compared with the untreated controls for the duration of the trial. The reductions were not statistically significant for all of the collection dates.
Table 1. Materials and application information for the 1998 LCO Weed Control Study.
|
Material |
Rate lb a.i./A |
Timing of application |
|
|
1. |
Untreated control |
N/A |
N/A |
|
2. |
Pendimethalin 60WDG* |
1.50 |
PRE |
|
Trimec Classic 3.32EC |
1.50 |
POST |
|
|
Trimec Classic 3.32EC |
1.50 |
LATE POST |
|
|
3. |
Drive 75DF + Pendimethalin 60WDG* + MSO |
0.75 1.00 1.00% |
EARLY POST EARLY POST EARLY POST |
|
Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.75 0.75 1.00% |
LATE POST LATE POST LATE POST |
|
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.75 0.75 1.00% |
EARLY POST EARLY POST EARLY POST |
|
Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.75 0.75 1.00% |
LATE POST LATE POST LATE POST |
PRE applied on May 6, EARLY POST on June 16, POST on July 14, and LATE POST on September 1, 1998
*Pendimethalin (Pre-M 60WDG) was substituted for Pendulum 3.3EC per Dave Eastman.
Table 2. Visual turf quality1 in turf treated for the 1998 LCO Weed Control Study (May 13 - July 7).
|
Material |
May 13 |
May 18 |
May 27 |
June 16 |
June 24 |
June 30 |
July 7 |
|
|
1. |
Untreated control |
9.0 |
9.0 |
9.0 |
9.0 |
7.0 |
7.0 |
7.0 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
9.0 |
9.0 |
9.0 |
9.0 |
6.3 |
7.0 |
7.0 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
9.0 |
9.0 |
9.0 |
9.0 |
5.7 |
7.0 |
7.0 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
9.0 |
9.0 |
9.0 |
9.0 |
5.0 |
7.0 |
7.0 |
|
LSD0.05 |
-- |
-- |
-- |
-- |
NS |
-- |
-- |
1Visual quality was assessed with a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = best quality.
-- = means separation tests are not appropriate for these data.
NS = means are not significantly different at the 0.05 level.
Table 3. Visual turf quality1 in turf treated for the 1998 LCO Weed Control Study (July 15 - August 26).
|
Material |
July 15 |
July 23 |
July 29 |
Aug 5 |
Aug 11 |
Aug 18 |
Aug 26 |
|
|
1. |
Untreated control |
8.0 |
7.0 |
7.0 |
7.0 |
7.0 |
8.0 |
7.0 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
6.3 |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
7.0 |
|
LSD0.05 |
1.2 |
-- |
-- |
-- |
-- |
-- |
-- |
1Visual quality was assessed with a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = best quality.
-- = means separation tests are not appropriate for these data.
Table 4. Visual turf quality1 in turf treated for the 1998 LCO Weed Control Study (Sept. 4 - Oct. 1).
|
Material |
Sept 4 |
Sept 9 |
Sept 16 |
Sept 23 |
Oct 1 |
Mean |
|
|
1. |
Untreated control |
7.0 |
6.0 |
6.7 |
8.0 |
6.0 |
7.5 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
7.0 |
6.0 |
6.3 |
7.0 |
6.0 |
7.2 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
7.0 |
6.0 |
6.0 |
7.0 |
6.0 |
7.2 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
7.0 |
6.0 |
6.0 |
7.0 |
6.0 |
7.2 |
|
LSD0.05 |
-- |
-- |
NS |
NS |
-- |
0.1 |
1Visual quality was assessed with a 9 to 1 scale with 9 = best, 6 = lowest acceptable, and 1 = best quality.
-- = means separation tests are not appropriate for these data.
NS = means are not significantly different at the 0.05 level.
Table 5. Dandelion and clover damage1 following treatment for the 1998 LCO Weed Control Study.
|
Dandelion |
Clover |
|||||||||
|
Material |
June 30 |
July 7 |
July 23 |
June 30 |
July 7 |
July 23 |
||||
|
1. |
Untreated control |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
9.0 |
|||
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
8.3 |
8.3 |
2.7 |
9.0
|
9.0
|
9.0 |
|||
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
3.3 |
3.7 |
9.0 |
2.3 |
1.7 |
9.0 |
|||
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
3.0 |
2.0 |
9.0 |
2.7 |
1.0 |
9.0 |
|||
|
LSD0.05 |
1.8 |
1.6 |
1.2 |
2.7 |
1.2 |
-- |
||||
1Damage was estimated using a 9 to 1 scale with 9 = no damage, 6 = 50% dead, 1 = 100% dead.
-- = means separation tests are not appropriate for these data.
Table 6. Percentage dandelion cover1 in turf treated for the 1998 LCO Weed Control Study (July 15 - Aug. 26).
|
Material |
July 15 |
July 23 |
July 29 |
Aug 5 |
Aug 11 |
Aug 18 |
Aug 26 |
|
|
1. |
Untreated control |
16.7 |
23.3 |
21.7 |
30.0 |
25.0 |
21.7 |
23.3 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
18.3 |
18.3 |
4.7 |
1.0
|
0.3 |
0.7 |
1.0 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
1.0 |
0.7 |
1.0 |
2.3 |
3.7 |
6.7 |
8.3 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.0 |
0.0 |
0.3 |
0.7 |
0.3 |
2.0 |
2.3 |
|
LSD0.05 |
12.5 |
8.5 |
6.0 |
9.5 |
2.2 |
7.6 |
7.3 |
1These figures represent the area per plot covered by dandelion.
Table 7. Percentage dandelion cover1 in turf treated for the 1998 LCO Weed Control Study (Sept. 4 - Oct. 1).
|
Material |
Sept 4 |
Sept 9 |
Sept 16 |
Sept 23 |
Oct 1 |
Mean cover |
|
|
1. |
Untreated control |
10.0 |
20.0 |
16.7 |
25.0 |
30.0 |
21.9 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
2.3 |
2.3 |
2.0 |
2.3
|
2.3 |
4.6 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
6.7 |
8.3 |
2.3 |
0.3 |
0.0 |
3.4 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
2.3 |
2.3 |
2.0 |
1.7 |
0.0 |
1.2 |
|
LSD0.05 |
4.3 |
7.4 |
7.7 |
3.9 |
2.3 |
3.7 |
1These figures represent the area per plot covered by dandelion.
PRE applied on May 6, EARLY POST on June 16, POST on July 14, and LATE POST on September 1, 1998
Table 8. Percentage clover cover1 in turf treated for the 1998 LCO Weed Control Study (July 15 - Aug. 26).
|
Material |
July 15 |
July 23 |
July 29 |
Aug 5 |
Aug 11 |
Aug 18 |
Aug 26 |
|
|
1. |
Untreated control |
6.7 |
18.3 |
16.7 |
18.3 |
8.3 |
26.7 |
23.3 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
20.0 |
20.0 |
2.0 |
2.0 |
0.3
|
0.0 |
2.3 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.3 |
0.0 |
0.0 |
0.3 |
0.7 |
0.3 |
0.3 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
0.0 |
|
LSD0.05 |
3.0 |
7.5 |
7.1 |
2.5 |
2.7 |
3.0 |
3.2 |
1These figures represent the area per plot covered by clover.
Table 9. Percentage clover cover1 in turf treated for the 1998 LCO Weed Control Study (Sept. 4 - Oct. 1).
|
Material |
Sept 4 |
Sept 9 |
Sept 16 |
Sept 23 |
Oct 1 |
Mean cover |
|
|
1. |
Untreated control |
56.7 |
41.7 |
56.7 |
56.7 |
53.3 |
31.9 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
2.7 |
1.0 |
2.0 |
0.7 |
0.0
|
4.4 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.7 |
0.3 |
0.0 |
0.0 |
0.0 |
0.3 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.3 |
0.3 |
0.0 |
0.0 |
0.0 |
0.1 |
|
LSD0.05 |
6.3 |
14.3 |
14.7 |
11.5 |
5.8 |
4.4 |
1These figures represent the area per plot covered by clover.
PRE applied on May 6, EARLY POST on June 16, POST on July 14, and LATE POST on September 1, 1998
Table 10. Percentage crabgrass cover1 in turf treated for the 1998 LCO Weed Control Study (July 15 - Aug. 26).
|
Material |
July 15 |
July 23 |
July 29 |
Aug 5 |
Aug 11 |
Aug 18 |
Aug 26 |
|
|
1. |
Untreated control |
0.3 |
2.3 |
4.0 |
6.7 |
11.7 |
16.7 |
6.9 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
0.0
|
0.7
|
1.7
|
0.7 |
5.3 |
2.3 |
1.8 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.0 |
3.7 |
0.3 |
0.0 |
3.3 |
0.7 |
1.3 |
|
4. |
Drive 75DF + 2, 4-D Amine 4.1SL + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.0 |
0.7 |
0.0 |
0.3 |
2.0 |
0.7 |
0.6 |
|
LSD0.05 |
NS |
NS |
NS |
NS |
2.7 |
P=0.07 7.4 |
P=0.07 13.3 |
1These figures represent the area per plot covered by crabgrass
NS = means are not significantly different at the 0.05 level.
Table 11. Percentage crabgrass cover1 in turf treated for the 1998 LCO Weed Control Study (Sept. 4 - Oct. 1).
|
Material |
Sept 4 |
Sept 9 |
Sept 16 |
Sept 23 |
Oct 1 |
Mean cover |
|
|
1. |
Untreated control |
3.7 |
5.7 |
13.3 |
12.0 |
16.7 |
8.5 |
|
2. |
Pendimethalin 60WDG & Trimec Classic 3.32EC & Trimec Classic 3.32EC |
2.3
|
0.3
|
5.0
|
2.0 |
0.0 |
1.8 |
|
3. |
Drive 75DF + Pendimethalin 60WDG + MSO & Drive 75DF + 2, 4-D Amine 4.1SL + MSO |
0.0 |
0.3 |
0.0 |
0.0 |
0.0 |
0.8 |
|
4. |
Drive 75DF + 2, 4-D amine 4.1SL + MSO & Drive 75DF + 2, 4-D amine 4.1SL + MSO |
0.7 |
0.0 |
0.0 |
0.3 |
0.0 |
0.5 |
|
LSD0.05 |
NS |
NS |
P = 0.06 10.1 |
NS |
NS |
NS |
1These figures represent the area per plot covered by crabgrass
NS = means are not significantly different at the 0.05 level.
 |
ISU Horticulture:Publications:1999 Turfgrass Report | College of Agriculture |