Nick E. Christians and Luke Dant
This study was conducted to evaluate the efficacy and speed of kill of several non-selective herbicides. This study was conducted at the Iowa State University Turfgrass Research Facility on 'Ram I' Kentucky bluegrass. The soil on the area is a Nicollett (fine-loamy, mixed, mesic Aquic Hapludoll) with 4.1 % organic matter, 11 ppm P, 96 ppm K, and a pH of 6.75.
All treatments were replicated three times and the experimental design was a randomized complete block. Individual plots were 5 ft by 5 ft in size. Each treatment was diluted to a total spray volume of 3 gal per 1000 sq ft and applied using a carbon dioxide backpack sprayer with #8002 flat fan TeeJet nozzles at 30-40 psi. All treatments were applied on July 17.
Turfgrass phytotoxicity was observed on 1, 2, 5, 7, 14, 21, 28 and 45 days after application. Phytotoxicity was reported on a scale ranging from 9-1, with 9 being no damage and 1 being complete death of the turf.
Data were analyzed using Statistical Analysis System (SAS) and the Analysis of Variance procedure. Treatment effects were tested using Least Significant Difference (LSD) test.
Grass treated with Reward 2 SL was the only turf that showed significant damage on the first and second day after treatment (Table 1). By day 5, all treated turf was showing significant damage, with Reward 2 SL still showing the greatest effect. By the 7th day, Roundup RTU and A13693 applied at the high rate had equaled the effect of the Reward 2 SL. Although Reward 2 SL had quick activity, by 8/7, 21 days after application, the turf had almost completely recovered. On 8/31, 45 days after treatment, Touchdown RTU and A13693 applied at the high rate had completely killed all of the turf.
Table 1. Comparison of the time required to kill Kentucky bluegrass among several non-selective herbicides. (9=no damage and 1=dead turf)
| Rate | Turfgrass Phytotoxcity | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Material | qt/A | 7/18 | 7/19 | 7/22 | 7/24 | 7/31 | 8/7 | 8/14 | 8/31 | |
| 1 | Untreated control | NA | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 |
| 2 | Touchdown RTU YF11614 | 36 | 9 | 9 | 7 | 7 | 4 | 3 | 2 | 1 |
| 3 | Touchdown 13.4% (152 AE) | 2 | 9 | 9 | 8 | 7 | 4 | 4 | 2 | 2 |
| 4 | Roundup RTU (AE) | 48.2 | 9 | 9 | 7 | 6 | 4 | 3 | 3 | 3 |
| 5 | Roundup Conc. 18% Al (13.4% AE) | 1.41 | 9 | 9 | 8 | 7 | 5 | 4 | 3 | 2 |
| 6 | Reward 2 SL | 0.5 | 7 | 7 | 6 | 6 | 7 | 8 | 8 | 9 |
| 7 | A13693 | 17.8 | 9 | 9 | 8 | 7 | 4 | 4 | 3 | 3 |
| 8 | A13693 | 35.6 | 9 | 9 | 7 | 6 | 3 | 3 | 2 | 1 |
| 9 | A13692 | 0.98 | 9 | 9 | 8 | 8 | 6 | 6 | 4 | 5 |
| 10 | A13692 | 2 | 9 | 9 | 8 | 6 | 4 | 4 | 3 | 2 |
| 11 | Roundup Conc. 18%Al (13.4% AE) & Reward 2 SL | 0.7 0.032 | 9 | 9 | 8 | 8 | 6 | 6 | 5 | 5 |
| 12 | Roundup Conc. 18% Al (13.4% AE) & Reward 2 SL | 0.032 0.066 | 9 | 9 | 8 | 8 | 5 | 5 | 3 | 3 |
| LSD 0.05 | 0.5 | 0.3 | 0.6 | 1.1 | 0.9 | 0.9 | 0.9 | 1.5 | ||
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ISU Turfgrass:2003 Turfgrass Report | College of Agriculture |
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