Steve D. Ruhl, Agriculture and Natural Resources Extension Agent
Jeff Stachler, Horticulture and Crop Sciences Extension Associate
To evaluate the effect of several different herbicides on the control of Canada thistle in corn.
| Cooperator: | Tom Weiler | ||||
| County: | Morrow | ||||
| Nearest town: | Chesterville | ||||
| Drainage: | Systematically tiled | ||||
| Soil type: | Centerburg silt loam | ||||
| Tillage: | Conventional | ||||
| Previous Crop: | Soybeans | ||||
| Hybrid: | Superior 109A | ||||
| Soil Test: | pH = 6.0, P = 11 ppm, K = 113 ppm, CEC = 11 | ||||
| Fertilizer: | 211 lb/A actual N, 52 lb/A P2O5, 162 lb/A K2O at planting | ||||
| Planting Date: | April 28, 2001 | ||||
| Planting Rate: | 30,200 seeds/A | ||||
| Row Width: | 30 in | ||||
| Harvest Date: | October 22, 2001 | ||||
| Herbicides: |
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The Canada thistle pressure in the study was moderate. Five herbicide treatments and an untreated check were replicated four times in a randomized complete block design. Plot size was 10 feet wide by 40 feet in length. The treatments were applied postemergence on June 8, 2001, with a carbon-dioxide-pressurized backpack sprayer. The sprayer had an output of 20 gallons per acre at 30 pounds of pressure. The corn was 10 inches tall and at the five-collar stage at time of application. The Canada thistle plants were 10 to 12 inches tall and mostly in the early bud stage. Canada thistle control was visually evaluated on June 26, 2001, (18 days after treatment) on a scale of 0 (no control) to 100% (complete plant death).
| Table 1. Visual Evaluation of Control of Canada Thistle in Corn. | ||||
| Herbicide Treatmentsa |
Rate | Canada Thistle Controlbc |
Herbicide/Adjuvant Costd |
Total Cost |
| % | $/A | $/A | ||
| Distinct 76.4DF | 4.0 oz/A | 77 ab | 8.96 | 10.05 |
| NIS | 0.25 % v/v | 0.80 | ||
| UAN | 1.25 % v/v | 0.29 | ||
| Distinct 76.4 DF | 6.0 oz/A | 82 ab | 13.44 | 14.53 |
| NIS | 0.25 % v/v | 0.80 | ||
| UAN | 1.25 % v/v | 0.29 | ||
| Hornet 78.5 DF | 5.0 oz/A | 83 ab | 20.88 | 22.26 |
| NIS | 0.25 % v/v | 0.80 | ||
| UAN | 2.5 % v/v | 0.58 | ||
| Hornet 78.5 DF | 5.0 oz/A | 90 a | 20.88 | 38.51 |
| Stinger 3L | 4.0 oz/A | 16.25 | ||
| NIS | 0.25 % v/v | 0.80 | ||
| UAN | 2.5 % v/v | 0.58 | ||
| Laddok S-12 5L | 2.33 pt/A | 69 b | 13.77 | 16.21 |
| COC | 1.0 % v/v | 1.52 | ||
| UAN | 4.0 % v/v | 0.92 | ||
| LSD (0.05) | 14.4 | |||
| F-test | 2.75 | |||
| CV | 11.7 % | |||
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a All treatments applied at 20 gallons per acre and 30 pounds per square inch.
b Treatments means followed by the same letter are not significantly different. c Weed control was visually evaluated on June 26. d All herbicide and adjuvant costs listed in the table were the 2001 in-season retail prices. |
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Hornet (5.0 oz/A) plus Stinger (4.0 oz/A) provided significantly greater Canada thistle control compared to Laddock S-12 (2.33 pt/A). All other treatments provided similar control. The Laddock S-12 burned off most of the thistle tissues shortly after application, but regrowth had occurred before rating. Distinct (4.0 oz/A) was the cheapest herbicide program to control Canada thistle at $10.05/A. Each of these treatments will be evaluated in the spring of 2002 for root control to determine their long-term effectiveness.
We would like to thank Tom Weiler for his assistance with this project.
For additional information, contact:
Steve Ruhl, Ohio State University Extension, Morrow County
871 W. Marion Rd., Suite 102, Mt. Gilead, OH 43338
419-947-1070
ruhl1@postoffice.ag.ohio-state.edu