The Georgia Agricultural Experiment Station
College of Agricultural and Environmental Sciences
The University of Georgia
Research Report Number 666
August 2000
Small Grains Updates
D. C. Bridges, J. L. Day, J. W. Johnson, and P. L. Raymer, Department of Crop and Soil Sciences, Georgia Station, Griffin, GA 30223-1797
*NOTE: A metribuzin sensitivity field trial was conducted during this small grain growing season (1999-2000). Extremely dry soil at planting caused uneven emergence of wheat and variation within varieties from application of metribuzin. Therefore, the data will not be included in this report. The experiment will be repeated this fall for the 2000-01 growing season. The following information and data are from the 1998-99 field trial.
In recent years Georgia wheat farmers have increasingly experienced difficulties controlling Italian (annual) ryegrass in wheat with Hoelon (diclofop). An option is to use Sencor (metribuzin) as a postemergence treatment for control of annual ryegrass, wild radish, and other broadleaf species. Approximately 10 years ago metribuzin use among Georgia wheat growers was fairly common, but use had declined over the intervening years. However, the current difficulties in controlling ryegrass with Hoelon have spurred interest in once again using Sencor.
Some wheat cultivars are sensitive to Sencor (metribuzin). If Sencor is applied to sensitive cultivars severe injury and/or stand loss may occur. The Sencor label contains a list of known tolerant and sensitive wheat and barley cultivars. However, the label does not contain all varieties that are currently grown in Georgia. Until about 10 years ago, field experiments were routinely conducted to determine cultivar sensitivity to metribuzin. Due to the increased interest in using metribuzin for winter wheat weed control we resumed cultivar evaluations using metribuzin during the 1997-98 wheat season and conducted trials again during the 1998-99 season.
The following table summarizes data collected in a field trial at Griffin, Georgia, during the 1998/99 growing season. Wheat was seeded 13 November 1998 at a seeding rate of 2 bu/acre. Paired treated and untreated plots were included in each of four replicates. Metribuzin (Sencor) was applied postemergence at a rate of 0.375 lb ai/acre to wheat in the 2-3 leaf stage on 4 December 1998. Wheat injury was visually estimated on 14 January 1999 and yields were determined in June 1999.
| Wheat variety response to Sencor (metribuzin) herbicide, Griffin, GA 1998-99. | ||||||||
| Yield | Sensitivity Classification1 | |||||||
| Cultivar | Wheat Injury | Untreated Weed-free |
Treated Weed-free |
Yield Difference2 | UGA Tests | Sencor Label | ||
| % | bu/acre | bu/acre | ||||||
| AgriPro D93*7163 | 10 | 56 | 56 | NS | T | NOL | ||
| AgriPro Hickory | 5 | 57 | 51 | NS | T | MT | ||
| AgriPro Mason | 2.5 | 66 | 60 | NS | T | T | ||
| AgriPro Patton | 0 | 65 | 60 | NS | T | T | ||
| AgriPro Shelby | 0 | 61 | 60 | NS | T | T | ||
| Delta King 1551W | 5 | 52 | 48 | NS | T | NOL | ||
| Jackson | 2.5 | 60 | 57 | NS | T | T | ||
| Terral LA 422 | 5 | 65 | 62 | NS | T | NOL | ||
| NK Coker 9134 | 5 | 71 | 63 | NS | T | T | ||
| NK Coker 9704 | 5 | 54 | 51 | NS | T3 | S3 | ||
| NK Coker 9803 | 5 | 57 | 48 | NS | T | M T | ||
| Pioneer 2684 | 2.5 | 58 | 55 | NS | T | T | ||
| Pioneer 26R46 | 2.5 | 66 | 66 | NS | T | NOL | ||
| Pioneer 26R61 | 2.5 | 69 | 68 | NS | T | NOL | ||
| Pocahontas | 5 | 59 | 50 | NS | T | T | ||
| UGA88622E51 | 10 | 59 | 54 | NS | T | NOL | ||
| UGA89482E7 | 2.5 | 74 | 70 | NS | T | NOL | ||
| Fleming | 12.5 | 63 | 52 | NS | MT | S | ||
| Pioneer 2643 | 15 | 65 | 45 | S | MT3 | NOL | ||
| Roberts | 12.5 | 66 | 57 | NS | MT | NOL | ||
| UGA881178E53 | 12.5 | 66 | 56 | NS | MT | NOL | ||
| Clemson 201 | 57.5 | 62 | 36 | S | S | NOL | ||
| FL8868 | 32.5 | 66 | 47 | S | S | NOL | ||
| GA-Dozier | 68.5 | 51 | 24 | S | S | S | ||
| GA-Gore | 27.5 | 66 | 52 | S | S | S | ||
| GA-Stuckey | 80 | 55 | 26 | S | S | S | ||
| Jaypee | 55 | 60 | 26 | S | S | S | ||
| Morey | 70 | 63 | 18 | S | S | S | ||
| NK BL931167 | 32.5 | 52 | 32 | S | S | NOL | ||
| NK Coker 9663 | 50 | 74 | 43 | S | S | NOL | ||
| NK Coker 9835 | 30 | 63 | 44 | S | S | S | ||
| Pioneer 2691 | 22.5 | 61 | 44 | S | S | NOL | ||
| Roane | 20 | 52 | 44 | NS | S | NOL | ||
| UGA881428LE2 | 50 | 67 | 43 | S | S | NOL | ||
| UGA901146E15 | 72.5 | 67 | 23 | S | S | NOL | ||
| UGA90524E35 | 42.5 | 70 | 43 | S | S | NOL | ||
| USG 3209 | 55 | 50 | 21 | S | S | NOL | ||
| 1. Sensitivity Classification: T = Tolerant (UGA studies indicated 10% or less visual injury and no stand loss); MT = Moderately Tolerant (UGA studies indicated visual injury from 11 to 20% with no stand loss); S = Sensitive (UGA studies indicated greater than 20% visual injury and/or stand loss); and NOL = not on label. | ||||||||
| 2. Where yield differences are marked with "S", differences between Sencor-treated plots and untreated plots were significantly different at the 10% probability level. For varieties marked "NS", yields were not significantly different. | ||||||||
| 3. NK Coker 9704 scored a rating of "Tolerant" in UGA tests. However, it is rated as "Sensitive" on the Sencor label, which indicates that in at least one trial severe injury and/or stand loss was observed with the cultivar. Therefore, NK Coker 9704 should be regarded as "Sensitive". Pioneer 2643 was initially rated as "Moderately Tolerant" based on early-season visual injury, but based on yields it should be regarded as "Sensitive". | ||||||||