2007 Generic Herbicide Efficacy for Weed Control Charles R. Hart, Extension Range Specialist, Stephenville C. Wayne Hanselka, Extension Range Specialist, Corpus Christi Shane McLellan, County Extension Agent, Freestone County Todd Vineyard, County Extension Agent, Erath County Dale Rankin, County Extension Agent, Colorado County Mike Hiller, County Extension Agent, Jackson County Jeff Stapper, County Extension Agent, San Patricio County Rogelio Mercado, County Extension Agent, Jim Wells County Summary For several years, Grazon P+D (Picloram + 2,4-D), manufactured by Dow AgroSciences, and Weedmaster (Dicamba + 2,4-D), manufactured by BASF, have been the recommended herbicides for the control of many weeds on Texas rangelands. Two generic versions of these herbicides with the trade names Gunslinger (Picloram + 2,4-D) and Range Star (Dicamba + 2,4D), manufactured by Albaugh, Inc. have recently become available in Texas for use on weed control. This project compares the efficacy of these generic products against the more recommended herbicides for range weed control. This project also compares three other Dow AgroSciences herbicides, Milestone, Forefront, and Surmount, to evaluate the most effective herbicide tested. In support of this project, herbicide plots were established in 6 counties across Texas. Some weeds treated were Texas Bullnettle, Dock, Western Ragweed, Oxeye daisy, Bee Balm, Western Horsenettle, Wooly Croton, Canadian Thistle, Annual Broomweed, Mexican Hat, Day Flower, Snow on the Prairie, Texas Poppy, Oxalis, Blackeyed Susan, Verbenas, Sorrel, Dollarweed, Amaranthus, Henbit, Wild Indigo, Texas Croton, Wild Geranium, Huisache Daisy, Queen’s Delight, Silverleaf Sunflower, Tallow Weed, Silverleaf Nightshade, Prickly poppy, Ragweed Parthenium, Lazy Daisy, and Coreopsis. Objectives This project was established to investigate the efficacy of the generic herbicides Gunslinger and Range Star for weed control. Methods Test sites were established in 6 counties in Extension Districts 8, 11, and 12. In Colorado, Jackson, San Patricio, and Jim Wells counties, plots were established in pairs comparing different effects of rates within Gunslinger and Grazon P+D, and to compare the two herbicides

against one another. In addition, plots were established and treated with Milestone, Forefront, and Surmount to compare their value to the other 2 herbicides used. These plots were also created in pairs for comparing different rates within each herbicide. In Freestone and Erath counties, plots were set up to compare Grazon P+D and Weedmaster with Gunslinger and Range Star. Also, additional plots were established and treated with Milestone and Forefront for comparison with the other 4 herbicides used. Plots were not replicated for rate comparison in Erath and Freestone counties. All plots were sprayed with ground broadcast spray equipment. Boom sprayers equipped with flat fan nozzles delivering 15-25 gallons per acre total spray volume were used. Plot sizes varied across sites. Rates were selected based on established rates for the non-generic herbicides. Plots in Colorado Co. were set up on April 12, 2007, Jackson Co. plots were set up on April 11, 2007, on April 3, 2007 plots were treated in San Patricio Co., and plots in Jim Wells Co. were established on April, 5, 2007. Test plots in Erath and Freestone counties were treated on June 21, 2007 and July 12, 2007, respectively Results/Discussion/Economic Impact Rates at which herbicides were applied and evaluations from treatments applied in each of the six counties are presented in Table 1. When comparing Gunslinger with Grazon P+D, percent control only varied between 2 and 5 percent, sometimes Gunslinger being better and sometimes Grazon P+D was better (Figure 1). In Freestone County, Range Star and Weedmaster had the same results for percent control. However, in Erath County, Range Star performed 30% better than Weedmaster (Figure 2). Results of this research indicate that generic herbicides can provide comparable weed control to the more recommended herbicides. When we compare the average control of each herbicide over all six counties, Forefront, Gunslinger, Grazon P+D, and Range Star showed the best overall control (Figure 3).

Table 1. Evaluations of percent weed control in each county 120 days post treatment Treatment Rate Colorado Jackson San Patricio Jim Wells Freestone Co. Co. Co. Co. Co. Milestone 3 oz/Ac 80% 40% 90% 70% Milestone 5 oz/Ac 80% 80% 100% 70% 90% Forefront 24 oz/Ac 90% 90% 100% 95% Forefront 32 oz/Ac 90% Forefront 40 oz/Ac 95% 90% 100% 100% Surmount 24 oz/Ac 85% 20% 70% 90% Surmount 16 oz/Ac 75% 30% 80% 95% Grazon P+D 16 oz/Ac 60% 80% 90% 85% Grazon P+D 32 oz/Ac 95% 90% 100% 95% Grazon P+D 48 oz/Ac 90% Gunslinger 16 oz/Ac 60% 90% 100% 85% Gunslinger 32 oz/Ac 90% 90% 90% 100% Gunslinger 48 oz/Ac 90% Range Star 32 oz/Ac 90% Weedmaster 32 oz/Ac 90%

% Control

Gunslinger vs Grazon P+D 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%

93% 95% 84%

80%

79%

85%

Gunslinger Grazon P+D

16 oz/ac

32 oz/ac

48 oz/ac

Rates at w hich Herbicides w ere Applied

Figure 1. Percent control of Gunslinger and Grazon P+D at different spray rates applied to perennial weeds.

Erath Co. 50% 50%

80%

70% 80% 50%

Range Star vs Weedmaster 100% % Control

80% 60%

Erath

40%

Freestone

20% 0% Range Star

Weedmaster

Herbicide (32 oz/ac)

Figure 2. Percent control of Range Star and Weedmaster applied to perennial weeds.

86%

85%

85% 70%

te r as dm

W ee

e an g R

G un

sli n

ge r

St ar

68%

P+ D

st on M ile

87%

Fo re fro nt Su rm ou nt

74%

G ra zo n

100% 80% 60% 40% 20% 0%

e

Average % Contro

Average Percent Control Overall

Herbicide (all rates) Figure 3. Average percent control for all herbicides used in this project applied to perennial weeds.

Acknowledgments The authors wish to express appreciation to the various ranches that served as cooperators for this project. Special thanks are extended to Albaugh Inc. for furnishing the herbicide used in the trials and for providing financial support for travel and expenses. ___________________________________ "The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Texas Cooperative Extension or the Texas Agricultural Experiment Station is implied."