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Progress Report-2002 |
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NOTICE |
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TITLE: Managing Imazamox-Resistant Wheat in Crop Rotations PERSONNEL: Philip Westra, Principle Investigator; Mark Collins, Research Associate; Reginald Sterling, Graduate Research Assistant. TIME LINE: Initiated fall, 2000; Projected completion fall, 2005 ORIGINAL HYPOTHESIS: Use of Clearfield wheat every 2 or 3 years in conjunction with crop rotations will provide more sustainable jointed goatgrass control and less risk of developing herbicide resistant jointed goatgrass than continuous use of Clearfield wheat. SUMMARY OF PROGRESS: Use of Clearfield wheat sprayed with Beyond herbicide has provided 100% jointed goatgrass control for the first 2 years of this project. The Clearfield system has provided consistently higher wheat yields. Severe drought conditions during the 2002 growing season precluded production of harvestable corn and millet, but sunflower yields were obtained and wheat yields were average to good at both locations. The drought severely reduced the amount of jointed goatgrass in plots. Clearfield winter wheat appears to have an excellent fit in Central Great Plains dryland cropping systems. Samples were collected in 2002 to determine if pollen mediated gene flow has occurred from Clearfield wheat to jointed goatgrass. OBJECTIVES: A. Determine the best use of Clearfield wheat for control of jointed goatgrass in wheat-based cropping systems of the Central Great Plains B. Determine the risk of developing Imazamox-resistant jointed goatgrass in cropping systems using Clearfield wheat C. Monitor the impact of Clearfield wheat technology on jointed goatgrass and jointed goatgrass x wheat hybrid population dynamics D. Determine if use of a summer crop improves jointed goatgrass control with Clearfield wheat while reducing potential development of imazamox resistant jointed goatgrass
EXPERIMENTAL DESIGN: Two research sites were established in the summer of 2000 with two farmers in eastern Colorado. The Anderson farm is located in Haxtun, CO, while the Palser farm is located in Otis, CO. The Palser site uses a winter wheat-fallow-proso-millet rotation on 12.1 acres, while the Anderson site uses a winter wheat-dryland corn-sunflower- fallow rotation on 13.2 acres. Both sites incorporate Clearfield and conventional wheat into a diverse rotation.
PROGRESS: Two research sites were established in the summer of 2000 with two farmers in eastern Colorado. The Anderson farm is located at Haxtun, CO, while the Palser farm is located at Otis, CO. The studies at both sites were drilled with the ‘Above’ Clearfield winter wheat on September 25 and 26, 2001, respectively. Both sites were sprayed with Roundup Ultra at 74 ounces of produce per acre pre-emergence to the ‘Above’ winter wheat. Half of the research plots were treated as conventional winter wheat, while the other half was treated with imazamox in order to compare wheat yields using the same variety. Due to dry fall and spring conditions, very little weed emergence was observed; therefore no conventional treatments were applied. Imazamox was applied at 0.032 lbs ai a-1 with NIS and UAN 32% at both locations on April 23, 2002. Jointed goatgrass was at the 1-2 tiller growth stage at both locations at the time of application. Treatments were made using a tractor mounted spray boom delivering 17 gal a-1. Weed control and crop response evaluations were made 28 days after treatment (DAT). Imazamox treated plots provided 100% jointed goatgrass control at the Otis and Haxtun sites, respectively and no crop injury. Jointed goatgrass reproductive tiller counts were taken using a 1x 1 meter quadrat using four quadrats per plot. No reproductive tillers were observed in the treated plots. Due to sparse weed populations in the conventional winter wheat plots, few reproductive tillers were observed. Wheat samples were harvested July 16, 2002 at both locations using a plot combine. Plot size for yield determination was 4’ x 100’. The imazamox treated winter wheat yields were 40 and 35 bu a-1, while the conventional winter wheat yields were 37 and 32 bu a-1at the Haxtun and Otis sites, respectively. Spring crops were planted at both locations. Corn and sunflower were planted at Haxtun, CO, while proso-millet was planted at Otis, CO. Due to drought conditions, yields were not taken on corn and proso-millet because the plants never produced harvestable grain. Sunflower yield was 1261 lbs a-1 at the Haxtun site in 2002.
In cooperation with Drs. Carol Mallory-Smith and Robert Zemetra, jointed goatgrass reproductive tillers were collected from both locations to determine if hybridization had occurred between ‘Above’ winter wheat and jointed goatgrass. Samples were boxed and shipped to Oregon State University for analysis.
Jointed Goatgrass Reproductive Tiller Counts – Four 10.6 square foot quadrats were sampled per block to determine jointed goatgrass reproductive tiller counts. Counts were taken on July 9, 2002 at both locations. No reproductive tillers were observed in the Beyond treated plots. Due to sparse weed populations in the conventional winter wheat plots, few reproductive tillers were observed.
TECHNOLOGY TRANSFER ACTIVITIES: These field studies will be shown to wheat producers on summer field tours. Research results were presented at wheat grower field days and research meetings. Results of this research will be published and will serve as the basis for development of best management practices for jointed goatgrass based on Clearfield wheat technology. These results show that producers with heavy jointed goatgrass pressure in wheat are well advised to utilize Clearfield wheat followed by an application of Beyond herbicide at .032 lbs per acre since initiation of this study has demonstrated excellent weed control with this approach. Clearfield wheat technology appears to be very compatible with diverse Central Great Plains cropping systems. |
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