National Jointed Goatgrass Research Program

 

Progress Report-2002

NOTICE
The following is a progress report containing preliminary data and results that may be modified by future research.
Please contact the listed authors
or Extension Coordinator for additional information.

 

Title: Managing Imazamox-Resistant Wheat in Crop Rotations for Control of Jointed Goatgrass in the Central Great Plains

Personnel:    Drew Lyon and Stephen Miller

Time Line:   The study was initiated in the fall of 2000 and is scheduled to run through the summer of 2005. The study is on schedule.

Original Hypothesis:    Use of Clearfield wheat every 2 or 3 years, or 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: Data from the first two years have been collected and summarized. Averaged over both years, the use of the imazamox-resistant wheat system resulted in a 94% reduction in jointed goatgrass reproductive tillers and a 91% reduction in grain dockage compared to the standard wheat treatment. In 2001, the standard wheat treatment yielded 28% more than the imazamox-resistant wheat treatment, while in 2002, the imazamox-resistant wheat treatment yielded 26% more than the standard wheat treatment.

Objectives:    

  • Determine the best use of Clearfield wheat for control of jointed goatgrass in wheat-based cropping systems of the Central Great Plains.

  • Determine the risk of developing imazamox-resistant jointed goatgrass in cropping systems using Clearfield wheat.

  •  Monitor the impacts of Clearfield wheat technology on jointed goatgrass and jointed goatgrass x wheat hybrid population dynamics.

Experimental Design: During the first two years of the study, there are just two treatments: a Clearfield wheat variety and a standard variety. Plots will be split in succeeding years and during the last two years of the experiment there will be eight treatments consisting of various temporal combinations of Clearfield and standard wheat varieties grown in a winter wheat-fallow rotation (Table 1). Clearfield treatments will receive an application of Beyond herbicide to control jointed goatgrass plants.

Progress/Conclusions: Data from the first two years have been collected and summarized. The third year of the study has been initiated and the herbicide treatment applied. In the first two years of the study, the use of imazomox-resistant wheat system resulted in a significant reduction in jointed goatgrass reproductive tillers and grain dockage compared to the standard wheat treatment (Table 2). There was a significant year x treatment interaction for wheat yield. In 2001, the standard wheat treatment yielded 28% more than the imazamox-resistant wheat treatment, while in 2002, the imazamox-resistant wheat treatment yielded 26% more than the standard wheat treatment. Winter came early in the fall of 2000. Wheat yields were low in 2001 and the imazamox-resistant wheat cultivar was apparently not as adapted to our eastern Wyoming location as the standard treatment wheat cultivar Buckskin. The fall of 2001 was warm and wheat was well-established going into the winter. Despite a very dry winter and spring, wheat yields were greater in 2002 than 2001. The imazamox-resistant wheat cultivar, Above, performed relatively well compared to the standard cultivar, Buckskin. Plots were searched for wheat x jointed goatgrass hybrids, but none were located. Jointed goatgrass seed was collected from the imazamox-resistant and standard wheat treatments in June 2002. Seedling response to 0.032 lb ai/acre imazamox was then compared and analyzed using categorical data analysis and Pearson's Chi-square test. No difference in response between the two seed sources was observed (P2 = 2.7, p = 0.379).

Publications:   None

Technology Transfer Activities: None; it is too early in the project for this type of activity. We anticipate beginning activities in 2004, following the second year of the four-way treatment comparisons.

                                                                      

Table 1. Treatment comparisons during the course of the study.

Yeara

Treatment comparisons

2001 & 2002

Standard wheat (SW)

Clearfield wheat (CW)

2003 & 2004

SW-F-SW

SW-F-CW

CW-F-CW

CW-F-SW

2005 & 2006

SW-F-SW-F-SW

SW-F-SW-F-CW

SW-F-CW-F-SW

SW-F-CW-F-CW

CW-F-CW-F-SW

CW-F-CW-F-CW

CW-F-SW-F-SW

CW-F-SW-F-CW

                 

 

Table 2. Comparison of an imazamox-resistant winter wheat-fallow system with a standard winter wheat-fallow system at Lingle, WY in the 2000/2001 and 2001/2002 crop years.

 

 

 

Wheat yield

Treatment

JGG tillers

Dockage

2001

2002

 

#/0.25 m2

g/kg

                                      kg/ha                                      

Standard

28.0

54.0

700

1400

Imazamox-resistant

1.5

4.7

550

1740

P value

0.001

0.003

0.032

0.027

 
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