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.

 

1.   TITLE:     Clearfield™ Winter Wheat Risk Assessment

2.   PERSONNEL:

      Phillip W. Stahlman          Research Weed Scientist             KSU Agric. Research Center-Hays

      Anthony D. White            Research Associate                     KSU Agric. Research Center-Hays

      T. Joe Martin                   Wheat Breeder                            KSU Agric. Research Center-Hays

      Victor L. Martin               Agronomist                                  KSU Department of Agronomy

3.   TIME LINE:  Initiated - August, 2001; Projected completion- August, 2006; On Schedule

4.   ORIGINAL HYPOTHESIS:  The prolonged use of Clearfield (imidazolinone resistant) winter wheat will increase the risk of transferring herbicide resistance to jointed goatgrass (Aegilops cylindrica Host) and hasten selection of herbicide resistant biotypes in other winter annual grass weed species.

5.   SUMMARY OF PROGRESS: 2001-2002:  The first of five planned crop years has been completed and the second crop has been seeded. In 2002, spraying Clearfield wheat grown using Best Management Practices (BMP) with imazamox (Beyond™) at 0.024 or 0.040 lb/A reduced jointed goatgrass tiller density at harvest by 81 and 99%, respectively.  In comparison, imazamox at 0.024 lb/A applied to Clearfield wheat grown using conventional (CONV) practices reduced tiller density by only 47%. Despite these differences, wheat yields and jointed goatgrass dockage were not different between treatments. Post-harvest plant density counts after summer rainfall revealed far fewer jointed goatgrass plants in plots treated with imazamox than in plots not receiving imazamox. To date, no wheat-jointed goatgrass hybrids have been found and resistance in jointed goatgrass or other winter annual weed species to imazamox is not yet suspected.

6.   OBJECTIVES:

  1. Assess the risk of moving imidazolinone herbicide resistance into a jointed goatgrass population and the possibility of selecting for resistance in other winter annual weed species in cropping systems using Clearfield winter wheat.

  2. Determine the rate of resistance integrating into grass weed populations and investigate jointed goatgrass-wheat hybrid population dynamics.

  3. Investigate management strategies to reduce the occurrence of herbicide-resistant hybrids/biotypes.

7.    EXPERIMENTAL DESIGN:  The experiment is set up in a randomized complete block design with three replications.  Plot size, currently 54 by 110 feet, was modified from the original proposal (55 by 120 feet) to fit the experimental area.  A total of 10 treatments were applied to the experimental area.  Additional information on individual treatments is listed in Table 1.  The CONV treatments were seeded using a Marliss double disk drill set on 10-inch row spacing and BMP treatments were seeded using a John Deere double disk opener drill set on 7.5-inch row spacing.  Jointed goatgrass count means are the average of four subsample quadrates (0.8361 yd2) in each plot.  Methods in the original proposal indicated using 0.032 and 0.048 lb/A of imazamox.  However, many producers in this area tend to use reduced herbicide rates in wheat to try and cut production costs.  This practice may lead to a more rapid development of resistance in jointed goatgrass populations.  Therefore, imazamox rates were reduced to 0.024 and 0.04 lb/A to better represent herbicide selection pressure from current production practices.

8.    PROGRESS 2002: Objective 1. Assess the risk of moving imidazolinone herbicide resistance into a jointed goatgrass population and the possibility of selecting for resistance in other winter annual weed species in cropping systems using Clearfield winter wheat.

The study was initiated by overseeding the experimental area with spikelets of three geographically-dissimilar jointed goatgrass accessions in the summer of 2001 to establish a baseline population. Jointed goatgrass populations prior to seeding wheat in the fall ranged from 12 to 16 plants/yd2; those were destroyed by final seed bed tillage. Post-plant precipitation was minimal until early-spring and jointed goatgrass plant populations in late March averaged less than 4 plants/yd2. No wheat-jointed goatgrass hybrids were expected in the first year of the study and none were found.

Objective 2. Determine the rate of resistance integrating into grass weed populations and investigate jointed goatgrass-wheat hybrid population dynamics.

No hybrids were expected or found at this early stage, therefore the rate of resistance integration could not be determined.

Objective 3. Investigate management strategies to reduce the occurrence of herbicide-resistant hybrids/biotypes.

Herbicide treatment effects on jointed goatgrass plant populations in March, wheat tiller density (data not shown), wheat grain yields, and dockage were not significant; however, imazamox treatments significantly reduced jointed goatgrass tiller density (Table 2).  Jointed goatgrass plant populations were less dense in March 2002 (<4 plants/yd2) than prior to seeding in fall 2001 (12-16 plants/yd2). Those plants were destroyed prior to seeding wheat and very little precipitation was received to stimulate additional emergence after seeding until mid-spring 2002.  Spraying Clearfield-BMP wheat with imazamox at 0.024 or 0.040 lb/A reduced jointed goatgrass tiller density at harvest by 81 and 99%, respectively.  In comparison, imazamox at 0.024 lb/A applied to Clearfield-CONV wheat reduced tiller density by only 47%. Although the percentage differences are large, variability was high and the difference between the BMP and CONV practices for Clearfield wheat sprayed with imazamox at 0.024 lb/A was not significant (3.8 vs. 10.6 tillers/yd2). However, the difference between Clearfield-BMP sprayed with imazamox at 0.04 lb/A and Jagger-CONV wheat sprayed with sulfosulfuron was significant (<0.1 vs 20 tillers/yd2).

Post-harvest plant counts in late August after summer rainfall showed the beneficial impact of imazamox treatments. Clearfield-BMP sprayed with imazamox at 0.024 and 0.040 lb/A reduced post harvest jointed goatgrass plant density by 87 and 96%, respectively, and Clearfield-CONV wheat sprayed with imazamox at 0.024 lb/A reduced jointed goatgrass plant density by 90%. Differences between BMP and CONV systems were not significant. Plots receiving imazamox treatments contained significantly fewer post-harvest jointed goatgrass plants than plots receiving sulfosulfuron.

9.   PUBLICATIONS:  None to date.

10.  TECHNOLOGY TRANSFER:  The rational and objectives of this study were presented at the Kansas Wheat Field Day at Hays in May 2002.  Stewardship practices involved with prolonging Clearfield technology and their relationship with jointed goatgrass were also discussed.  Confirmed treatment differences were not available for presentation due to the recent initiation of this study.

11.  PRODUCER RECOMMENDATIONS IN THE CENTRAL GREAT PLAINS:

·        Follow current Clearfield Wheat stewardship guidelines to prolong the technology.  To ensure that the benefits of Clearfield wheat are available to producers in the future, certain stewardship guidelines should be followed.  Practice crop and herbicide rotation and do not use Beyond herbicide at lower than labeled rates.  This study showed a loss of jointed goatgrass control when a lower-than-labeled rate was used.

·        Implement Best Management Practices to battle jointed goatgrass.  Integrating BMPs, i.e. 50% higher-than-normal seeding rates, narrow row spacing, use of large-sized seed, and in-furrow starter fertilizer, along with Beyond herbicide improved jointed goatgrass control compared to using Beyond in Clearfield wheat grown using conventional practices.

 

Table 1. Treatments and timeline for Clearfield Winter Wheat Risk Assessment.

 

 

Treatments

Crop year

 

1

2

3

4

5

36 ft alley

2001-02

wheat

CRCF .048-BMP

CRCF .032-BMP

CRCF-.032-Conv

CRCF-.048-BMP

Jagger-BMP

 

2002-03

wheat

CRCF .048-BMP

CRCF .032-BMP

BRCF-.032-Conv

BRCF-.032-BMP

Jagger-BMP

 

2003-04

wheat

CRCF .048-BMP

CRCF .032-BMP

BRCF-.032-Conv

Jagger-BMP

Jagger-BMP

110 ft

2004-05

wheat

CRCF .048-BMP

CRCF .032-BMP

BRCF-.032-Conv

CRCF-.048-BMP

Jagger-BMP

2005-06

wheat

CRCF .048-BMP

CRCF .032-BMP

BRCF-.032-Conv

BRCF-.032-BMP

Jagger-BMP

 

 

 

 

 

 

 

 

36 ft alley

 

 

6

7

8

9

10

2001-02

wheat

CRCF .048-BMP

CRCF .032-BMP

CRCF-.032-Conv

CRCF-.048-BMP

Jagger-BMP

2002-03

wheat

CRCF .048-BMP

CRCF .032-BMP

BRCF-.032-Conv

BRCF-.032-BMP

Jagger-BMP

2003-04

row crop

crop rotation

crop rotation

crop rotation

crop rotation

crop rotation

110 ft

2004-05

wheat

CRCF .048-BMP

CRCF .032-BMP

BRCF-.032-Conv

CRCF-.048-BMP

Jagger-BMP

2005-06

wheat

CRCF .048-BMP

CRCF .032-BMP

BRCF-.032-Conv

BRCF-.032-BMP

Jagger-BMP

 

 

 

 

 

 

 

 

36 ft alley

 

 

54 ft; 50 ft sprayed

54 ft; 50 ft sprayed

54 ft; 50 ft sprayed

54 ft; 50 ft sprayed

54 ft; 50 ft sprayed

 

 

 

 

 

 

 

 

Total area:  328 by 810 ft including 3-36 ft alleys = 6.1 acres

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CRCF = Certified Clearfield winter wheat; sprayed late fall or early spring with imazamox at 0.024 or 0.040 lb ai/A

 

              BRCF = Bin-run Clearfield winter wheat; sprayed late fall or early spring with imazamox at 0.024 lb ai/A

 

 

 

 

 

 

 

 

 

 

BMP = Best Management Practices

 

 

Conv = Conventional Practices

 

 

 - inversion tillage after second crop; noninversion tillage other years

- noninversion tillage

 

 

 - 50% higher-than-normal seeding rate, 90 lb/A

 

- normal seeding rate, 60 lb/A

 

 

 - narrow row spacing, 6-7.5-inch

 

 

- 10-inch row spacing

 

 

 - in-furrow starter fertilizer plus spring N topdress

 

- broadcast fertilizer without in-furrow starter plus spring N topdress

 - large-sized seed

 

 

 

- nonsized seed

 

 

 

 

 

 

 

 

 

 

 

 

 

                 

 

Table 2.  Jointed goatgrass population density and wheat yield effects, St. John, KS 2002.

 

Jointed goatgrass counting date

Jointed goatgrass tiller density at harvest

 

 

Treatmenta

March 21

August 29

Wheat yield

Dockage

 

              _______ Plants/yd2 ______

         Tillers/yd2

Bu/Ab

 %c

 

 

 

 

 

 

Clearfield - BMP

 3.4 a

  1.6 a

   0.08 a

41.6 a

  3.6 a

    Imazamox (0.04 lb/A)

 

 

 

 

 

 

 

 

 

 

 

Clearfield - BMP

 3.0 a

  5.5 a

   3.8 a

41.2 a

  3.3 a

    Imazamox (0.024 lb/A)

 

 

 

 

 

 

 

 

 

 

 

Clearfield - Conventional

 2.4 a

  4.3 a

   10.6 ab

41.5 a

  3.6 a

    Imazamox (0.024 lb/A)

 

 

 

 

 

 

 

 

 

 

 

Jagger - Conventional

 2.2 a

 41.9 b

  20.0 b

40.4 a

  4.3 a

    Sulfosulfuron (0.023 lb/A)

 

 

 

 

 

LSD (α=0.05)

1.5

21.8

12.0

8.9

1.8

             

aEach treatment for 2002 were grouped since subsequent rotations have not been implemented.

bCombine-cleaned grain including foreign material.

cTotal foreign material. Very few jointed goatgrass spikelets.

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