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Progress Report-2001 |
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FINAL REPORT |
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TITLE: How Agronomic Practices Affect Herbicide Resistance in Jointed Goatgrass: Simulated Consequences of Clearfield™ Winter Wheat Use
PERSONNEL: Carol Mallory-Smith, Associate Professor, Oregon State University, Corvallis D. Eric Hanson, Faculty Research Assistant, Oregon State University, Corvallis
TIME LINE: July 1, 2000 - June 30, 2001
ORIGINAL HYPOTHESIS: Data are available from various sources that can be used to help predict the impact of management strategies on the development of imidazolinone resistant jointed goatgrass.
SUMMARY OF PROGRESS: A population model was constructed to simulate the development of imazamox-resistant jointed goatgrass in imazamox-resistant (Clearfield™) wheat. The model was created using a single-page, menu-driven, user interface with a series of population projection matrices (Caswell 1989) to simulate ten years of crop production. A manuscript has been accepted for publication in Weed Technology.
OBJECTIVE: Develop a simulation tool to provide management recommendations for the use of imidazolinone resistant wheat in combination with other agronomic practices to prevent or delay the occurrence of herbicide resistant jointed goatgrass.
EXPERIMENTAL DESIGN: The project uses a population modeling approach to assess the development of herbicide resistant jointed goatgrass under different management strategies (Ball 1992; Maxwell et al 1990; Sagar and Mortimer 1976). Population regulation occurs both through natural intrinsic processes (e.g., mortality probability) and weed control efficacy. Weed control techniques used include cultural, mechanical, and chemical. The crop rotation effects are considered by simulating the response of a population established in one crop and regenerating in another (Jordan 1993). Data on seed production, seed longevity, seed dormancy, seed germination, and plant survival are included in the model.
CONCLUSIONS: A population model was constructed to simulate the development of resistant jointed goatgrass in Clearfield wheat. The model was created using a single-page, menu-driven, user interface with a series of population projection matrices (Caswell 1989) to simulate ten years of crop production. The model included four management scenarios: 1) continuous no-till Clearfield wheat without hybridization with jointed goatgrass; 2) continuous no-till wheat with hybridization with jointed goatgrass; 3) Clearfield wheat-fallow-Clearfield wheat rotation; and 4) Clearfield wheat-fallow-non-Clearfield wheat. The model computed changes in the surface and the buried jointed goatgrass seedbank for both resistant and susceptible biotypes. Simulations started with an initial density of 1000 susceptible, and no resistant seeds/m2 in each seed bank. Simulation of continuous, no-till, Clearfield wheat production resulted in rapid development of resistant jointed goatgrass without hybridization with wheat and extremely rapid resistance development with hybridization. In less than 10 years, the resistant population was growing exponentially in both simulations. However since tillage was not included, resistant seed were not introduced into the soil seed bank, which might allow easier cleanup of the resistant population if another control option became available.
Adding a fallow year with tillage into the simulated rotation did not slow the appearance of resistance substantially but did delay the rate of resistant population increase by several orders of magnitude over 10 years. Although the projected population was much lower under this system, the resistant jointed goatgrass seed would be moved into the seed bank creating a long-term problem.
Alternating Clearfield and a non-resistant winter wheat in combination with fallowing prevented establishment of a significant resistant jointed goatgrass population and prevented the susceptible seed population from increasing exponentially. This system allowed the use of tillage and a non-ALS herbicide to be used in the fallow year for control of jointed goatgrass. These projections suggest Clearfield wheat can be a tool for managing jointed goatgrass populations especially if combined with rotations that include fallow and crops other than Clearfield winter wheat.
The model requires refinement in several areas including: 1) parameterization, 2) population genetics, and 3) noncereal crop effects of jointed goatgrass population dynamics. Information on local dispersal, seed loss through predation and harvest, and competitive effects needs to be added to the existing model. Initial resistance levels in the population will influence how that level changes over time. Data on the growth and development of jointed goatgrass in crops other than wheat (e.g., Anderson 1997) will also be required to simulate the effects of crop rotation.
LITERATURE CITED:
Anderson, R. L. 1997. Cultural systems can reduce reproductive potential of winter annual grasses. Weed Tech. 11:608-613.
Ball, D. A. 1992. Weed seedbank response to tillage, herbicides, and crop rotation sequence. Weed Sci. 40:654-59.
Caswell, H. 1989. Matrix Population Models. Sinauer Associates, Inc. Sunderland, MA. 328 pp.
Jordon, N. 1993. Simulation analysis of weed population dynamics in ridgetilled fields. Weed Sci. 41:468-74.
Maxwell, B. D., M. L. Roush, and S. R. Radosevich. 1990. Predicting the evolution and dynamics of herbicide resistance in weed populations. Weed Tech. 4:2-13.
Sagar, G. R. and A. M. Mortimer. 1976. An approach to the study of the population dynamics of plants with special reference to weeds. Ann. Appl. Biol. 1:1-47.
PUBLICATIONS:
Hanson, D. E., D. A. Ball, and C. A. Mallory-Smith. 2002. Herbicide Resistance in Jointed Goatgrass (Aegilops cylindrica): Simulated Responses to Agronomic Practices. Weed Technology (in press)
PLANNED TECHNOLOGY TRANSFER: Model results will be presented and discussed with agrichemical manufacturers (i.e. BASF and other marketers of ALS inhibitor herbicides) to assist in the development of company policy on resistance management recommendations. The information will be provided to wheat producers at Extension meetings and in publications. The final outcome will help growers and industry representatives to predict the risk of resistance and how their management strategies could prevent or delay resistance of jointed goatgrass to imazamox. |
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