Progress 07/01/02 to 09/30/07

Outputs
OUTPUTS: Growers in intermediate rainfall zones are trying chemical fallow systems to replace the more erosive dust-mulch fallow. Two primary problems associated with chemical fallow are the loss of seed-zone soil moisture due to evaporative loss in un-tilled soil, and weed problems associated with the elimination of tillage and subsequent reliance on herbicides. Currently, most growers rely on repeated broadcast applications of glyphosate for season-long weed control in chem-fallow. Moreover, plants grown under moisture stress typically require greater herbicide rates to provide the same level of control compared to plants grown under adequate moisture. Another concern with repeated applications in chem-fallow is the development of herbicide resistant weed populations. A concept for reducing repeated broadcast applications of glyphosate is through the use of optical sensor controlled spot-treatment (WeedSeeker) technology. This technology has the potential to reduce herbicide costs through directed spot-treatment of weeds. In addition, others have shown that properly timed sweep tillage operations followed by rod weeding may reduce evaporative losses of seed-zone soil moisture with relatively little loss of surface crop residue, and with possible enhancement of overall fallow weed control. This previous work with sweep tillage utilizing an undercutter relied on rod weeding for weed control and seed-zone moisture retention. This project is investigating the potential for sweep tillage with chemical fallow. Four systems were evaluated for their impact on seed-zone soil moisture, surface residue and roughness, weed population dynamics, and response of the winter wheat crop following these fallow treatments. Imazamox herbicide, a group 2 acetolactate synthase inhibitor, is used to selectively control weeds, such as jointed goatgrass, downy brome, wild oat and Italian ryegrass, in imidazolinone-resistant winter wheat. Imazamox can persist in the soil for 3 to 26 months, and thus affect growth of rotational crops such as barley, canola, and mustard. Tillage practices used in the dry land winter wheat cropping systems can affect herbicide carryover and injury to rotational crops. This study is being conducted to determine the effect of tillage on the persistence of imazamox herbicide. Fall and spring applications of imazamox were applied at one, two, and three times the maximum labeled rate to (Clearfield ORCF-101) winter wheat. Grain was harvested at all sites during summer 2006 and tillage strips were implemented in the fall 2006. Yellow mustard was seeded during spring 2007 and harvested during summer 2007. PARTICIPANTS: D. Thill, University of Idaho J. Yenish, Washington State University TARGET AUDIENCES: wheat growers

Impacts
Research to evaluate undercutter and chemical fallow was conducted near Davenport at the Wilke Research and Extension farm and on a commercial wheat farm near Helix, OR, both in intermediate rainfall production zones. Tumble pigweed, Russian thistle, wild oat and downy brome were main weed species at Davenport and prickly lettuce and Russian thistle at the Helix location. Treatment comparisons in year one showed greater tumble pigweed density and biomass in non-rodweeded treatments compared to rodweeded treatments at Davenport, but no difference in density and biomass of Russian thistle or grasses. At Davenport, most weeds present in non-rodweeded treatments were in the tractor sprayer track path. At the Helix site, there were no differences in weed density among tillage treatments, but there was a greater number of Russian thistles in plots utilizing an optical sensor-controlled (OSC) sprayer for herbicidal weed control. At the Helix site, dust conditions appeared to impact weed control with the OSC sprayer, and rodweeding did provide slightly improved weed control. There were slight differences in soil moisture among treatments at both locations. Additional studies in WA and OR evaluated the efficacy of various herbicides using OSC sprayer in chemical fallow systems. Again, the dominant broadleaf weed species were tumble pigweed, Russian thistle, and prickly lettuce. Glyphosate alone at different rates and in combination with 2,4-D or pyrasulfotole plus bromoxynil, or paraquat provided greatest weed control at both Davenport and Pendleton sites. Carfentrazone plus dicamba, bromoxynil, or 2, 4-D 4 pt/A alone proved to be the least efficient herbicides, mainly due to lack of grass weed control at Davenport or prickly lettuce at Pendleton. Imazamox applied in the fall at the two highest rates to winter wheat injured mustard 21 to 86% at all locations, while imazamox applied to winter wheat in the spring injured mustard 5 to 91%. At Pendleton, the most injury was in conventional tillage followed by minimum, with the least injury in the direct-seeded plots. At Genesee, the most injury was in minimum tillage followed by direct-seed, with the least injury in conventional tillage. At Davenport, the minimum and direct-seed tillage had the most injury followed by conventional tillage with the least injury. This study is being repeated except soil samples are not being collected. Grain was harvested at all sites during summer 2007. Imazamox applied in the fall at the highest rate injured wheat 20 to 30% at all locations, while spring applied imazamox injured wheat 6 to 68%. No treatments adversely affected grain yield compared to the untreated control. Work on the soil bioassay has begun but no results are available.

Publications

• Ball, D. A. and C. J. Peterson. 2007. Herbicide Tolerance in Imidazolinone-Resistant Wheat for Weed Management in the Pacific Northwest U.S.A. pg. 243-250 in: H. T. Buck et al. (eds.). Wheat Production in Stressed Environments, Springer.
• Ball, D. A., S. M. Frost, L. H. Bennett, D. C. Thill, T. Rauch, E. Jemmett, C. Mallory-Smith, C. Cole, J. P. Yenish, and R. Rood. 2007. Control of rattail fescue (Vulpia myuros) in winter wheat. Weed Technology 21(3):583-590.
• Ball, D. A., S. M. Frost, and L. H. Bennett. 2007. ACCase-inhibitor herbicide resistance in downy brome (Bromus tectorum) in Oregon. Weed Science 55:91-94.
• Tarasoff C. S., D. A. Ball, and C. Mallory-Smith. 2007. Extreme ionic and temperature effects on germination of weeping alkaligrass, Nuttalls alkaligrass and Kentucky bluegrass. Weed Science 55:305-310.
• Tarasoff, C. S., D. A. Ball, and C. Mallory-Smith. 2007. Comparative plant responses of Puccinellia nuttalliana and Puccinellia distans to sodic versus normal soil types. Journal of Arid Environments 70:403-417.
• Tarasoff, C. S, D. A. Ball, and C. A. Mallory-Smith. 2007. Afterripening requirements and optimal germination temperatures for Nuttalls alkaligrass and weeping alkaligrass. Weed Science 55:36-40.
• Machado, S., L. Pritchett, E. Jacobsen, R. Smiley, D. Ball, S. Petrie, D. Wysocki, S. Wuest, H. Gollany, and W. Jepsen. 2007. Long-term experiments at CBARC-Moro and Center of Sustainability, Heppner, OR 2005-2007. In: 2007 Dryland Agricultural Research Annual Report. OSU Ag. Exp. Stn. Spec. Rpt. 1074. Pg 82-91.
• Bennett, L. H., S. M Frost, and D. A. Ball. 2007. Weed control with metam-sodium during establishment of Kentucky bluegrass. West. Soc. Weed Sci. Res. Prog. Rpt. p. 89.
• Rood, J. R., D. C. Thill, R. J. Rood, J. P. Yenish, D. A. Ball, S. M. Frost. 2007. Tillage affects imazamox persistence in soil. West. Soc. Weed Sci. Res. Prog. Rpt. p. 141.

Progress 01/01/06 to 12/31/06

Outputs
Rattail fescue, a winter annual grass weed, has been increasing in Pacific Northwest (PNW) dryland cereal producing areas. Although rattail fescue is not a new weed species in the PNW, its incidence is expanding rapidly in circumstances where soil disturbances are minimized such as in direct seed systems. Options for effective rattail fescue control in winter wheat cropping systems had not been adequately investigated, and needed to be developed. Rattail fescue control with herbicide treatments was investigated in imidazolinone-resistant winter wheat using imazamox and other herbicides. Across multiple sites and two growing seasons, crop injury from herbicide treatments was minor to negligible with some exceptions. Treatments containing imazamox or mesosulfuron produced minor, transient winter wheat crop injury at some locations in some years. With the exception of flufenacet applied preemergence (PRE), control of rattail fescue in wheat was variable with single herbicide applications, but improved with sequential herbicide treatments. Rattail fescue biomass was greatly reduced by several treatments especially those containing flufenacet or from sequential herbicide application. Crop yield varied among sites due to growing season precipitation, and in some cases from rattail fescue control or herbicide related crop injury. In spring 2005, a downy brome (Bromus tectorum) population with possible resistance to fluazifop-P-butyl, an ACCase inhibitor (Group 1) herbicide was found in a commercial creeping red fescue seed production field, near La Grande, Oregon, USA where fluazifop-P-butyl had been used to control downy brome repeatedly over a seven year period. Greenhouse experiments were conducted to confirm resistance to a number of Group 1 herbicides. The suspected resistant downy brome accession was tested for resistance to fluazifop-P-butyl, and tested for cross resistance to other APP and CHD herbicides, including quizalofop-P, sethoxydim, and clethodim. Data recorded included plant mortality counts and biomass. Tests revealed that the La Grande downy brome accession was highly resistant to fluazifop-P-butyl and sethoxydim at all tested rates. The La Grande accession suffered no mortality from fluazifop-P-butyl or sethoxydim treatments up to the maximum tested rate of 8 times (8x) the labeled recommendation. The La Grande accession was resistant to quizalofop-P-ethyl and clethodim at the labeled rate or less, but was susceptible to application rates higher than the labeled rate. The control downy brome accession was completely susceptible to fluazifop-P-butyl, quizalofop-P and clethodim at all rates, and exhibited increasing susceptibility with increasing sethoxydim rate. This pattern of cross resistance differs from that of a previously reported case of ACCase resistance in downy brome.

Impacts
Rattail fescue infestations in wheat cropping systems in the PNW will be substantially reduced due to newly recognized options for control. Use of ACCase herbicides in grass seed cropping systems will be more judiciously used, and crop rotations will be modified to shorten the number of seasons in which perennial grass seed production fields will be maintained.

Publications

• Bennett, L. H., S. M. Frost, and D. A. Ball. 2006. Grass weed control with flucarbozone-sodium in seedling Kentucky bluegrass seed production. West. Soc. Weed Sci. Res. Prog. Rpt. p. 131.
• Bennett, L. H., S. M. Frost, and D. A. Ball. 2006. Rattail fescue control in chemical fallow. West. Soc. Weed Sci. Res. Prog. Rpt. p. 135.
• Bennett, L. H., S. M. Frost, and D. A. Ball. 2006. Downy brome control in Clearfield winter wheat. West. Soc. Weed Sci. Res. Prog. Rpt. p. 171.
• Frost, S. M., L. H. Bennett, and D. A. Ball. 2006. Downy brome control in Clearfield winter wheat with propoxycarbazone-sodium. West. Soc. Weed Sci. Res. Prog. Rpt. p. 177.
• Frost, S. M., L. H. Bennett, and D. A. Ball. 2006. Rattail fescue control with imazamox and adjuvants in Clearfield winter wheat. West. Soc. Weed Sci. Res. Prog. Rpt. p. 179.
• Frost, S. M., L. H. Bennett, and D. A. Ball. 2006. Interactions of wild oat herbicides with thifensulfuron-methyl and tribenuron-methyl. West. Soc. Weed Sci. Res. Prog. Rpt. p. 191.
• Machado, S., L.Pritchett, E.Jacobsen, S.Petrie, R.Smiley, D.Ball, D.Wysocki, S.Wuest, H.Gollany, and W.Jepsen. 2006. Long-term experiments at CBARC-Moro and Center of Sustainability, Heppner, OR. In 2006 Dryland Agricultural Research Annual Report. OSU Ag. Exp. Stn. Spec. Rpt. 1068. Pg 50-67.
• Frost, S. M., L. H. Bennett, and D. A. Ball. 2006. Medusahead rye control in rangeland. West. Soc. Weed Sci. Res. Prog. Rpt. p. 16.

Progress 01/01/05 to 12/31/05

Outputs
Winter annual grass weeds such as jointed goatgrass, downy brome, feral rye, wild oat, and Italian ryegrass have the same life-cycle as winter wheat and are difficult to control in conventional wheat production systems. Before use of imazamox herbicide with imidazolinone-resistant (CLEARFIELD*) wheat, there was no herbicide that could selectively control jointed goatgrass, feral rye, or volunteer cereals in winter wheat. Plant breeders are developing imidazolinone-resistant winter wheat varieties adapted to a range of Pacific Northwest production regions. Wheat tolerance to imazamox application can vary with time of herbicide application relative to wheat stage of growth, environmental conditions that reduce wheat plant ability to metabolize imazamox and, possibly, with specific wheat varieties. Studies were conducted to evaluate imazamox tolerance in CLEARFIELD* wheat lines being developed for Pacific Northwest production regions. During specific years and locations, single-gene CLEARFIELD* varieties differed slightly in their relative tolerance to imazamox. However, when averaged across years and location, varietal response to imazamox did not differ significantly. The most important determinant of crop tolerance was related to herbicide application rate and timing. In multiple location studies of chemical fallow, glyphosate was more effective at controlling rattail fescue than paraquat + diuron. Split applications of glyphosate provided the most consistent control across locations and provided the greatest overall reduction in late-season rattail fescue panicle density and subsequent seed production. Control of rattail fescue was also investigated in CLEARFIELD* winter wheat. Across locations, crop injury was minor and control of rattail fescue was generally marginal from single applications, but excellent from multiple herbicide treatments. A vernalization study indicated that rattail fescue plants required vernalization to produce spikes and germinable seeds, thereby supporting the classification of rattail fescue as a true winter annual. Two species of alkaligrass found in arid, saline environments of eastern Oregon, Puccinellia distans and P. nuttalliana, were studied to determine dormancy attributes and optimal temperature conditions for seed germination . Both species were found to have a high level of embryonic dormancy immediately following seed harvest, which is primarily eliminated through afterripening at an incubation temperature of 20 C. A pre-chill treatment of 5 days at 5 C had an inconsistent effect on germination in P. distans yet markedly improved germination of P. nuttalliana following adequate afterripening. The afterripening requirement for P. distans was 90 days, where as P. nuttalliana required 180 days. Following adequate afterripening, both species had rapid and well synchronized germination at fluctuating temperatures of 30/10 C given unlimited moisture conditions. Given these results, it is unlikely that seeds of either species would germinate in eastern Oregon during the summer months, but would more likely exhibit a rapid, well synchronized germination in the spring.

Impacts
Winter annual grass weeds such as jointed goatgrass, downy brome, feral rye, wild oat, and Italian ryegrass have the same life-cycle as winter wheat and are difficult to control in conventional wheat production systems. Plant breeders are developing imidazolinone-resistant winter wheat varieties adapted to a range of Pacific Northwest production regions. It is estimated that in 2005, approximately 400,000 acres of CLEARFIELD wheat will be planted in the Pacific Northwest. Control of jointed goatgrass, feral rye, or volunteer cereals in winter wheat is now possible with this technology and will lead to a minimum 5% yield increase, and reduced dockage of 0.5% in more than half of these acres. Positive environmental benefits from improved control techniques include decreased use of herbicides, reduced nitrogen fertilizer loss from agricultural soils, and less herbicide drift and soil residue loss. In some cases where an increase in herbicide applications is needed, no adverse environmental impact is likely. Meanwhile, consideration must be given to public negative perceptions about herbicide use. Reduced soil erosion results from farmer adoption of recommendations from this project. This lowers county/state maintenance costs for road and ditch repair. Reduced herbicide use translates to less drift and associated damage to off-site agricultural crops, ornamentals, and nonfarm neighboring property. Overall, the recommended management changes also result in an improved public image of agriculture.

Publications

• Ball, D.A., S.M. Frost, C. Tarasoff, and C. Mallory-Smith, 2005. Biology of rattail fescue and its management in direct-seeded winter wheat and chemical fallow. In: 2005 Dryland Agricultural Research Annual Rpt. OSU Ag. Exp. Stn. Spec Rpt. 1061, June 2005. P. 92.
• Ball, D. A., L. H. Bennett, and S. M. Frost. 2005. Wild oat control in seedling Kentucky bluegrass grown for seed. In: 2004 Seed Production Research Report, OSU Ext / CrS 124: 58-59.
• Ball, D. A. and C. J. Peterson. 2005. Herbicide tolerance in imidazolinone-resistant wheat for weed management in the Pacific Northwest. Abstracts of 7th International Wheat Conf. Mar del Plata, Argentina.
• Bennett, L.H., S.M. Frost, and D.A. Ball. 2005. Rattail fescue control in chemical fallow. West. Soc. Weed Sci. Res. Prog. Rpt. P.105.
• Bennett, L.H., S.M. Frost, and D.A. Ball. 2005. Downy brome control with propoxycarbazone-sodium and mesosulfuron-methyl. West Soc. Weed Sci. Res. Prog. Rpt. P.151.
• Bennett, L.H., S.M. Frost, and D.A. Ball. 2005. Rattail fescue control in CLEARFIELD winter wheat. West. Soc. Weed Sci. Res. Prog. Rpt. P.153.
• Bennett, L.H., S.M. Frost, and D.A. Ball. 2005. Interrupted windgrass conttol in established Kentucky bluegrass grown for seed production. West Soc. Weed Sci. Res. Prog. Rpt. P.99.
• Frost, S.M., L.H. Bennett, and D.A. Ball. 2005. Downy brome control in winter barley. West. Soc. Weed Sci. Res. Prog. Rpt. P.68.
• Frost, S.M., L.H. Bennett, and D.A. Ball. 2005. Wild oat control in seedling Kentucky bluegrass grown for seed production. West. Soc. Weed Sci. Res. Prog. Rpt. P.92.
• Frost, S.M., L.H. Bennett, and D.A. Ball. 2005. Russian thistle control in chemical fallow. West. Soc. Weed Sci. Res. Prog. Rpt. P.103.
• Rauch, T., E. Jemmet, D. Thill, D. Ball, L. Bennett, S. Frost, C. Mallory-Smith, C. Cole, J. Yenish, and R.Rood. 2005. Rattail fescue control in imazamox-tolerant winter wheat. In: Proc. West. Soc. Weed Sci. 58:21.
• Tarasoff, C.S., M. Louhaichi, C.A. Mallory-Smith, and D.A. Ball. 2005. Using geographic information systems to present non-geographical data: An example using a two-way thermogradient plate. Rangeland Ecology and Management 58(2): 315-318.
• Tarasoff, C, L. Fandrich, C. Mallory-Smith, D. Ball and S. Frost. 2005. Reproductive strategies: A study of rattail fescue seed biology and plant vernalization requirements. In: Proc. West. Soc. Weed Sci. 58:44.
• Ball, D. A., L. H. Bennett, and S. M. Frost. 2005. Interrupted windgrass control in established Kentucky bluegrass grown for seed In: 2004 Seed Production Research Report. OSU Ext/CrS 124: 60.

Progress 01/01/04 to 12/31/04

Outputs
Herbicide resistant wheat, commercially known as Clearfield wheat, was widely available this past year for commercial use in the Pacific Northwest. Wheat farmers, seed dealers, and herbicide distributors have questions about the use of this technology including appropriate timing and application methods for the herbicide used on Clearfield wheat, wheat tolerance to the herbicide, and questions about what to expect for weed control. Our project worked cooperatively with the wheat production industry to answer relevant questions on weed control, crop tolerance to herbicide treatment, soil persistence of herbicides, and control of particular weeds. In addition, information on the appropriate use of Clearfield technology was communicated to prevent the development of herbicide resistant weed populations from inappropriate use of Clearfield technology. Acreage of chemical fallow is increasing in the region due to decreasing herbicide cost and increasing fuel cost. Chemical fallow relies on the use of herbicides for weed control rather than multiple tillage operations that can lead to soil erosion, degradation of soil structure, and organic matter loss. Weed control is a major constraint to successful chemical fallow. Our project has worked cooperatively with farmers and the agrichemical industry to identify effective methods for weed control in chemical fallow. Seed characteristics of rattail fescue (Vulpia myuros) and alkaligrass (Puccinellia spp.) were studied and include optimum seed germination temperature, occurrence, and characteristics of seed dormancy, seed longevity under field conditions, and whole plant vernalization requirements. Growth chamber and thermogradient plate studies determined optimum seed germination temperatures of freshly harvested and one-year old, dry stored seed of V. myuros and Puccinellia spp. Germination studies determined that primary seed dormancy exists in V. myrous and Puccinellia sp. Dormant seeds will be subjected to germination promoting treatments to characterize the type of dormancy existing in these species. Seed longevity studies were continued at three locations in Union and Umatilla Counties in Oregon. Seeds of V. myuros, Puccinellia sp., and B. tectorum were buried in mesh packets at 10, 20, 30, and 60 cm depths in the soil. Packets are being recovered at six-month intervals for a period of 4 years, seeds separated from soil, and tested for viability by germination testing. Initial results have shown that viability of V. myrous seed decreases at the rate of approximately 75% loss per year when buried in the soil. This rate of decline varies according to location.

Impacts
Development of resistance management strategies for Clearfield winter wheat cropping systems utilizing crop rotations will reduce the incidence of herbicide resistant weed populations. Improved weed control in chemical fallow will lead to reductions in soil eroding tillage while maintaining effective weed control. Studies on V. myuros and Pucinellia sp. will significant implications in the development of management strategies for rattail fescue

Publications

• Rainbolt, C. R., D. C. Thill, J. Yenish, and D. A. Ball. 2004. Herbicide-resistant grass weed development in imidazolinone-resistant wheat: Weed biology and herbicide rotation. Weed Technology 18 (3): 860-868.
• W. A. Payne, C. Chen, and D. A. Ball. 2004. Agronomic Potential of Narrow-Leafed and White Lupins in the Inland Pacific Northwest Agron. Journal. 96: 1501-1508.
• Park, Kee Woong, C. A. Mallory-Smith, D. A. Ball, and G. W. Mueller-Warrant. 2004. Ecological fitness of acetolactate synthase inhibitor-resistant and susceptible downy brome (Bromus tectorum) biotypes. Weed Science. 52:768-773.
• Ball, D. A., S. M. Frost, and A. I. Gitelman. 2004. Predicting timing of downy brome (Bromus tectorum) seed production using growing degree-days. Weed Science 52:518-524.
• Rainbolt, C., D. A. Ball, D. Thill, J. Yenish. 2004. Management Strategies for Preventing Herbicide-Resistant Grass Weeds in Clearfield Wheat Systems. PNW Extension Publication (PNW 572). p. 8.
• Ball, D. A., R. Parker, J. Colquhoun, and I. Dami. 2004. Preventing Herbicide Drift and Injury to Grapes. OSU Extension Publication (EM 8860) p. 8.
• M. Corp, S. Machado, D. Ball, R. Smiley, S. Petrie, M. Siemens, and S. Guy. 2004. Chickpea Production Guide. OSU Extension Publication (EM8791-E Rev. Jan. 2004).
• Campbell, J.M., D. C. Thill, R. Stougaard, D. A. Ball, J. Yenish. 2004. Preplant applied graminicide effects on wheat and barley. Proceed. 2004 Western Soc. Weed Sci. pg 19.
• Corp. M. K., D. A. Ball, M. C. Siemens. 2004. Wheat straw management and its effects on weed populations, stand establishment and yield in direct-seed chickpea. Proceedings 2004 Western Soc. Weed Sci. pg 20.
• Anderson, R., D. C. Thill, T. Rauch, B. Hanson, D. A. Ball, M. Ensminger, K. Howatt, S. Seefeldt, M. Corp, J. Harbour. 2004. Guides to help producers manage weed resistance. Proceedings 2004 Western Soc. Weed Sci. pg 38.
• Tarasoff, C. S., D. A. Ball, S. Frost, C. A. Mallory-Smith. 2004. Seed dormancy and germination characteristics of two alkaligrass species: Puccinellia distans and Puccinellia nuttalliana. Proceedings 2004 Western Soc. Weed Sci. pg 43.
• Ball, D. A. 2004. Biology and management of rattail fescue in direct-seed systems. Pg. 93-97 in: NW Direct Seed Cropping Systems Conf. Proceedings. Jan. 7-9, 2004, Pendleton, OR.
• Ball, D. A., L. H. Bennett, S. M. Frost, and E. Jacobsen. 2004. Post-harvest tillage is inconsistent for managing jointed goatgrass. In: 2004 Columbia Basin Ag. Res. Ctr. Annual Rpt. OSU Ag. Exp. Stn. Spec Rpt. 1054. Pg. 77-83.
• Ball, D. A., L. H. Bennett, and L. Lutcher. 2004. Agronomic considerations for chemical fallow. In: 2004 Columbia Basin Ag. Res. Ctr. Annual Rpt. OSU Ag. Exp. Stn. Spec Rpt. 1054. Pg. 15-19.
• Ball, D. A., L. H. Bennett, and S. M. Frost. 2004. Metam sodium for weed control during establishment period of chewings fine fescue. In: 2003 Seed Production Research Report, OSU Ext / CrS 123: 57-58.
• Ball, D. A., L. H. Bennett, and S. M. Frost. 2004. Wild oat control in seedling Kentucky bluegrass. In: 2003 Seed Production Research Report, OSU Ext / CrS 123: 59.

Progress 01/01/03 to 12/31/03

Outputs
Changes in downy brome population susceptibility to sulfosulfuron due to herbicide use patterns in direct-seeded winter wheat were studied. Downy brome counts were correlated with the number of sulfosulfuron treatments applied over the course of a three-year study. As expected, sulfosulfuron applications made in the last year reduced downy brome count when evaluated in the third and final study year. Plots treated with sulfosulfuron or triallate in previous seasons had reduced downy brome counts compared to plots left untreated for three years. Untreated wheat following fallow had the same number of downy brome spikes as three consecutive untreated wheat crops, despite sulfosulfuron treatment in the crop previous to fallow. Downy brome seed collected from individual plots are currently being analyzed for possible changes in susceptibility to sulfosulfuron due to repeated exposure to sulfosulfuron over a period of three years. Seed characteristics of rattail fescue (Vulpia myuros) and alkaligrass (Puccinellia spp.) were studied and include optimum seed germination temperature, occurrence and characteristics of seed dormancy, seed longevity under field conditions, and whole plant vernalization requirements. Growth chamber and thermogradient plate studies determined optimum seed germination temperatures of freshly harvested and one-year old, dry stored seed of V. myuros and Puccinellia spp. Germination studies determined that primary seed dormancy exists in V. myrous and Puccinellia sp. Dormant seeds will be subjected to germination promoting treatments to characterize the type of dormancy existing in these species. Seed longevity studies were initiated at three locations in Union and Umatilla Counties in Oregon. Seeds of V. myrous and Puccinellia sp. were buried in mesh packets at 10, 20, 30, and 60 cm depths in the soil. Packets are being recovered at six month intervals for a period of 4 years, seeds separated from soil, and tested for viability by germination testing. Initial results have shown that viability of V. myrous seed decreases rapidly (approximately 75% loss per year) when buried in the soil. Location of Union County grass seed production fields is currently being mapped with ArcView GIS mapping software using USDA-FSA field photos, USDA-NRCS soils maps and ground observation. Weed seed contaminant data from OSU seed certification reports, private seed laboratory reports, and cooperating seedsmen in the area is currently being overlaid on field location maps to document the occurrence and spatial distribution of rattail fescue and alkaligrass in Grande Ronde Valley grass seed production fields. As data become available on soil physical and chemical characteristics, this information is being entered into the GIS database to provide correlation between weed occurrence and soil physical and chemical properties. This project coordinated multi-state herbicide trials to determine optimum treatment rates and timings for control of rattail fescue in chemical fallow systems and for control of rattail fescue in direct seed winter and spring wheat.

Impacts
Development of resistance management strategies for downy brome control in direct-seeded winter wheat cropping systems utilizing herbicide mode-of-action rotation will reduce the incidence of herbicide resistant weed populations. Studies on V. myuros and Pucinellia sp. will significant implications in the development of management strategies for rattail fescue in dryland wheat and fallow.

Publications

• Ball, D. A., J. P. Yenish, and T. Alby III. 2003. Effect of Imazamox Soil Persistence on Dryland Rotational Crops. Weed Technology. 17:161-165.
• Young, F. L., J. P. Yenish, D. L. Walenta, and D. A. Ball. 2003. Spring-germinating jointed goatgrass produces viable spikelets in spring seeded wheat. Weed Sci. 51:379-385.
• Ball, D. A., D. C. Thill, M. Ensminger, K. Howatt, S. Seefeldt, P. A. Banks, and R. L. Anderson. 2003. Development of weed resistance as affected by frequency of herbicide application. Proceedings 2003 Western Soc. Weed Sci. pg 89.
• Ball, D. A., C. Rainbolt, D. C. Thill, J. P. Yenish. 2003. Weed Management Strategies for Clearfield Wheat Systems Across PNW Precipitation Zones. Pg. 90-96 in: NW Direct Seed Cropping Systems Conf. Proceedings. Jan. 8-10, 2003, Pasco, WA.
• Ireland, T. M., D. C. Thill, D. A. Ball, and J. Yenish. 2003. Annual grass control with glyphosate formulations and application timings in direct seed, dryland winter wheat cropping systems in the inland northwest. Proceedings 2003 Western Soc. Weed Sci. pg 77.
• Thill, D. C., C. Rainbolt, T. Ireland, J. Campbell, J. Yenish, and D. A. Ball. 2003. Alternatives to Glyphosate as Part of a Resistance Management Strategy. Pg. 105-118 in: NW Direct Seed Cropping Systems Conf. Proceedings. Jan. 8-10, 2003, Pasco, WA.
• Yenish, J. P., T. Ireland, D. A. Ball, D. C. Thill. 2003. Evaluation of Glyphosate Formulations for Burndown in Direct Seed Systems. Pg. 97-104 in: NW Direct Seed Cropping Systems Conf. Proceedings. Jan. 8-10, 2003, Pasco, WA.