Source: MONTANA STATE UNIVERSITY submitted to
INTEGRATED WEED MANAGEMENT IN DRYLAND AND IRRIGATED CROPPING SYSTEMS OF NORTHERN GREAT PLAINS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
REVISED
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1003091
Grant No.
(N/A)
Project No.
MONB00658
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2014
Project End Date
Sep 30, 2019
Grant Year
(N/A)
Project Director
Jha, P, .
Recipient Organization
MONTANA STATE UNIVERSITY
(N/A)
BOZEMAN,MT 59717
Performing Department
Southern Agri Res Center
Non Technical Summary
The proposed integrated research will be focused on developing sustainable and cost-effective weed management strategies for NGP producers. Developing integrated weed management (IWM) strategies, utilization of herbicide-resistant crops, and weed control solutions for new crops will be critical for the diversification of agriculture in Montana. Research aimed at developing IWM strategies is needed to reduce on-farm weed control failures and managing or preventing the occurrence of herbicide resistance issues in dryland and irrigated cropping systems. A key focus of this research will be assessing weed populations for herbicide resistance and evaluating short- and long-term impact of current weed management tactics on herbicideresistant weed development. The goal of this research is to provide growers and agricultural professionals with unbiased tools and research-based information on weed management for enhanced profitability and sustainability of agriculture production systems in the NGP region.
Animal Health Component
0%
Research Effort Categories
Basic
15%
Applied
70%
Developmental
15%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
21623001140100%
Knowledge Area
216 - Integrated Pest Management Systems;

Subject Of Investigation
2300 - Weeds;

Field Of Science
1140 - Weed science;
Goals / Objectives
Develop weed biology and ecology information and integrated strategies for management of herbicide-resistant kochia in Northern Great Plains (NGP) cropping systems (This objective is divided into different sub-objectives).Evaluate weed control and herbicide efficacy with registered and experimental herbicides in dryland and irrigated cropping systems.
Project Methods
Objective 1. Develop weed biology information and integrated strategies for management of herbicide-resistant weeds in NGP cropping systems Objective 1.1. Characterize growth and emergence of kochia accessions: Growth Analysis: Accessions from North Dakota, South Dakota, Montana, Kansas, New Mexico, Idaho, and Oklahoma will be included. Plant height, canopy width, primary branches, and shoot dry weight will be recorded at weekly intervals (12 destructive harvest) for each accession. Days to flowering, seed set, seed production, and seed viability will be recorded. Emergence Pattern: Cumulative emergence will be calculated as a percent of the initial seed bank or as a percent of the total emergence during the season. Seedling emergence of kochia accessions (ecotypes) will be modeled using: 1) thermal time assuming the base temperature of 0 C for kochia and 2) hydrothermal time using the estimated base temperatures and water potentials.Objective 1.2. Efficacy and economics of cultural and mechanical weed control practices for mitigating herbicide resistance: Experimental kochia population: Kochia resistant to ALS-inhibiting herbicides is widespread across the MT-WY-NE region. An experimental population with approximately 3% ALS-R seed will be selected. A split-split-plot randomized complete block design will be established. Main plot: Tillage. Main plots will consist of a no-tillage treatment and a reduced tillage treatment (spring or fall tillage as appropriate for the crop rotation). Split-plot: Crop rotation. Within each tillage main plot, there will be four crop (corn, dry bean, sugar beet, winter wheat) rotations, ranging in crop diversity from simple to complex. Four replicates will be established within each tillage main plot, and each replicate will initiate the crop rotation at a different point, so that each crop is represented in each year. Split-split-plot: Herbicide use pattern. Three separate herbicide programs (complete reliance on ALS-inhibitors, ALS-inhibitor tank mixtures, and no ALS-inhibitors) will be applied. Data collection: Kochia density and seed production m-2 and crop yields will be determined in each plot. In late fall of each year, soil samples will be collected from each plot. Each year, soil samples will be split into half; one sub-sample will be used for exhaustive germination, and the other will be used for herbicide screening to determine the R:S ratio of each sample. A linear programming model will be used to assess the economic impact of tillage and crop rotation at the farm-level for each herbicide use pattern.Objective 1.3: Occurrence, characterization, molecular mechanism(s), and ecological fitness of herbicide-resistant kochia in Montana:Objective 1.3.1. Survey of herbicide-resistant kochia: A random field survey design will be used to determine the distribution and frequency of herbicide-resistant kochia in the study area in northern Montana. A total of 150 populations were collected throughout the survey in 2013 (GPS coordinates were recorded). Based on the discriminating dose screening, the suspected resistant populations will be further screened to determine the level of resistance compared to the known susceptible biotype. Glyphosate dose response: Glyphosate rates will be 0 (control), 0.19, 0.38, 0.77 (equivalent to 22 oz/a of Roundup Weathermax), 1.54, 3.08, 4.62, 6.16, 7.7, and 9.24 lb ae/acre. Dicamba dose response: Dicamba rates will be 0 (control), 0.16, 0.25, 0.5, 1, 2.0, 3.0, 4.0, 6.0, 9.0 lb ae/a. The discriminating dose will be 0.28 kg ae ha-1 (visible symptoms of leaf curling and chlorosis). Sulfonylurea (ALS-inhibitor herbicide) dose response: Among sulfonylurea group, chlorsulfuron, metsulfuron, and thifensulfuron-tribenuron premix (Ally Extra) will be tested and herbicide doses will be 0 (control), 1/4, 1/2, 1, 2, 4, 8, 16, 32, and 64-times the recommended rate (equivalent to 0.5 oz/a of Ally Extra®). Based on ED50 or GR50 values, R/S ratios (resistance index) will be calculated to determine the level of resistance of the kochia accessions to SU (ALS), dicamba, and glyphosate herbicides relative to a known susceptible accession (collected from an organic field in Montana).Objective 1.3.2. Molecular mechanisms of herbicide resistance: Resistant plants will be selected from the highest rates survived by each survey population, with live tissues used for further molecular work. The protocol developed by Wiersma et al. (2012) and Gaines et al. (2010) will be used to quantify EPSPS gene amplification (increased EPSPS copy numbers) and target-site mutation for glyphosate and ALS-inhibitor herbicide resistance, respectively. The steps involved for investigating glyphosate-resistance mechanism in kochia will be: DNA extraction, EPSPS gDNA sequencing, EPSPS genomic copy number, relative EPSPS to ALS quantification, and further confirmation of the gene copy number on the cDNA. ALS gene sequencing will be performed to determine specific ALS-target site mutations conferring resistance to ALS-inhibitor herbicides (sulfonylurea).Objective 1.3.3. Ecological fitness of herbicide-resistant kochia Separate experiments will be conducted to study the fitness cost (if any) related to the EPSPS gene amplification mechanism for glyphosate resistance, target-site mutation at Pro197 for resistance to the ALS-inhibitor herbicide (SU), and dicamba resistance (mechanism unknown so far). Seeds of confirmed resistant kochia biotypes to be used are subjected to recurrent selection for four to six generations in the greenhouse to obtain homogenous lines. Germination Differences: Seed germination will be compared at constant and alternating temperatures in the incubators at the Weeds Lab. in MSU-Southern Agricultural Research Center, Huntley, MT. Temperature treatments included: 1) Constant temperatures of 5, 10, 15, 20, 25, 30, and 35 C; 2) Alternating temperatures (12-hour interval) of 5/10, 10/15, 15/20, 20/25, 25/30, and 30/35 C. All experiments will be conducted in a completely randomized design with six replications, and will be repeated. Cumulative germination (as a percent of total viable seeds) will be calculated. Growth and Seed Production Differences: Experiments will be conducted in an environmentally-controlled greenhouse (16-h photoperiod, 25/20 C). At least twelve plants of each biotype will be transplanted for each replication to allow for multiple destructive harvests. At each harvest, growth characteristic data will be measured. Plant height, canopy width, primary branches, total leaf area, and shoot dry weight will be analyzed using PROC REG in SAS. Flowering initiation, pollen viability, seed set, seed number, seed weight, and seed viability will be analyzed using PROC MIXED in SAS. Furthermore, to evaluate the pleiotropic effect of EPSPS gene amplification on fitness cost for glyphosate resistance, correlation analysis will be performed to study the relationship of individual traits (growth, seed production, seed weight, etc.) with increased EPSPS gene copy numbers.Objective 1.3.4. Investigate alternative herbicide programs for glyphosate-resistant kochia controlGreenhouse and field trials will be continued to determine the effectiveness of PRE- and POST-applied herbicides (alone or tank-mix) for control of glyphosate and other multiple herbicide-resistant kochia. Alternative herbicide programs to control glyphosate-resistant kochia will be developed for chemical-fallow winter wheat rotation, and glyphosate-resistant corn, soybean, and sugar beet grown in NGP.Objective 2: Evaluate Weed Control Strategies and Herbicide Efficacy with Registered and Experimental Herbicides in irrigated and dryland cropping systemsExperiments will be continued to evaluate herbicide efficacy and application timing with registered and experimental herbicides in wheat, barley, sugar beet, corn, dry bean, pea, lentil, and alfalfa. This research will be performed each year in collaboration with chemical industry.

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:The target audience(s) comprised of local and regional growers across the three state western region (MT, WY, NE), University extension agents, crop consultants, industry representatives, commodity groups (Western Sugar Cooperative, Montana Wheat and Barley Committee, Nebraska Bean Growers Association), agronomists and weed extension specialists, and regional/national weed science researchers. Changes/Problems:There are no anticipated changes/problems in fullfilling the goals of this project. What opportunities for training and professional development has the project provided?Published abstracts/Proceedings Jha P., V. Kumar, A. R. Kniss, G. Sbatella, N. Lawrence. 2017. Herbicide-Resistant Kochia in the US Great Palins: What We Know and Path Forward. Global Herbicide Resistance Challenge. Denver, CO, USA. May 14 18 Kumar V., P. Jha, J. F. Spring, Anjani J, D. Lyon, I. C. Burke. 2017. Confirmation and Management of Glyphosate-Resistant Russian thistle (Salsola tragus L.) from Montana and Washington. Proc. West. Weed Sci. 78 Lim C.A., P. Jha, V. Kumar, S. Leland, Anjani J. 2017. Survival, Growth, and Reproductive Fitness of Dicamba-Resistant Kochia in the Presence of Dicamba. Proc. West Weed Sci. 127 Kumar V., P. Jha, Anjani J., S. Leland. 2017. Confirmation and Mechanism of Resistance to Imazamox in Downy Brome (Bromus tectorum L.) from Montana. Proc. West. Weed Sci. 164. Jha P., J. Shaw, V. Kumar, P. Nugent. 2017. Hyperspectral Imaging to Detect Herbicide-Resistant Weeds In-Crop: Convergence of Optical and Ag Technologies. Proc. West. Weed Sci. 166. Kumar V., P. Jha, J. F. Spring, Anjani J, V. K. Nandula, K. N. Reddy, D. Lyon, I. C. Burke. 2017. Characterization of Glyphosate-Resistant Russian thistle (Salsola tragus L.) Populations in Montana and Pacific Northwest. Proc. Weed Sci. Soc. Am. 330. Jha P., V. Kumar, Anjani J., S. Leland. 2017. Field-evolved Resistance of Downy brome (Bromus tectorum L.) to Imazamox in Cereal Production. Proc. Weed Sci. Soc. Am. 327. Kumar V., P. Jha, Anjani J., C. A. Lim, S. Leland. 2017. Evolution and Management of Glyphosate-Resistant Weeds in Wheat-Fallow in Montana. Global Herbicide Resistance Challenge. Denver, USA. May 14-18. Jha P., V. Kumar, Anjani J., J. F. Spring, D. J. Lyon, I. C. Burke, V. K. Nandula, K. N. Reddy. 2017. Evolution of Glyphosate-Resistant Salsola tragus L. (Russian thistle) in Montana and Pacific Northwest. Global Herbicide Resistance Challenge. Denver, USA. May 14-18. Jha P., V. Kumar, S. Leland, Anjani J, C. A. Lim. 2017. Evolution of Glyphosate-Resistant Horseweed and Russian thistle in Montana Cereal Production. Proc. West Soc. Weed Sci. 31. Lim C. A., P. Jha, V. Kumar, S. Leland, Anjani J. 2017. Survival, Growth, and Fecundity of Kochia Cohorts with Varying Densities Under Different Crop Canopies. Proc. West Soc. Weed Sci. 47). Kumar V., P. Jha, Anjani J., C. A. Lim, S. Leland. 2017. Confirmation and management of newly evolved glyphosate-resistant Russian-thistle (Salsola tragus L.) and horseweed (Conyza Canadensis L.) in Montana cereal production. Proc. Weed Sci. Soc. Am. 34. Jha P., V. Kumar, P. Nugent, A. Donelick, B. Scherrer, J. Shaw. 2017. Hyperspectral imaging to detect glyphosate-resistant vs. glyphosate-susceptible Kochia scoparia: Implications for site-specific management. Proc. Weed Sci. Soc. Am. 62. How have the results been disseminated to communities of interest?Invited Presentations at Grower/Ag. Industry Meetings and Field Days Precision weed management in Montana cropping systems. Crop and Pest Management School, Bozeman, MT, Jan 3, 2017. Hyperspectral imaging to detect herbicide-resistant weeds in-crop. Malt Barley and Sugar Beet Symposium, Billings, MT, Jan 10-11, 2017. Herbicide resistance management in Montana. CHS Grower Meeting, Malta, MT, Jan 9, 2017. Status of herbicide resistance in Montana and integrated strategies. CCA Field Day, Southern Agricultural Research Center, Huntley, MT, August 8, 2017. Other Extension Activities Statewide survey of glyphosate-resistant kochia, Russian thistle, and marestail (horseweed) from grower fields in Montana. June-October, 2017. Survey of glyphosate-resistant kochia in sugar beet fields in MT and WY. June-August, 2017. Presentation on integrated strategies for kochia management in Roundup Ready® sugar beet. Annual Western Sugar Cooperative Research Meeting, January 2017. Total Number of outreach meetings 2017: 8 • Field days and Field Tours 2017: 6 • Total attendance: 750 What do you plan to do during the next reporting period to accomplish the goals?Research and extension activities will be continued to fulfill the objectives as proposed in the research goals (1 and 2) of the project. In Objective 1, the emphasis is not only on kochia, but also on other new cases of field-evolved herbicide-resistant weeds in Montana and the US Great Plains cropping systems.

Impacts
What was accomplished under these goals? Objective 1 1.1. Emergence Dynamics of Kochia (Kochia scoparia) Populations from the US Great Plains: Evolution of kochia biotypes resistant to multiple herbicide sites of action is an increasing concern for growers across the US Great Plains. Field experiments were conducted near Huntley, MT in 2013 and 2014, and in Manhattan and Hays, KS in 2013 to characterize the timing and pattern of emergence of several kochia populations collected from the US Great Plains' states. Kochia populations exhibited an extended emergence period (early April through middle July). Among all kochia populations, in 2013, KS-GC, KS-MN, OK, and MT populations began to emerge earlier, with a minimum of 151 cumulative GDD to achieve 10% cumulative emergence (E10 values) in Montana. The NM-LL population exhibited a delayed onset but a rapid emergence rate, while the ND and KS-CB populations emerged over a longer duration (E90-E10 of 556 and 547 GDD, respectively) in 2013 in Montana. In 2013 at the two locations in Kansas, kochia populations exhibited a similar emergence pattern, with no differences in the time to initiate germination (E10), rate of emergence (parameter b), or duration of emergence (E90-E10). At Hays, KS, GDD for E50 and for E90 were less for ND compared with KS-MN and KS-GC local populations. In 2014, the KS-MN kochia population exhibited an early (ED10 value of 215 GDD) but a more gradual emergence pattern (E90-E10 = 526 GDD) in Montana. In contrast, OK and NM-LC populations had an early and a more rapid emergence pattern (E90-E10 = 153 and 154 GDD, respectively). Kochia in Montana exhibited two to four emergence peaks. This differential emergence pattern of kochia populations reflects the occurrence of different emergence "biotypes", and emphasizes the need to adopt more location-specific and diversified weed control tactics. 1.2. First report of Ser653Asn mutation endowing high-level resistance to imazamox in downy brome: Bromus tectorum L. (downy brome) is one of the most troublesome grass weed species in cropland and non-cropland areas of the northwestern United States, including Montana. The acetolactate synthase (ALS) inhibitor herbicides are predominantly used to control B. tectorum in wheat. In summer 2016, a B. tectroum accession (R) that survived imazamox at the field-use rate (44 g ha-1) in an imidazolinone-tolerant (IMI-tolerant or Clearfield™) winter wheat field was collected in Carter County, MT, USA. The R B. tectorum accession had a high-level resistance (110.1-fold) to imazamox (IMI) and low to moderate-levels cross-resistance to pyroxsulam (TP) (4.6-fold) and propoxycarbazone (SCT) (13.9-fold). The R accession was susceptible to sulfosulfuron (SU, ALS inhibitor) and quizalofop and clethodim (ACCase inhibitors), paraquat (PS I inhibitor), glyphosate (EPSPS inhibitor), and glufosinate (GS inhibitor). Sequence analysis of the ALS gene revealed a single, target-site Ser653Asn mutation in R plants. 1.3. Confirmation of Glyphosate-Resistant Horseweed (Conyza Canadensis L.) in Montana Cereal Production: During late summer 2015, seeds of a putative glyphosate-resistant (GR) horseweed (GR-MT) accession were collected from wheat-fallow fields in McCone County, MT to confirm and characterize the level of glyphosate resistance. Whole-plant glyphosate dose-response experiments conducted at the early (5- to 8-cm diam)- and late (12- to 15-cm diam)-rosette stages of horseweed indicated that GR-MT accessions had 2.5- to 4.0-fold level of resistance to glyphosate relative to the GS-NE accession, on the basis of shoot dry weight (GR50 values). At the whole plant level, about 2.1- to 4.5-fold higher shikimate accumulation was observed in the GS-NE accession compared with the GR-MT and GR-NE accessions over a 10 d period after glyphosate applied at 1,260 g ae ha-1. Bromoxynil + pyrasulfotole or MCPA, diflufenzopyr + dicamba + 2,4-D, glufosinate, paraquat alone or in combination with metribuzin, saflufenacil alone or in combination with 2,4-D, thifensulfuron + tribenuron in combination with clopyralid + fluroxypyr, and 2,4-D alone at the field-use rates provided ≥ 90% control at 21 d after treatment (DAT). 1.4. Glyphosate-Resistant Russian-thistle (Salsola tragus L.) Identified in Montana and Washington: Two putative glyphosate-resistant (GR) Russian-thistle accessions were collected from chemical fallow fields (wheat-fallow rotation): one from Choteau County, MT (MT-R), and a second from Columbia County, WA (WA-R) in summer/fall of 2015. Based on GR50 values of the progeny plants, the MT-R accession exhibited 4.5-fold and 5.9-fold resistance to glyphosate relative to the MT-S accession under greenhouse and outdoor conditions, respectively. The WA-R accession showed 2.6- to 4.2-fold resistance relative to the WA-S accession in greenhouse experiments, and 1.9- to 7.5-fold resistance in multi-site field experiments. In a separate greenhouse study on alternative POST herbicides to control GR Russian-thistle, bicyclopyrone + bromoxynil, bromoxynil + fluroxypyr, bromoxynil + pyrasulfotole, bromoxynil + MCPA, paraquat alone, paraquat + metribuzin, saflufenacil alone, saflufenacil + 2,4-D, and 2,4-D + bromoxynil + fluroxypyr provided effective control (≥95%) of GR accessions. Objective 2 2.1. Using Pyroxasulfone for Downy Brome (Bromus tectorum L.) Control in Winter Wheat: Multiple field experiments were conducted near Huntley, MT from 2012 through 2016 to determine the efficacy of pyroxasulfone for downy brome control in imidazolinone (IMI)-tolerant (Clearfield™) winter wheat. Pyroxasulfone did not cause any injury to wheat in any of the three studies. Downy brome control with pyroxasulfone preemergence (PRE) only program did not differ between 89 and 178 g ai (active ingredient) ha-1 rates, and averaged 82% and 84% in 2 separate studies. In a preplant (PP) burndown program, the addition of pyroxasulfone (178 g ai ha-1) to glyphosate improved downy brome end-season control from 15 to 74%. In a separate study, the end-season control with pyroxasulfone was greater when applied PRE (84%) compared to the delayed PRE (DPRE) timing (74%). In addition, the water dispersible granule (WDG) formulation of pyroxasulfone performed slightly better than the suspension concentrate (SC) formulation for downy brome control. Pyroxasulfone applied PRE in the fall at a rate of 89 g ai ha-1 followed by (fb) imazamox (44 g ai ha-1 rate) applied postemergence (POST) in the spring effectively controlled downy brome (99% end-season control). 2.2. Pulse Crop Tolerance and Weed Control with Fall-Applied Soil-Residual Herbicides: Multi-location trials were conducted in Montana to evaluate crop safety and weed control in spring-planted pulse crops from soil-residual herbicides applied the previous fall in postharvest wheat stubble. Dry pea, lentil, and chickpea were planted the subsequent spring in herbicide-treated plots. Metribuzin (210 or 420 g ha-1), flumioxazin (107 or 214 g ha-1), pyroxasulfone (119 or 238 g ha-1) + carfentrazone (8 or 16 g ha-1), pendimethalin (532 or 1064 g ha-1) + dimethenamid-P (945 or 1890 g ha-1), sulfentrazone (164 or 328 g ha-1) + carfentrazone (18 or 36 g ha-1), sulfentrazone (101 or 202 g ha-1) + metribuzin (151 or 302 g ha-1) applied the previous fall had no significant visual injury (≤8% early-season) or yield reductions in dry pea and chickpea. However, sulfentrazone-based programs caused unacceptable crop injury (up to 75% early-season) and yield reductions in lentil. Unacceptable early season injury and yield reductions were observed in pulse crops with thiencarbazone + isoxaflutole-based programs. Metribuzin or pyroxasulfone + carfentrazone at twice the recommended fall-use rate(s) and flumioxazin, sulfentrazone + carfentrazone, or sulfentrazone + metribuzin even at the recommended fall-use rate(s) provided 75 to 99% end-season control of kochia and Russian-thistle.

Publications

  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Kumar, V. and P. Jha. 2017. First report of Ser653Asn mutation endowing high?level resistance to imazamox in downy brome (Bromus tectorum L). Pest Management Science. DOI:10.1002/ps.4673.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Kumar, V., P. Jha, A. Dille, and P. W. Stahlman. 2017. Emergence dynamics of kochia (Kochia scoparia) populations from the US Great Plains: A multi-site-year study. Weed Science. DOI: 10.1017/wsc.2017.55.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Jha, P., and V. Kumar. 2017. Pulse crop tolerance and weed control with fall-applied soil-residual herbicides. Agronomy Journal. 109:1-11.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Chauhan B.S., A. Matloob, G. Mahajan, F. Aslam, S. K. Florentine, and P. Jha. 2017. Emerging challenges and opportunities for education and research in weed science. Frontiers in Plant Science. DOI:10.3389/fpls.2017.01537
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Kumar, V., P. Jha, and A. J. Jhala. 2017. Confirmation of glyphosate-resistant horseweed (Conyza canadensis L.) in Montana cereal production and response to POST herbicides. Weed Technology. DOI: 10.1017/wet.2017.49
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Kumar, V., J. Felix, D. Morishita, and P. Jha. 2017. Confirmation of glyphosate-resistant kochia (Kochia scoparia L.) from sugar beet fields in Idaho and Oregon. Weed Technology. https://doi.org/10.1017/wet.2017.80
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: N. Iqbal, A. A. Bajwa, S. Manalil, A. M. Khan, L. Kebaso, D. Frimpong, H. Mamubiru, G. Rasool, H. H. Ali, P. Jha, and B.S. Chauhan. 2017. Biology and management of Hordeum glaucum and H. leporinum. Crop and Pasture Science. Accepted.
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Shaw, J., P. Jha, P. Nugent, A. Donelick, B. Scherrer, and V. Kumar. 2017. Discrimination of herbicide-resistant weeds with hyperspectral imaging. Journal of Applied Remote Sensing. Accepted
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Ganie Z. A., S. Kaur, P. Jha, V. Kumar, and A. J. Jhala. 2017. Effect of late-season herbicide applications on inflorescence and seed production of glyphosate-resistant giant ragweed (Ambrosia trifida L.). Weed Technology. Accepted
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Jha, P., V. Kumar, C. A. Lim, and R. Yadav. 2017. Evaluation of preemergence herbicides for crop safety and weed control in safflower. American Journal of Plant Science. DOI: https://doi.org/10.4236.10/2017.
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Chahal PS, S. Irmak, T. Gaines, K. Amundsen, M. Jugulam, P. Jha, I. S. Travlos, and A. J. Jhala. 2017. Control of atrazine- and 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor-resistant Palmer amaranth (Amaranthus palmeri) in conventional corn. Weed Technology. Accepted
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: V. Kumar, P. Jha, and A. J. Jhala. 2017. Using pyroxasulfone for downy brome (Bromus tectorum L.) control in winter wheat. American Journal of Plant Science. DOI: https://doi.org/10.4236.12/.2017
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Kumar, V. and P. Jha. 2017. Effect of temperature on germination characteristics of glyphosate-resistant and -susceptible Kochia scoparia. Weed Science. 65:361-370.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Jha, P., V. Kumar, R. K. Godara, and B. S. Chauhan. 2017. Weed management using crop competition in the United States: A review. Crop Protection 95: 31-37
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Kumar, V., J. F. Spring, P. Jha, D. J. Lyon, and I. C. Burke. 2017. Glyphosate-resistant Russian-thistle (Salsola tragus L.) identified in Montana and Washington. Weed Technology. 31:238-251.
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Kumar, V. and P. Jha. 2017. Influence of nitrogen rate, seeding rate, and weed removal timing on weed interference in barley and effect of nitrogen on weed response to herbicides. Weed Science. 65: 189-201
  • Type: Book Chapters Status: Published Year Published: 2017 Citation: Jha, P., R. K. Godara, and A. J. Jhala. 2017. Targeting weed seedbanks: Implications to weed management. In Biology, Physiology and Molecular Biology of Weed. CRC Press, Tylor and Francis Group. Pp 12-26
  • Type: Book Chapters Status: Published Year Published: 2017 Citation: A.J. Jhala, D. Sarangi, P. Chahal, A. Saxena, M. Bagavathiannan, B. Chauhan, and P. Jha. 2017. Inter-specific gene flow from herbicide-tolerant crops to wild relatives. In Biology, Physiology and Molecular Biology of Weed. CRC Press, Tylor and Francis Group. Pp 87-122.
  • Type: Book Chapters Status: Published Year Published: 2017 Citation: Shrestha, G. P. Jha, and G. V. P. Reddy. 2017. Impact of genetically-modified herbicide-resistant oilseed rape on non-target organisms: natural enemies of oilseed rape pests. In Integrated Management of Insect Pests on Canola and other Brassica Oilseed Crops. Vol 1. Pp. 295-304. Commonwealth Agricultural Bureaux International (CABI), UK
  • Type: Book Chapters Status: Published Year Published: 2017 Citation: Jha, P. and K. N. Reddy. 2017. The role of herbicide-resistant crops in integrated weed management. In Integrated Weed Management for Sustainable Agriculture, ed. Robert Zimdahl. Burleigh Dodds Science Publishing Limited, 2017.
  • Type: Other Status: Published Year Published: 2017 Citation: McVay, K.A., P. Jha, and F. Crutcher. 2017. Chickpea Production. Montana State University Extension Publications. MT201703AG.


Progress 10/01/15 to 09/30/16

Outputs
Target Audience:The target audience(s) comprised of local (Montana) and regional growers, MSU extension agents, crop consultants, industry representatives, commodity groups, MSU agronomists and extension specialists, and regional/national weed science researchers. Changes/Problems:There are no anticipated changes/problems in fullfilling the goals of this project. What opportunities for training and professional development has the project provided?Published Abstracts/Proceedings Jha. P., J. Felix, and D. Morishita. 2016. Survey of glyphosate-resistant kochia in eastern Oregon sugar beet field. Proc. Weed Sci. Soc. Am. 141. Kumar, V., P. Jha, C. A. Lim, Anjani. J, S. Leland. 2016. Distribution of multiple herbicide-resistant kochia in Montana. Proc. Weed Sci. Soc. Am. 204. Kumar, V., P. Jha, C. A. Lim, Anjani J, S. Leland. 2016. Correlation between dormancy and herbicide resistance levels in kochia. Proc. Weed Sci. Soc. Am. 372. Jha, P., C. A. Lim, V. Kumar, Anjani J, S. Leland. 2016. Effect of glyphosate selection on survival and fecundity characteristics of glyphosate-resistant kochia with variable EPSPS gene copies. Proc. Weed Sci. Soc. Am. 376. Lim, C.A., P. Jha, V. Kumar, S. Leland, Anjani J. 2016. Survival and fecundity of glyphosate-resistant kochia with variable EPSPS gene copies in response to glyphosate selection. Proc. West. Soc. Weed Sci. 33. Jha, P., J. Felix, D. Morishita, V. Kumar, and Anjani J. 2016. Survey of glyphosate-resistant kochia in eastern Oregon sugar beet fields. Proc. West. Soc. Weed Sci. 35. Kumar, V., P. Jha, S. Leland, Anjani J., C. A. Lim. 2016. Seed germination dynamics of herbicide-resistant and susceptible populations of Kochia scoparia. Proc. West. Soc. Weed Sci. 64. Kumar, V., P. Jha, S. Leland, Anjani J., S. Leland. 2016. Biology and Management of Volunteer Buckwheat in Wheat. Proc. West. Soc. Weed Sci. 108. How have the results been disseminated to communities of interest?Invited Presentations at Grower and Industry Meetings and Field days Advanced optical sensor-based hyperspectral imaging and spot spray technologies for precision weed control in fallow and in-crop. MSU Post Farm Field Day, Bozeman, MT, July 7, 2016. Weed control options in pulse crops in eastern MT. MSU Eastern Agricultural Research Center Field Day, Sidney, MT, June 24, 2016. Integrated strategies to manage herbicide resistance in dryland, cereal production systems of the Golden Triangle. MSU Western Triangle Research Center Field Day, Conrad, MT, June 23 2016. Fall-applied soil residual herbicides in wheat stubble and rotational crop safety and weed control in pulse crops. MSU Northern Agricultural Research Center Field Day, Havre, MT, June 22, 2016. Other Activities Statewide survey of glyphosate-resistant kochia, Russian thistle, and marestail (horseweed) from grower fields in Montana. June-October, 2016. Presentation on integrated strategies for kochia management in Roundup Ready® sugar beet. Annual Western Sugar Cooperative Research Meeting, Colorado Springs, CO, January 2016. Attended Western SARE- Professional Development Program grant workshop. Great Falls, MT, March 1, 2016. Total Number of outreach meetings 2016: 7 Field days and Field Tour 2016: 8 Total attendance: 850 What do you plan to do during the next reporting period to accomplish the goals?Research and extension activities will be continued to fullfill the objectives as proposed in the research goals (1 and 2) of the project.

Impacts
What was accomplished under these goals? Objective 1 1.1. Differences in Germination, Growth, and Fecundity Characteristics of Dicamba-Fluroxypyr-Resistant and -Susceptible Kochia scoparia The widespread occurrence of herbicide-resistant (HR) Kochia scoparia is an increasing concern for growers in the US Great Plains and Canada. K. scoparia populations resistant to dicamba have been reported in six US states. Populations cross-resistant to dicamba and fluroxypyr have been reported from wheat fields in Montana, USA. It is unclear whether resistance to the auxinic herbicides (dicamba and/or fluroxypyr), can alter the fitness traits of K. scoparia. The objectives of this research were to compare the germination dynamics in response to thermal environment, vegetative growth and fecundity characteristics, and the relative competitive ability of dicamba-fluroxypyr-susceptible (S) vs. -resistant (R) K. scoparia selected from within a single segregating population (collected from wheat-fallow field in MT). S and R selected lines were developed after three generations of recurrent group selection. Compared to the S selected line, the R selected line had lower cumulative germination at all constant temperatures except 25 °C, and at all alternating temperatures except 30/35 °C. Also, the R selected line had delayed germination relative to the S selected line. The R had lower plant height, plant width, primary branches, total leaf area, stem diameter, and shoot dry weight compared with the S plants in the absence of competition. The reduction in seed production per plant resulted in a 39% fitness cost. The 1000-seed weight of R (1.6 g) was also less than that of S (2.6 g). When grown in an intraspecific competition at different mixture proportions, replacement series indices for the growth parameters further indicated that the R was less competitive than the S. Evident from this research, the dicamba-fluroxypyr-resistant R selected line is less likely to persist in a field population in the absence of the auxinic herbicides. 1.2 Effect of EPSPS Gene Amplification on Growth and Reproductive Traits of Glyphosate-Resistant Kochia scoparia The EPSPS (5-enol-pyruvylshikimate-3-phosphate synthase) gene amplification confers glyphosate resistance in Kochia scoparia (L.) Schrad. Experiments were conducted in spring to fall 2014 (run 1) and summer 2014 to spring 2015 (run 2) to investigate the effect of EPSPS gene amplification on growth and reproductive traits of GR K. scoparia, and the effect of EPSPS gene amplification on the level of glyphosate resistance. GR K. scoparia inbred lines (CHES01 and JOP01) exhibited 2 to 14 relative copies of the EPSPS gene compared with a susceptible (SUS) inbred line with only one copy. In the absence of glyphosate, 2- to 14-fold amplification of the EPSPS gene did not influence the growth and reproductive traits of GR K. scoparia compared with the SUS inbred line, across an intraspecific competition gradient (1 to 170 plants m-2). GR K. scoparia plants with 2 to 4 copies of the EPSPS gene survived the field-use rate (870 g ha-1) of glyphosate, but failed to survive the 4,350 g ha-1 rate of glyphosate (five-times the field-use rate). In contrast, GR plants with 5 to 14 EPSPS gene copies survived the 4,350 g ha-1 of glyphosate. No negative effects of EPSPS gene amplification on growth and reproduction and the additive effect of EPSPS gene copy number on the level of glyphosate resistance indicate that GR K. scoparia with 5 or more EPSPS gene copies will most likely persist in field populations, irrespective of glyphosate selection pressure. 1.3. Effect of Temperature on Germination Characteristics of Glyphosate-Resistant and -Susceptible Kochia scoparia Glyphosate-resistant (GR) kochia is an increasing concern for growers across the US Great Plains and Canadian prairies. Integrated strategies to mitigate resistance will require an improved understanding of the seed germination dynamics of GR kochia populations. Experiments were conducted to characterize the germination of GR vs. glyphosate-susceptible (GS) kochia populations under different constant (5 to 35 C) and alternating temperatures (5/10 to 30/35 C). Seven GR and two GS populations were collected from wheat-fallow fields in northern Montana. Selected lines of GR and GS were obtained after three generations of recurrent group selection in the greenhouse. The GR selected lines had 4.1 to 10.8 average EPSPS copies compared to a single EPSPS gene copy for the GS selected lines. Four out of seven GR selected lines had lower final germination (d parameter) and took more time to complete 50% cumulative germination (I50 values) under all constant and alternating temperatures, compared to the GS selected lines. Those GR selected lines also had a delayed germination initiation (I10 values) particularly at lower temperatures (5 to 10 C constant or 5/10 C alternating). In contrast, the final germination (d) of the other three GR selected lines did not differ from GS lines at a majority of temperatures tested. The I50 values of those GR lines were also comparable to GS lines under a majority of the temperatures. There was no significant correlation of observed percent cumulative germination and EPSPS gene copy number of selected kochia lines. The temperature-dependent dormancy and altered germination characteristics of the four GR kochia lines reflect the common selection of resistance and avoidance (glyphosate or other pre-seeding treatments) mechanisms. This is most likely attributed to the long-term, intensive cropping practices and less diverse weed control methods, rather than a fitness cost or pleiotropic effect of multiple copies of the EPSPS gene. Objective 2 Field experiments were conducted at the Montana State University Southern Agricultural Research Center, Huntley, MT, in 2011 through 2013 to determine the effect of nitrogen (N) rate, seeding rate, and weed removal timing on weed interference in barley. A delay in weed removal timing from the 3- to 4-lf stage to the 8- to 10-lf stage of barley resulted in up to 3.5-folds increase in total weed biomass and 10% reduction in barley biomass, and this was unaffected by N rate that ranged from 56 (low) to 168 (high) kg ha-1. The effect of N rate on barley biomass was more pronounced when weed removal was delayed from 3- to 4-lf stage to 8- to 10-lf stage of barley and in nontreated plots. Increasing the barley seeding rate from 38 to 152 kg ha-1 increased the barley plant density by 50%, biomass by 13%, and grain yield by 29%, averaged over N rates and weed removal timings. On the basis of 5 and 10% levels of acceptable yield loss (AYL), the addition of ≥112 kg N ha-1 delayed the critical timing of weed removal (CTWR) at least by 1.3 wk in barley, compared with the 56 kg N ha-1 rate. Medium or high N rate prevented reductions in barley grain quality (plumpness and test weight) observed when the seeding rate was increased from 38 to 76 or 152 kg ha-1 at the low N rate. In a separate greenhouse study, the effect of N rate on the effectiveness of various herbicides for controlling wild oat, green foxtail, kochia, or Russian thistle was investigated. Results highlighted that wild oat or green foxtail grown under 56 kg N ha-1 (low N) soil required 1.4- to 2.6-times higher doses of clodinafop, fenoxaprop, flucarbazone, glyphosate, glufosinate, pinoxaden, or tralkoxydim for 50% reduction in shoot dry weights (GR50), compared with the plants grown under 168 kg N ha-1 (high N). Similarly, a reduced efficacy of thifensulfuron methyl + tribenuron methyl, metsulfuron methyl, or bromoxynil + pyrasulfotole was observed (evident from the GR50 values) for kochia or Russian thistle grown under low vs. high N soil. Information gained from this research will aid in developing cost-effective, integrated weed management (IWM) strategies in cereals, and in educating growers on the importance of fertilizer N management as a component of IWM programs.

Publications

  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Kumar, V. and Jha, P. 2016. Differences in germination, growth, and fecundity characteristics of dicamba-fluroxypyr-resistant and susceptible Kochia scoparia. PLoS ONE, 11(8), e0161533.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Kumar, V. and Jha, P. 2016. Influence of nitrogen rate, seeding rate, and weed removal timing on weed interference in barley and effect of nitrogen on weed response to herbicides. Weed Science. doi: http://dx.doi.org/10.1614/WS-D-16-00047.1
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Jha, P., V. Kumar, R. Godara, and B. S. Chauhan. 2016. Weed management using crop competition in the United States: A review. Crop protection. doi: http://dx.doi.org/10.1016/j.cropro.2016.06.021
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Jha, P., V. Kumar, and C. A. Lim. 2016. Herbicide resistance in cereal production systems of the US Great Plains: A review. Indian Journal of Weed Science. 48:112-116
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: Kumar, V. and P. Jha. 2015. Growth and reproduction of glyphosate-resistant and susceptible populations of Kochia scoparia. PLoS ONE. 11(1), e0147779
  • Type: Journal Articles Status: Accepted Year Published: 2016 Citation: Kumar, V. and P. Jha. 2016. Effect of Temperature on Germination Characteristics of Glyphosate-Resistant and -Susceptible Kochia scoparia. Weed Science, Accepted.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Reddy K. N. and P. Jha. 2016. Herbicide-resistant weeds: Management strategies and upcoming technologies. Indian Journal of Weed Science. 48:108-111.


Progress 10/01/14 to 09/30/15

Outputs
Target Audience:The target audience(s) comprised of local (MT) and regional growers, MSU extension agents, crop consultants, industry representatives, commodity groups, MSU agronomists and extension specialists, and regional/national weed science researchers. Changes/Problems:There will be no major changes/problems in approach for fullfilling the goals of this project. What opportunities for training and professional development has the project provided?Extension Publication: Jha, P and I. Heap. 2014. Status of herbicide-resistant weeds in Montana. International Survey of Herbicide Resistant Weeds. http://weedscience.org/details/usstate.aspx?StateID=27. Published Abstracts/Proceedings: 1. Jha, P., C. A. Lim, V. Kumar, and S. Leland. 2015. Characterization of multiple herbicide resistance in kochia accessions from Montana. Proc. Weed Sci. Soc. Am. 271. 2. Jha, P., V. Kumar, S. Leland, and C. A. Lim. 2015. Variable response of kochia to dicamba and fluroxypyr in Montana. Proc. West. Soc. Weed Sci. 28. 3. Jha, P. Kochia biology and ecology: Deciphering the weed adaptive process to guide IWM. Proc. of 8th International IPM symposium. March 24-26, 2015, Salt Lake City, UT. 4. Jha, P., D. W. Morishita, J. Felix, V. Kumar, and M. Flenniken. 2015. Confirmation of glyphosate-resistant kochia in Idaho and Oregon. Proc. Weed Sci. Soc. Am. 104. 5. Jha, P., V. Kumar, S. Leland, and C. A. Lim. 2015. Management of herbicide-resistant kochia in Montana. Proc. Montana/Wyoming Sugar beet and Barley Symposium, Billings, MT, January 6-7. 6. Kumar V., P. Jha, S. Leland, C. A. Lim, and S. Misra. 2015. Correlation of EPSPS gene amplification with resistance level and fitness of glyphosate-resistant kochia. Proc. West. Soc. Weed Sci. 95. 7. Morishita, D., J. Felix, P. Jha, and V. Kumar. 2015. EPSPS gene amplification confers glyphosate resistance in kochia from Idaho and Oregon sugar beet fields. Proc. West. Soc. Weed Sci. 27. 8. Lim, C.A., P. Jha, V. Kumar, and S. Leland. 2015. Survey of multiple herbicide-resistant kochia in Montana. Proc. West. Soc. Weed Sci. 31. 9. Lim, C. A., P. Jha, V. Kumar, and S. Leland. 2015. Influence of pyroxasulfone rate and application timing on downy brome control in Clearfield winter wheat. Proc. West. Soc. Weed Sci. 40. 10. Kumar, V., P. Jha, M. Flenniken, and S. Misra. 2015. Does EPSPS gene amplification confer fitness cost in glyphosate-resistant kochia? Proc. Weed Sci. Soc. Am. 110. How have the results been disseminated to communities of interest?Invited Presentations at Grower & Industry Meetings and Field Days Management of glyphosate-resistant kochia in wheat-fallow rotation in the Golden Triangle. Western Triangle Research Center Field Day, Conrad, MT, July 19, 2015. Proactive strategies for glyphosate-resistant kochia management in Roundup Ready® sugar beet. Eastern Agricultural Research Center Field Day, Sydney, MT, July 14, 2015. Precision weed control:WeedSeeker technology. Northern Agricultural Research Center Field Day, Havre, MT, July 1, 2015. Biology and management of volunteer buckwheat. US-Japanese Wheat Trade Team. Sponsored by Montana Wheat and Barley Committee and North Dakota Wheat Commission, Dickinson, ND, June 26-27, 2015. Kochia biology and ecology: Deciphering the weed adaptive process to guide IWM. 8th International IPM symposium, Salt Lake City, UT, March 24-26, 2015. Best management practices to mitigate occurrence of multiple herbicide-resistant kochia in Montana wheat-fallow cropping system. MABA/MGEA Convention, Great Falls, MT, January 29, 2015. Evolution and management of glyphosate-resistant weeds in Montana. Montana/Wyoming Sugar Beet and Barley Symposium, Billings, MT, January 5-6, 2015. Other Activities Herbicide recommendations for weed control in field pea. North-central Montana pulse producer, telephonic conversation, June 15, 2015. Field-plot demonstration on herbicide evaluation for weed control in wheat, barley, safflower, dry bean, sugar beet, corn, alfalfa, lentil, and field pea at SARC, Huntley. Industry sales and R&D team, June-July, 2015. (5 tours) Herbicide recommendation for glyphosate-resistant kochia control in chemical fallow in north-central Montana. Wheat producer, telephonic conversation, April 15, 2015. Presentation on kochia management in Roundup Ready® sugar beet. Annual Western Sugar Cooperative Research Meeting, Billings, MT, January 2014. Media Contributions Clethodim Application during the Bloom Period in Field Peas can Cause Severe Crop Injury. MSU Extension: MT AG Alert. July 27, 2015. http://www.mtagalert.org/alertDocs/MSU%20Ag%20News%20article_Clethodim_peas.pdf MSU herbicide recommendations for glyphosate-resistant kochia control. http://www.agweek.com/event/article/id/22671/publisher_ID/80/. What do you plan to do during the next reporting period to accomplish the goals?Research and extension activities will be continued to fullfill the objectives as proposed in the research goals (1 and 2) of the project.

Impacts
What was accomplished under these goals? Objective 1: 1.1. Emergence Characterization of Kochia Accessions from Northern and Central Great Plains: Kochia is a problem weed in the Great Plains of North America. Understanding the seedling emergence patterns of kochia has direct implications for effective management of the weed, especially with the increasing occurrence of herbicide-resistant kochia in this region. A field study was initiated at the Montana State University Southern Agricultural Research Center near Huntley, MT to characterize the seedling emergence of nine kochia accessions from Northern and Central Great Plains. Kochia accessions from North Dakota (ND), Garden city, KS (GC), Colby, KS (Cb), Manhattan, KS (Mn), Hays, KS (Hy), Huntley, MT (Hn), Las Lunas, NM (LL), Idaho (Id), and Artell, OK (At) were included. Highest total cumulative emergence (as percent of initial seed bank) was observed for ND and Hy accessions, whereas Mn accession exhibited the least total emergence. Among all accessions, Mn accession emerged early, with significantly lower cGDD required for 10% (145, April 26), 50% (286, May 9), and 90% (564, May 26) of the total emergence during the growing season. ND and Cb accessions showed similar emergence patterns, and emerged over a longer duration with higher cGDDs (avg. 895, June 16) required for 90% of the total in-season emergence compared with other accessions. Forecasting seedling emergence patterns will help producers make proactive decisions for managing herbicide-resistant kochia seed bank in this region. 1.2.Comparative Growth of Kochia Accessions from Northern and Central Great Plains: A field study was conducted to compare the growth characteristics of nine kochia accessions from the Northern and Central Great Plains of North America. Kochia accessions from North Dakota (ND), South Dakota (SD), Huntley, MT (Hn), Manhattan, KS (Mn), Hays, KS (Hy), Las Cruzes, NM (LC), Las Lunas, NM (LL), Idaho (Id), and Arnett, OK (An) were included in the study. Rate of increase in plant height was higher in LC (19.9 cm wk-1) and Hn (18.85 cm wk-1) accessions compared to other accessions. Hn and ND accessions had the highest rate of increase in shoot dry weight (11.69 and 9.62 g wk-1, respectively) followed by the two New Mexico accessions, LL and LC (average of 8.51 g wk-1). Hn accession also had a greater rate of increase in canopy width (17.14 cm wk-1) than other accessions. ND accession flowered earliest (95 d) followed by Hn and SD accessions (102 d average). All accessions had similar RGR in the early stages of growth; however, RGR was higher (average of 0.12 g g-1 d-1) for Hn, ND, and SD accessions by the end of growing season. The seed production from kochia accessions ranged from 150,000 to >500,000 seeds per plant in the non-competitive environment. This research demonstrates the need for location (environment)-specific biological data for management of kochia with wide morphological, biological, or genetic traits. 1.3. Survey of Multiple Herbicide-Resistant Kochia from Wheat-Fallow Fields in Montana: Experiments were initiated in the greenhouse at MSU-SARC, Huntley, in fall of 2014. Separate experiments were conducted for screening dicamba, sulfonylurea (ALS-inhibitor), and glyphosate resistance. Seeds from the 2013 and 2014 survey kochia populations were used. Plants that survived the discriminate dose (field-use rate) screening were grown in the greenhouse under pollen isolation conditions. The selfed progeny (F1 seeds) was used for the dose-response studies. Glyphosate dose-response were conducted on 18 confirmed glyphosate-resistant (GR) populations collected from wheat-fallow fields in Hill, Liberty, Toole, Glacier, Choteau, and Blaine Counties, MT to detect the level of resistance to glyphosate. SUS was the susceptible population (control) from MT. Jop population from Hill County was the most resistant to glyphosate, with 17-fold level of resistance (based on R/S ratio). The resistance levels of the remaining GR populations varied from 3- to 14-fold. The populations with R/S ratios < 5 were considered to have low level of resistance, populations with R/S ratios of 5 to 6 were moderately resistant, and the ones with R/S ratios > 8 were most likely highly resistant. ALS-inhibitor SU resistance was found in >95% of the survey populations. The level of resistance to the SU herbicide in kochia populations was high (80 to >150-fold), which suggests that SU herbicides are no longer an effective option for kochia control. Eleven populations from Liberty, Toole, Glacier, Fergus, and Choteau Counties were found to be tolerant to dicamba, with R/S ratios of 3- to 5-fold. However, there were four populations identified from Choteau County wheat fields with high level of resistance to dicamba (>15-fold), which is concerning. All the glyphosate-resistant populations were also highly resistant to the ALS-inhibitor SU herbicide (two-way multiple resistance). There were 3 populations from Toole County confirmed with two-way multiple resistance to SU herbicide and dicamba. More concerning, there were two populations from Toole County with three-way multiple resistance to glyphosate, ALS-inhibitor, and dicamba herbicides. 1.4. Molecular Basis of Evolved Resistance to Glyphosate and Acetolactate Synthase-Inhibitor Herbicides in Kochia: In an in vivo leaf-disk shikimate assay, MHR plants accumulated less shikimate than the SUS plants at a discriminate dose of 100 μM glyphosate. Sequencing of the conserved region of EPSPS revealed no target-site mutation at Thr102 or Pro106 residue. MHR kochia accessions had increased relative EPSPS gene copies (~ 4 to 10) compared with the SUS accession (single copy). Furthermore, MHR kochia accumulated higher EPSPS protein compared with the SUS plants. Resistance to the ALS-inhibitor herbicides was conferred by Pro197 amino acid substitution (proline to glutamine). EPSPS gene amplification and a single target-site mutation at Pro197 in ALS gene confer resistance to glyphosate and ALS-inhibitor herbicides, respectively, in MHR kochia accessions from Montana. This is the first confirmation of occurrence of MHR kochia in Montana. Objective 2 2.1. Herbicide Programs for Kochia Management in Postharvest Wheat Stubble: Paraquat + atrazine, paraquat + linuron, and paraquat + metribuzin applied at the early bloom stage were the most effective postharvest treatments for late-season control (100% at 28 DAT), biomass reduction (70 to 73%), and seed prevention of K. scoparia, and did not differ from glyphosate, glufosinate, saflufenacil + 2, 4-D, saflufenacil + atrazine, tembotrione + atrazine, or topramezone + atrazine treatments. Dicamba alone, dicamba + 2, 4-D, or diflufenzopyr + dicamba + 2, 4-D applied at the early bloom stage were ineffective, with < 70% late-season control, < 45% biomass reduction, and < 55% seed reduction of K. scoparia. In the absence of a postharvest herbicide, uncontrolled kochia plants at a density of 8 to 10 plants m-2 contributed > 100,000 seeds m-2. Addition of atrazine to dicamba improved late-season control (80%) and seed reduction (78%) compared to dicamba alone, and reduced seed viability and 100-seed weight. There was no significant effect of any of the dicamba-containing herbicides applied at the early bloom stage on K. scoparia progeny fitness, including height, width, primary branches, and shoot dry weight of seedlings at 42 DAP. The effective postharvest-applied herbicides investigated in this research should be utilized to prevent late-season K. scoparia seed bank replenishment in wheat, and as a component of herbicide resistance management program for the containment of glyphosate- and/or ALS-inhibitor-resistant K. scoparia in wheat-based crop rotations in the U.S. Great Plains.

Publications

  • Type: Journal Articles Status: Published Year Published: 2015 Citation: 1. Jha, P., V. Kumar, J. Garcia, and N. Reichard. 2015. Tank-mixing pendimethalin with pyroxasulfone and chloroacetamide herbicides enhances in-season residual weed control in corn. Weed Technology. 29:198-206. 2. Kumar, V., P. Jha, D. Giacomini, E. Westra, and P. Westra. 2015. Molecular basis of evolved resistance to glyphosate and acetolactate synthase-inhibitor herbicides in kochia (Kochia scoparia) accessions from Montana. Weed Science. In press (doi: http://dx.doi.org/10.1614/WS-D-15-00021.1). 3. Jha, P., V. Kumar, and C.A. Lim. 2015. Variable response of kochia [Kochia scoparia (L.) Schard.] to auxinic herbicides dicamba and fluroxypyr in Montana. Canadian Journal of Plant Science. 95:965-972. 4. Kumar, V. and P. Jha. 2015. Effective preemergence and postemergence herbicide programs for kochia control. Weed Technology. 29:2434. 5. Kumar, V. and P. Jha. 2015. Influence of herbicides applied postharvest in wheat stubble on control, fecundity, and progeny fitness of Kochia scoparia in the US Great Plains. Crop Protection. 71:144149. 6. Jha, P., J. K. Norsworthy, V. Kumar, and N. Reichard. 2015. Annual changes in temperature and light requirements for Ipomoea purpurea seed germination with after-ripening in the field following dispersal. Crop Protection. 67:8490. 7. Kumar, V. and P. Jha. 2015. Control of volunteer glyphosate-resistant canola in glyphosate-resistant sugar beet. Weed Technology. 29:93100. 8. Kumar, V. and P. Jha. 2015. Effect of glyphosate timing on Kochia scoparia demographics in glyphosate-resistant sugar beet. Crop Protection. 76:3945. 9. Jha, P., J. K. Norsworthy, and J. Garcia. 2014. Depletion of an artificial seed bank of Palmer amaranth (Amaranthus palmeri) over four years of burial. American Journal of Plant Science. 5:15991606. 10. Kumar, V., P. Jha, and N. Reichard. 2014. Occurrence and characterization of kochia (Kochia scoparia) accessions with resistance to glyphosate in Montana. Weed Technology. 28:122130.