Development of the building blocks for Integrated Weed Management programs for control of glyphosate- and multiple herbicide-resistant weeds

Objectives:

• To develop the building blocks for Integrated Weed Management (IWM) strategies for the control of glyphosate-resistant (GR) and multiple-herbicide-resistant (MHR) weeds in Ontario.
• To improve the consistency of MHR Canada fleabane in corn, soybean and cereals.
• To improve the consistency of MHR waterhemp in corn, soybean and cereals.
• To improve the consistency of GR giant ragweed control in soybean and cereals.
• To evaluate building blocks of an IWM program – such as new herbicides, crop row widths, crop rotations and cover crops as part of a diversified IWM strategy.

Impacts:

• The potential financial loss to Ontario farmers resulting from MHR Canada fleabane competition in corn, soybean and cereals is $559 million annually if no weed management tactics were employed by Ontario farmers. Assuming that yield loss is reduced by 90% with current weed management strategies, Ontario farmers still incur a financial loss of $56 million annually. If yield loss due to MHR Canada fleabane were decreased to only 5%, it would result in a benefit to Ontario farmers of $28 million annually.
• The potential financial loss due to competition from uncontrolled GR giant ragweed in Ontario corn, soybean and cereals could be as high as $134 million annually. Assuming that current weed management strategies limit yield loss to 10%, Ontario farmers are still losing $13.4 million annually. If this research can decrease yield loss due to MR giant ragweed across Ontario to only 5%, the annual benefit to Ontario farmers would be $6.7 million.
• Without weed management tactics, the financial loss attributable to MHR waterhemp competition in corn, soybean and cereals in Ontario is reach $10 million annually. Assuming that with current weed management strategies, the yield loss is reduced by 90%, the annual loss to Ontario farmers is still $1.0 million. Through this research program, if yield loss due to MR waterhemp across Ontario were decreased to 5% it would result in a benefit to Ontario farmers of $0.5 million annually.
• It is expected that the areas infested with MHR waterhemp in Ontario will increase rapidly. From studies conducted on Ontario farms, in the most competitive environments waterhemp interference in corn and soybean resulted in yield losses of 84 and 93%, respectively. In corn, assuming an average yield of 159 bu/ac and selling price of $4.87 (OMAFRA 2016) this represents a potential loss $648/ac due to waterhemp interference. In soybean, this translates to a loss of $546/ac due to waterhemp interference, assuming an average yield of 46 bu/ac and selling price of $12.78 (OMAFRA 2016). On a provincial basis, the potential monetary loss to Ontario farmers is millions of dollars if growers do not implement effective MHR waterhemp control strategies. It is anticipated that the results of this research will substantially reduce the financial loss to Ontario farmers due to MR waterhemp.
• This research program will help Ontario corn, soybean and cereal producers determine exactly which herbicide(s)/herbicide tank mixes to use to address MHR weeds on their farm and how to incorporate this information into a diversified IWM program.

Project Overview:

Glyphosate resistant (GR) weeds are present on more than 60% of Ontario farms (CCA survey completed by Peter Sikkema in 2023). GR Canada fleabane, giant ragweed, waterhemp and common ragweed have been confirmed in numerous counties in Ontario. The number of acres infested continues to increase. Based on studies completed on Ontario farms, GR Canada fleabane, giant ragweed, waterhemp and common ragweed interference reduced corn yield on average of 64, 72, 23 and 75% while in soybean the average yield loss was 70, 73, 43 and 75%, respectively.

In 2022, the challenge of GR and MHR weeds was exacerbated with the confirmation of five-way MR waterhemp (Groups 2, 5, 9, 14 and 27) in seven Ontario counties. This is the first weed biotype with five-way herbicide resistance documented in Ontario. It is expected that this MHR biotype will be found at more sites over time which will dramatically increase the challenge for Ontario farmers. The rapidly changing and widespread presence of GR and now MHR weed biotypes necessitates continued research on development of new weed management solutions for Ontario farmers. Research from only a few years ago may no longer be relevant.

Control of MHR Canada fleabane is variable across Ontario and the USA. Continued research is required to improve the consistency of control, especially in soybean to minimize yield and financial losses for farmers. This project included studies of both fall and spring herbicide applications as well as examining the impact of crop rotation and cover crops.

New strategies need to be developed for the control of MHR waterhemp to improve control, reduce yield and financial losses and slow its migration across the province. Ultimately, the goal of MHR waterhemp weed control programs may have to be zero weed seed return to the soil to stop its spread across Ontario. This project evaluated several new herbicides, including, but not limited to Bayer-478, tolpyralate, trifludimoxazin and V-10456 (and others as they were released for public testing) for the control of MHR waterhemp in the province. It is important that these new herbicides be evaluated under Ontario conditions and at use rates registered in Canada, to continue to move the science of weed management forward. These new herbicides need to be compared to the current industry standards to determine if control can be improved and/or costs can be reduced for growers. Studies were completed in corn, soybean, and cereals.

The overall goal of this research was to develop the building blocks for integrated weed management (IWM) programs based on sound science. The identification of effective building blocks will allow Ontario farmers to implement unique IWM programs tailored to their unique farming operation.

Results:

MHR Canada Fleabane Control in Corn

Shieldex (30 or 40 g/ha) and atrazine controlled GR Canada fleabane 79-84%. The tankmixes of Shieldex + atrazine controlled GR Canada fleabane 91-95% which was similar to the industry standards Marksman (90%), Callisto + atrazine (96%) and Integrity (98%).

At 2, 4 and 8 WAA, Shieldex + atrazine controlled GR Canada fleabane 68, 77, and 86%, respectively. At 2, 4 and 8 WAA, Shieldex + atrazine + MSO controlled GR Canada fleabane 94, 96 and 97%, respectively. There was no improvement in GR Canada fleabane control with the addition of urea ammonium nitrate (UAN). GR Canada fleabane density and biomass followed a similar trend.

Callisto, Shieldex and Armezon, applied POST, controlled GR Canada fleabane 81, 80 and 69%, respectively. Atrazine, Pardner and Basagran, applied POST, controlled GR Canada fleabane 33, 68 and 75%, respectively. The tankmixes of Callisto, Shieldex or Armezon plus a PSII-inhibiting herbicide controlled GR Canada fleabane ≥87%. 

Insight at 12.5, 25 and 37.5 g/ha, applied POST, controlled GR Canada fleabane 56, 59 and 68%, respectively. Tankmixes of Insight plus Shieldex, Pardner or dicamba controlled GR Canada fleabane ≥87, 75, and 82%, respectively. The industry standards Marksman and Integrity controlled GR Canada fleabane 95 and 100%, respectively.

Roundup + Converge + AAtrex and Roundup + Acuron Flexi controlled GR Canada fleabane 93 and 90%, respectively. Roundup + Test Compound # 1 + AAtrex, Roundup Xtend + Test Compound # 1, Roundup Xtend + Test Compound # 1 + AAtrex, Roundup + Integrity, Roundup + Callisto + AAtrex, Roundup + Lumax EZ, and Roundup + Acuron, applied preplant, controlled GR Canada fleabane ≥96. There are excellent herbicide tankmixes applied preplant for the control of GR Canada fleabane in corn.

Roundup + 2,4-D amine Roundup + Lontrel, Roundup + Shieldex + Aatrex, Roundup + Lumax EZ and Roundup + Acuron Flexi controlled GR 80-89%. Roundup + Marksman, Roundup + Xtendimax, Enlist Duo, Roundup + Callisto + Aatrex, Roundup + Acuron and Halex + Aatrex controlled GR Canada fleabane 90-95%. Roundup + Pardner + Aatrex, Roundup + Laudis + Aatrex, Roundup + Laudis + Pardner, Roundup Xtend + Laudis and Roundup Xtend + Laudis + Aatrex controlled GR Canada fleabane 96-100%. There are excellent herbicide tankmixes applied postemergence for the control of GR Canada fleabane in corn.

MHR Canada Fleabane Control in Soybean

At 8 WAA, Roundup + Elevore, applied PP, controlled GR Canada fleabane 72%. There was no improvement in control with the addition of Classic or Classic + Valtera. In contrast, Roundup + Elevore plus Eragon, Sencor, Eragon + Sencor or Classic + Sencor controlled GR Canada fleabane >90% which was similar to the industry standards Roundup + Eragon + Sencor (95%) and Roundup Xtend (92%)

At 8 WAA, Roundup + Eragon, applied PP, controlled GR Canada fleabane 90%, the addition of Sencor improved control to 96%. Roundup + 2,4-D, applied PP, controlled GR Canada fleabane 58%, the addition of Sencor improved control to 92%. Roundup + BlackHawk, applied PP, controlled GR Canada fleabane 57%, the addition of Sencor or Bifecta improved control to 92 and 91%, respectively. Enlist Duo, applied PP, controlled GR Canada fleabane 66%, the addition of Canopy PRO improved control to 92%. Roundup + Elevore, applied PP, controlled GR Canada fleabane 70%, the addition of Canopy PRO improved control to 89%.

At 8 WAA, Roundup Xtend, applied PP, controlled GR Canada fleabane 89%. There was no improvement in control with the addition of Sencor or Canopy PRO. In contrast, Roundup Xtend + Eragon controlled GR Canada fleabane 97%.  Roundup + Tavium, applied PP, controlled GR Canada fleabane 83%. There was no appreciable improvement in control of GR Canada fleabane with the addition of Sencor.  In contrast, Roundup + Tavium + Eragon controlled GR Canada fleabane 97%. 

At 8 WAA, Pardner at 35, 70, 140, 280, 560 and 1120 g/ha controlled GR Canada fleabane 31, 42, 61, 78, 84 and 96%, respectively; the addition of metribuzin improved control to 89, 94. 95, 97, 99 and 100%, respectively. Pardner (280 /ha) + Sencor, Eragon + Sencor and dicamba + Eragon controlled GR Canada fleabane similarly at 97-100%.

At 8 WAA, BlackHawk at 66, 132, 264, 527, 1054 and 2108 g/ha controlled GR Canada fleabane 20, 30, 40, 60, 79 and 90%, respectively; the addition of metribuzin improved control to 88, 85, 92, 97, 97, and 98%, respectively. BlackHawk (527 g /ha) + Sencor, Eragon + Sencor and dicamba + Eragon controlled GR Canada fleabane similarly at 97-99%.

At 8 WAA, Insight at 3.125, 6.25, 12.5, 25, 50, 100 and 200 g/ha controlled GR Canada fleabane 25, 28, 32, 54, 61, 75 and 88%, respectively; the addition of metribuzin improved control to 82, 82, 88, 88, 93, 93 and 96%, respectively. Insight (50 g /ha) + Sencor, Eragon + Sencor and dicamba + Eragon controlled GR Canada fleabane 93, 98 and 100%, respectively.

At 8 WAA, Pardner controlled GR Canada fleabane 61%. At 8 WAA, 2,4-D, Elevore, dicamba, Sencor, Eragon, Tergeo and BlackHawk controlled GR Canada fleabane 72, 80, 94, 54, 85, 46, and 59%, respectively; when applied in a tankmix with Pardner Canada fleabane control was 75, 79, 92, 70, 87, 57, and 72%, respectively. GR Canada fleabane control was optimized when Pardner was tankmixed with dicamba or Eragon.

At 8 WAA, dicamba controlled GR Canada fleabane 94%; when applied in a tankmix with 2,4-D, Elevore, BlackHawk, Pardner, Sencor, Eragon or Insight GR Canada fleabane control was 96, 96, 96, 91, 90, 96 and 90%, respectively. GR Canada fleabane control was optimized when dicamba was tankmixed with 2,4-D, Elevore, BlackHawk or Eragon. The tankmixes with Pardner, Sencor, and Insight appear to antagonize GR Canada fleabane control.

At 8 WAA, Liberty controlled GR Canada fleabane 33%. Pyraflufen-ethyl, BlackHawk, Eragon, Authority, Valtera and Reflex (at 5% of the label rate) controlled GR Canada fleabane 9, 14, 24, 22, 19, and 18%, respectively; there was no appreciable improvement in GR Canada fleabane control when a low rate of a PPO herbicide was added to Liberty.

At 8 WAA, Liberty controlled GR Canada fleabane 57%. Eragon at 1.5625, 3.125, 6.25, 12.5, 25, 50 and 100 g/ha controlled GR Canada fleabane 26, 32, 54, 68, 85, 93, and 98%, respectively; when Liberty was added Eragon Canada fleabane control was 33, 45, 56, 76, 83, 94, and 97%, respectively.

At 8 WAA, Liberty at 500 and 1000 g/ha controlled GR Canada fleabane 60 and 70%, respectively. The application of Liberty with UAN at 50 and 100% of the carrier volume controlled GR Canada fleabane 65 and 68%, respectively. The tankmixes of Liberty plus 2,4-D, dicamba, Elevore, Eragon or Sencor controlled GR Canada fleabane 71, 92, 63, 73, and 89%, respectively. GR Canada fleabane control was optimized when Liberty was tankmixed with Sencor (the tankmix of Liberty with dicamba is not recommended due to increased volatility of dicamba).

At 8 WAA, 2,4-D, applied with water as the carrier, controlled GR Canada fleabane 66%, 2,4-D applied with UAN as the carrier at concentrations of 1.0, 2.5, 5, 10, 25, 50 and 100% controlled GR Canada fleabane 71, 66, 66, 65, 57, 18, and 7%, respectively. There was no appreciable improvement in GR Canada fleabane control when 2,4-D was applied with UAN at 1.0, 2.5 5, and 10 v/v. The application of 2,4-D with UAN at 25, 50 and 100% v/v reduced GR Canada fleabane control.

At 8 WAA, dicamba, 2,4-D and Elevore controlled GR Canada fleabane 94, 69, and 88%, respectively (consistent with previous research). The 2-way tankmixes of dicamba + 2,4-D, dicamba + Elevore, and 2,4-D + Elevore controlled GR Canada fleabane 98, 98, and 92%, respectively. The 3-way tankmix of dicamba + 2,4-D + Elevore controlled GR Canada fleabane 98%. The industry standard of dicamba + Eragon controlled GR Canada fleabane 97%.

At 8 WAA, Eragon and Sencor controlled GR Canada fleabane 94, 48%, respectively. Dicamba controlled GR Canada fleabane 96%, there was no appreciable improvement in control with the addition of Eragon or Sencor. 2,4-D controlled GR Canada fleabane 75%; the addition of Eragon or Sencor improved control to 94 and 84%, respectively. Elevore controlled GR Canada fleabane 70%; the addition of Eragon or Sencor improved control to 98 and 94%, respectively. BlackHawk controlled GR Canada fleabane 53%; the addition of Eragon or Sencor improved control to 98 and 83%, respectively.

At 8 WAA, Liberty and Enlist Duo, applied POST, controlled GR Canada fleabane 73 and 85%, respectively. Enlist Duo, applied PP, controlled GR Canada fleabane 50%; when followed by a POST application of Liberty or Enlist Duo the control was improved to 79 and 93%, respectively. Elevore, applied PP, controlled GR Canada fleabane 72%; when followed by a POST application of Liberty or Enlist Duo the control was improved to 92 and 93%, respectively. Eragon, applied PP, controlled GR Canada fleabane 83%; when followed by a POST application of Liberty or Enlist Duo the control was improved to 92 and 97%, respectively. Enlist Duo + Eragon, applied PP, controlled GR Canada fleabane 92%; when followed by a POST application of Liberty or Enlist Duo the control was improved to 96 and 93%, respectively.

MHR Canada Fleabane Control in Winter Wheat

At 8 WAA, MCPA and Trophy A, applied POST, controlled GR Canada fleabane 38 and 82%, respectively, while Elevore and Trophy controlled GR Canada fleabane 93%. Pixxaro, Pixxaro M, 2,4-D ester, Lontrel and Infinity controlled GR Canada fleabane 95-96%.

At 8 WAA, Barricade M, Simplicity, Luxxur, Luxxur M, Enforcer M, and Shieldex, applied POST, controlled GR Canada fleabane <90%. Infinity, Infinity FX, Velocity, Velocity M, Pixxaro, Pixxaro M, Pixxaro + Simplicity + MCPA and 2,4-D ester controlled GR Canada fleabane >90%.

At 8 WAA, MHR Canada fleabane control with Infinity applied in the fall and spring was 72 and 95%, respectively; with Infinity FX applied in the fall and spring was 79 and 96%, respectively; with Pixxaro M applied in the fall and spring was 93 and 98%, respectively; with Lontrel applied in the fall and spring was 98 and 99%, respectively. On average the fall compared to spring herbicide applications controlled MHR Canada fleabane 85 and 97%, respectively. There was an average increase in MHR Canada fleabane control of 9% with a sequential application.    

MHR Waterhemp Control in Corn

At 8 WAA, Shieldex (30 or 40 g/ha) and atrazine controlled GR waterhemp 58-62%. The tankmixes of Shieldex + atrazine controlled GR waterhemp 77-78% which was less than the industry standards Callisto + atrazine (90%) and Acuron (99%).

At 2, 4, 8 and 12 WAA, Shieldex + atrazine controlled GR waterhemp 78, 83, 90 and 91%, respectively. At 2, 4, 8 and 12 WAA, the addition of MSO to Shieldex + atrazine improved GR waterhemp control to 95, 97, 98 and 97%, respectively. There was no appreciable improvement in GR waterhemp control with the addition of UAN.

At 8 WAA, Converge + atrazine, Acuron and Shieldex + atrazine, applied PRE, controlled GR waterhemp 89, 97 and 84%, respectively. Liberty, applied POST, controlled GR waterhemp 85%. The sequential application of Converge + atrazine, Acuron or Shieldex + atrazine, applied PRE, followed by Liberty, applied POST controlled GR waterhemp 97, 98 and 97%, respectively. This study is complete.

At 8 WAA, Primextra, Integrity and Marksman, applied PRE, controlled GR waterhemp 92, 98 and 84%, respectively. Callisto + atrazine, applied POST, controlled GR waterhemp 94%. The sequential application of Primextra, Integrity or Marksman, applied PRE, followed by Callisto + atrazine, applied POST controlled GR waterhemp 99%.

At 12 WAA, atrazine, applied POST, controlled GR waterhemp 68% and the HPPD inhibiting herbicides, Converge, Callisto, Armezon Laudis and Shieldex controlled GR waterhemp 79, 88, 82, 95, and 92%, respectively. The tankmixes of Converge, Callisto, Armezon Laudis or Shieldex + atrazine controlled GR waterhemp 91, 94, 89, 99 and 93%, respectively. On average, the addition of atrazine to the HPPD-inhibiting herbicide improved GR waterhemp control 6%.

At 8 WAA, Shieldex at 3.75, 7.5, 15, 30, 60 and 120 g/ha controlled GR waterhemp 58, 70, 73, 81, 85 and 88%, respectively; the addition of atrazine improved control to 70, 75, 81, 86, 95 and 98%, respectively. The industry standards, Callisto + atrazine and Marksman controlled GR waterhemp 88 and 82%, respectively which is similar to Shieldex (30 g/ha) + atrazine (1000 g/ha) at 86%.

Atrazine, Sencor and Lorox, applied PRE, controlled GR waterhemp 64, 81 and 89%, respectively. Converge, applied PRE, controlled GR waterhemp 74%. The tankmixes of Converge plus atrazine, Sencor or Lorox controlled GR Canada fleabane 88-95%. 

Callisto, Shieldex and Armezon, applied POST, controlled GR waterhemp 81, 83 and 73%, respectively. Atrazine, Pardner and Basagran, applied POST, controlled GR waterhemp 69, 63 and 53 respectively. The tankmixes of Callisto, Shieldex or Armezon plus a PSII-inhibiting herbicide controlled GR Canada fleabane 83-98%.

At 12 WAA, Roundup plus Zidua + Marksman, Armezon PRO + Marksman, Converge + atrazine, Shieldex + atrazine, Callisto + atrazine, Lumax,  Acuron Flexi and Acuron; Enlist Duo + Engarde, Enlist Duo + Engarde + atrazine and Halex + atrazine controlled GR waterhemp ≥95%; Roundup + Marksman controlled GR waterhemp 88%; and Roundup + Primextra controlled GR waterhemp 83%.

Roundup + Integrity and Roundup + Converge + Aatrex controlled MHR waterhemp 65-67%. Roundup + Integrity + Callisto, Roundup + Converge + Aatrex +Cadou, Roundup + Laudis + Aatrex, + Cadou, Roundup + Focus + Focus, Roundup + Callisto + Aatrex, Roundup + Acuron Flexi and Halex + AAtrex controlled MHR waterhemp 72-77%. Roundup Laudis + Xtendimax + Cadou and Roundup + Lumax controlled MHR waterhemp 83-86%. Roundup + Test # 1+ Aatrex + Cadou and Roundup + Acuron controlled MHR waterhemp 90-98%.

Harness at 1225, 2100 and 2950 g/ha, applied PP, controlled GR waterhemp 63, 71 and 76%, respectively; Harness at 1225, 2100 and 2950 g/ha, applied PRE, controlled GR waterhemp 72, 78 and 86%, respectively; and Harness at 1225, 2100 and 2950 g/ha, applied POST, controlled GR waterhemp 78, 76 and 86%, respectively. Across all application timings, Harness at 1225, 2100 and 2950 g/ha, controlled GR waterhemp 71, 75, and 83%, respectively. Across all rates, Harness applied PP, PRE, and POST controlled GR waterhemp 70, 79 and 80%, respectively.

MHR Waterhemp Control in Soybean

Warrant at 1050, 1375 and 1700 g/ha, applied PP, controlled GR waterhemp 56, 64 and 77%, respectively; Warrant at 1050, 1375 and 1700 g/ha, applied PRE, controlled GR waterhemp 56, 61 and 67%, respectively; and Warrant at 1050, 1375 and 1700 g/ha, applied POST, controlled GR waterhemp 44, 51 and 52%, respectively. Across all application timings, Warrant at 1050, 1375 and 1700 g/ha, controlled GR waterhemp 52, 59 and 65%, respectively. Across all rates, Warrant applied PP, PRE, and POST controlled GR waterhemp 65, 61 and 49%, respectively.

MHR Giant Ragweed Control in Soybean and Winter Wheat

At 8 WAA, Roundup + Elevore, Roundup + 2,4-D, Enlist Duo and Roundup Xtend controlled GR giant ragweed 11, 76, 82 and 87%, respectively. The addition of Elevore to Roundup + 2,4-D, Enlist Duo and Roundup Xtend did not improve GR giant ragweed control.

Elevore, Trophy A, Pixxaro, MCPA and Simplicity, applied POST, controlled GR giant ragweed <90%. Pixxaro M, Trophy, Pixxaro + Simplicity, 2,4-D, Lontrel and Barricade M controlled GR giant ragweed ≥90%.

External Funding Partners:

BASF

Bayer

Corteva

FMC

Syngenta

Valent / Nufarm

Project Related Publications:

Benoit, L., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2019. Efficacy of HPPD-inhibiting herbicides applied preemergence or postemergence for control of multiple-resistant waterhemp (Amaranthus tuberculatus var. rudis). Canadian Journal of Plant Science. 99:379-383.

Benoit, L., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2019. Control of multiple-resistant waterhemp (Amaranthus tuberculatus var. rudis) with pre-emergence and post-emergence herbicides in corn in Ontario. Canadian Journal of Plant Science. 99:364-370.

Benoit, L., Hedges, B., Schryver, M., Soltani, N., Hooker, D. C., Robinson, D. E., Laforest, M., Soufiane, B., Tranel, P. J., Giacomini, D., and Sikkema, P. H. 2020. The first record of protoporphyrinogen oxidase and four-way herbicide resistance in eastern Canada. Canadian Journal of Plant Science. 100(3):327-331.

Byker, H., Nissen, P. S., Gaines, T., Westra, P., Martin, S., Tardif, F., Robinson, D., Lawton, M., and Sikkema, P. H. 2022. Mechanisms of glyphosate resistance in common ragweed (Ambrosia artemisiifolia): patterns of absorption, translocation, and metabolism. Weed Science. 70:151-159.

Dilliott, M. A., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2022. The addition of very low rates of PPO-inhibiting herbicides to glufosinate does not improve the control of GR Canada fleabane. Weed Technology. 36:358-367.

Dilliott, M. A., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2022. When using glyphosate plus dicamba, 2,4-D ester, halauxifen-methyl or pyraflufen-ethyl/2,4-D for glyphosate-resistant Canada fleabane control in soybean, which third tankmix partner is better, saflufenacil or metribuzin? Weed Technology. 36:295-302.

Dilliott, M. A., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2022. Strategies to improve glyphosate-resistant Canada fleabane with glufosinate applied preplant to soybean. Weed Technology. 36:289-294.

Dilliott, M. A., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2022. The addition of saflufenacil to glyphosate plus dicamba improves glyphosate-resistant Canada fleabane (Erigeron canadensis L.) control in soybean. Agronomy. 12(3), 654.

Dilliott, M. A., Soltani, N., Robinson, D. E., Hooker, D. C., and Sikkema, P. H. 2022. Will the addition of 2,4-D ester, halauxifen-methyl, dicamba, metribuzin, saflufenacil, tiafenacil or pyraflufen-ethyl/2,4-D to bromoxynil applied preplant improve the level and consistency of glyphosate-resistant Canada fleabane control in soybean? Journal of Agricultural Science. 14(1).

Ferrier, J., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2022. The interaction of pyroxasulfone and flumioxazin applied preemergence for the control of multiple-herbicide-resistant waterhemp (Amaranthus tuberculatus) in soybean. Weed Technology. 36:318-323.

Ferrier, J., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2022. Biologically effective dose of flumioxazin and pyroxasulfone for control of multiple herbicide-resistant waterhemp (Amaranthus tuberculatus) in soybean. Weed Science. 70:243-248.

Fluttert, J. C., Soltani, N., Galla, M., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2022. Additive and synergistic interactions of 4-hydroxyphenylpyruvate dioxygenase (HPPD) and photosystem II-inhibitors for the control of glyphosate-resistant horseweed in corn. Weed Science. 70:319-327.

Hedges, B. K., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2019. Influence of glyphosate/dicamba application rate and timing on the control of glyphosate-resistant waterhemp in glyphosate/dicamba-resistant soybean. Canadian Journal of Plant Science. 99:371-374.

Hedges, B. K., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2019. Control of glyphosate-resistant Canada fleabane in Ontario with multiple effective sites-of-action in glyphosate/dicamba-resistant soybean. Canadian Journal of Plant Science. 99:78-83.

Hedges, B. K., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2019. Control of glyphosate-resistant waterhemp with preemergence herbicides in glyphosate- and dicamba-resistant soybean. Canadian Journal of Plant Science. 99:34-39.

Langdon, N., Soltani, N., Raeder, A., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2020. Tolpyralate + atrazine applied preemergence provides residual GR Canada fleabane control similar to current industry standards. Agricultural Science. 11:417-424.

Langdon, N., Soltani, N., Raeder, A., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2020. Influence of adjuvants on the control of glyphosate-resistant Canada fleabane and waterhemp in corn with tolpyralate. American Journal of Plant Science. 11:354-371.

Quinn, J., Soltani, N., Ashigh, J., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2020. Halauxifen-methyl controls glyphosate-resistant horseweed but not giant ragweed in winter wheat. Weed Technology. 34:607-612.

Quinn, J., Soltani, N., Ashigh, J., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2021. Control of glyphosate-resistant marestail and giant ragweed in soybean with halauxifen-methyl applied preplant. Weed Technology. 35:324-329.

Soltani, N., Brown, L. R., and Sikkema, P. H. 2020. Multiple-resistant waterhemp control in herbicide-resistant soybean. Canadian Journal of Plant Science. 100:692-696.

Soltani, N., Shropshire, C., and Sikkema, P. H. 2020. Glyphosate-resistant Canada fleabane control with three-way tankmixes in soybean. American Journal of Plant Science. 11:1478-1486.

Soltani, N., Shropshire, C., and Sikkema, P. H. 2020. Glyphosate-resistant Canada fleabane control in winter wheat with postemergence herbicides. International Journal of Agriculture 2020, Article ID 8840663.

Soltani, N., Shropshire, C., and Sikkema, P. H. 2020. Control of glyphosate-resistant marestail in soybeans with preplant herbicides. American Journal of Plant Science. 6:851-860.

Soltani, N., Shropshire, C., and Sikkema, P. H. 2021. Control of glyphosate-resistant horseweed (Conyza canadensis) with tiafenacil tankmixes in corn. Weed Technology. 35:908-911.

Soltani, N., Willemse, C., and Sikkema, P. H. 2021. Does the inclusion of atrazine in S-metolachlor/mesotrione/bicyclopyrone improve glyphosate-resistant Canada fleabane control in corn? Journal of Agricultural Sciences.

Soltani, N., Shropshire, C., and Sikkema, P. H. 2022. Control of glyphosate-resistant horseweed with Group 4 herbicides in soybean. Weed Technology. 36:643-647.

Soltani, N., Shropshire, C., and Sikkema, P. H. 2023. Control of multiple herbicide-resistant Canada fleabane with fall, spring and sequential herbicide applications in winter wheat. Journal of Agricultural Science 15(5).

Symington, H. E., Soltani, N., and Sikkema, P. H. 2022. Confirmation of 4-hydroxyphenylpyruvate dioxygenase inhibitor-resistant and 5-way multiple-herbicide-resistant waterhemp in Ontario, Canada. Journal of Agricultural Science.

Symington, H. E., Soltani, N., and Sikkema, P. H. 2023. Impact of acetochlor rate and application timing on multiple-herbicide-resistant waterhemp control in corn and soybean. Journal of Agricultural Science 15(2).

Westerveld, D. B., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2021. Biologically-effective-dose of pyraflufen-ethyl/2,4-D for the control of glyphosate-resistant Canada fleabane in soybean. Weed Technology. 35:824-829.

Westerveld, D. B., Soltani, N., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2021. Efficacy of tiafenacil applied alone or mixed with metribuzin for glyphosate-resistant horseweed control in soybean. Weed Technology. 35:817-823.

Westerveld, D. B., Soltani, N., Hooker, D. C., Robinson, D. E., Tranel, P. J., Laforest, M., and Sikkema, P. H. 2021. Biologically effective dose of metribuzin for the control of waterhemp (Amaranthus tuberculatus) with resistance to photosystem II-inhibitors. Weed Science. 69:631-641.

Willemse, C., Soltani, N., Benoit, L., Hooker, D. C., Jhala, A. J., Robinson, D. E., and Sikkema, P. H. 2021. Herbicide programs for the control of waterhemp resistant to three herbicide modes of action in maize. Weed Technology. 35:753-760.

Willemse, C., Soltani, N., Benoit, L., Jhala, A. J., Hooker, D. C., Robinson, D. E., and Sikkema, P. H. 2021. Is there a benefit of adding atrazine to HPPD-inhibiting herbicides for control of multiple-herbicide-resistant waterhemp in corn? Journal of Agricultural Plant Science.

Willemse, C., Soltani, N., Hooker, D. C., Jhala, A. J., Robinson, D. E., and Sikkema, P. H. 2021. Interaction of HPPD- and atrazine-alternative photosystem II-inhibitors for control of multiple-herbicide-resistant waterhemp in corn. Weed Science. 69:485-491.

Willemse, C., Soltani, N., Metzger, B., Hooker, D. C., Jhala, A. J., Robinson, D. E., and Sikkema, P. H. 2021. Biologically-effective-dose of tolpyralate and tolpyralate plus atrazine for control of multiple-herbicide-resistant waterhemp in corn. Agricultural Sciences 12.

Willemse, C., Soltani, N., Hooker, D. C., Jhala, A. J., Robinson, D. E., and Sikkema, P. H. 2021. Early postemergence herbicide tank-mixtures for control of waterhemp resistant to four herbicide modes of action in corn. Agricultural Sciences. 4.