Survey of glyphosate- and dicamba-resistant kochia (<i>Bassia scoparia</i>) in Saskatchewan

Sharpe, Shaun M.; Leeson, Julia Y.; Geddes, Charles M.; Willenborg, Christian J.; Beckie, Hugh J.

doi:10.1139/cjps-2023-0016

Cited by 5 publications

(1 citation statement)

References 31 publications

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“…Kochia, while one of the predominant weed issues in the southern Prairies, particularly due to rapid emergence of herbicide resistance to multiple herbicide groups (Geddes et al, 2021a;Geddes et al, 2021b;Geddes et al, 2022;Sharpe et al, 2023) did not show obvious impacts of increased seeding rate, crop rotation, or early cut silage. In Lethbridge, only the rotation with increased seeding rates of peas, winter wheat and canola in rotation, with chaff collection reduced kochia densities (Supplementary Figure 3A), which may have been a result of their lack of efficacy on grass weed management, rather than efficacy on kochia.…”

Section: Broadleaf Weedsmentioning

confidence: 99%

Using integrated weed management systems to manage herbicide-resistant weeds in the Canadian Prairies

Tidemann,

Harker,

Shirtliffe

et al. 2023

Front. Agron.

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Although herbicides have been a dominant and effective weed control strategy for decades in Western Canada, herbicide resistance and the lack of new modes of action have resulted in weed management challenges. Integrated weed management strategies have been shown to be successful in controlling certain weed species that are problematic in cropping systems. The objective of this study was to investigate integrated weed management strategies that have been successful on individual species to determine their applicability to a multiple weed species that may coexist in a field. In addition, harvest weed seed control was incorporated into these integrated weed management strategies to determine its impact in western Canadian cropping systems. A 5-year rotational study was conducted from 2016 to 2020 at Beaverlodge, Lacombe, and Lethbridge, AB; Scott and Saskatoon, SK; and Carman, MB, that incorporated integrated weed management strategies such as rotational crop diversity (including winter annuals and perennials), increased seeding rates, crop silaging, chaff collection, and with or without in-crop herbicides. This research confirmed success in managing some species of weeds such as wild oat when increased seeding rates, 2 years of early cut silage barley, and competitive winter cereals were incorporated into a cropping system, even when no in-crop herbicides were applied. However, some weed growth morphologies (e.g., twining weeds) or life cycles (e.g., facultative winter annuals) were not managed successfully with this combination of strategies. Chaff collection provided incremental weed control benefits but did not serve as a replacement for herbicidal weed control. Weed densities had an apparent impact on the success of these integrated weed management strategies, suggesting that the sooner they are adopted, the more likely they are to be successful at maintaining or reducing weed densities. This study not only showed the ability to reduce reliance on herbicides with strategies that can be effective in Western Canada but also highlighted the need for further understanding of different weed species and their responses to integrated weed management strategies, as well as the complexity of managing a weed community with integrated weed management.

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Section: Broadleaf Weedsmentioning

confidence: 99%

Using integrated weed management systems to manage herbicide-resistant weeds in the Canadian Prairies

Tidemann,

Harker,

Shirtliffe

et al. 2023

Front. Agron.

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Sublethal dosing exposure risk of kochia (Bassia scoparia (L.) A.J. Scott) to carfentrazone-ethyl

Sharpe,

Novak

2024

Can. J. Plant Sci.

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Kochia is a troublesome, multiple herbicide-resistant tumbleweed which infests Prairie field crops. Kochia has developed resistance to systemic, foliar-applied herbicides from Groups 2, 4, and 9, leaving only contact herbicides for post-emergence control. Group 14 chemistry is an important mode of action for resistance management. Weed staging considerations are important as recurrent sub-lethal herbicide exposure can increase risk of nontarget site resistance evolution. The study objective was to evaluate loss-of-control and estimate sublethal dosing exposure risk (SLDER) with a contact-type herbicide (carfentrazone-ethyl) based on initial kochia height, leaf number, and branch number. The SLDER from a single application to a single plant was conceptualized to increase due to escaping plant “volume” or immediate flowering. Kochia was only consistently controlled (100% injury) when dosed at ≤ 5cm in height. The estimated maximum size for treated kochia was 21 cm in height, 18 branches plant-1, and the maximum accumulated biomass was between 2.6 to 5.1 g plant-1 for models developed using the initial plant height, branch number, or leaf number as predictors. These estimates represent the largest plant escapes, which would be associated with 100% risk through vegetative considerations into SLDER. Kochia plant size for a 5% risk scenario using the SLDER model was 4 cm in height, 0 branches plant-1, and 11 leaves plant-1 when carfentrazone-ethyl was applied at the labeled dosing. Caution is advised when spraying kochia above 5 cm as incorrect staging may lead to sublethal exposure, escape, reproduction, and escalated risk of nontarget site resistance evolution.

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Palmer amaranth (Amaranthus palmeri S. Wats.) and waterhemp (Amaranthus tuberculatus (Moq.) J.D. Sauer) biovigilance in Canadian Agro-ecosystems

Sharpe,

Martin,

Page

et al. 2024

Can. J. Plant Sci.

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The evolution and spread of herbicide-resistant weeds threatens long-term sustainability of Canadian agro-ecosystems. Herbicide-resistant weeds increase management inputs and costs, increases off-target and environmental exposure to pesticides, reduces yield quality and quantity, and impedes harvest efficiency. Amaranthus species including Palmer amaranth (Amaranthus palmeri S. Wats.) and waterhemp [Amaranthus tuberculatus (Moq.) J.D. Sauer] are particularly concerning due to both their propensity towards herbicide resistance evolution, their history of invasion, and their spread in agro-ecosystems. A biovigilance approach is taken to build awareness of these pigweeds initial invasion and spread in the USA. Characteristics of their identification, potential hybridization, and known herbicide resistance evolution are reviewed. Fourteen species of Amaranthus are found in Canada, nine of which (including waterhemp) possess herbicide-resistant biotypes. A total of forty-five hybrids between various Canadian Amaranthus species with each other or Palmer amaranth have been noted. Hybrids have been experimentally produced or observed from herbarium specimens, with three cases of herbicide resistance transfer notably with Palmer amaranth or waterhemp. Mitigation strategies will depend on successful species identification and herbicide resistance status determination. Common pathways for Palmer amaranth introductions in the northern USA include both animal feed systems with grain screenings and crop production systems including seed and equipment contamination. Regional awareness campaigns will be critical to support Canadian farmers in identifying and quickly mitigating invasions of Palmer amaranth and waterhemp to prevent establishment and spread of infestations into new areas.

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Survey of glyphosate- and dicamba-resistant kochia (Bassia scoparia) in Saskatchewan

Cited by 5 publications

References 31 publications

Using integrated weed management systems to manage herbicide-resistant weeds in the Canadian Prairies

Using integrated weed management systems to manage herbicide-resistant weeds in the Canadian Prairies

Sublethal dosing exposure risk of kochia (Bassia scoparia (L.) A.J. Scott) to carfentrazone-ethyl

Palmer amaranth (Amaranthus palmeri S. Wats.) and waterhemp (Amaranthus tuberculatus (Moq.) J.D. Sauer) biovigilance in Canadian Agro-ecosystems

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