Giant Ragweed Research Articles

Chemical Composition of Ambrosia trifida L. and Its Allelopathic Influence on Crops.

Phytotoxic substances released by invasive plants have been reported to have anti-pathogen, anti-herbivore, and allelopathic activity. The aim of this study was to determine the allelopathic influence of the Ambrosia trifida L. on oxidative stress parameters (the lipid peroxidation process; reduced glutathione (GSH) content; and activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (PX)) and phenolic compounds (total phenolic and tannin content) in maize (Zea mays L.), soybean (Glycine max L.), and sunflower (Helianthus annuus L.) crops to explore the effect of released allelochemicals through A. trifida root on crops. An analysis by HPLC confirmed the presence of protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, and syringic acid as major components in the A. trifida. Based on the obtained results for oxidative stress parameters, it can be concluded that the sunflower was the most sensitive species to A. trifida allelochemicals among the tested crops. The other two crops tested showed a different sensitivity to A. trifida. The soybean did not show sensitivity, while the maize showed sensitivity only 10 days after the sowing.

CLINICAL AND IMMUNOLOGICAL EFFECTIVENESS OF TREATMENT OF RAGWEED POLLINOSIS IN THE SAMARA REGION

Allergic rhinitis and bronchial asthma are widespread respiratory allergic diseases. In some territories of the Russian Federation, the dominant cause of pollinosis is ragweed. The aim of the study was to evaluate the clinical and immunological efficacy of ASIT with the allergen Ambrosia artemisiifolia in patients sensitized to Ambrosia trifida in the Samara region. Patients with proven sensitization to Ambrosia trifida was held immunotherapy with Ambrosia artemisiifolia allergoid preseason. After treatment, patients had a decrease in the severity of symptoms of allergic rhinitis according to VAS (p = 0.00001), a decrease in the need for medications (p = 0.0003), as well as the need for corticosteroids against the background of therapy from 34.6% to 0% (p = 0.00001). In 8% of cases, the result of treatment was good, in 69% satisfactory, in 23% unsatisfactory. In the control group, there were no changes in the severity of symptoms (p = 0.858). Also, in the control group, the need for medications remained unchanged and 14.3% of patients continued to use corticosteroids.After ASIT, there was a decrease in the level of IL-4 (p = 0.002), and a decrease in the ratio of IL-4/ IL-10 (p = 0.0063); at the same time, changes in the level of other cytokines (IL-10; IFNγ) were statistically insignificant (p > 0.05). Before treatment, the levels of IL-4/ IL-10 in both groups were comparable, and after treatment, the differences became statistically significant (p = 0.031). We did not get a statistically significant change in the level of IgG4 Amb a 1 or IgG4 Amb trifida. There was no correlation between the level of individual cytokines and the results of treatment. As a result of the conducted ASIT, positive clinical and immunological results were obtained. In most patients, the disease has acquired a controlled course. At the same time, the lack of excellent and low number of good results of ASIT is probably due to the intraspecific allergenic properties of ragweed.

A non‐native earthworm shifts seed predation dynamics of a native weed

Abstract Introduced seed dispersers can shift seed predation dynamics in native species, impacting native plant establishment and spread. We studied the effect of the non‐native earthworm, Lumbricus terrestris, on seed loss dynamics in the large‐seeded native annual, Ambrosia trifida (giant ragweed), an expanding agricultural weed whose seeds are heavily predated by mice. Lumbricus terrestris may protect seeds against rodent predation by caching them in its burrows from which seedlings can emerge unharmed; however, little is known about the ability of earthworms to compete with rodents for seeds. We investigated this interaction and how environmental factors affected the competitive outcome. In a 2‐year field study, we analysed relative rates of seed removal by earthworms and mice for seeds dispersed at various times in habitats that varied in vegetative cover. Species‐specific responses to environmental conditions drove variation in the share of seeds taken by earthworms versus mice, with earthworms gaining relatively more seeds under warmer, wetter conditions and in low plant cover habitats, and mice obtaining more seeds under colder, drier conditions and in high cover habitats. Environmental factors also determined which competitor accessed seeds first, and this conferred a competitive advantage that was compounded over time. Earthworms cached some seeds under all experimental conditions, suggesting that L. terrestris can act mutualistically with giant ragweed in diverse environments. Synthesis and applications. Our results support the hypothesis that the non‐native earthworm Lumbricus terrestris behaves as a seed dispersal mutualist for the native annual giant ragweed by caching its seeds in its burrows, thereby reducing their availability to rodent seed predators. The data also support the view that interactions among the environment and competing seed predators determine the fate of seed pools in response to species‐specific environmental preferences. In crop fields where L. terrestris is abundant, additional efforts to prevent giant ragweed seed return may be warranted due to the likelihood that earthworms will increase giant ragweed soil seed pools. Lumbricus terrestris is expanding its range throughout temperate regions and may similarly affect secondary seed dispersal and seed predation dynamics of large‐seeded species in other plant communities.

Utilizing cover crops for weed suppression within buffer areas of 2,4-D-resistant soybean

AbstractCover crops can be utilized to suppress weeds via direct competition for sunlight, water, and soil nutrients. Research was conducted to determine if cover crops can be used in label-mandated buffer areas in 2,4-D-resistant soybean cropping systems. Delaying termination of cover crops containing cereal rye to at or after soybean planting resulted in a 25 to more than 200 percentage point increase in cover crop biomass compared to a control treatment. Cover crops generally improved horseweed control when 2,4-D was not used. Cover crops reduced grass densities up to 54% at four of six site-years when termination was delayed to after soybean planting. Cover crops did not reduce giant ragweed densities. Cover crops reduced waterhemp densities by up to 45%. Cover crops terminated at or after planting were beneficial within buffer areas for control of grasses and waterhemp, but not giant ragweed. Yield reductions of 14% to 41% occurred when cover crop termination was delayed to after soybean planting at three of six site-years. Terminating the cover crops at planting time provided suppression of grasses and waterhemp within buffer areas and had similar yield to the highest-yielding treatment in five out of six site-years.

The significance of biomass allocation to population growth of the invasive species Ambrosia artemisiifolia and Ambrosia trifida with different densities

BackgroundAmbrosia artemisiifolia and Ambrosia trifida are globally distributed harmful and invasive weeds. High density clusters play an important role in their invasion. For these two species, the early settled populations are distributed at low densities, but they can rapidly achieve high population densities in a short period of time. However, their response to intraspecific competition to improve the fitness for rapid growth and maintenance of high population densities remains unclear. Therefore, to determine how these species form and maintain high population densities, individual biomass allocations patterns between different population densities (low and high), and plasticity during seedling, vegetative, breeding and mature stages were compared. In 2019, we harvested seeds at different population densities and compared them, and in 2020, we compared the number of regenerated plants across the two population densities.ResultsMost biomass was invested in the stems of both species. Ambrosia trifida had the highest stem biomass distribution, of up to 78%, and the phenotypic plasticity of the stem was the highest. Path analysis demonstrated that at low-density, total biomass was the biggest contributor to seed production, but stem and leaf biomass was the biggest contributors to high-density populations. The number of seeds produced per plant was high in low-density populations, while the seed number per unit area was huge in high-density populations. In the second year, the number of low-density populations increased significantly. A. artemisiifolia and A. trifida accounted for 75.6% and 68.4% of the mature populations, respectively.ConclusionsHigh input to the stem is an important means to regulate the growth of the two species to cope with different densities. These two species can ensure reproductive success and produce appropriate seed numbers. Therefore, they can maintain a stable population over time and quickly form cluster advantages. In the management, early detection of both species and prevention of successful reproduction by chemical and mechanical means are necessary to stop cluster formation and spread.

Effect of Heating by Microwave Oven on Weeds Seed Germination in Imported Shipments

LABORATORY and wirehouse experiments were conducted in Weed Research CentralLaboratory, Agricultural Research Center, Giza, Egypt to investigate the possibility of using microwave energy to prevent the germination of weed seeds and find applicable treatments which can completely devitalize quarantine weed seeds. The present work evaluated the effect of microwave on germination of six weed species: wild oats, darnel, white bursage, Giant ragweed, field bindweed and dodder and improvement of some traits of two imported crops soybean and wheat (oil percentage of soybean seeds and protein content of wheat grains), which were contaminated by these weed species. Results showed that microwave power and time required for preventing germination varied considerably among the species studied. Microwave power 80% for 15min prevented completely germination percentage of wild oats and darnel and reduced germination percentage of field bindweed to 10%. The microwave power 50%, 15min was enough to prevent seeds germination completely and weaken dooder quarantine. In regard to Giant ragweed and white bursage, under all microwave power treatments, there were no germination of these weeds. Microwave powers 50% for 10min and 80% for 15min had no effect on the oil percentage extracted from soybean seeds and protein content of wheat grains, respectively. The present results suggest clearly that the exposure to microwave can weaken quarantine weed seeds in imported soybean and wheat without injury of oil percentage of soybean seeds and protein content of wheat grains.

Subpollen particle release from different species of the invasive allergenic genus Ambrosia: the effect of rainwater composition and wind speed

Allergen-containing subpollen particles (SPPs) are micrometric or sub-micrometric particles (0.12–5 µm) released from pollen. They are able to reach the lower airways, causing allergenic reactions. SPP release occurs through the pore of intact grains or by rupture of the whole grain. In this paper the results of two laboratory experiments investigating the dynamics of SPP release for three alien species of Ambrosia genus are shown. Rainwater composition and wind speed were considered, by simulating different conditions, in accordance with a fully orthogonal experimental design. The principle response variable was the total percentage of SPPs-releasing pollen grains; also the percentage of intact grains releasing SPPs through the pore and of broken SPPs-releasing grains were considered. Both osmotic and mechanical shock caused the discharge of SPPs but different results were observed. The highest number of releasing grains was recorded in case of acid solution and 20 knots wind speed. Moreover, wind and rainfalls caused SPPs release through different mechanisms. Wind mainly provoked a mechanical shock leading to grain rupture, whereas rainfall caused mainly SPPs release through the pore of intact grains. Comparing species, the effect of wind and at least in some cases also that of rainwater appeared to be less relevant for Ambrosia trifida than for Ambrosia psilostachya and Ambrosia artemisiifolia. The obtained results suggest a species-specific response of Ambrosia species to wind speed and rainwater that lead to a different release of SPPs and then to a species-specific impact on allergy according to the characteristics of their growth environment.

Prediction of potential intrusion areas of Ambrosia L. plant in Jilin Province

Ambrosia L. plant refers to one of the critical alien invasive species in Jilin Province, which can significantly jeopardize the environment. In this study, the MaxEnt model and the ArcGIS were combined to predict the potential intrusion areas of Ambrosia plant in Jilin Province. Subsequently, the dominant environmental factors affecting the geographical distribution of Ambrosia plant we’re determined. Next, the geographical distributions and ecological niche overlap degrees of two species of Ambrosia plant were analyzed. As revealed from the results, the total areas of Ambrosia artemisiifolia L. and Ambrosia trifida L. in potential high and middle suitable distribution areas of Jilin Province reached 11988.71km2 and 48039.68 km2, respectively. According to results, the environmental factors primarily affecting the distributions of Ambrosia artemisiifolia L. and Ambrosia trifida L. consisted of solar radiation (sard9) and annual mean temperature range (bio7) in September, as well as solar radiation (sard9) and isothermality in September (bio). Ambrosia plant was suggested to exhibit a high degree of ecological niche overlap and a large geographical distribution overlap. For the mentioned reason, this study laid a scientific basis for monitoring and controlling the spread of alien invasive species of Ambrosia plant in Jilin Province.

Comparative analyses of transcriptional responses of Dectes texanus LeConte (Coleoptera: Cerambycidae) larvae fed on three different host plants and artificial diet

Dectes texanus is an important coleopteran pest of soybeans and cultivated sunflowers in the Midwestern United States that causes yield losses by girdling stems of their host plants. Although sunflower and giant ragweed are primary hosts of D. texanus, they began colonizing soybeans approximately 50 years ago and no reliable management method has been established to prevent or reduce losses by this pest. To identify genes putatively involved when feeding soybean, we compared gene expression of D. texanus third-instar larvae fed soybean to those fed sunflower, giant ragweed, or artificial diet. Dectes texanus larvae differentially expressed 514 unigenes when fed on soybean compared to those fed the other diet treatments. Enrichment analyses of gene ontology terms from up-regulated unigenes in soybean-fed larvae compared to those fed both primary hosts highlighted unigenes involved in oxidoreductase and polygalacturonase activities. Cytochrome P450s, carboxylesterases, major facilitator superfamily transporters, lipocalins, apolipoproteins, glycoside hydrolases 1 and 28, and lytic monooxygenases were among the most commonly up-regulated unigenes in soybean-fed larvae compared to those fed their primary hosts. These results suggest that D. texanus larvae differentially expressed unigenes involved in biotransformation of allelochemicals, digestion of plant cell walls and transport of small solutes and lipids when feeding in soybean.

Giant ragweed (Ambrosia trifida L.) in the territory of the Vladimir region

Relevance. The article provides data on the distribution of Ambrosia trifida L. in the Vladimir region, beyond its borders in Russia and in the world as a whole. A new place of growth of Ambrosia trifida L. was revealed in the city of Vladimir. The use of ragweed as a medicinal plant and its role in human life are described. Taking into account the fact that ragweed damages agriculture and is included in the list of quarantine objects, the work provides general and specific measures to combat it.

Competition between Ambrosia artemisiifolia and Ambrosia trifida: Is there a threat of a stronger competitor?

AbstractRecent reports of the presence of Ambrosia trifida (AT) in areas infested by A. artemisiifolia (AA) in Serbia warn of the impending establishment of a more damaging crop weed. Here, we test the potential competitive effects of these two weed species. We conducted a field competition study in 2016 and 2017 as a replacement series experiment arranged in a split plot, with main plots (20.5 m × 2 m) at total plant densities of 10 and 100 plants/m2, and sub‐plots (3 m × 2 m) at the proportion of AT to AA of 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100. Individual plant biomass (IPB) for AT was lowest when grown in monoculture, while AA reached its highest IPB in its monoculture. With AT < 40%, the AT IPB was larger than (2017) or the same as AA (2016). With AT > 40%, its IPB decreased due to increased intraspecific competition. We obtained the lowest sub‐plot biomass (SPB) of AT + AA in mixtures with 40:60 and 60:40 ratios, and also the highest SPB of other weed species. We show that despite a larger leaf area, AT may not fully replace AA and thus not become a new threat to crops, as it not only suffers from intraspecific competition at high densities, but also from interspecific competition with AA. Therefore, crops may benefit from a stable coexistence of both species as compared to highly dominant AT or AA. Further studies in the presence of crops are needed to confirm this hypothesis.

Performance of deep learning models for classifying and detecting common weeds in corn and soybean production systems

Knowing precise location and having accurate information about weed species is a prerequisite for developing an effective site-specific weed management (SSWM) system. Due to the effectiveness of deep learning techniques for vision-based tasks such as image classification and object detection, its use for discriminating between weeds and crops is gaining acceptance among the agricultural research community. However, limited studies have used deep learning for identifying multiple weeds in a single image and most of the studies have not compared the effectiveness of deep learning based image classification and object detection by using a common, annotated imagery dataset of early season weeds under field conditions. This study addresses the research gap by evaluating comparative performance of three different pre-trained image classification models for classifying weed species and also assesses the performance of an object detection model for locating and identifying weed species. The image classification models were trained on two commonly used deep learning frameworks i.e., Keras and PyTorch, to assess any performance differential due to the choice of framework. An annotated dataset comprising of RGB images of four, early season weeds, found in corn and soybean production system in the Midwest US, namely, cocklebur (Xanthium strumarium), foxtail (Setaria viridis), redroot pigweed (Amaranthus retroflexus), and giant ragweed (Ambrosia trifida) was used in this study. VGG16, ResNet50, and InceptionV3 pre-trained models were used for image classification. The object detection model, based on the You Only Look Once (YOLOv3) library, was trained to locate and identify different weed species within an image. The performance of image classification models was assessed using testing accuracy and F1-score metrics. Average precision (AP) and mean average precision (mAP) were used to assess the performance of the object detection model. The best performing image classification model was VGG16 with an accuracy of 98.90% and an F1-score of 99%. Faster training times and higher accuracies were observed with PyTorch. The detection model helped locate and identify multiple weeds within an image with AP scores of 43.28%, 26.30%, 89.89%, and 57.80% for cocklebur, foxtail, redroot pigweed, and giant ragweed respectively and an overall mAP score of 54.3%. The results suggest that under field conditions, use of pre-trained models for image classification and YOLOv3 for object detection are promising for identifying single and multiple weeds, respectively, given that sufficient data is available. Additionally, unlike image classification, the localization capabilities of object detection are desirable for developing a system for SSWM.

Monographs on invasive plants in Europe N° 5: Ambrosia trifida L.

ABSTRACT Ambrosia trifida L. (giant ragweed, Asteraceae) is native to the North American continent and was introduced into Europe and Asia at the end of the 19th century. In its native range, this tall annual species is common in riparian and ruderal habitats and is also a major weed in annual cropping systems. For nearly a century, A. trifida has also been of great concern in the U.S. for its highly allergenic pollen, necessitating targeted control measures to reduce its impact on human populations. Based on the distribution of A. trifida in North America and in its introduced range, riparian systems in the rest of the world may be particularly at risk to invasion, with potential negative consequences for their biodiversity. Currently, A. trifida has invaded Asia more widely than Europe, likely due to the more favourable local conditions in Asia. Throughout its introduced range, A. trifida is host to a limited number of invertebrates and pathogens and only a few biological agents are available for its control. The main impacts of A. trifida at a global level are on crop yield and human health, resulting in significant socio-economic impacts. The success of A. trifida invasion in areas in which it has been introduced is still unclear, but climate change may increase climate suitability, increasing the potential for A. trifida to spread. While effective management in cultivated fields seems potentially possible, the development and control of A. trifida in natural riparian habitats is of great concern due to the difficulty of management in these areas.

Ambrosia trifida L. - trolisna ambrozija

Ambrosia trifida L. (AMBTR, fam. Asteraceae/Compositae) is native to North America. It was introduced accidentally to Europe at the end of the 19th century, with contaminated animal feed and seeds for planting. Today A. trifida is present in ruderal and agricultural habitats of many European countries (France, Italy, Germany, Russia, Spain, Romania, Slovakia, Czech Republic, Poland, Serbia, Bulgaria, etc.). Giant ragweed was detected for the first time in 1981 in Serbia (site Čoka). Over the following period it disappeared from this site, but was recorded again in 2006 in another site (central Bačka: Despotovo, Kucura, Savino Selo, Ravno Selo, Ruski Krstur). Currently in Serbia it has the status of an alien naturalized weed species. This summer annual plant can grow up to 6 m in height and exhibits a high degree of morphological and reproductive plasticity in response to encroachment by neighboring plants. It is present in disturbed habitats, such as agriculture fields, where it plays the role of the dominant species throughout the entire growing season. In most cases, leaves are opposite and always simple and generally have 3 distinct lobes but can also have as many as 5. It is a diploid (2n = 24), meso-hygrophilic species, preferring wet habitatse and can tolerate a wide variety of soil types. Also, this is a monoecious plant, where male and female flowers are separated on the same individual. A. trifida can hybridise with A. artemisiifolia (A. x helenae Rouleau, with 2n= 27 and 2n= 33), but this hybrid has been described as sterile. Compared to other summer annual species, A. trifida is among the first to emerge in early spring, at optimal temperatures from 10-24°C. Under optimal environmental conditions, giant ragweed produces around 1,800 (max 5,100) seeds plant-1. It flowers and bears fruit from July to September (October).The pollen of this species has allergenic potential. Additionally, in the USA and Canada giant ragweed populations have developed resistance to acetolactate synthase inhibitor herbicides and glyphosate. Giant ragweed can be a problematic weed in row crops (corn, soybean, sunflower, sugerbeet) and vegetables. In A. trifida the control measures should prevent further spread, and existing populations should be controlled by integrated weed management practices. Furthermore, A. trifida has a relatively low fecundity, a transient soil seedbank and a high percentage of non-viable or low-survivorship seeds, which are features that may have constrained its establishment and spread in the current environmental conditions in Serbia.

Pre‐emergence herbicides, not carrier volume, impacted weed management in conventional tillage systems

AbstractThe use of pre‐emergence (PRE) herbicides is resurging as a standard practice for weed management in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] in the U.S. north‐central region. The increased use of PRE herbicides warrants investigation on the impact of spray carrier volume on weed control. Field experiments were established at Arlington, WI, in 2018 and 2019 and Janesville, WI, in 2018 to evaluate the influence of carrier volume on weed control of PRE herbicides in conventional tilled corn and soybean. Each experiment included three PRE herbicide premixes applied at crop planting at five carrier volumes (2.5, 5, 10, 15, and 17.5 gal acre−1). A nontreated control was also included in the experiment. Carrier volume did not influence weed control but PRE herbicide selection did. In corn, acetochlor + clopyralid + mesotrione and bicyclopyrone + mesotrione + S‐metolachlor provided 10–13% better annual grass, common ragweed (Ambrosia artemisiifolia L.), and giant ragweed (A. trifida L.) control than fluthiacet‐methyl + pyroxasulfone. In soybean, dimethenamid‐P + saflufenacil resulted in similar common ragweed control as the flumioxazin + pyroxasulfone treatment (79–85%), and 6 and 14% higher annual grass control and biomass reduction, respectively, compared to metribuzin + chlorimuron‐ethyl at Arlington. At Janesville, due to the high giant ragweed density in soybean, all herbicide treatments provided low levels of giant ragweed control (48–56%). Results from these field experiments suggest that lower carrier volumes could be used for PRE herbicide applications without compromising weed control in conventional tillage systems.

Ambrosia trifida L. (Giant ragweed)

Ambrosia trifida L. belongs to the group of invasive weeds, which in colonized areas cause great damage to the biodiversity of autochthonous flora and vegetation as well as in plant production. It originates from North America wherefrom it has spread to many parts of Europe. In Serbia it is currently locally present in the area of Backa (the northern region of the country). Early and rapid growth rate, vegetative and generative production, high degree of morphological and reproductive plasticity have given it a competitive advantage over many other weeds, hence in many countries it is considered one of the most problematic weeds in agricultural production. A. trifida could cause great damage in root crops, vegetable gardens and orchards and its harmfulness is measured by the negative impact on biodiversity by suppressing indigenous and other non-indigenous species. With its allergens, A. trifida negatively affects human health. Observing its vegetative and generative potential and climate change on the other hand, recent research indicates the potential for the spread of A. trifida in our country and in Europe, which could be a serious risk for agrophytocenoses and the ecosystem as a whole. In 2019, it was added to the EPPO A2 List of quarantine pests recommended. It can be controlled with the use of mechanical, biological and chemical measures.

Zastupljenost Polygonum aviculare L. u koasocijaciji Ambrosia artemisiifolia L. i Ambrosia trifida L

Ambrosia artemisiifolia L. and Ambrosia trifida L. belong to allochthonous invasive weeds species. They cause great damage in colonized areas because they reduce the yield of agricultural crops, and also with their competitive abilities affect the suppression of other plants and thus affect the change of plant community. As Polygonum aviculare L. is one of the most common weeds on the European continent and a very common companion of rural and urban habitats, this study examined the impact of different ratios of A. artemisiifolia and A. trifida on the occurrence and abundance of P. aviculare. Presence P. aviculare was incereased in treatments with increasing A. trifida and decreased A. artemisiifolia/m2 .

Verification of the Antioxidant Effects and Whitening Activity of fermented Ambrosia trifida L. Extracts in B16F10 Cells

Verification of the Antioxidant Effects and Whitening Activity of fermented Ambrosia trifida L. Extracts in B16F10 Cells

Effects of cutting and sowing seeds of native species on giant ragweed invasion and plant diversity in a field experiment

BackgroundAmbrosia trifida is a highly invasive annual plant, but effective control methods have not been proposed. Among various eradication methods, cutting is a simple measure to control invasive plants, and sowing seeds of native plants may effectively increase biotic resistance to invasion. In this study, we conducted a field experiment with two treatments: cutting and sowing seeds of six native or naturalized plants.ResultsWe found a significantly lower A. trifida abundance after cutting than in the control (77% decrease). Sowing seeds of native species did not provide any additional benefit for the control of A. trifida, but increased the importance values and diversity of other native vegetation. The abundance of A. trifida was negatively correlated with that of other plant taxa based on plant cover, biomass, and density. However, biotic resistance of sown plants was not effective to control invasion because A. trifida was so competitive.ConclusionsWe concluded that cutting is an effective measure to control Ambrosia trifida while sowing seeds of native plants can increase native plant diversity.

Control of glyphosate-resistant horseweed and giant ragweed in soybean with halauxifen-methyl applied preplant

AbstractHorseweed and giant ragweed are competitive, annual weeds that can negatively impact crop yield. Biotypes of glyphosate-resistant (GR) giant ragweed and horseweed were first reported in 2008 and 2010 in Ontario, respectively. GR horseweed has spread throughout the southern portion of the province. The presence of GR biotypes poses new challenges for soybean producers in Canada and the United States. Halauxifen-methyl is a recently registered selective herbicide against broadleaf weeds for preplant use in corn and soybean. There is limited literature on the efficacy of halauxifen-methyl on GR horseweed and giant ragweed when combined with currently registered products in Canada. The purpose of this study was to determine the effectiveness of halauxifen-methyl applied alone and tank-mixed to control GR giant ragweed and GR horseweed in glyphosate and dicamba-resistant (GDR) soybean in southwestern Ontario. Six field experiments were conducted separately for each weed species over 2018 and 2019. Halauxifen-methyl applied alone offered 72% control of GR horseweed at 8 wk after application (WAA). Control was improved to >91% when halauxifen-methyl applied in combination with metribuzin, saflufenacil, chlorimuron-ethyl + metribuzin, and saflufenacil + metribuzin. At 8 WAA, halauxifen-methyl provided 11% control of GR giant ragweed, and 76% to 88% control when glyphosate/2,4-D choline, glyphosate/dicamba, glyphosate/2,4-D choline + halauxifen-methyl, and glyphosate/dicamba + halauxifen-methyl were used. We conclude that halauxifen-methyl applied preplant in a tank-mixture can provide effective control of GR giant ragweed and horseweed in GDR soybean.