Weed Stem Research Articles

Evaluation of Diode Laser Treatments to Manage Weeds in Row Crops

Herbicides have been the primary weed management practice in agriculture for decades. However, due to their effects on the environment in addition to weeds becoming resistant, alternative approaches to weed control are critical. One approach is using lasers, particularly diode lasers because of their portability, low power demand, and cost effectiveness. In this research, weeds’ response to diode laser treatments was investigated. Three experiments were conducted. The first experiment involved treating two species of weeds with four different laser powers to determine the time it takes to sever the weed stem. The second experiment involved monitoring the status of two species of weeds for a week after treating them with two lasers at constant application times of 1 s, 2 s, and 3 s. The third experiment was a repeat of the second with higher laser powers and shorter treatment times. The results showed diode lasers have a potential to be an effective weed controlling tool. Weed stem diameter, laser power, treatment duration, and distance between laser and weed were all statistically significant in weed mortality, with weed species having no significance. Furthermore, it was found that weed management is possible by exposing the stem of the two weed species between 0.8 and 2.65 mm diameter to a laser beam dosage without necessarily severing it, with 80% effectiveness at 0.5 s treatment time, and 100% effectiveness using a 6.1 W laser for 1.5 s.

Weed Pressure, Nutrient Content, and Seed Yield in Field Grown Sulfonylurea-Resistant Camelina sativa and Brassica napus

Camelina [(Camelina sativa (L.) Crantz], an oilseed species of Brassicaceae, does not have approved herbicides for weed control, which limits its expansion as a commercial crop. To evaluate agronomic traits and ecosystem services of non-transgenic cultivars of sulfonylurea-resistant camelina and canola (Brassica napus L.), a field study was conducted near Fargo, North Dakota. Two replicated locations (NDSU and NW22) were set up in a randomized complete block design including four blocks of camelina, canola, and fallow per location. Camelina and canola were seeded (18 May) at 4.9 and 2.9 kg ha−1, respectively, using 19-cm row spacing. Data was collected mid- and late-season (29 June and 22 July 2020 respectively) for crop and weed stem count (no. m−2), biomass dry matter (kg m−2), and nutrient (N, P, K, S) content (kg ha−1), as-well-as final season (7 August) seed yield (kg ha−1) for camelina and canola treated with and without sulfonylurea. Using Prefer 90 (NIS) at 0.25% v/v, camelina was treated with thifensulfuron at 6.3 g a.i. ha−1, and canola was treated with thifensulfuron at 10.5 g a.i. ha−1 and tribenuron at 5.3 g a.i. ha−1. Sulfonylurea-resistant camelina and canola reduced late-season dry weight biomass of weeds by >75% and ≥60%, respectively, compared with fallow plots. Application of sulfonylurea herbicides to camelina or canola prior to mid-season analyses was not a significant factor (p ≤ 0.05) for reducing weed pressure and generally had little impact on altering crop biomass, seed yield, and nutrient retention. However, in some cases, herbicide treatment had an additive effect of reducing weed pressure over that of camelina or canola alone. Depending on the rotational cropping system, sulfonylurea-resistant camelina and canola should provide additional options for integrated weed management approaches and reducing nutrient leaching in the upper Midwest and northern Great Plains of the USA.

Synthesis and Herbicidal Activities of Novel Thiazole PPO Inhibitors

Background:Protoporphyrinogen oxidase (PPO, EC 1.3.3.4) is a key enzyme in the biosynthesis of chlorophyll and heme, also the target of different types of herbicides. Thiazole compounds shown excellent biological activity, can be designed by using active groups docking for new PPO inhibitors.Objective:The objective of this study was to synthsize a series of aryl thiazole compounds as PPO inhibitors.Methods:In this study, a series of aryl thiazole compounds derivatives 11a-l were obtained from 2- chloro-5-nitrobenzoic acid as the starting material via esterification, Iron powder reduction, diazotization, Hantzsch reaction and final acylation. All synthesized compounds have been tested for their herbicidal activities as a PPO inhibitors.Results:The Petri dish test indicated that all compounds exhibited good herbicidal activities at 200 mg/L using culture dish. And the post-emergence tests showed that at 150g.ai/ha on weed stem leaf spray treatment, some of the title compounds exhibited 80% inhibition rate against the dicotyledonou weeds Amaranthus retroflexus and Eclipta prostrate.Conclusion:Good activity was noted for some compounds that compounds 11a, 11b, 11c, 11g, 11h had 80% inhibition on stems and leaves of Amaranthus retroflexus at 150g.ai/ha.

OPTIMALITY CONDITIONS FOR NONSMOOTH OPTIMISATION PROBLEMS VIA GENERALISED DERIVATIVES

Aquatic plants are integral components of freshwater ecosystems and provide essential ecosystem services. However, when invasive species establish in new aquatic environments, there are few natural checks and balances to inhibit their growth and spread. Overabundant aquatic vegetation can harm aquatic systems if left unchecked and negatively impact on agricultural productivity, social amenity and biodiversity values. Prevention and early intervention are recognised as the most cost effective means to manage invasive species that pose a biosecurity risk. This thesis contributes to the development of effective management strategies for one of the world’s most invasive aquatic plant species, known as alligator weed (Alternanthera philoxeroides (Mart.) Griseb.). It focusses on developing management strategies in an early stage of invasion, in order to achieve extirpation of this species from catchments and waterways. Developing effective detection and surveillance strategies are required for invasive aquatic plants, as a key impediment to achieving extirpation is the ability to detect infestations, so that control strategies can be enacted. This thesis investigates the effectiveness of aerial surveillance for detection of alligator weed at different spatial scales, using high altitude aerial imagery (orthophotos) and unmanned aerial vehicle (UAV) technology. An examination of the growth rate of alligator weed in Victoria, Australia, over a five year period, demonstrates the effective use of orthophotos to detect and monitor large infestations of aquatic alligator weed. The efficacy of unmanned aerial vehicle technology, including the use of automated algorithms, to detect patches of alligator weed growing in waterways is evaluated against current detection techniques. Effective management of invasive aquatic plants targeted for extirpation requires the coupling of effective detection and control efforts to prevent reproduction. To date, development of control strategies for aquatic alligator weed has been limited to evaluating the efficacy of short-term control at a local scale without regard to the effects of management strategies on dispersal of propagules throughout catchments. This thesis determines that viable alligator weed stem fragments are produced following herbicide application, which comprises extirpation efforts. This thesis has gone further than current practice in that it has evaluated the efficacy of current and novel control techniques, in both laboratory and field trials and has developed methods to manage viable fragment production post-herbicide application, to limit dispersal throughout catchments. In this respect, the application of the herbicides glyphosate, metsulfuron-methyl and imazapyr, and their effectiveness when incorporating surfactant systems and plant growth regulators, have been evaluated in field and laboratory studies to optimise control techniques for aquatic alligator weed. Results have shown that our approaches, when used in an early stage of invasion, are capable of eliminating…

Postemergence Control of Microstegium vimineum on Riparian Restoration Sites with Aquatic‐Use Registered Herbicides

AbstractMicrostegium vimineum is an invasive grass introduced from Asia that has spread throughout riparian areas of the eastern United States threatening native riparian vegetation. Postemergence (POST) herbicides registered for aquatic use were evaluated for control of M. vimineum on two riparian restoration sites in the Piedmont and Upper Coastal Plain of North Carolina. This study found that standard and lower than standard rates of diquat, fluridone, flumioxazin, glyphosate, imazamox, and imazapyr reduced weed stem density and biomass at 6 and 30 weeks after treatment (WAT). Both rates of bispyribac and penoxsulam provided less control of M. vimineum. Visual ratings showed both rates of diquat, flumioxazin, imazamox, and imazapyr controlled 63‐100% of M. vimineum at 6 WAT and 84‐100% at 30 WAT. Fluridone and glyphosate provided slightly less control. Bispyribac and penoxsulam treatments provided less control at 6 and 30 WAT compared to the other treatments. Plots treated with both rates of diquat, flumioxazin, imazamox, and imazapyr were nearly devoid of all vegetation at 30 WAT. Recommendations include POST application of lower than standard rates of diquat, flumioxazin, fluridone, glyphosate, imazamox, and imazapyr on riparian restoration sites infested with M. vimineum. Immediate vegetation management measures including temporary and permanent plant cover should be employed on treated sites where weeds are completely eradicated to prevent erosion.

Allelopathic effects of the weed,Polygonum orientaleL. on jute

The allelopathic potential of Polygonum orientale L. was investigated under laboratory conditions and pot experiments in field conditions. Air-dried different parts (viz. leaf, stem, and root) and whole plant of the weed aqueous leachate at 2.5, 5, and 10% (w/v) concentrations were applied to determine their effect on jute (Corchorus olitorious L. cv. JRO 524) seed germination and seedling growth under laboratory conditions. Increasing concentrations of P. orientale whole weed plant leachates inhibited seed germination and seedling growth of jute than the individual leaf, stem, and root leachates of the weed. Increasing concentrations from whole weed plant followed by weed leaf, stem, and root of this weed significantly inhibited water uptake by jute seeds. The decrease in germination of jute seeds was also correlated with increased electrolyte leakage. Air-dried weed residues of whole weed plant (i.e. 2.5, 5, and 10g) incorporation in soil or application in soil surface also inhibited seed germination and seedling growth of jute seeds in pots at field conditions. The germination, root and shoot lengths inhibition were higher in soil surface placed dry weed residues than soil incorporated dry weed residues.

Colonization and infestation ability of Bolboschoenus maritimus Palla in rice paddies of the Camargue, France

Bolboschoenus maritimus is one of the major weed constraints for irrigated rice‐cropping systems in the Camargue, France. This perennial plant propagates mainly through the production of numerous tubers. Observations in both controlled conditions and on‐field studies were used to enhance the level of knowledge of the biology, functioning and infestation dynamics of B. maritimus, with a view to rationalize weed control practices. It was found that B. maritimus displayed a great potential to produce a large number of shoots, rhizomes and tubers. Its propagation in the field plots depended on the initial weed density and its spatial colonization did not show any preferred direction (isotropic). Further observations that were made in the paddy fields showed an interaction between the different cultural practices that were tested and the infestation dynamics of B. maritimus. Efficient control of B. maritimus infestation in the field should make use of the data reported here, based on three levels: (i) prevention of weed stem proliferation during the cropping season with specific herbicides; (ii) elimination of the tubers after the rice crop; and (iii) reduction of the tuber‐germinating ability.

Chemical and thermal characteristics of lignins isolated from Siam weed stem by acetic acid and formic acid delignification

The stem of Siam weed, an invasive exotic plant, was delignified by Acetosolv and Milox processes. The lignin products, Acetosolv lignin (AL) and Milox lignin (ML), were characterized in order to investigate the chemical structures and thermal characteristics. It was found that the weed lignin was syringyl-guaiacyl (GS) type lignin. Both lignins showed similarity in elemental components, functional groups and molecular weights. However, ML had higher methoxyl and phenolic hydroxyl group contents, while AL showed more acetyl group content. UV and FTIR spectra showed that few p-coumaric acid or hydroxycinnamic acid type structures were present in both lignins. According to differential scanning calorimetry (DSC), the glass-transition temperature ( T g) of AL and ML was determined as 149.6 and 144.0 °C, respectively. Thermogravimetric analysis (TGA) showed that both lignins had the maximum rate of weight loss at 372.7 and 368.9 °C, respectively. The activation energy for the pyrolytic degradation of AL and ML were 31.84 and 34.61 kJ mol −1, respectively.

Pretreatment of Siam weed stem by several chemical methods for increasing the enzymatic digestibility

Siam weed [Chromolaena odorata (L.) King & Robinson], an invasive exotic weed in China, was proposed as a feedstock for bioethanol production. This would be a promising way of using for an invasive weed that needs management and control. It was found that the glucan content of the weed stem was similar to that of sugarcane bagasse, but higher than those of corn stover and wheat straw. Several chemical pretreatment methods were applied to the weed stem to increase its enzymatic digestibility. Mild sulfuric acid (<120 degrees C) or alkali pretreatment did not markedly increase the enzymatic digestibility. However, peracetic acid (PAA) pretreatment dramatically enhanced the enzymatic hydrolysis of the weed stem. Compared to some other common agricultural residues, the weed stem was more difficult to pretreat and digest by cellulase. Fourier transform infrared (FTIR) spectra analysis indicated that the cellulose-related bands became more intensive after pretreatment, especially for PAA-pretreated samples. According to X-ray diffraction spectra, the biomass solids had higher crystallinity indices after pretreatment, although these indices were similar for all of the pretreated samples.

Direct application end effector for a precise weed control robot

A direct chemical application end effector was developed to directly apply chemical via a weed's vascular tissue by cutting the weed's stem and wiping chemical on to its cut surface. The end effector consists of two micro-pumps, a custom-designed circular saw with a DC motor, an applicator, a chemical tank, a flow controller, and a micro reservoir. The field robot, equipped with a computer and a 5-degree of freedom arm, controls the movement of the direct chemical application end effector. A direct chemical application end effector was tested to quantify the application dose and to examine the potential for controlling weeds. The average application dose of the end effector ranged from 21.89 mg to 56.18 mg per target, with a coefficient of variation (CV) range of 33.79–60.85%. Using the direct chemical application end effector, chemical was applied to two species of weeds, yellow foxtail (Setaria glauca) plants and velvetleaf plants (Abutilon theophrasti) as representative grass and broadleaf weeds, respectively. The majority of the weeds (90.9%) treated by the end effector showed symptoms of chemical application on the sixth day and was dead ten days after application although the end effector used only 22% of active ingredient of a broadcast application. The developed end effector may provide a solution to reduce chemical use in field application, to increase herbicide efficacy, and to limit the herbicide contamination in the environment by directly applying a minute amount of herbicide only to weeds.

Characterization and comparison of Acetosolv and Milox lignin isolated from crofton weed stem

AbstractCrofton weed (Eupatorium adenophorum Spreng) is an invasive species in China, which has damaged native ecosystems and caused great economic losses. To use the weed instead of simple control and management of it, the weed stem of was delignified by Acetosolv and Milox processes to obtain lignin. The lignins (Acetosolv lignin, AL; and Milox lignin, ML) were characterized and compared through several analysis methods. It was found that both of AL and ML were syringyl‐guaiacyl type (GS) lignin, but that the chemical composition and structure of the two lignins were somewhat different. The obtained C9 expanded formulas for AL and ML were C9H9.16O3.50N0.13(OCH3)0.97(PhOH)0.34Ac0.22 and C9H7.96O3.13N0.13(OCH3)1.23(PhOH)0.51Ac0.14, respectively. According to an elementary analysis, the two lignins had similar higher heat value of 20.0–21.0 MJ kg−1, which were similar to that of raw coal. Gel permeation chromatography analysis indicated the two lignins had similar molecular weights. Notwithstanding that the Ultraviolet, Fourier transform infrared, and 1H‐NMR spectra illustrated that the two lignins had similar chemical functional groups, the AL showed more acetyl groups signals. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Nitrogen Rate, Vine Density, and Weed Management Affect Colonization of Cranberry Beds following Disturbance

The interactive effects of nitrogen rate (0, 28, 56, and 112 kg/ha), vine density (0, 1.8, 3.6, and 5.4 t/ha of the cultivar ‘Stevens’), and weed management (preemergence herbicide, postemergence control, inoculation with weed seeds, and untreated) were determined on the recolonization of open spaces caused by localized biomass removal in a newly planted commercial cranberry bed. To assess the effect of the 64 treatment combinations on initial colonization, all cranberry and weed biomass was removed from a randomly selected 930-cm2area in each plot in Year 1. To quantify recolonization of the disturbed area, the same quadrat was resampled and all plant biomass was collected in Year 2. Cranberry biomass production in the disturbed area increased in a quadratic fashion with increasing N rates for all vine densities except zero. Cranberry biomass in the year after disturbance was positively correlated with cranberry biomass present in the previous year. Weed stem biomass in the year after disturbance was positively correlated with weed stem biomass from Year 1 and negatively correlated with percentage cranberry biomass from Year 1 and Year 2. Less than one-third of the treatment combinations recovered enough to produce at least 200 g/m21 yr postdisturbance (a reasonable expectation of biomass production). Growers who have low weed pressure and extensive cranberry cover on their farms can expect that disturbed areas will be recolonized by cranberry vines when they utilize adequate, but not excessive, nitrogen regimes.

Comparative study on chemical pretreatment methods for improving enzymatic digestibility of crofton weed stem

In order to utilize and control the invasive weed, crofton weed ( Eupatorium adenophorum Spreng), a potential pathway was proposed by using it as a feedstock for production of fermentable sugars. Three chemical pretreatment methods were used for improving enzymatic saccharification of the weed stem. Mild H 2SO 4 pretreatment could obtain a relatively high yield of sugars in the pretreatment (32.89%, based on initial holocellulose), however, it led to only a slight enhancement of enzymatic digestibility. NaOH pretreatment could obtain a higher enzymatic conversion ratio of cellulose compared with H 2SO 4 pretreatment. Peracetic acid (PAA) pretreatment seemed to be the most effective for improving enzymatic saccharification of the weed stem in the three chemical pretreatment methods under the same conditions. The conversion ratio of cellulose in the sample pretreated by PAA under the “optimal” condition was increased to 50% by cellulase loading of 80 FPU/g cellulose for 72 h incubation. A number of empirical quadratic models were successfully developed according to the experimental data to predict the yield of sugar and degree of delignification.

Adequabilidade de diferentes substratos à oviposição do predador Orius insidiosus (Say) (Hemiptera: Anthocoridae)

Fêmeas de Orius insidiosus (Say) colocam seus ovos endofíticamente, em diversas plantas, e um obstáculo para a criação massal desse predador é a seleção de um substrato de oviposição que seja de fácil obtenção e aceito pelo inseto. O objetivo deste estudo foi avaliar a preferência e a adeqüabilidade de diferentes substratos de oviposição para O. insidiosus. Os testes foram conduzidos em câmaras climatizadas reguladas a 25 ± 1°C, UR de 70 ±10% e fotofase de 12h. Os substratos avaliados quanto à preferência e adequabilidade foram caule de caruru (Amaranthus viridis L.), caule e vagem de feijão (Phaseolus vulgaris L.), vagem de feijão-de-vagem (Phaseolus vulgaris L.) e inflorescências de picão-preto (Bidens pilosa L.). Na adequabilidade também foi avaliado o caule de poaia-do-campo (Spermacoce latifola Aubl.). Fêmeas submetidas aos testes com e sem chance de escolha preferiram ovipositar em inflorescências de picão-preto. O período de pré-oviposição foi influenciado pelo tipo de substrato, sendo menor na presença da inflorescência de picão-preto (3,0 dias) e no feijão, tanto no caule (3,1dias) como na vagem (3,7 dias) comparado aos demais substratos. O período de oviposição, bem como a longevidade foram cerca de três a quatro vezes menores na presença do caule de poaia-do-campo (8,9 dias). O número total de ovos/fêmea de O. insidiosus foi maior em inflorescências de picão-preto (163,3 ovos). Os resultados indicam a adeqüabilidade das inflorescências de picão-preto como substrato de oviposição para O. insidiosus, sendo o preferido nos testes, com e sem chance de escolha, e onde as fêmeas apresentaram melhor performance reprodutiva.

Weed Control as a Rationale for Restoration: The Example of Tallgrass Prairie

Blumenthal, D. M., N. R. Jordan and E. L. Svenson 2003. Weed Control as a Rationale for Restoration: The Example of Tallgrass Prairie. Conservation Ecology 7(1):6. https://doi.org/10.5751/ES-00480-070106

FACTORS AFFECTING COLOR-BASED WEED DETECTION

Color differences between weeds and crops have been used to develop an image-based sensor to detect weedsin wheat and soybean fields for post-emergency herbicide spot spray. Several field factors were found to affect thecorrect-classification rate (CCR) of the sensor. CCR is defined as the ratio between the number of weed-stem pixelscorrectly classified and the total number of weed-stem pixels in an image. The first factor was soil moisture content.Images of weeds and soil at 10 different moisture contents were analyzed using a statistical method. It was found that,within a large variation range of soil moisture content, the values of relative color indices of soil varied within asufficiently narrow range, which did not seriously overlap with the range for weed stems. As a result, variations in soilmoisture content did not cause significant misclassification between soil and weeds. The second factor was illumination.Images of standard RGB primary-color plates were taken at nine different illumination intensities. The effect ofillumination on color indices was found significant. However, the variation ranges of the relative color indices on imagesof the color plates did not overlap, and the variations of the index values followed noticeable patterns, which could beused in color-index calibration. The third factor studied was spatial resolution. Nine different spatial resolutions of weedimages were achieved by taking images at different camera-plant distances. The optimum resolution, at which the CCRwas maximized, was found to be about 0.5 mm. The classifier was tested on field images obtained under natural lightingconditions. The classifier detected 28-day old yellow foxtail and redroot pigweed with CCRs of 40.2% and 54.9%,respectively. The misclassification rate (MCR), which was defined as the ratio between the number of non-weed stempixels misclassified as weed stem and the total number of non-weed stem pixels, was below 0.2% for both weed species.

Effective Criteria for Weed Identification in Wheat Fields Using Machine Vision

A machine vision system was used to identify weeds commonly found in Kansas wheat fields, including Russian thistle, redroot pigweed, Palmer amaranth, wild buckwheat, and kochia. Three different approaches, color analysis, shape analysis, and texture analysis, were used in the study. For the color analysis approach, ratios of pixel gray levels in images taken using four selected color filters were useful in classifying pixels into five different categorieswheat leaf, weed leaf, weed stem, soil, and sand. A red/green filter pair was found effective in identifying reddish stems of redroot pigweed, Russian thistle, and kochia. Five shape parameters, eccentricity, compactness, and three invariant moments, were used in leaf shape studies and were found effective in distinguishing broadleaf weed species such as redroot pigweed, wild buckwheat, and kochia from wheat. For the texture analysis approach, Fourier spectra of selected windows within leaf areas of wheat and weed species were analyzed. An index of fineness was defined using the spectra. Leaves with fine textures such as kochia can be distinguished from others using this index. Curves of normalized radial spectral energy were derived from the spectra. Leaves with distinct directionality features such as wheat and some broadleaf weed species can be distinguished using parameters defined using these curves. This study is the first step of a project with an overall goal of developing techniques of selective herbicide application based on weed detection.

Itchgrass (Rottboellia cochinchinensis) Interference in Soybean (Glycine max)

Interference between itchgrass and soybean was evaluated over two years using area-of-influence procedures. Soybean seed weight within 20 cm of the weed was reduced 15 to 21%. In the first year, seed weight reduction of 9% was detected at a distance of 40 to 60 cm from the weed. Weight reductions were attributed to decreases in seed number of 12 to 22% within 40 cm of the weed compared with the 140 to 160 cm control area. Itchgrass interference increased soybean height within 40 cm of the weed, but soybean canopy width was generally unaffected. Soybean interference did not affect height of itchgrass plants, but did reduce weed stem numbers 89 to 94% when compared with weeds growing alone. With interference of 8 wk or less, both itchgrass green and dry weights were similar when weeds were growing alone or within the soybean row. Green and dry weights were reduced approximately 80% when itchgrass was in competition with soybean for 10 wk.