Tool For Weed Control Research Articles

Electricity as an effective weed control tool in non‐crop areas

AbstractWhile weed management is often thought of as an agricultural issue, weeds are also problematic for homeowners, public space managers and utilities. In these situations, weeds are typically hand‐pulled, mechanically treated or managed via herbicides. Hand pulling and mechanical treatments are labour‐intensive, and all control methods may have unintended off‐target impacts, necessitating new alternatives for weed control. We have developed a method of using electricity to effectively manage unwanted plants. A series of experiments was conducted with the aim of developing operating protocols with consideration to specific scenarios: we tested a system on Morus alba (mulberry) and Ulmus pumila saplings, determined the response of Tamarix spp. (tamarisk) to different electricity doses, evaluated electricity as pre‐emergent weed control in xeriscaping, and tested the ability of electricity to prevent climbing growth by the vine Convolvulus arvensis (field bindweed). Tests on M. alba and U. pumila demonstrated that low doses of electricity applied over several days are effective in killing trees up to 20 cm in diameter. The Tamarix experiment showed that the plants displayed typical dose–response characteristics with higher doses leading to less plant growth. Results of the pre‐emergent weed control experiment demonstrated the excellent ability of electricity to prevent weed growth, with treated plots having a mean weed cover of 4% compared to 94% in control plots after 4 months. Finally, electricity was shown to be 100% effective in preventing C. arvensis from climbing poles. Our results indicate that electricity is a viable alternative to manual, mechanical or chemical methods for small tree control, pre‐emergent weed control in xeriscaping, and prevention of climbing weeds.

Assessment of Acacia dealbata as green manure and weed control for maize crop

AbstractAcacia dealbata Link is one of the main invasive species in southwestern Europe and a resource with potential value for agriculture. Our objective was to assess the value of A. dealbata vegetative aerial biomass used as green manure and as a tool for weed control in maize crops through three sequential experiments. In 2017, an experiment was carried out with acacia green manure vs inorganic fertilization of pots sown with a field corn and a sweet corn hybrid with strong and weak nutrient demand, respectively. Nutrients were not released from acacia green manure at an appropriate timing, and maize suffered nutrient deficit. In 2018, a pot experiment was made outdoors incorporating acacia green manure at different times before maize sowing, and we found that a 4-month period was required for maximum nutrient release from acacia green manure. In 2019, an early and a late-field experiments were performed by incorporating acacia green manure 4 months before maize sowing. Physiological and agronomic data were recorded in maize, along with soil data, for all years, and weed data the last year. Altogether, most effects and interactions between genotype or environment and fertilization treatment were not significant, and some deficiencies caused by acacia green manure fertilization depend on genotype and environment. Incorporation of acacia green manure 4 months before maize sowing partially controlled weeds and replaced inorganic fertilization. However, deficiencies should be corrected with additional weed control practices and fertilization treatments, according to the nutrient demand of the crop and the soil environment.

Devising newer cropping strategy for eradicating weed niches – A review

The world's population will continue to expand in the future, necessitating increased food production to meet people's nutritional needs. Weed infestation is a key stumbling block in increasing global food productivity. In conventional agriculture, herbicides are the primary weed-control tool. Herbicide use has, however, led in the emergence of herbicide-resistant weeds, making weed control difficult. Weed management practises that are both sustainable and environmentally benign favour crop plants by reducing weed-crop competition. Concerted efforts have been taken with the objective to formulate suitable cropping strategies for reducing weed niches. Hence, the current literature evaluation focuses on the extent to which cropping strategies aids to reduce weed habitat.

Determining the utility of an unmanned ground vehicle for weed control in specialty crop systems

Specialty crop herbicides are not a target for herbicide discovery programs, and many of these crops do not have access to relevant herbicides. High-value fruit and vegetable crops represent high potential liability in the case of herbicide-induced crop damage and low acres for revenue. Labour shortages and higher manual weeding costs are an issue for both conventional and organic specialty crop growers. Robotic weeders are promising new weed control tools for specialty crops because they are cheaper to develop and, with fewer environmental and human health risks, are less regulated than herbicides. However, many of the robotic weeders are too expensive for small growers to use. In the future, greater investment into robotic weeders for small-scale growers will be important. The Clearpath robotics platform Husky may provide a cheap and autonomous way to control weeds in small diversified specialty crop farms. Being able to work autonomously in multiple soil moisture environments is the driving factor behind optimizing the Husky platform for weed control. Research has been conducted to evaluate the impact of soil moisture and mechanical actuator on mobility and weed control. Though weed control was not commercially acceptable in these studies, future optimizations to the Husky robotics platform can achieve commercial success. Highlights - Specialty crop production is labor-intensive and vulnerable to rising labor expenses. - Robotic weeders are promising weed control tools, with fewer environmental and human health risks.

Search of New Tools for Weed Control Using Piptocarpha rotundifolia, a Dominant Species in the Cerrado.

Piptocarpha rotundifolia (Less.) Baker stands out as one of the species with the highest frequency, density, and relative dominance in the Cerrado formations. However, no phytochemical studies have been carried out with this species to date. The aim of this study was to evaluate the phytotoxic activity of P. rotundifolia leaves in the search of new environmentally friendly tools for weed control. Thus, a wheat coleoptile and phytotoxic bioassay, using relevant agricultural weeds, was used to identify the most active extracts and fractions. The subsequent purification process allowed the isolation of 11 compounds, the phytotoxicity of which was evaluated in terms of wheat coleoptile elongation and with the most sensitive weeds. Piptocarphin A was found to be the major compound and the most active. To confirm its phytotoxic potential, the effect on Ipomea grandifolia grown in a hydroponic culture and on metaxylem cells was studied. The results obtained in this study demonstrate that the inhibitory activity displayed by P. rotundifolia leaf extract is mainly due to the presence of piptocarphin A. The phytotoxicity shown by P. rotundifolia leaf extract, and the isolated compounds, on weeds could provide new tools for weed control in agricultural fields.

Morphogenic responses and biochemical alterations induced by the cover crop Urochloa ruziziensis and its component protodioscin in weed species

Urochloa ruziziensis, a cover plant used in no-till systems, can suppress weeds in the field through their chemical compounds, but the mode of action of these compounds is still unknown. The present study aimed to investigate the effects of a saponin-rich butanolic extract from U. ruziziensis straw (BfUr) and one of its components, protodioscin on an eudicot Ipomoea grandifolia and a monocot Digitaria insularis weed. The anatomy and the morphology of the root systems and several parameters related to energy metabolism and antioxidant defense systems were examined. The IC50 values for the root growth inhibition by BfUr were 108 μg mL−1 in D. insularis and 230 μg mL−1 in I. grandifolia. The corresponding values for protodioscin were 34 μg mL−1 and 54 μg mL−1. I. grandifolia exhibited higher ROS-induced peroxidative damage in its roots compared with D. insularis. In the roots of both weeds, the BfUr and protodioscin induced a reduction in the meristematic and elongation zones with a precocious appearance of lateral roots, particularly in I. grandifolia. The roots also exhibited features of advanced cell differentiation in the vascular cylinder. These alterations were similar to stress-induced morphogenic responses (SIMRs), which are plant adaptive strategies to survive in the presence of toxicants. At concentrations above their IC50 values, the BfUr or protodioscin strongly inhibited the development of both weeds. Such findings demonstrated that U. ruziziensis mulches may contribute to the use of natural and renewable weed control tools.

ВПЛИВ ЗМІННИХ ШВИДКІСНИХ ПОКАЗНИКІВ РОБОТИ ротаційної БОРОНИ БЗР-9,0 НА ЯКІСТЬ ВИКОНАННЯ МІЖРЯДНОГО ОБРОБІТКУ СОНЯШНИКУ

The purpose of the research is to investigate the quality of inter-row tillage with a rotary harrow depending on the speed regimes in conditions of high soil hardness.Research methods: theoretical - analysis of information resources and research results of rotary harrows; experimental field - testing of the machine in the economic conditions of LLC "Nosivka Agro", village Ploske Nosiv district of Chernihiv region with the fixation of agronomic indicators; instrumental measurements and expert evaluation; statistical - mathematical processing of the obtained indicators.Results.Experimental field studies of the influence of the speed modes of the rotary harrow BZR-9.0 on the efficiency of inter-row cultivation have been carried out.The nomenclature of quality criteria and their achieved level have been established by expert evaluation.It has been analytically established that the rotary harrow mulches the topsoil well, destroys the soil crust, loosens the soil and destroys filamentous weeds, thus creating ideal conditions for the initial development of the plant root system and providing a strong start to their growth. Conclusions. Rotary harrows, widely available on the Ukrainian market, are increasingly in demand as an effective tool for weed control and soil crust destruction in order to improve aeration and water saturation of crops in conditions of increased soil dryness. Theoretical analysis of information sources confirms that needle harrows can be successfully used for continuous and inter-row cultivation of crops in small and medium-sized farms. The physical parameters obtained as a result of experimental researches testify that with change of speed from 9 km / h to 15 km / h the harrow tooth rotary BZR-9,0 in interrow spacing with a protective zone of 11 cm provides qualitative cultivation of soil with a sufficient level of agrotechnical indicators - degree of destruction. soil crust in the range of 91-98 %, and the percentage of damaged plants is at the level of excellent and satisfactory values. There are no undamaged areas of crust with an area of more than 5 cm2, which significantly impede water and air permeability.

Power on! Low-energy electrophysical treatment is an effective new weed control approach.

Environmental concerns are driving the call for adoption of alternative nonchemical weeding approaches. This study aimed to develop and evaluate a novel, precise, low-energy electrophysical treatment weeding systems and to provide new insight into their control mechanism. Two electrophysical treatment systems, based on AC (2.2 kV) and DC (40 kV) energy sources, were developed and evaluated. The impacts of various operational and biological factors on the weed control effectiveness were evaluated. Additionally, thermal images were taken during the treatments to document plant temperature. Treatments via direct leaf contact caused greater damage to Amaranth plants than the stem contact treatments, with 75% and 20% biomass reduction compared to control, respectively. Treatment of early growth stages was favorable over later growth stages, with 100% and 75% biomass reduction for Trifolium pretense plants treated with 0.0125 W h 2 and 4 weeks after seeding, respectively, compared to control. Additionally, the applied energy affected treatment performance, with its impact varying across the growth stages and species; at the two-leaf growth stage, 0.0025 W h treatment was sufficient for plant death. A >40 °C increase in plant temperature was measured during the electrophysical treatment, with the temperature of some plant organs reaching ~70 °C. Results from this study demonstrate the potential use of electrophysical treatment as an effective weed control tool. The low energetic demands in the new systems provide suitable control results when applied at early stages. Temperature increase seemed to be one of the main control factors, yet efficacy was affected by various biological factors.

Bioherbicidal Potential of the Essential Oils from Mediterranean Lamiaceae for Weed Control in Organic Farming.

In all farming systems, weeds are the most expensive pest to manage, accounting for 30% of potential losses. In organic farming, the problem may be further amplified by restrictions on herbicides, thus making weeds the main problem faced by organic farmers in the field. In this sense, much research is focusing on the allelopathic potential of plants as an ecological weed control tool. Many plant species can release allelopathic compounds with high phytotoxicity that can be used in weed control. Species belonging to the Lamiaceae family have been studied widely for this purpose, and their essential oils (EOs) appear to be promising bioherbicides. However, there are still many challenges for their development. Considering these aspects, a review of the bioherbicidal effect of EOs from Mediterranean Lamiaceae could help identify the most effective ones and the challenges for their actual development.

Evaluation of the accuracy of the recognition algorithm of an autonomous robotic device to control weeds

The main problem in the agro-industrial sector is the use of harmful herbicides, resulting in some of the weeds becoming more resistant to common herbicides and therefore using more and more powerful and expensive options. To overcome this problem, t is necessary to reduce the amount of herbicide use. The proposed study aims to develop a system that can detect and map weeds and perform mechanically applied spot spraying. The weed detection techniques described in this study include several aspects: imaging, a new algorithm for detecting plants through contour and colour segmentation. The method developed can detect weeds at early stages of growth. Further development of the methods is aimed at solving problems related to complex background without soil treatment, faster image acquisition speed and shorter processing time for spot injection in real time. The results of the experiment show that the proposed hybrid method can be used as a tool for weed control.

Identification and Application of Bioactive Compounds from Garcinia xanthochymus Hook. for Weed Management

The allelopathic potential of plant species and their related compounds has been increasingly reported to be biological tools for weed control. The allelopathic potential of Garcinia xanthochymus was assessed against several test plant species: lettuce, rapeseed, Italian ryegrass, and timothy. The extracts of G. xanthochymus leaves significantly inhibited all the test plants in a concentration- and species-specific manner. Therefore, to identify the specific compounds involved in the allelopathic activity of the G. xanthochymus extracts, assay-guided purification was carried out and two allelopathic compounds were isolated and identified as methyl phloretate {3-(4-hydroxyphenyl) propionic acid methyl ester} and vanillic acid (4-hydroxy-3-methoxybenzoic acid). Both of the substances significantly arrested the cress and timothy seedlings growth. I50 values (concentrations required for 50% inhibition) for shoots and roots growth of the cress and timothy were 113.6–104.6 and 53.3–40.5 μM, respectively, for methyl phloretate, and 331.6–314.7 and 118.8–107.4 μM, respectively, for vanillic acid, which implied that methyl phloretate was close to 3- and 2-fold more effective than vanillic acid against cress and timothy, respectively. This report is the first on the presence of methyl phloretate in a plant and its phytotoxic property. These observations suggest that methyl phloretate and vanillic acid might participate in the phytotoxicity of G. xanthochymus extract.

Low Energy Laser Treatments Control Annual Ryegrass (Lolium rigidum)

Increasing concern for the ongoing availability and efficacy of herbicides is driving interest in the development of alternative physical and thermal weed control methods. Fortunately, improvements in weed detection through advancements in computing hardware and deep learning algorithms are creating an opportunity to use novel weed control tools, such as lasers, in large-scale cropping systems. For alternative control options, there are two key weed control timing opportunities, early and late post-crop emergence. Weed density for the early timing is typically higher, with a shorter window for control. Conversely, late post-emergent treatment of surviving and late-emerging weeds would occur in lower densities of larger and more variably sized weeds, given a prior weed control effort, but with a longer available weed control period. Research in laser weeding to date has primarily focused on early growth stage weeds and the ability of this approach to control larger weeds remains unknown. This study used a 25 W, 975 nm fiber-coupled diode laser to evaluate the opportunity for control of annual ryegrass (Lolium rigidum Gaudin) and the influence of four different growth stages (three-leaf, seven-leaf, mid-tillering, and late-tillering). Annual ryegrass plants at each growth stage were treated using a laser-focused to a 5 mm diameter with five different irradiation durations developing energy densities of 1.3, 2.5, 6.4, 19.1, and 76.4 J mm−2. At the three-leaf stage, all plants were controlled at 76.4 J mm−2 and 93.3% controlled at 19.1 J mm−2. Complete control of seven-leaf plants was only achieved at 76.4 J mm−2. Although laser treatments did not control mid-tillering stage plants, 76.4 J mm−2 reduced biomass by 60.2%. No similar reductions in biomass were recorded for the largest plants. This initial research assists in the development of novel weed control options in the context of large-scale conservation cropping systems. Future research should investigate the influence of laser treatments on additional weed species and the impact of increased laser power on larger weeds.

Assessment of allelopathic compounds to develop new natural herbicides : A review

Herbicides are a crucial tool for weed control in crops. However, their continuous and indiscriminate uses have caused environmental pollution and development of weed resistance. Hence, there is an urgent need to minimise the dependence on synthetic herbicides. Allelopathy may be used to develop new bioherbicides to inhibit germination and growth of weeds. There is a great potential to develop eco-friendly herbicides from plants, but little research has been done so far in this context. Identification and quantification of natural weed control compounds (allelochemicals) of plants may help to develop natural herbicides (based on indigenous/invasive weed species), to reduce the dependence on synthetic herbicides and improve the integrated weed management programme in crops. This review describes thepotential allelochemicals present in plants, which may be used as a tool to develop new natural herbicides.

Long-Term Effect of Cover Crops on Species Abundance and Diversity of Weed Flora.

Cover crops are gaining in popularity as an eco-friendly tool for weed control in organic and low-input agricultural systems. A 5-year study was carried out in a Mediterranean environment (Sicily, south Italy) to (1) quantify cover crop biomass production and (2) evaluate the effects on weed soil seed bank, aboveground biomass, species richness, species composition and associations between communities. Cover crop treatments included subterranean clover (Trifolium subterraneum L.) and spontaneous flora, both with and without burying dead mulch into the soil, compared to a conventional management treatment. Weed biomass was significantly reduced by subterranean clover, contrariwise to spontaneous flora, with season-dependent results. Cover crop biomass, which ranged from 44 to more than 290 g DW m−2, was negatively correlated to weed biomass. Moreover, subterranean clover decreased the size of the soil seed bank and species richness. Based on relative frequency, a low similarity was found between the conventional management and cover crop treatments. In addition, no significant differences in species composition across treatments were observed, whereas principal component analysis highlighted some associations. The results suggest that subterranean clover cover cropping is a good option for weed management in Mediterranean agroecosystems.

The Use of Herbicide Safener Increases the Selectivity of Nicosulfuron to Maize Crops

The herbicide nicosulfuron is an important tool for weed control in maize crops; however, its incorrect use can cause yield losses to crops due to its high toxicity. The objective of this work was to evaluate the efficiency of using herbicide safener to increase selectivity of nicosulfuron to maize crops. The experiment was conducted in field conditions, and the treatments consisted of dose-response curves, using nicosulfuron at rates of 0, 15, 30, 45, and 60 g ha-1, applied with safener and/or malathion to maize crops at the V5-V6 stage. The use of organophosphorus insecticides such as malathion decrease the selectivity of nicosulfuron to maize crops. Rates of up to 60 g ha-1 were selective to the maize crops when using nicosulfuron or nicosulfuron + safener. However, plant height decreased 0.19 and 0.91 cm for each gram of nicosulfuron in the treatments nicosulfuron + safener + malathion, and nicosulfuron + malathion, respectively, at 28 days after the application. The phytotoxicity increased 0.19% and 0.97% in the treatments nicosulfuron + safener + malathion and nicosulfuron + malathion, respectively. The number of grains per row and grain yield were affected by the treatments with nicosulfuron + malathion, presenting decreases of 0.09 grains and 52 kg ha-1, respectively. Thus, adding safener to the herbicide mixture increases the selectivity of nicosulfuron to maize crops, decreases damages regarding plant height and phytotoxicity, and prevents effects of the herbicide on the number of grains per row and grain yield, up to the rate of 60 g ha-1.

Efficacy of Guava (Psidium guajava) Mulch Allelopathy in Controlling Tomato (Solanum lycopersicum) Weeds

Tomato (Solanum lycopersicum) is one of the most important vegetable crop whose production involves the use of synthetic herbicides with detrimental impact on biodiversity. Allelopathy effectively controls horticultural crop weeds. Different plant parts (flowers, leaves, stems, bark, roots) have allelopathic activity that varies over a growing season when used as mulch. Mulching is a horticultural technique that protects the roots of plants from heat and cold by use of mulch to cover the soil surface around plants. Tomato production in Kakamega County is below 2% and weeds are ranked high among the yield reducing factors. This study assessed the allelopathic effect of guava leaves mulch type (18.0 cm thick) as a management tool for weed control in tomato crops and no mulch as control treatment with three most popular determinate tomato varieties. The mulch treatments were arranged as factorial in a Randomized Complete Block Design (RCBD) to minimize non–experimental bias. Tomato variety sub-treatments were replicated three times in the experimental plots at Masinde Muliro University of Science and Technology (00171N, 340451E). The field project was conducted during the short rains and long rains season of 2016-2017. Data obtained was subjected to analysis of variance (ANOVA) using SAS software, version 9.3 at p<0.05 confidence level. Least Significance Difference (LSD) was used to separate the means. Weed density incidence was significantly highest in control plots up to 100% and lowest in mulched plots (13.41%). Allelopathic control of weeds sustains global food and nutrition security for future generations.

Investigation of physiological and molecular mechanisms conferring diurnal variation in auxinic herbicide efficacy.

The efficacy of auxinic herbicides, a valuable weed control tool for growers worldwide, has been shown to vary with the time of day in which applications are made. However, little is known about the mechanisms causing this phenomenon. Investigating the differential in planta behavior of these herbicides across different times of application may grant an ability to advise which properties of auxinic herbicides are desirable when applications must be made around the clock. Radiolabeled herbicide experiments demonstrated a likely increase in ATP-binding cassette subfamily B (ABCB)-mediated 2,4-D and dicamba transport in Palmer amaranth (Amaranthus palmeri S. Watson) at simulated dawn compared to mid-day, as dose response models indicated that many orders of magnitude higher concentrations of N-1-naphthylphthalamic acid (NPA) and verapamil, respectively, are required to inhibit translocation by 50% at simulated sunrise compared to mid-day. Gas chromatographic analysis displayed that ethylene evolution in A. palmeri was higher when dicamba was applied during mid-day compared to sunrise. Furthermore, it was found that inhibition of translocation via 2,3,5-triiodobenzoic acid (TIBA) resulted in an increased amount of 2,4-D-induced ethylene evolution at sunrise, and the inhibition of dicamba translocation via NPA reversed the difference in ethylene evolution across time of application. Dawn applications of these herbicides were associated with increased expression of a putative 9-cis-epoxycarotenoid dioxygenase biosynthesis gene NCED1, while there was a notable lack of trends observed across times of day and across herbicides with ACS1, encoding 1-aminocyclopropane-1-carboxylic acid synthase. Overall, this research indicates that translocation is differentially regulated via specific protein-level mechanisms across times of application, and that ethylene release, a chief phytotoxic process involved in the response to auxinic herbicides, is related to translocation. Furthermore, transcriptional regulation of abscisic acid involvement in phytotoxicity and/or translocation are suggested.

Ecotoxicological Assessment of a Glyphosate-Based Herbicide in Cover Plants: Medicago sativa L. as a Model Species

Despite the several innovations that have been incorporated in agriculture, the use of herbicides, especially glyphosate (GLY), is still the major tool for weed control. Although this herbicide has a notable worldwide representation, concerns about its environmental safety were recently raised, with a lot of divergence between studies on its non-target toxicity. Therefore, it is of utmost importance to understand the risks of this herbicide to non-target plants, including cover crop species, which have a crucial role in maintaining agroecosystems functions and in preventing soil erosion. Thus, this work aims to evaluate the growth and physiological responses of a cover plant species (Medicago sativa L.) exposed to increasing concentrations of a GLY-based herbicide (GBH), particularly focusing on the oxidative metabolism. The growth of roots and shoots was affected, being this effect accompanied by a rise of lipid peroxidation, suggesting the occurrence of oxidative stress, and by an activation of the antioxidant (AOX) system. Indeed, the results showed that adverse effects are visible at active ingredient concentrations of 8.0 mg kg−1, with the lowest EC50 being 12 mg kg−1, showing that GBH-contaminated soils may pose a risk to the survival of non-target plants in the most contaminated areas. Overall, these findings proved that GBH greatly impairs the growth of a non-target plant, strengthening the need of additional studies to unravel the real risks associated with the over usage of this pesticide, since there is an evident lack of studies performed with contaminated soils.

Weed control and crop tolerance with S-metolachlor in seeded summer squash and cucumber

AbstractResidual herbicides remain the primary tool for efficient weed control in cucurbit crops because of the lack of crop tolerance to many POST herbicide options. Field experiments were conducted in New Jersey in 2018 and 2019 to determine weed control efficacy and tolerance of direct-seeded cucumber ‘Python’ and summer squash ‘Gold Prize’ to S-metolachlor applied at 0.7 or 1.4 kg ai ha−1 at planting (PRE) or when crops reached the second- to third-leaf stage (EPOST). Regardless of applied rate, S-metolachlor PRE or EPOST provided 96% to 100% control 3 wk after planting (WAP) of smooth pigweed, large crabgrass, and giant foxtail. S-metolachlor PRE significantly improved American black nightshade and carpetweed control 3 WAP with respect to bensulide, and smooth pigweed with respect to clomazone + ethalfluralin. Summer squash showed excellent tolerance, regardless of S-metolachlor rate or timing of application, with stunting not exceeding 17% 4 WAP and 3% 7 WAP at the 1.4 kg ha−1 rate. Marketable yield decreased by 15% with S-metolachlor PRE or POST at 1.4 kg ha−1 with respect to clomazone + ethalfluralin, a reduction not noted when comparing with bensulide or the handweeded control. Marketable fruit number plant−1 and individual fruit weight were not affected by S-metolachlor applications. Conversely, cucumber was more sensitive to S-metolachlor than summer squash was with 30% seedling emergence reduction and 36% to 43% stunting 4 WAP when S-metolachlor was applied PRE at 1.4 kg ha−1. EPOST application resulted in 15% to 26% cucumber injury 1 wk after treatment. Marketable yield declined by 21% and 39% with the 0.7 and 1.4 kg ha−1 rates of S-metolachlor, respectively, compared with clomazone + ethalfluralin. Therefore, S-metolachlor may be a novel alternative to already labeled residual herbicides for summer squash, but unacceptable injury and yield reduction do not support its registration on cucumber.

Weed-sensing technology modifies fallow control of rush skeletonweed (Chondrilla juncea)

AbstractRush skeletonweed is an aggressive perennial weed that establishes itself on land in the Conservation Reserve Program (CRP), and persists during cropping following contract expiration. It depletes critical soil moisture required for yield potential of winter wheat. In a winter wheat/fallow cropping system, weed control is maintained with glyphosate and tillage during conventional fallow, and with herbicides only in no-till fallow. Research was conducted for control of rush skeletonweed at two sites in eastern Washington, Lacrosse and Hay, to compare the effectiveness of a weed-sensing sprayer and broadcast applications of four herbicides (aminopyralid, chlorsulfuron + metsulfuron, clopyralid, and glyphosate). Experimental design was a split-plot with herbicide and application type as main and subplot factors, respectively. Herbicides were applied in the fall at either broadcast or spot-spraying rates depending on sprayer type. Rush skeletonweed density in May was reduced with use of aminopyralid (1.1 plants m−2), glyphosate (1.4 plants m−2), clopyralid (1.7 plants m−2), and chlorsulfuron + metsulfuron (1.8 plants m−2) compared with the nontreated check (2.6 plants m−2). No treatment differences were observed after May 2019. There was no interaction between herbicide and application system. Area covered using the weed-sensing sprayer was, on average, 52% (P < 0.001) less than the broadcast application at the Lacrosse location but only 20% (P = 0.01) at the Hay location. Spray reduction is dependent on foliar cover in relation to weed density and size. At Lacrosse, the weed-sensing sprayer reduced costs for all herbicide treatments except aminopyralid, with savings up to US$6.80 per hectare. At Hay, the weed-sensing sprayer resulted in economic loss for all products because of higher rush skeletonweed density. The weed-sensing sprayer is a viable fallow weed control tool when weed densities are low or patchy.