Winter Weeds Research Articles

Using weed emergence and phenology models to determine critical control windows for winter-grown carinata (Brassica carinata)

AbstractAdoption of the new biofuel crop carinata (Brassica carinata A. Braun) in the southeastern United States will largely hinge on sound agronomic recommendations that can be economically incorporated into and are compatible with existing rotations. Timing of weed control is crucial for yield protection and long-term weed seedbank management, but predictive weed emergence models have not been as widely studied in winter crops for this purpose. In this work, we use observed and predicted emergence of a winter annual weed community to create recommendations for timing weed control according to weed and crop phenology progression. Observed emergence timings for four winter annual weed species in North Carolina were used to validate previously published models developed for winter annual weeds in Florida by accounting for temperature and daylength differences, and this approach explained more than 70% of the variability in observed emergence. Emergence of stinking chamomile (Anthemis cotula L.) and cutleaf evening primrose (Oenothera laciniata Hill.) followed biphasic patterns comparable to wild radish (Raphanus raphanistrum L.), which were predicted with previously published models accounting for 82% and 84% of the variation, respectively. Using the predictive models for weed emergence and carinata growth, critical control windows (CCW) were estimated for Clayton, NC, and Jay, FL, according to different planting dates. The results demonstrated how early planting coincided with the emergence of three competitive winter weeds, but early control could also remove a large proportion of the predicted emergence of these species. The framework for how planting timing will affect winter weed emergence and crop growth will be an instructive decision-making tool to help prepare farmers to manage weeds in carinata, but it could also be useful for weed management planning for other winter crops.

Weed suppression capacity of camelina (Camelina sativa) against winter weeds: The example of corn-poppy (Papaver rhoeas)

Crop rotation is one of the most relevant tools for Integrated Weed Management (IWM). In semiarid Mediterranean areas, the crop rotation is limited by climatic conditions. Camelina (Camelina sativa (L.) Crantz) is an interesting option to introduce due to its tolerance to cold and drought and because of its short life cycle, which allows a flexible management for weed control. In this study, the capacity of camelina to reduce the growth and seed rain of corn poppy (Papaver rhoeas L.) was studied. The experiment was carried out at the University of Lleida during three seasons (2018–19, 2019–20 and 2020–21). In each season, three camelina varieties (GP204, Sonny and Joelle) and barley were sown on two sowing dates (SD) (between November and February) in 1.5 m wide × 10 m long plots with three replications. Three 0.5 × 0.5 m2 quadrates were established, where five P. rhoeas plants from a natural population were allowed to grow in each SD. Additionally, every season in March, weed surveys were performed to observe the effect of the SD in the weed flora. Results show that delaying the SD effectively controlled winter weeds, including P. rhoeas, which could not establish in the second SD plots. The growth of P. rhoeas in the first SD was reduced similarly in the presence of the crops in 2018–19, but camelina competed better against it in 2020–21, while barley competed better in 2019–20. Due to the short life cycle of camelina and its earlier harvest date, the potential seed production of P. rhoeas was reduced by 34% in 2018–19, 52% in 2019–20% and 70% in 2020–21, while this reduction was of 23% in 2018–19% and 56% in 2020–21 in barley. The capacity of camelina to reduce the presence of corn poppy and its seed production in semiarid conditions should be considered as a tool for IWM.

Allelopathic potential of summer weeds on germination and growth performance of wheat and chickpea

The biochemical interference between weed-crop for the available resources is one of the most crucial and burning issues for this modern and technologically blessed farming community. Because-of, the early adaptative nature, rapid growth, and fast distribution of weed make it able to inhibit the desired crop growth and reduce the final estimated yields. Thus, our interest was raised in examining the bio-efficacy of some winter weeds against two main agronomic crop germination and seedling growth, and weeds were collected from two different districts D.I. Khan and Peshawar. Wheat variety (Atta Habib) and Chickpea variety (Karak-1) varieties were used in the trial. The experiment was conducted in (2020) in a Completely Randomized Design (CRD) with a factorial arrangement having three replications. We used the following weeds extracts; Trianthema portulacastrum L., Cyperus rotundus L., Plantago lenceolata L., Xanthium strumarium L., Oxalis corniculata L., Eleusine indica L. and distilled water as a control in this study, and introduced them to chickpea and wheat seeds. Our results show that weeds collected from district Dera Ismail Khan were more phytotoxic as compared to Peshawar and greatly inhibited the overall seed germination of wheat and chickpea respectively i.e., 44.53%, and 37.97%. In the case of weeds extract inhibitory effect, the T. portulacastrum was declared more repressive for both crops in terms of germination inhibition and seedling growth retardation. Taken together, the T. portulacastrum weed extract of D.I Khan was highly phytotoxic to inhibit the germination and germination of both crops, therefore, eco-friendly and proper weed management tactics require from the farming community in the early stages or before crop sowing.

Regularities of weeding in crop rotation fields against the background of different tillage systems

It was found that during the research in winter wheat crops, 40 species of weeds of different biological groups and classes were registered. The most common weeds in the research are: spring (Polygonum aviculare, Fumaria officinalis); winter (Descurainiasophia, Capsella bursa-patoris, Veronica hederifolia, Thlaspiarvense), perennial (Cirsium arvense, Convolvulus arvensis). All of these weeds are non-parasitic weeds. They have roots, stems and green leaves, resulting in an independent diet. It is shown that on average for 5 years of research the least number of weeds was recorded after black fallow (53,7 pcs / m²). Weeds were 22,0 % higher after winter weeds, 55,9 % more after a mixture of peas and mustard, and 95,3 % higher after peas for grain. In the experiments, almost identical results on weediness of winter wheat crops were obtained with two tillage schemes, namely tillage and chisel tillage. However, there is a slight tendency to reduce the number of weeds (0,8 %) during chisel tillage. There was an increase in the number of weeds on the 2nd (83,5 pcs / m2) and on the 4th (76,6 pcs / m2) crops compared to the 1st (64,3 pcs / m2). The highest tweediness (83,5 units / m2) of winter wheat crops was observed in the 2nd crop. This indicates a large potential contamination of the arable soil layer. Key words: crop rotation, tillage, black fallow, green fallow, weeds, winter wheat, oats.

Low Temperature Delays Metabolism of Quizalofop in Resistant Winter Wheat and Three Annual Grass Weed Species

Quizalofop-resistant wheat is the core component of the recently commercialized CoAXium™ Wheat Production System. As with other herbicides, quizalofop provides better weed control at early growth stages and under optimum temperature. However, in regions with winter wheat production, quizalofop application may be affected by unpredictable, rapid temperature decreases. Temperature shifts can cause crop injury or impact weed control efficacy. In the following study, we examine the effect of reduced temperature on quizalofop content and metabolism in CoAXium™ winter wheat and three winter weed species: downy brome (Bromus tectorum L.), feral rye (Secale cereale L.), and jointed goatgrass (Aegilops cylindrica Host). Temperature conditions include either 19 or 4.5°C daytime temperatures with tissue sampling over 5 timepoints (1–16 or 18 days after treatment, DAT). Analysis features liquid chromatography coupled to tandem mass spectrometry detection of the active form of quizalofop, quizalofop acid. Quizalofop content trends reveal delayed metabolism under cooler conditions for wheat and weeds. Quizalofop content peaks within 1–2 DAT in the warmer temperatures for all species and decreases thereafter. In contrast, content peaks between 8 and 9 DAT at cooler temperatures except for downy brome. Minimal decreases in content over time generally follow cooler temperature peaks. Further, the absence of differences in maximum quizalofop content in all species suggests absorption and/or de-esterification of quizalofop proherbicide to the active form is not reduced at cooler temperatures. Final dry shoot tissue biomass does not necessarily correspond to differences in metabolism, as biomass of wheat treated with a field rate of quizalofop does not differ between temperatures. Weeds were treated with sublethal doses of quizalofop in order to monitor herbicide metabolism without causing plant death. Under this condition, weed biomass only differs for jointed goatgrass, which has a greater biomass in the cooler temperature.

Carbon decomposition and nitrogen mineralization of foxtail and milk vetch incorporated into paddy soils for different durations of organic farming

ABSTRACT Foxtail (Alopecurus aequalis) and milk vetch (Astragalus sinicus) are typical winter weeds grown in single-cropping rice fields during the fallow season in central Japan. These winter weeds are generally incorporated into the soil as green manure during plowing, and before rice transplanting, to improve soil fertility and rice yield. To understand the carbon (C) decomposition and nitrogen (N) mineralization behavior of fallow weeds in organic rice farming, we carried out two experiments. Firstly, we examined the effect of adding 1% foxtail to soils that were sampled from fields that were farmed conventionally or organically for different durations (4–12 years). The results showed that net N mineralization of incorporated foxtail was not affected by the duration of organic farming, although the N mineralization of indigenous soil increased with organic farming duration. Secondly, 1% pulverized young and old foxtail (YF and OF; C/N ratios of 47.0 and 54.9, respectively), and milk vetch (YM and OM; C/N ratios of 13.0 and 14.6, respectively), were mixed with soil samples from fields that had been farmed organically for 15 years to determine the role of each plant. More than half of weed C was decomposed during 4 weeks of anaerobic incubation at 30°C. In addition, the net weed C decomposition potentials were significantly higher in YF and YM than those in OF and OM. The lower C/N ratio of milk vetch was contributed to a net N mineralization rate that was 8.4 times higher than that of foxtail. The percentage of N mineralized from milk vetch was significantly higher (about 2.3 times) than that from foxtail. Even though foxtail incorporation can contribute to the growth of organic rice as an N nutrient source, it should be noted that net N immobilization occurred for 2 weeks of incubation at 30°C, and sometimes extended to 4 weeks before net N mineralization became tangible. Considering this early net N immobilization following incorporation of foxtail, it is recommended to wait at least 4 weeks between the start of flooding after weed incorporation and transplanting rice to facilitate initial growth and avoid N exhaustion.

Germination behaviour of

Context Avena sterilis subsp. ludoviciana (wild oats) is one of the major winter weeds of the Northern Grains Region of Australia. The abundance of this weed increased dramatically after the adoption of no-tillage conservation agriculture (NTCA). However, information is lacking on the germination characteristics of the two types of seed (i.e. primary and secondary) that it produces. Aims We aimed to determine the light and temperature requirements for germination and the time to germination of primary and secondary seeds of A. ludoviciana, in order to find ways to manage this weed effectively under NTCA systems. Methods Primary and secondary seeds and caryopses from two southern and two northern biotypes were exposed to a range of temperature and light regimes in the glasshouse, and germination was assessed. Key results All biotypes had ∼25% higher germination from primary than secondary seeds. Removing the hull increased caryopsis germination by ∼70%. The use of a light/dark photoperiod stimulated germination of both types of seed and caryopses compared with continuous darkness. Based on data for caryopses, 7°C and 9°C were found to be optimal germination temperatures for southern and northern biotypes, respectively. At optimum germination temperature, primary caryopses germinated 7–20 days earlier than secondary caryopses. In addition, a light/dark environment resulted in germination 2–6 days earlier than continuous darkness. Conclusions In the Northern Grains Region, seeds retained on or close to the soil surface (i.e. in NTCA systems) can undergo maximum germination during May–June (late autumn–winter), when long-term average temperatures match optimum germination temperatures. This coincides with winter crop plantings. Implications The seasonal timing of germination and the difference in germination timing between primary and secondary seeds, which help to stagger emergence of this weed, are major issues that need to be addressed in NTCA systems.

Cover crops and no-tillage reduce crop production costs and soil loss, compensating for lack of short-term soil quality improvement in a maize and soybean production system

Conservation agriculture has been marketed to producers as a sustainable way to increase soil productivity and buffer the effects of anticipated fluctuations in both climate and the price of fuel and fertilizer. Despite US Farm Bill financial incentives promoting the use of conservation practices such as no-tillage and cover crops among producers, widescale adoption of cover crops in the US remains low. Implementing no-tillage and cover crop use may take years of consistent management to show measurable soil quality improvement. Conversely, costs associated with cover crop planting and management must be incurred immediately and before the accrual of any benefits. Current research has largely focused on the soil quality benefits of cover crops without considering the short-term implementation costs for producers comparing their current production systems to conservation systems they may adopt. To help fill this knowledge gap, soil properties, cash crop yield, and annual production costs were evaluated in a three-year maize /soybean study comparing a conservation system to a conventional production system in Mississippi from 2016 to 2018. The conventional system included frequent tillage and control of winter weeds with a residual soil herbicide (conv. till + bare). We compared five different levels of conservation systems, including a conservation system with no-tillage and cover crops (no-till + cover). We found a lack of consistent improvement in soil properties such as soil organic matter increase or crop yield in the conservation system over the three-year period. The economic benefits of substituting no-tillage and cover crops for expensive conventional inputs were much greater than the modest soil property improvements observed from 2016 to 2018 crops. Though crop yields varied, the cost of cash crop production in the conservation system (no-till + cover) was 43% less than the cost of the conventional system ($29.67 per Mg of crop yield in the conv. till + bare to $17.04 per Mg of crop yield in the no-till + cover system), highlighting a short-term economic incentive for producers to switch to conservation agriculture. The greatest resource benefit from the conservation system was a reduction in estimated soil loss, as mean soil loss in no-till and cover crop decreased by 86% compared to the conventional system (3.5–25.1 t ha-1). These results demonstrate that conservation agriculture has the potential to decrease overall production cost while decreasing the risk of accelerated soil erosion during expected weather extremes associated with climate change, potentially making both farming operations and agroecosystems more resilient.

Response of Occurrence of Winter Weeds to Physico-Chemical Characteristics of Soil of Gandhinagar District, Gujarat, India

Gandhinagar is the capital city of Gujarat State. The paper deals with the estimation of nutrients (pH, EC, N, P, K, Zn) in soil of different talukas of Gandhinagar district. This district has four talukas with 290 villages and 10 urban habitations in the district. For the study purpose, the entire district was divided into 20 sites. Five sites of each talukas were selected. Total 20 sampling sites were selected to collect samples. The study was carried for a period of 2 year (2011 to 2013). Soil samples were colleted and analysed for their parameters like pH, EC, Nitrate, Phosphorus, Potassium and Zinc (Zn) at monthly. Zn was recorded critical in Mansa and Dehgam taluka and quite low in Kalol taluka. The occurrence types and distribution of Amaranthus viridis L., Achyranthus aspera L., Trianthema portulacastrum L, Boerhavia diffusa L., Cyperus rotundus L., Cynodon dactylon (L.) Pers., Tridex procumbens L., Parthenium hysterophorus L., Euphorbia hirta L., Vernonia cinera (L.) Less., Digera muriata (L.) Mart., Cassia tora L., Chenopodium album L., Portulaca oleracea L. in the study area of Gandhinagar showed relations with the soil in which they occur.

Biological effectiveness of herbicides in winter wheat crops of autumn sowing

An effective measure for controlling the most harmful wintering and winter weed species, such as Apera spica-venti, Galium aparine, Veronica persica, Consolida regalis, Capsella bursa-pastoris, Descurainia Sophia, Vicia villosa, etc. in winter wheat crops is the autumn application of herbicides, especially in the early stages of crop development, starting from the seed germination stage, when it is most sensitive to their presence. The study presents the results of two-year studies on the biological effectiveness of applying the herbicide Pledge 50, WP in different stages of development of winter wheat (BBCH 00, 11, 12, 14, and 16) independently and in a mixture with herbicides partners: Zenkor Liquid 600, SC, Marathon, SC, Granstar Gold 75, WG, Grodil Maxi 375, OD, and adjuvant Skaba, EC. As a result, it is identified that the biological effectiveness of the drugs under study against Apera spica-venti and other winter and wintering weeds substantially differed depending on the phase of development of winter wheat during the period of herbicide application. Pre-emergence application of herbicides does not ensure proper control of Apera spica-venti and other winter and wintering weeds. In particular, during the spring resumption of vegetation, the control of Apera spica-venti with the use of 0.1 kg/ha Pledge 50, WP was 69.0%, with an overall efficiency of 68.0%. Application of 0.4 l/ha Sencor Liquid 600, CS provided indicators of 66.1 and 71.4%, respectively. The introduction of 0.1 kg/ha of Pledge 50, WP in the BBCH 11 development phase provided high efficiency in controlling Apera spica-venti and all weeds in general with indicators of 91.2 and 87.6%, respectively. The use of a reduced rate of 0.08 kg/ha Pledge 50, WP in the BBCH 12 phase did not reduce both the overall effectiveness against weeds – 87.4%, and Apera spica-venti in particular – 93.1%. The use of Pledge 50, WP (0.1 kg/ha) in the BBCH 16 phase had a worse, but acceptable effect with efficiency indicators of 84.2% against Apera spica-venti and 83.6% overall. The best control of Apera spica-venti and all weeds, in general, was obtained by using a mixture of Pledge 50, WP + Granstar Gold 75, WG + adjuvant Skaba, EC (0.06 kg/ha + 0.025 l/ha + 0.05 l/ha) in the BBCH 14 phase – 97.5 and 99.2%, which is at the level of Sencor Liquid 600, SC + Grodil Maxi 375, OD (0.35 l/ha + 0.11 kg/ha). The highest yield of winter wheat in the experiment was obtained by applying a mixture of Pledge 50, WP + Granstar Gold 75, WG + adjuvant Skaba, EC (0.06 kg/ha + 0.025 l/ha + 0.05 l/ha) in the BBCH 14 phase – 7.56 t/ha, which is 59.8% better than the control

Winter Weed Emergence during Carinata (Brassica carinata) Production

This publication provides information for predicting emergence timing of common winter weed species for carinata production. Written by Ruby Tiwari, Pratap Devkota, and Michael J. Mulvaney, and published by the UF/IFAS Agronomy Department, June 2021.

A, The Evaluating Allelopathic potential of aqueous extracts of Sow thistle (Sonchus oleraceus L.) on emergence and seedling growth of Red rice (Oryza punctata)

ABSTRACT Chemical weed control method caused environmental hazards and residual effects in crops and soil. Alternate approach to control weeds is getting attentions in sustainable production system. Use of aqueous extracts of weed is getting scientific attention as eco-friendly alternative to chemical herbicides especially under scenario of fast increasing herbicide resistance in weeds. To investigate the herbicidal potential of aqueous extract of winter weed of Sonchus oleraceus L. (Sow thistle) on summer weed Oryza punctate L. (red rice) seed emergence and initial seedling growth, a study was planned. In this study, seeds of O. punctate were incubated in seven concentrations (0, 0.25, 0.50, 1, 2, 4, and 8%) of different parts i.e. leaves, stem, flower of S. oleraceus. All the tested concentrations of various plant parts of S. oleraceus significantly inhibited the mean emergence time, emergence index, emergence percentage (%), time taken to 50% emergence as well as growth of O. punctata weed. However, maximum mean emergence time (5.26 days), minimum germination index (1.69), germination percentage (40%), root length (2.04 cm), shoot length (5.71 cm), fresh weight (59 g), dry weight (4.06 g) was noted at 8% concentration with fruit aqueous extract of S. oleraceus. Seed of O. punctata take maximum time to complete 50% emergence (3.33 days) under control where we applied distilled water. Results suggested fruit extract of S. oleraceus at 8% concentration can be used potential bio-herbicide for the control of O. punctate. Key words: Chemical, eco-friendly, herbicidal potential, fruit extract

Resistance Mechanism to Metsulfuron-Methyl in Polypogon fugax.

Polypogon fugax is a common winter weed in China and other Asia countries. We have previously found a P. fugax biotype (R) resistant to acetyl co-enzyme A carboxylase (ACCase) herbicides also cannot be effectively controlled by some acetolactate synthase (ALS) herbicides. This study evaluated the level of resistance to four ALS herbicides (metsulfuron-methyl, chlorsulfuron, monosulfuron, pyribambenz isopropyl) in the R biotype and the associated resistance mechanism. The R biotype exhibited moderate level of resistance to metsulfuron-methyl (6.0-fold) compared with the sensitive biotype (S). Sequence analysis of ALS gene revealed that two ALS genes existed in P. fugax. However, no substitution associated with ALS resistance mechanism were found in ALS genes between the S and R biotypes. The activity of ALS enzyme isolated from the R biotype was inherently higher and less sensitive to metsulfuron-methyl than the S biotype. Glutathione S-transferases (GST) activity was also less sensitive to metsulfuron-methyl in the R than as the S biotypes. Malathion, a cytochrome P450 (CYP) monooxygenase inhibitor, had much greater synergistic effect with metsulfuron-methyl on the R than as the S plants, reducing the ED50 value (herbicide dose to inhibit growth by 50%) of metsulfuron-methyl by 23- and 6-fold, respectively, suggesting that CYP mediated enhanced metabolism might contribute to the resistance to ALS herbicides. These results suggest that metsulfuron-methyl resistance in the R biotype was associated with the up-regulated ALS enzymatic activity and the GST and CYP-mediated enhanced herbicide metabolism.

Establishing white clover (Trifolium repens) as a living mulch: weed control and herbicide tolerance

AbstractWith the increasing focus on herbicide-resistant weeds and the lack of introduction of new modes of action, many producers have turned to planting annual cover crops as a method for reducing weed populations. Recent studies have suggested that perennial cover crops such as white clover could be used as living mulch. However, white clover is slow to establish and is susceptible to competition from winter weeds. Therefore, the objective of this study was to determine clover tolerance and weed control in established stands of white clover to several herbicides. Studies were conducted in the fall and winter of 2018 to 2019, and 2019 to 2020, at the J. Phil Campbell Research and Education Center in Watkinsville, GA, and the Southeast Georgia Research and Education Center in Midville, GA. POST applications of imazethapyr, bentazon, or flumetsulam at low and high rates, or in combination with 2,4-D and 2,4-DB, were applied when clover reached the 2- to 3-trifoliate stage. Six weeks after the initial POST application, a sequential application of bentazon and flumetsulam individually, and combinations of 2,4-D, 2,4-DB, and flumetsulam, were applied over designated plots. Clover biomass was similar across all treatments except where it was reduced by sequential applications of 2,4-D + 2,4-DB + flumetsulam in the 2019 to 2020 season, indicating that most treatments were safe for use on establishing living mulch clover. A single application of flumetsulam at the low rate or a single application of 2,4-D + 2,4-DB provided the greatest control of all weed species while minimizing clover injury compared with the nontreated check. These herbicide options allow for control of problematic winter weeds during clover establishment, thereby maximizing clover biomass and limiting canopy gaps that would allow summer weed emergence.

Emergence patterns of winter and summer annual weeds in Ethiopian mustard (Brassica carinata) cropping system

Abstract Ethiopian mustard (Brassica carinata A. Braun) is a biofuel crop recently introduced in the southeastern United States. For this crop to be successful, integrated weed management strategies that complement its rotation with summer cash crops must be developed. The objectives of this research were to evaluate the effect of previous season summer crops on winter weed emergence patterns during Ethiopian mustard growing season and to assess the impact of planting Ethiopian mustard on the emergence patterns of summer weed species. Gompertz models were fit to winter and summer weed emergence patterns. All models represented more than 80% of the variation, with root mean-square error values less than 0.20. The emergence pattern for winter weed species was best described using growing degree-day accumulation, and this model can be utilized for implementing weed control strategies at the critical Ethiopian mustard growth stages. The results also showed that summer weeds can emerge during the winter in northern Florida but do not survive frost damage, which might create off-season seedbank reductions before the summer crop growing season.

ETHYL ACETATE EXTRACT OF Chenopodium murale ROOT, A SOURCE OF BIOACTIVE COMPOUNDS

Chenopodium murale L. is a winter weed of Chenopodiaceae. In this study, bioactive compounds present in ethyl acetate fraction of root extract of C. murale were identified. The weed plants were collected from Jehlem, Pakistan. Its roots were dried, powdered and extracted in methanol. After evaporation of the solvent, the remaining extract was mixed in water and partitioned with n-hexane, chloroform and finally with ethyl acetate. The last fraction was analyzed through GC-MS that indicated the presence of 15 compounds. These included the three major compounds namely o-xylene (15.03%), cyclopentanol (13.42) and 2-hexanol (13.99%). The moderately and less abundant compounds were ethylbenzene (5.47); methyl acetate (6.00%); cholestrol (4.33%); 2-phenanthrenol (3.01%); cyclohexanone (5.32%); p-xylene (5.12%); furostan-3,26-diyl dibenzoate (3.29%); dihexyl phthalate (4.99%); tricosanoic acid (2.74%); dioctyl phthalate (4.99%), hexanal (3.05%) and ergostane (1.29%). Literature survey showed that 10 of the identified compounds exhibited various biological activities including antifungal, antibacterial, antioxidant, anticancer and antipsoriatic. Most of the compounds were antimicrobial in nature.

Growing winter Brassica carinata as part of a diversified crop rotation for integrated weed management

AbstractBrassica carinata A. Braun is a non‐edible, oilseed winter crop for biofuel production that can diversify crop rotations and improve integrated weed management. The research objective was to evaluate the influence of B. carinata on weed population dynamics in the southeastern United States cropping systems. B. carinata was grown after cotton (Gossypium hirsutum L.), peanut (Arachis hypogea L.), or a clean summer fallow, and winter weed pressure was modified with or without S‐metolachlor. The emergence of Lamium amplexicaule L. increased at least 40% after cotton or peanut in 2018–2019 and 50% after cotton in 2019–2020 compared to summer fallow. Stellaria media (L.) Vill. emergence was increased over threefold after peanut or cotton in 2019–2020. Senna obtusifolia (L.) H.S. Irwin & Barneby emergence after cotton was increased at least 43% during both experimental years, whereas Amaranthus hybridus L. emergence was increased over 50% after peanut in 2019–2020 compared to summer fallow. Even without S‐metolachlor, B. carinata reduced A. hybridus (>27%) and S. obtusifolia (>25%) emergence compared to weedy winter fallow. After B. carinata harvest, A. hybridus emergence was reduced >40% with or without S‐metolachlor compared to winter fallow in 2018–2019. Overall, B. carinata biomass was highest after peanut for both seasons. B. carinata seed yield did not differ among crop history treatments in the first season, whereas in 2019–2020, the yield was higher after peanut (2417 kg ha−1) or fallow (2520 kg ha−1) compared to cotton (1710 kg ha−1). Weed management treatments were not different for B. carinata biomass or yield in any year. The results indicate that B. carinata can enhance integrated weed management strategies at the rotational level for summer crops by reducing seed banks of summer weed species, in addition to its potential as a winter biofuel crop for the southeastern United States.

Біологічна ефективність гербіцидів у посівах пшениці озимої за осіннього внесення

The autumn application of herbicides in is an effective measure to control the most harmful species of winter weeds, such as Apera spica-venti, Galium aparine, Veronica persica, Consolida regalis, Capsella bursa-pastoris, Descurainia Sophia, Vicia villosa etc. These measures are especially effective in the early stages of wheat growth, starting from the seed germination stage, when it is most sensitive to the presence of weeds. The article presents the results of two-year studies on the biological effectiveness of herbicide Pledge 50, WP in different periods of development of winter wheat (BBCH 00, 11, 12, 14 and 16) alone and in a mixture with herbicides partners: Zenkor Liquid 600, SC, Marathon, SC, Granstar Gold 75, WG, Grodil Maxi 375, OD and adjuvant Skaba, EC. As a result, it was found that the biological effectiveness of the studied herbicides against Apera spica-venti and other winter and winter weeds differed significantly depending on the phase of development of winter wheat at the time of their application. Pre-ceed application of herbicides does not provide proper control of Apera spica-venti and other winter and winter weeds. For the period of spring vegetation of wheat, the control of Apera spica-venti with the use of 0.1 kg / ha of Pledge 50, WP was 69.0 %, with an overall efficiency of 68.0 %. Application of 0.4 l / ha Zenkor Liquid 600, SC provided indicators, respectively, 66.1 and 71.4 %. The application of 0.1 kg / ha of Pledge 50, WP to the BBCH 11 phase of wheat provided high control efficiency of Apera spica-venti and all weeds in general with rates of 91.2 and 87.6 %, respectively. The use of a reduced rate of 0.08 kg / ha Pledge 50, WP in the BBCH 12 phase did not reduce both the overall effectiveness against weeds – 87.4 % and Apera spica-venti, in particular – 93.1 %. The use of Pledge 50, WP (0.1 kg / ha) in the BBCH 16 phase was slightly worse, but the acceptable effect was 84.2 % against Apera spica-venti and 83.6 % overall. The best control of Apera spica-venti and all weeds in general was obtained using a mixture of Pledge 50, WP + Granstar Gold 75, WG + Skaba adjuvant, EC (0.06 kg / ha + 0.025 l / ha + 0.05 l / ha) in the phase of BBCH 14 – 97.5 and 99.2 %, which is at the level of Zenkor Liquid 600, SC + Grodil Maxi 375, OD (0.35 l / ha + 0.11 kg / ha). Significantly the highest yield of winter wheat in the experiment was obtained by application of a mixture of Pledge 50, WP + Granstar Gold 75, WG + adjuvant Skaba, EC (0.06 kg / ha + 0.025 l / ha + 0.05 l / ha) in the phase BBCH 14 – 7.56 t / ha, which is 59.8 % better than control.

HEXANE SOLUBLE BIOACTIVE COMPONENTS OF Chenopodium murale STEM

Chenopodium murale L. is a common winter weed mostly growing along the road-sides. In the present study, n-hexane soluble fraction of methanolic stem extract of this weed was subjected to GC-MS analysis that showed the presence of 28 compounds in this fraction. Major compounds included oleic acid (16.55%), palmitic acid (11.22%), β-sitosterol (9.63%), hexadecanoic acid (7.71%) and methyl oleate (5.90%). Other prominent compounds were piperine (4.75%), nonacosane (4.69%), monoplalmitin (4.21%), γ-sitosterol (3.91%), methyl linoleate (3.88%), neocurdione (3.86%) and ethanonone (3.25%). The compounds such as stigmasterol (2.92%), 1,4-benzenedicarboxylic acid (2.78%), tetracosanoic acid (1.19%), stearic acid (1.36%), tridecanoic acid (1.35%), tridecanal (1.30%), phytol (1.29%), docosanoic acid, methyl ester (1.23%), octadecanoic acid (1.20%), 4-pyrimidinecarboxylic acid (1.05%), 2-hydroxy-2-phenylbutanamide (0.91%), hexacosanoic acid (0.76%), cholestrol (0.61%), methyl octacosanoate (0.55%) and tetracosanoic acid (0.30%) were present in low concentrations. A thorough literature survey showed that most of the identified compounds possessed antifungal and/or antibacterial properties while very few of them also possessed antioxidant potential. This study concludes that n-hexane soluble fraction of methanolic stem extract of C. murale is a big storehouse of antimicrobial compounds.

Weed Management in Small Grains Harvested for Grain

Successful weed control in small grains involves using good management practices in all phases of production. In Florida, winter weeds compete with small grains for moisture, nutrients, and light, with the greatest amount of competition occurring during the first six to eight weeks after planting. Weeds also cause harvest problems the following spring when the small grain is mature. This 4-page publication discusses crop competition, knowing your weeds, and chemical control. Written by J. A. Ferrell, G. E. MacDonald, and P. Devkota, and published by the UF/IFAS Agronomy Department, revised May 2020.