Showing papers in "Planta Daninha in 2018"
TL;DR: It was observed that the populations exhibit differential sensitivities to herbicides and the one originated in Brazilian city Ribeirão Preto was resistant to ametryn and the population originated in Portuguese city Santa Cruz das Posses was less sensitive to diuron.
Abstract: Weed interference reduces the productive potential of crops. Among the control methods used, chemical ones occupy a major position. The repeated application of the same mechanism of action selects tolerant plants. Among the species that affect sugarcane, crabgrass is one of them. This study has aimed to know the tolerance of different populations of this species to herbicides inhibiting photosystem II. Three populations were collected, identified and submitted to the application of ametryn and diuron herbicides in ten different doses, and the experiment was conducted in a experimental design of complete randomized blocks with four repetitions in a factorial arrangement of 10 x 3 (10 doses x 3 populations), being one trial for each herbicide. Sixty days after application, visual control and plants shoot dry biomass were evaluated. The data were submitted to an analysis of variance by the F test and, when significant, their means were compared using the Tukey’s test. The averages related to the herbicide doses were submitted to a graphical analysis by applying a log-logistic regression where the herbicide doses required to cause 50 or 80% of injury and reduction of dry biomass of plants were calculated. The resistance factor was calculated to determine the difference in herbicide tolerance among populations. Based on the results, it was observed that the populations exhibit differential sensitivities to herbicides and the one originated in Brazilian city Ribeirao Preto was resistant to ametryn. The population originated in Brazilian city Santa Cruz das Posses was less sensitive to diuron. The RF values ranged between 1.0 and 2.34.
34 citations
TL;DR: This review covers biological activity of secondary metabolites, coumarin and their derivatives on different organisms (pests, pathogens, weeds), as well as their applications in agriculture as eco-friendly pesticides and weed control agents.
Abstract: This review covers biological activity of secondary metabolites, coumarin and their derivatives on different organisms (pests, pathogens, weeds), as well as their applications in agriculture as eco-friendly pesticides and weed control agents. Naturally occurring coumarins have shown biological and allelopathic potential on a broad range of organisms. Coumarin inhibits seed germination, root growth, morphology, histology, water uptake, respiration, photosynthesis, cell elongation, cell division and differentiation. Coumarin demonstrate excellent insecticidal potential against eggs, larvae and adult insects. Coumarin showed antifeedent responses in a wide range of memebers from invertebrates to vertebrates. The information provided in this review also shed light on further research and development of coumarin and its derivatives as potential plant protection lead compounds to control weeds and harmful pests.
20 citations
TL;DR: In this article, the influence of adjuvants added to the herbicides saflufenacil and glyphosate, isolated or in combination, and the effects on the surface tension, deposition and effectiveness in post-emergence applications to control Conyza sumatrensis was evaluated.
Abstract: The use of herbicides is widespread in weed management, and adjuvants are added to the spray solution to improve the effectiveness of applications The goal was to evaluate the influence of adjuvants added to the herbicides saflufenacil and glyphosate, isolated or in combination, and the effects on the surface tension, deposition and effectiveness in post-emergence applications to control Conyza sumatrensis Experiments were conducted completely randomized experimental design to evaluate surface tension (TS), deposition and herbicide effectiveness The treatments were glyphosate, glyphosate + saflufenacil and saflufenacil with or without the adjuvants Natur’al oleo®, Assist®, Aterbane®, Sillwet L-77 and Dash HC® (surface tension) For the experiments about mixture deposition and herbicide effectiveness, the factorial scheme 3 x 5 was adopted in the experiment performed in April, where factor A corresponded to the combination of the herbicieds glyphosate, saflufenacil and glyphosate + saflufenacil, and factor B was the addition of the adjuvants Natur’al oleo®, Assist®, Aterbane®, Sillwet L-77 For experiments conducted in November, the adjuvant Dash HC® was added, and the 3x6 factorial design was adopted The adjuvants reduced the ST of the herbicide mixture, and Silwet L-77® was the most effective one However, the ST reduction did not influence the mixture deposition on C sumatrensis plants The use of adjuvants did not result in an effective control for the applications with sole glyphosate
19 citations
TL;DR: It is concluded that basal rot of onion can be controlled by combined application of W. somnifera dry leaf material and biological control agent T. harzianum.
Abstract: Onion is attacked by destructive soil-borne fungal plant pathogen Fusarium oxysporum f. sp. cepae, resulting in basal rot disease. In the present study, three Trichoderma species (T. pseudokoningii, T. harzianum and T. reesei) and leaves of solanaceous weed Withania somnifera were used for management of this disease. The in vitro interaction study revealed T. harzianum as the most effective biocontrol agent against the pathogen. In a pot trial, dried leaf material of W. somnifera (1%, 2% and 3% w/w) and inoculum of T. harzianum were mixed in the pot soil previously inoculated with the pathogen. The highest incidence of the disease (87%) was found in positive control (pathogen inoculation without any amendment). Different rates of dry leaf material reduced the incidence of the disease to 41-66%. T. harzianum in combination with leaf material reduced the incidence of the disease to 20-53%. In a laboratory bioassay, the dry leaf extract of W. somnifera was prepared in methanol and partitioned with n-hexane, chloroform, ethyl acetate and n-butanol. The highest concentration (200 mg mL-1) of all except for the n-butanol fraction significantly decreased fungal biomass over control. This study concludes that basal rot of onion can be controlled by combined application of W. somnifera dry leaf material and biological control agent T. harzianum.
19 citations
TL;DR: The present study documented the first case of weedy rice that was cross-resistant to Imazapic and imazapyr in Malaysian Clearfield® rice field, confirming imidazolinone-resistant weedy Rice in Malaysia.
Abstract: The Clearfield® rice production system is an effective management tool for weedy rice and other weeds in the direct-seeded rice culture. However, if farmers cultivating the Clearfield® rice disregard stewardship recommendations, the industry could face a problem of herbicide-resistant weedy rice which would occur through the selection of outcrosses. This study aimed to confirm imidazolinone-resistant weedy rice in Malaysia. The resistant weedy rice (R-WR) was found to be 67 fold more resistant to OnDuty® (premix of imazapic and imazapyr) than the susceptible weedy rice (S-WR) based on the GR50 values (rate that causes 50% inhibition of shoot growth). The Clearfield® rice cultivar was 32-fold more tolerant to OnDuty® than the S-WR. Furthermore, the R-WR was 54 and 89 fold more resistant to imazapic and imazapyr applied separately than the S-WR, respectively. The Clearfield® rice was 140- and 40-fold more tolerant to imazapic and imazapyr, respectively than the S-WR. The R-WR biotype was susceptible to non-selective herbicides glyphosate and glufosinate, as well as the selective graminicide quizalofop. Oxadiazon controlled the R-WR biotype, but pretilachlor was ineffective. The present study documented the first case of weedy rice that was cross-resistant to imazapic and imazapyr in Malaysian Clearfield® rice field.
17 citations
TL;DR: Application of 3% C. didymus biomass had a pronounced effect on crop growth resulting in 101%, 233% and 342% increase in shoot length, root length and plant biomass, respectively, over the positive control.
Abstract: A pot experiment was carried out to check the effect of Coronopus didymus (L.) Sm. dry biomass application (1%, 2% and 3% w/w) and two species of Trichoderma (T. viride and T. aureoviride) on growth and physiology of mungbean [Vigna radiata (L.) WIlczek] under biotic stress of Macrophomina phaseolina (Tassi) Goid. Inoculation of M. phaseolina (positive control) reduced plant survival, shoot and root length as well as plant dry biomass by 22%, 52%, 61% and 64%, respectively, over the negative control (without any amendment). There was 100% plant survival in treatments with T. aureoviride alone or in combination with 1% and 2% C. didymus biomass. Likewise, T. viride in combination with 2% biomass also showed 100% plant survival. Application of 3% C. didymus biomass had a pronounced effect on crop growth resulting in 101%, 233% and 342% increase in shoot length, root length and plant biomass, respectively, over the positive control. Sole inoculation of either of the two Trichoderma spp. significantly enhanced various plant growth parameters over the positive control. In general, in combination with 2% biomass of C. didymus, both Trichodermaspp. proved to be the best choice for improving mungbean biomass under stress of M. phaseolina. Activity of denfense related enzymes viz. peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) was generally higher in treatments in which 1% C. didymus biomass was applied either alone or combined with Trichoderma spp. in M. phaseolina inoculated soil.
14 citations
TL;DR: The production systems with Urochloa ruziziensis, Pennisetum glaucum, Crotalaria spectabilis and intercropped with maize and sunflower were the best alternatives for integrated weed management, reducing the incidence and increasing control of the main species that were detected during the conduction of the experiment.
Abstract: The objective of this work was to evaluate the effect of cover crops on weed suppression in no-tillage soybean production systems in Rondonopolis, Mato Grosso. The experiment was carried out in an experimental area and consisted of the evaluation of nine cover treatments and soil management in a randomized complete block design. The treatments were: NT fallow, CT fallow, Crotalaria spectabilis, Crotalaria breviflora, maize + Crotalaria spectabilis, Pennisetum glaucum, Urochloa ruziziensis, Cajanus cajan, sunflower + Urochloa ruziziensis, Stylosanthes, Vigna unguiculata, Urochloa brizantha, maize + Urochloa ruziziensis. The evaluations were carried out before the desiccation for soybean sowing in the crops (10/23/2014) and (09/21/2015), before the post-emergence of soybean (09/12/2014) and (12/11/2015) and in the second season (12/06/2015). The useful area was 5 x 5 m and all weeds were counted and identified, but only the four species with the largest population were collected. The weeds evaluated were: Digitaria horizontalis, Digitaria insularis, Porophyllum ruderale and Tridax procumbens. Fallow treatments presented higher weed populations in relation to the others, in all periods of evaluation. Digitaria horizontalis presented the highest phytomass production in most seasons. The production systems with Urochloa ruziziensis, Pennisetum glaucum, Crotalaria spectabilis and intercropped with maize + Urochloa ruziziensis, sunflower + Urochloa ruziziensis and maize + Crotalaria spectabilis were the best alternatives for integrated weed management, reducing the incidence and increasing control of the main species that were detected during the conduction of the experiment.
14 citations
TL;DR: Antifungal potential of aerial parts of an allelopathic grass Cenchrus pennisetiformis (Hochst. & Steud.) Wipff.
Abstract: Antifungal potential of aerial parts of an allelopathic grass Cenchrus pennisetiformis (Hochst. & Steud.) Wipff. was evaluated against Fusarium oxysporum f. sp. lycopersici Snyder & Hansen, a fungal pathogen causing wilt disease in tomato (Solanum lycopersicum L.). Different concentrations (1% to 6%) of methanolic leaf, stem and inflorescence extract of the grass significantly reduced fungal biomass by 40-88%, 13-89%, and 26-76%, respectively. Methanolic shoot (leaf + stem) extract was fractionated using four organic solvents viz. n-hexane, chloroform, ethyl acetate and n-butanol. All the sub-fractions of methanolic shoot extract showed remarkable antifungal potential to variable extents. Different concentrations (1.56-200 mg mL-1) of ethyl acetate sub-fraction exhibited the best antifungal activity resulting in 49-100% suppression in the fungal biomass. GC-MS analysis of ethyl acetate sub-fraction showed the presence of 10 compounds. Phenol, 2,4-bis{1,1-dimethlethyl}- was the major compound (30.99%) followed by hexadecanoic acid, ethyl-ester (21.72%), benzofuran 2,3-dihydro (10.65%), 1-propanol-2-2-hydroxypropxy (10.60%) and 1-eicosene (8.32%).
13 citations
TL;DR: The foliage applied 5% brassica water extract and BAP (5 ppm) was the most effective and had a stimulating impact on the growth and productivity of wheat.
Abstract: ABSTRACT: This study was conducted to explore the growth stimulating effect of foliage applied brassica water extract on growth and productivity of bread wheat (cv. Punjab 2011) at low and high fertilizer doses. The brassica water extract (5%) and the commercial growth regulator benzyl amino purine (BAP) (5 ppm) were applied alone and in combination at 30 and 45 days after sowing (DAS) under low fertilizer dose (125 kg ha-1 N and 90 kg ha-1 P) and high fertilizer doses (225 kg ha-1 N and 150 kg ha-1 P). Application of the brassica water extract (5%) significantly improved morphological traits such as crop growth rate, leaf elongation, leaf area index, plant height and number of productive tillers under both fertilizer regimes. Similarly, growth regulator benzyl amino purine (5 ppm) application enhanced the growth and yield components of wheat. However, maximum grain yield (6.20 t ha-1) was recorded with combined application of the brassica water extract (5%) and BAP (5 ppm) under the high fertilizer dose followed by individual application of the brassica water extract (5%) and BAP where 5.39 and 5.94 t ha-1 grain yields were recorded. Biological yield also showed an almost similar trend under the influence of the allelopathic water extract of brassica and BAP. Economic and marginal net benefits of 1521.6 and 237.0 USD ha-1 were respectively achieved with the application of the brassica water extract under the lower and higher fertilizer applications, respectively. The foliage applied 5% brassica water extract and BAP (5 ppm) was the most effective and had a stimulating impact on the growth and productivity of wheat.
12 citations
TL;DR: It can be suggested that the use of allelopathic plant water extracts in a mixture may act as a potential weed control strategy in wheat.
Abstract: Use of synthetic herbicides to control weeds poses serious threats to sustainable agricultural production around the globe. The phytotoxic effect of different plant water extracts (i.e., sorghum, sunflower and mulberry) against weeds has been previously studied; however, their combined effects at different rates are yet to be explored. In this study, mixtures of allelopathic water extracts of sorghum + sunflower and sorghum + sunflower + mulberry were sprayed each at 12, 15, 18 and 21 L ha-1 at 40 and 55 days after sowing in wheat to control wild oats (Avena fatua), little seed canary grass (Phalaris minor), lamb’s quarters (Chenopodium album) and swine cress (Coronopus didymus). A synthetic herbicide Affinity 50 WP (Carfentrazone-ethyl 0.75% + Isoproturon 50% applied at 1000 g a.i., ha-1) and a weedy check were kept as a control treatment. The increasing order of water extract dose 12-21 L ha-1 showed substantial reduction in total weed density and their dry biomass production of both narrow and broad-leaved weeds in all the treatment combinations. Mixture of sorghum + sunflower + mulberry water extracts each at 18 L ha-1 applied at 40+55 DAS resulted in an 87.14% decrease in total weed dry matter with a 19.5% increase in grain yield of wheat and higher net benefits of Rs. 100525 with 777.5% marginal rate of return. Nonetheless, application of sorghum + sunflower water extracts each at 12 L ha-1 at 40+55 DAS was more economical than the other treatments in terms of higher marginal rate of return of 799.82%. Based on this study, it can be suggested that the use of allelopathic plant water extracts in a mixture may act as a potential weed control strategy in wheat.
11 citations
TL;DR: Eucalyptus grown as an intercrop changed the composition and size of the weed seed bank, in a different way for functional traits, families and species depeding on the distance from trees.
Abstract: : Trees can modify the weed seed bank composition and distribution in the cropped area of an agroforestry system. This study aimed at analyzing the eucalyptus (Eucalyptus dunnii) effect on spatial distribution, functional traits abundance and weed seed bank botanic composition in an agroforestry system under no-tillage in Subtropical Brazil. The experiment was conducted in a randomized block design with five replications, and five positions between 4.5-year-old eucalyptus double rows [(4x3) x 20 m] as treatments. Soil sampling was performed at 0-20 cm and the method to quantify and identify seeds was the seedling emergence in trays, inside a greenhouse. Weed phytosociological indices (relative density, frequency and importance), functional traits abundance (life cycle, shade tolerance, reproduction, spread and seed form) and seed densities (m-2) of families and species were evaluated; 17 weed families and 49 species were found. The indices that contributed to the relative importance of families and species differed among the positions between rows. Eucalyptus grown as an intercrop changed the composition and size of the weed seed bank, in a different way for functional traits, families and species depeding on the distance from trees.
TL;DR: The results indicate that degradation enhancement caused by cytP450 enzymes is involved in the resistance mechanism of barnyardgrass to imazethapyr, and appropriate measures should be taken to manage these populations.
Abstract: Non-target site (NTS) herbicide resistance by degradation enhancement is an increasing problem in several weeds around the world. In this study, the occurrence of degradation enhancement by cytochrome P450 monooxygenases (cytP450) was evaluated as the mechanism of resistance to imazethapyr in barnyardgrass. The cytP450 inhibitors malathion and piperonyl butoxide (PBO) and the inducer naphthalic anhydride (NA), applied in mixture or sequentially with imazethapyr, were evaluated on imidazolinone-susceptible and -resistant barnyardgrass byotipes. In addition, the degradation of imazethapyr was analyzed in plants treated with imazethapyr applied alone or two hours after malathion or NA. The spraying of malathion and PBO reduced the resistance factor (RF) from 15.92 to 3.44 and 4.99, respectively, in the resistant population PALMS01. Conversely, the cytP450 inducer NA increased the RF from 4.45 to 8.32. Malathion increased imazethapyr concentrations in resistant barnyardgrass in comparison with plants sprayed with the herbicide alone, indicating the inhibition of imazethapyr degradation. The simultaneous spraying of malathion and imazethapyr was less efficient than the previous application of this cytP450 inhibitor. These results indicate that degradation enhancement caused by cytP450 enzymes is involved in the resistance mechanism of barnyardgrass to imazethapyr, and appropriate measures should be taken to manage these populations.
TL;DR: The authors found that volunteer corn in the form of clumps predominates in soybean crops, but little information about its effect on soybean production is known. But, volunteer corn can be harvested from seeds that were lost during harvest or from non-harvested seeds from the field.
Abstract: The cultivation of GR® maize prior to soybean, mainly in the no-tillage system favors the higher occurrence of GR® volunteer corn interfering in soybean crops. Volunteer corn originate from seeds that were lost during harvest or from non-harvested seeds from the field; these are individual seeds, originating individual plants, or several seeds adhered to segments of the rachis, which originate clumps. Volunteer corn in the form of clumps predominates in soybean crops, but little information about its effect on soybean [...]
TL;DR: In conclusion, a greater control of horseweed and crabgrass occurred when S-metolachlor or pendimethalin was applied PRE, and the soybean yield was higher with weed-free, S- metolACHlor and metribuzin treatments.
Abstract: A 3-year field study was conducted to assess the potential for using pre-emergent (PRE) herbicides tank mixed with glyphosate as a means of controlling weed species in soybean. In 2011/12, 2012/13 and 2013/14 growing sessions soybean cultivar Brasmax Apollo RR was planted under residues of rye. The herbicide treatments glyphosate (gly) (1,296 g a.i. ha-1), gly + S-metolachlor (1,296 + 1,920), gly + imazaquin (1,296 +161), gly + pendimethalin (1,296 + 1,000), gly + metribuzin (1,296 + 480), gly + 2.4-D amine (1,296 + 1,209) was applied in pre-emergence (PRE) over rye crop residues two days before soybean sowing. In addition, full season weed-free and weedy control plots were included. Gly + S-metolachlor and gly + pendimethalin reduced the horseweed density from 48 to 3 and 6 plants m-2, respectively. The mix containing gly + metribuzin and gly + 2.4-D amine and gly applied alone had no effect in the horseweed control. The mix containing gly + metribuzin, gly + 2.4-D amine, gly + imazaquin and gly applied alone had no effect in the crabgrass control. In contrast gly + S-metolachlor and gly + pendimethalin reduced the crabgrass density from 70 to 0 and 1 plant m-2, respectively. The soybean yield was higher with weed-free, S-metolachlor and metribuzin treatments. The use of an herbicide with residual effect had impact on weed management and soybean yield. In conclusion, a greater control of horseweed and crabgrass occurred when S-metolachlor or pendimethalin was applied PRE.
TL;DR: The results on occurrence and distribution of viruses infecting weeds in watermelon commercial plantations in the State of Tocantins provide important information about the role of weeds as virus reservoirs contribute to the knowledge of the epidemiology of these diseases, and enable a proper weed management aiming at reducing the secondary spreading control of viruses by insect vectors.
Abstract: Watermelon is one of the most important vegetable crops in Brazil, which is grouped among the greatest producers worldwide. Viruses stand out among the most damaging disease agents, which can drastically reduce fruit production. In this context, weeds present in the field can also interfere in crop production, acting as reservoirs for viruses. Thus, this study aimed to investigate virus occurrence in weeds at the main watermelon-growing regions in the State of Tocantins. Viruses identification (e.g. potyviruses: Watermelon mosaic virus - WMV; Papaya ring spot virus - type watermelon -PRSV-W; Zucchini yellow mosaic virus- ZYMV; the cucumovirus Cucumber mosaic virus - CMV, and the orthotospovirus Zucchini lethal chlorosis virus - ZLCV) infecting weeds was performed by serology and confirmed by RT-PCR tests. Serological and molecular test results indicate that Amaranthus spinosus, Nicandra physaloides, Physalis angulata and Heliotropium indicum were infected by at least one virus species. The highest infection rate was represented by ZYMV (52.7%), followed by PRSV-W (22.2%); CMV, WMV, and ZLCV that showed the same infection rate (8.3%) each. Plants of P. angulata were infected by all five viruses, singly or in mixed infection, and represented 50% of the total number of infected samples. The highest virus infection rates, 50% and 44.4%, occurred in weeds collected at Lagoa da Confusao and Formoso do Araguaia, respectively. The results on occurrence and distribution of viruses infecting weeds in watermelon commercial plantations in the State of Tocantins provide important information about the role of weeds as virus reservoirs contribute to the knowledge of the epidemiology of these diseases, and enable a proper weed management aiming at reducing the secondary spreading control of viruses by insect vectors.
TL;DR: In this paper, the results showed that with the increasing concentration of P. hysterophorus, all the parameters studied in the six test species were significantly decreased, while for the species x parthenium concentration interaction, the differences were only significant (P?0.05) for plant height in the pot experiment.
Abstract: Parthenium hysterophorus being a declared invasive weed worldwide is threatening the biodiversity of Pakistan. To study its allelopathic potential, laboratory and pots based studies were undertaken during July-August and October-November, 2010 in Weed Research Laboratory, Department of Weed Science, The University of Agriculture Peshawar, Khyber Pakhtunkhwa Pakistan. The experiments were conducted to investigate the allelopathic effect of parthenium on crops Triticum aestivum, Cicer arietinum and Brassica campestris, and weeds including Avena fatua, Asphodelus tenuifolius and Lolium rigidum The fresh leaves of P.hysterophorus were dried in shade and grinded. The desired quantity of powder was soaked for 16 hr. in the desired quantity of water to make the stock solution of the maximum concentration viz. 75 g L-1. Five seeds of each species were placed in Petri dishes and in pots, extracts were applied when needed. Control (0 g L-1) was also included for comparison. Both experiments were laid out as Factorial in completely randomized design (CRD) with four replications and two runs each. Since the statistical differences between the runs were non-significant the data were pooled before subjecting it to ANOVA and mean separation. The differences among the test species and the rates of parthenium extracts were different statistically (P?0.05) for all the traits examined, while for the species x parthenium concentration interaction, the differences were only significant (P?0.05) for plant height in the pot experiment. The results showed that with the increasing concentration of P. hysterophorus, all the parameters studied in the six test species were significantly decreased. Hence, the present study suggests that P. hysterophorus affects the agro-ecosystem and needs to be properly managed, moreover, its allelopathy on weeds is an encouraging finding for the weed managers for the sustainable management of weeds.
TL;DR: The phytotoxicity of soybean crops containing the technologies Cultivance® (CV) and tolerance to sulphonylurea and Roundup Ready® (RR), deriving from increasing doses of the imazapyr andImazapic herbicide mixture, applied in the irrigated rice crop management.
Abstract: Soybean crop rotation with irrigated rice is an alternative for the management of weedy rice (Oryza sativa) resistant to herbicides from the imidazolinone chemical group This work had the purpose to evaluate the phytotoxicity of soybean crops containing the technologies Cultivance® (CV) and tolerance to sulphonylurea and Roundup Ready® (RR), deriving from increasing doses of the imazapyr and imazapic herbicide mixture, applied in the irrigated rice crop management Thus, the experiment was performed on field, where treatments consisted in three soybean cultivars (BRS382CV, CD249STS and NA5909RR) and five doses of the imazapyr and imazapic herbicides mixture (0, 49, 98, 196 and 392 g ai ha-1) The evaluated variables were phytotoxicity, yield components and physiological quality of the seeds Soybean cultivar BRS382CV is tolerant to herbicide carryover, applied in the management of weedy rice in irrigated rice crops, but the other cultivars are susceptible to it Cultivar productivity, yield components and physiological quality of the seeds are affected by the carryover increase of the imazapyr and imazapic herbicide mixture
TL;DR: Keeping in view the spatial variability of soil and nature of weeds, site-specific/orchard-specific weed management practices are recommended to be opted for successful weed management.
Abstract: Citrus is an important export commodity, mostly grown on Mediterranean and Aegean coasts of Turkey. Weeds are hidden foes impairing citrus productivity. Limited knowledge of weed distribution and factors affecting the distribution are among major hurdles in successful weed management. In this study, weed flora of citrus orchards and factors affecting its distributions in Mugla province of Turkey were determined. Sixty orchards were surveyed in spring and autumn seasons of 2010 and 2011. Data relating to frequency, coverage and density of weed species were recorded. Soil samples (0-30 cm depth) were collected and analyzed for physicochemical properties. Climatic variables, altitude and soil properties were correlated with weed flora. Sixty-eight weed species belonging to 30 families were documented. Higher number of weed species (54) was recorded in spring season compared with autumn (29 weed species). Annuals and therophytes were the most dominant growth and life forms, respectively. Canonical Correspondence Analysis (CCA) to correlate soil properties and weed vegetation data yielded three distinct groups dominated by phosphorus, sand and silt contents, which affected weed distribution. CCA to correlate vegetation data and weather attributes produced two distinct groups affected by altitude and precipitation. Generally, cosmopolitan weeds adapted to different ecosystems were observed during the survey. Keeping in view the spatial variability of soil and nature of weeds, site-specific/orchard-specific weed management practices are recommended to be opted for successful weed management.
TL;DR: In this paper, the effect of water soluble phenolics of weeds associated with wheat crop (Vicia sativa, Trigonella polycerata, Lathyrus aphaca, Medicago polymorpha, Melilotus indica) on germinability and biomass production of wheat seedlings by using their water extracts at 2.5% and 5% (w/v) concentrations, respectively.
Abstract: Weeds associated with crops may impose their phytotoxic effects on crop plants through the release of their allelochemicals and hence seriously reduce crop productivity. The present study was conducted to investigate the allelopathic effect of water soluble phenolics of weeds associated with wheat crop (Vicia sativa, Trigonella polycerata, Lathyrus aphaca, Medicago polymorpha, Melilotus indica) on germinability and biomass production of wheat seedlings by using their water extracts at 2.5% (w/v) and 5% (w/v) concentrations and residues of the same weeds with 0, 15 and 30 d decomposition periods at 2% (w/w) concentration. The results showed that the water extracts of M. indica and V. sativa at 5% concentration imposed the most inhibitory effect on energy of germination (81%) and prolonged time to 50% germination (226%), respectively; by contrast, T. polycerata and M. indica extracts at the same concentration inhibited shoot (8%) and root fresh biomass (64%). However, shoot dry biomass was exalted by the weed extracts at both concentrations with maximum increase (29%) caused by the M.indica extract at 2.5% concentration; however, root dry biomass (46%) and root/shoot ratio (51%) were decreased by M. polymorpha and M. indica extracts at 5% concentration, respectively. Residues of L. aphaca and M. polymorpha with a 30 d decomposition period proved the most toxic regarding energy of emergence (85%) and time to 50% emergence (138%), respectively; while, shoot fresh (41%) and dry biomass (26%) production were hindered mostly by M. indica and M. polymorpha residues with a 30 d decomposition period. There was the highest decrease in root fresh (64%) and dry biomass (64%), and root/shoot ratio (64%) when treatment was performed with V. sativa residues without decomposition. The results show that leachates and residues of weeds inhibit wheat germinability and biomass production through release of allelochemicals, and they are a threat to profitable crop production.
TL;DR: Overall, there was a reduction in plant density in the pre-harvest period, however, Echinochloa colona and Oryza sativa occurred in density levels that may interfere with the cereal yield, indicating possible cases of herbicide resistance.
Abstract: The phytosociological method helps evaluate the vegetation composition. The objective of this study was to identify and quantify the main weed species present in irrigated rice. The phytosociological survey was carried out in three mainly rice monoculture, Clearfield® technology using properties in Itaqui-RS, between 2013 and 2014. For each property and period, a ½ ha representative area was selected and 10 random samples were collected, using a quadrat square of 1 m2. The sample colletion was conducted in two periods of time: during the irrigated rice crop initial growth and during the cereal’s pre-harvesting phase. All collected plants were identified and counted, allowing for their frequency, relative frequency, density, relative density, abundance, relative abundance, relative importance index and similarity index to be calculated. Eleven weed species belonging to five families were identified. Poaceae and Cyperaceae occurred more frequently. During the initial growth of rice, the Poaceae family presented the largest index of relative importance, mainly to Echinochloa crus-galli, Echinochloa colona and Digitaria horizontalis. Overall, there was a reduction in plant density in the pre-harvest period. However, Echinochloa colona and Oryza sativa occurred in density levels that may interfere with the cereal yield. Aeschynomene denticulata, Cyperus iria and Oryza sativa are not controlled efficiently, indicating possible cases of herbicide resistance. Our conclusions emphasize the importance of correct weed species identification for the management of Echinochloa colona and Cyperus ferax. Integrated management practices are necessary for efficient weed control, avoiding productivity loss in the region’s flooded rice fields.
TL;DR: Weed control using herbicides with the same mechanism of action can encourage the emergence of resistant biotypes or tolerant plants, an example of this is the occurrence of morning-glory in soybean crops in southern Brazil.
Abstract: Weed control using herbicides with the same mechanism of action can encourage the emergence of resistant biotypes or tolerant plants An example of this is the occurrence of morning-glory (Ipomoea sp) in soybean crops in southern Brazil In this sense, the aim of this study was to quantify the losses arising from two species of morning-glory weeding coexisting with soybean crop A field study was conducted in the 2013/2014 season The experimental design was a randomized block with four replications, with treatments being distributed in a factorial arrangement (2x2x5), which assessed the effect of competition on two soybean cultivars (TEC6029 and TEC7849) of morning-glory species (I triloba and I purpurea) in different population (0, 4, 8, 16 and 32 plants m-2) The interaction of soybean with different densities of morning-glory affects yield components The first eight morning glory plants have a more intense competition, reducing productivity by 45% and 27% for TEC6029 and TEC7849 cultivars, respectively
TL;DR: The results showed that the effects of nicosulfuron and glyphosate depended on treatment rate, duration of activity, test parameters and soil types, and in general, application of the herbicides significantly increased the activity of dehydrogenase and urease.
Abstract: The effects of the nicosulfuron and glyphosate herbicides on microbial activity in two soils with different physical and chemical properties (loam and sand) were investigated. Nicosulfuron was applied at the rates of 0.3, 0.6, 3.0 and 30.0 mg kg-1 soil and glyphosate at 32.6, 65.2, 326.0 and 3260.0 mg kg-1 soil in the laboratory. Changes in dehydrogenase and urease activity, as well as in microbial biomass carbon, were examined. Samples for the analysis were collected at 3, 7, 14, 30 and 45 days after herbicide application. The results showed that the effects of nicosulfuron and glyphosate depended on treatment rate, duration of activity, test parameters and soil types. In general, application of the herbicides significantly increased the activity of dehydrogenase and urease. Nicosulfuron had a stimulating activity on microbial biomass carbon in loam, while both herbicides demonstrated negative effects on the parameter in the sandy soil.
TL;DR: In this paper, a two-year field study was carried out to examine the impact of sunflower residues on soil properties, weed dynamics and productivity of mung beans, and concluded that sunflower residue incorporation at 6 ton ha-1 improved soil health, suppressed weeds and resulted in better seed yield (36%) and profitability of spring-planted mung bean.
Abstract: Continuous and excessive use of herbicides to control various weed biotypes is posing severe threats to soil and human health. Nevertheless, the strategy of using allelopathic crop residues and water extracts for weed control seems to be a sustainable and friendly option to reduce dependence on synthetic herbicides. In addition to controlling weeds, residues of allelopathic crops positively affected soil health. A two-year field study was carried out to examine the impact of sunflower residues on soil properties, weed dynamics and productivity of mung bean. The study was comprised of five treatments viz., control, sunflower water extracts at 10 and 20 L ha-1, and sunflower residues incorporation at 4 and 6 ton ha-1. Results indicated that application of sunflower water extracts reduced weed density by 5-26% and weed dry weight by 9-31%, while sunflower residue incorporation caused 44-57% reduction in weed density and 58-70% reduction in weed dry weight compared with the control. At mung bean harvest, total nitrogen and organic matter in soil were increased by 86% and 74%, respectively, with the incorporation of sunflower residues at 6 ton ha-1 as compared with the control. In case of soil enzymes, alkaline phosphatase and dehydrogenase were recorded at 186 mg NP g-1 soil h-1 and 38 mg TPF g-1 soil h-1, respectively, when sunflower residue was incorporated at 6 ton ha-1. In conclusion, sunflower residue incorporation at 6 ton ha-1 improved soil health, suppressed weeds and resulted in better seed yield (36%) and profitability (339 $ ha-1) of spring-planted mung bean.
TL;DR: Wild poinsettia and Alexandergrass negatively modified the LA and DM of the crop, demonstrating a greater competitive ability for the resources that are available in the environment.
Abstract: The objective of this work was to determine the competitive interaction of sweet sorghum cultivars BRS 506, BRS509, and BRS 511 with biotypes of Alexandergrass and wild poinsettia The adopted experimental design was the randomized block one, with four replications Treatments were arranged in a substitution series by proportions of 100:0, 75:25, 50:50, 25:75, and 0:100%, corresponding to 20:0, 15:5, 10:10, 5:15 and 0:20 plant per pot of sweet sorghum (cultivars BRS 506, BRS 509 and BRS 511) withweeds (Alexander grass/wild poinsettia) The leaf area (LA) and dry matter (DM) of sweet sorghum, Alexandergrass and wild poinsettia plants were determined 50 days after emergence Data about competitive abilities were analysed through the graphical analysis method, constructing diagrams based on yield or relative and total variations Indices of relative competitiveness, clustering coefficient and aggressiveness were also determined; all of them were relative indices There was competition for the same environmental resources between sweet sorghum cultivars and weeds, with mutual injury to the species involved in the community Wild poinsettia and Alexandergrass negatively modified the LA and DM of the crop, demonstrating a greater competitive ability for the resources that are available in the environment Wild poinsettia was less competitive than sweet sorghum cultivars, while Alexandergrass showed higher competitive ability than them The highest losses for the LA and DM variables were observed when species were in interspecies competition rather than intraspecies competition
TL;DR: The results indicate that barnyardgrass resistant accessions present a high resistance level to imazapyr+imazapic, and Integrated weed management should be adopted and alternative mechanisms of action as ACCAse and EPSPS inhibitors are still eficients controlling barnyard Grass ALS resistant accession.
Abstract: The introduction of Clearfield® system for irrigated rice production provided an effective management strategy in the selective control of weeds. However, the selection pressure caused by the continuous use of herbicides such as imazapyr+imazapic belonging to the imidazolinone chemical group, without the proper integrated management of weeds, has favored the selection of resistant accessions. The goals of this work were to confirm the resistance to ALS inhibitors in accessions of E. crusgalli var. mitis collected in rice fields of the state of Rio Grande do Sul and to evaluate the control with alternative herbicides registered for weed control. Three experiments were conducted in a greenhouse using plant seeds that survived the application of the herbicide imazapyr+imazapic, collected in irrigated rice producing regions with suspected resistance escapes. For dose-response curve study, three resistant accessions (ECH1 - Pelotas/Rio Grande do Sul, ECH27 - Arroio Grande/Rio Grande do Sul and ECH38 - Rio Grande/Rio Grande do Sul) and two susceptible accessions (ECH14 - Pelotas/Rio Grande do Sul and ECH44 - Rio Grande / Rio Grande do Sul) (factor A) and 11 doses of the herbicide imazapyr+imazapic (factor B) were selected. The results indicate that barnyardgrass resistant accessions present a high resistance level to imazapyr+imazapic. ALS inhibiting herbicides such as imazethapyr+imazapic, bispyribac-sodium and penoxsulam did not control the resistant accessions either. Integrated weed management should be adopted and alternative mechanisms of action as ACCAse (cyhalofop-butyl, profoxydim and clethodim) and EPSPS (glyphosate) inhibitors are still eficients controlling barnyardgrass ALS resistant accessions.
TL;DR: In this paper, the authors identify cross-resistance to herbicides from different chemical groups of ALS inhibitors (imidazolinones, sulfonylureas, pyrimidyl benzoates and sulfonanilides) and also PPO inhibitors (diphenylethers, phthalamides, oxadiazoles, triazolinone and pyrinogen oxidase) in E. heterophylla biotypes with multiple resistance to these herbicides.
Abstract: The characteristics of multiple resistance in Euphorbia heterophylla biotypes to herbicides that are inhibitors of ALS (Acetolactate synthase) and PPO (Protoporphyrinogen oxidase) and their responsible mechanisms are still not completely elucidated. The objectives of this study were to identify cross-resistance to herbicides from different chemical groups of ALS inhibitors (imidazolinones, sulfonylureas, pyrimidyl benzoates and sulfonanilides) and also PPO inhibitors (diphenylethers, phthalamides, oxadiazoles, triazolinones and pyrimidinediones) in E. heterophylla biotypes with multiple resistance to these herbicides; to analyze whether the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) constitute mechanisms that are responsible for the resistance to PPO inhibitors. Initially, the response to doses of herbicides from these different chemical groups was determined, using doses below and above the one recommended for the species. The control of E. heterophylla was determined, estimating the required doses for a 50 and 80% control reduction and calculating the resistance factors. The constitutive and induced activities of the SOD and POD enzymes were also determined. The results confirmed cross-resistance for all chemical groups of ALS and PPO inhibitors in the Bom Sucesso do Sul and Vitorino biotypes. The constitutive and induced activities of the SOD and POD enzymes were superior in plants from the E. heterophylla biotypes Vitorino and Bom Sucesso do Sul, contributing to their resistance to PPO inhibiting herbicides.
TL;DR: Evaluating the allelopathic potential of cover crops on the weed shrubby false buttonweed found the straw of the cover crops inhibited the germination and initial growth of the target plants, including lettuce and Spermacoce verticillata.
Abstract: Searching for alternatives to deal with weeds without the exclusive use of herbicides can increase the sustainability of agricultural production in the Amazon region. This study aimed to evaluate the allelopathic potential of cover crops on the weed shrubby false buttonweed (Spermacoce verticillata L.). Three straw levels (1; 2.5 and 5 mg cm-2) of thirteen cover crops (Cajanus cajan, Canavalia ensiformis, Crotalaria juncea, C. ochroleuca, C. spectabilis, Mucuna aterrima, M. cinereum, Pennisetum glaucum, Sorghum bicolor, S. sudanense, Urochloa brizanha cv. Xaraes, U. brizantha cv. Piata and U. ruziziensis) were assessed on germination and initial growth of weed and lettuce. We carried out two experiments (weed and lettuce) in a factorial scheme (cover crops x straw levels) with additional treatment (control without straw) in a completely randomized experimental design, with four replicates. The straw of the cover crops inhibited the germination and initial growth of the target plants. The highest straw levels promoted 44.0 and 78.8% reductions in radicle length in relation to the lowest dose (1 mg cm-2), for lettuce and Spermacoce verticillata, respectively. The highest sensitivity to allelochemicals occurred on the radicle. The major suppressive effects on weed germination were promoted by Cajanus cajan, Urochloa brizanha cv. Xaraes, Mucuna cinereum, M. aterrima, Canavalia ensiformis, Crotalaria juncea, C. spectabilis and U. ruziziensis. Cover crops use is an integrated practice management to control Spermacoce verticillata under no-tillage system.
TL;DR: Results showed that aqueous extracts of M. lathyroides mitotic caused reduced index with increased concentration, and cytotoxic activity was also observed for both extracts tested, since composition resulted in cell cycle changes and chromosomal abnormalities.
Abstract: The monitoring of phytochemicals with potentially toxic properties can be assessed by observing the physiological and cellular alterations of the test organism exposed. This present study aimed to evaluate the cytotoxic and genotoxic potential of aqueous extracts of leaves and roots of Macroptilium lathyroides weed on the cell cycle of lettuce. Bioassays were conducted in a germinator (25 oC) with aqueous extract at concentrations of 0, 5, 10, 20 and 40% p v-1, obtained from fresh leaves and roots. For biological, lettuce root meristems were used for the preparation of slides using the technique of squashing. All blades were observed with an optical microscope at a magnitude of 400x. A total of 5,000 cells were analyzed for each treatment, and the number of cells in each phase of mitosis was recorded. Possible presence of chromosomal abnormalities was verified, such as chromatid breaks, anafasic bridges, loss of whole chromosomes or micronuclei formation. These analyzes were conducted only on a qualitative level. Results showed that aqueous extracts of M. lathyroides mitotic caused reduced index with increased concentration. Genotoxic activity was also observed for both extracts tested, since composition resulted in cell cycle changes and chromosomal abnormalities.
TL;DR: It is possible to state that guineagrass under water restriction have less control efficacy when treated with glyphosate, because the routes of penetration of hydrophilic herbicides are reduced due to the lower hydration of the cuticle in these plants.
Abstract: The action of herbicides on weeds that develop under water deficit can be compromised, because the routes of penetration of hydrophilic herbicides are reduced due to the lower hydration of the cuticle in these plants. Moreover, hydrophobic compounds found in the epicuticular wax coating of plants under water stress, hinder the penetration of hydrophilic compounds. This study evaluated the control efficiency of glyphosate on guineagrass plants when submitted to different water deficits. The study was conducted in a greenhouse, and treatments were composed of guineagrass plants submitted to three soil water conditions [low water deficit (13%), intermediate water deficit (10%) and high water restriction (8%)], three doses of glyphosate (0.0, 270.0 and 540.0 g ha-1) and two phenological stages of plant development (4-6 leaves and 1-3 tillers). The water management started when plants presented two developed leaves. Visual evaluations were performed 7, 14, 21 and 35 days after the application of the herbicide; the morpho-physiological parameters of the specific leaf area, stomatal conductance and the difference between the environment temperature and the leaf temperature on the day of the herbicide application were also analyzed at the end of the study, as well as the dry matter of shoot and root. With the increase of the water restriction, there was a decrease in the analyzed morpho-physiological parameters, as well as in the dry matter accumulation of the shoot and roots of the studied plants. Plant control was more efficient when a 540 g ha-1 dose of glyphosate was applied, and when they were controlled at their vegetative stage of 1-3 tiller, and with a water management of 13%. It is possible to state that guineagrass under water restriction have less control efficacy when treated with glyphosate.
TL;DR: In this article, the authors compare the efficacy of different weed management through a burndown application followed by sequential applications of herbicides to control Conyza spp in a randomized block design with four replications.
Abstract: The goal of this study was to compare the efficacy of different weed management through a burndown application followed by sequential applications of herbicides to control Conyza spp Thus, four field experiments were conducted, two in the western region of Parana state (E1 and E2), one in Jatai, Goias state (E3) and another one in Ibiruba, Rio Grande do Sul state (E4) Conyza spp in this area had a height ranging between 25 and 60 cm Treatments were arranged in a randomized block design with four replications The primary herbicide treatments were 2,4-D + glyphosate + diclosulam, chlorimuron-ethyl + glyphosate + 2,4-D, and four doses of diclosulam + halauxifen-methyl + glyphosate These treatments were applied singly or in sequential applications, made 10 days before the application of ammonium glufosinate, paraquat or saflufenacil In all experiments, results showed efficient (90%) control of treatments containing diclosulam + halauxifen-methyl in combination with glyphosate on day 35 DAA, regardless of sequential applications Applications of 2,4-D + glyphosate + diclosulam or chlorimuron-ethyl + glyphosate + 2,4-D were not effective against Conyza spp at E1 and E2 locations, possibly due to the greater weed size (50 to 60 cm) at these sites However, the same treatments were effective at E3 and E4 locations, where weeds were smaller Diclosulam + halauxifen-methyl + glyphosate associated with ammonium glufosinate, paraquat or saflufenacil in sequential applications, proved to be an important tool to manage Conyza spp at different growth stages