Journal of Research in Weed Science

Abstract The present study was conducted to evaluate the relative phytotoxic effects of different concentrations (15, 25, 50, 75 and 100%) of aqueous extract from stem and root of Parthenium hysterophorus on the rate of seed germination, length of root and shoot, and Seed Vigour Index (SVI) of Cicer aeritinum. In laboratory condition the experiment was set up in petri dishes, each petri dish contained ten seeds. Each treatment had ten replicates. A control condition was maintained using distilled water in place of stem or root aqueous extracts of Parthenium. The rate of seed germination in Cicer aeritinum in stem and root aqueous extracts of different concentrations decreased from 5% to 79%, and 0.0% to 22%, respectively. The inhibition value in root length in stem extracts varied from 11.14% to 85.96% and in root extract was from 13.14% to 64.25%. The inhibition in shoot length in stems and roots extracts varied from 14.67% to 50.19% and 73.68% to 85.86%, respectively. The Seed Vigour Index (SVI) value decreased from 16.38% to 94.99% in stem extract and 32.11% to 77.37% in root extract. The stem extract of Parthenium was more phytotoxic than the root extract in Cicer aeritinum. When the data collected were analysed using Tukey HSD and Post HOC Tests the phytotoxic impacts of plant parts (stem and root); treatments (15, 25, 50, 75 and 100% concentrations); and interactions between plant parts and treatments were highly significantly different at p < 0.000. Thus the present study indicated that the aqueous extracts of stem of Parthenium were recorded more phytotoxic than root extract on germination and growth of Cicer aeritinum.

Abstract The objective of this work is to evaluate the allelopathic effects of the aqueous and methanolic extract of rice straw (Oryza sativa L.) on wheat (Triticum aestivum L.) and wheat weeds, including wild oat (Avena fatual L.) andcanary grass (phalaris minor). Three concentrations (5, 10 and 20%) of each aqueous and methanolic extract as well as the recommended dose of chemical herbicide clodinafop propargyl (140 g/ fed) and diclofop-methyl (750 ml/fed) were used on the tested plants as a post-emergence treatments. Response of the treated plants were measured by using 7 parameters includes: germination %, seedling shoots and root length, dry weight, chlorophyll content, plant height, plant number and spike length and weight of treated wheat. Data of each parameter were discussed separately. Generally, treatments with higher concentrations (20% rice straw aqueous and methanolic extract) showed negative effects on wheat weeds at the same time cause increasing the wheat productivity. However, rice straw methanolic extracts showed suppressive effect on wheat seed. Comparing the efficacy of the straw extract with the tested conventional herbicides, the obtained data showed that clodinafop propargyl and diclofop-methyl were the most effective against the time tested weeds as it severely reduced the weed population and other tested parameters.

Abstract Herbicides have increasingly become a key component on crop production system because they offer the easiest, cheapest and timely weed management, resulting in higher yield and profit. A single herbicide application in field conditions in most of the cases is not enough to control diverse weed flora. In such situations, tank mixtures of herbicides may provide a prime option to control a broad spectrum of weeds. Cyperus rotundus L., a world’s most tenacious weed, is becoming a problematic weed in conservation crop production systems. A two-year study (2013/14 and 2014/15) was established in South-West Bangladesh to evaluate the effect of application timings and sole and tank mixtures of 2,4-D and ethoxysulfuron herbicides on weed suppression and performance of wheat. 2,4-D and ethoxysulfuron were applied solely and as tank mixtures at 10, 20, and 30 days after sowing (DAS) and these treatments were compared with completely weedy and weed-free treatments. In controlling weeds, tank mixtures of 2,4-D and ethoxysulfuron performed better than their sole application at any application timing; however, at the earliest time (10 DAS), the combination created toxicity to wheat plants, resulting in 10-22% and 11-32% less wheat plant density and biomass, respectively, compared with their sole application. Tank-mix herbicides reduced C. rotundus biomass by 87-91%, 88-100%, and 79-80% when applied at 10, 20, and 30 DAS, respectively, compared with the weedy plots. The plots applied with tank mixtures at 20 and 30 DAS produced wheat grain yield similar to that of weed-free plots, indicating that the tank mixture of 2,4-D plus ethoxysulfuron herbicides is the best option to control weeds without any toxicity to wheat plants.

Abstract Parthenium hysterophorus (Asteraceae) is known as one of the most troublesome weeds, causing severe environmental, economic, human and animal health problems in India and around the world. During a series of surveys for natural enemies of P. hysterophorus, a leaf blight pathogen was isolated from the affected parts of the Parthenium following the standard isolation techniques using potato dextrose agar (PDA) media. Koch’s postulates were performed and found satisfactory for the isolate and proved to be pathogenic to this weed. On the basis of cultural, morphological and molecular characteristics, the pathogen was identified as Alternaria macrospora MKP1. The pathogen was studied for various histopathological parameters and the results showed that this pathogen has a good potential to control Parthenium weed.

Abstract Seed germination of some crops (Brassica campestris and Triticum aestivum) and weed seeds (Ageratum conyzoides, Bidens pilosa, Cyperus rotundus and Galinsoga parviflora) was studied under different environmental conditions like moisture (concentrations 3, 6, 9, 12, 15ml), temperature (5, 10, 15, 20 and 25˚C), pH (value 4, 5, 6, 7, 8 and 9) and light (normal, red, yellow, blue, green and dark color). For the crops too much lower or higher moisture was not favorable for germination and growth. Experiments under different moisture conditions showed that C. rotundus and G. parviflora do not require more moisture to germinate and grow. Seed germination of both crops enhanced insignificantly at 15 to 20˚C treatments. Seed germination of all weed seeds was insignificantly high at 10 to 15˚C. The percentage of seed germination of both crops increased significantly in normal and green light. Seed germination of A. conyzoides, C. rotundus and G. parviflora was insignificantly different in normal, red, yellow and green light. Germination of all weed seeds was completely inhibited by blue and dark light. The shoot and root length of weed A. conyzoides was found to be significantly high (P=0.05) in yellow light treatment, but in B. pilosa, it was high in red and green light. Similarly in C. rotundus, shoot and root length were high in normal light but in of G. parviflora it was high in green light treatment. Seed germination and seedling growth were higher in pH5-7 in most cases.

Abstract A field experiment was conducted to assess the growth, productivity and profitability of rice (Sukhadhan-3 variety) under different methods of weed management at Bhanu-11 Rupakot, Tanahun during rainy season 2017. The experiment was laid out in randomized complete block design with three replications and ten treatments. The phenological, growth, yield and yield attributing characters were observed in the experiment. Results revealed that maximum grain yield (5.91 ton ha^-1) was obtained in application of butachlor at 4 days after transplanting (DAT) which was statistically at par with all other treatments except single manual weeding, single cono-weeding and non-weeding plots (3.66 ton ha^-1). The highest grain yield obtained from this treatment was might be due to higher number of effective grains per panicle (203 grains), less sterility (6.4%), high test weight (30.7g) with good harvest index (38.4%). Although the single application of butachlor as pre emergence spray showed highest grain yield which seems economically viable and profitable practice to the farmers but it is not environmentally safe to the whole universe.

Abstract A study was conducted to determine the effect of climate gradient and previous crop on weed flora structure in pearl millet crop. Thus, floristic surveys were carried out during 2016 and 2017 crop years on station in Sahelian, Sudano-sahelian and Sudanian zones of Senegal. The results revealed that flora consisted of 81 species distributed in 59 genera and 19 families. Higher number of species were recorded in Sudanian zone (Kolda and Séfa) with respectively 61 and 45 species and the lowest number of species were found at Vélingara in Sudano-sahelian zone (28 species) and Sinthiou Malème in sahelian zone (28 species). According to previously crop, the higher number of species was registered in previous fallow (64 species) followed by previous pearl millet (57 species). In previous mucuna and peanut, flora is 14 percent lower than species recorded in previous fallow. Spectrum analysis indicated that the flora is largely dominated by therophytes, which includes 81.5% of the recorded species. It’s presence in pearl millet field was higher in Sahelian zone (93%) followed by Sudano-sahelian zone (89%) and Sudanian zone (Kolda and Séfa) with respectively 80 and 84% of recorded species. Domination of therophytes is more accurate in plot with previous fallow (86%) followed by previous millet (82%), previous peanut (81%) and previous mucuna (79%). Also, it was observed a decreasing of perennial species from Sudanian to Sahelian zone.

Abstract Glyphosate is an effective post emergence herbicide for weed control in tea. However, dose and timing of any new formulation need to be evaluated before being its recommendation to the growers. The weed flora of the experimental field was composed of Ageratum conyzoides (21.9%), Ageratum houstonianum (21.3%), Chromolaena adenophorum (13.0%), Bidens pilosa (9.6%), Lantana camara (6.2%), Cynodon dactylon (6.0%), Fragaria vesca (5.6%), Imperata cylindrica (5.2%), Polygonum alatum (5.1%) and Erigeron canadensis (5.1%). The new formulation glyphosate 71% SG was found to be comparable to the existing formulation glyphosate 41% SL against Ageratum conyzoides, A. houstonianum, Chromolaena adenophora, Bidens pilosa, Fragaria vesca, Polygonum alatum, Erigeron canadensis, Imperata cylindrica and Cynodon dactylon in reducing their population upto 120 days after application (DAA). Glyphosate 71% SG did not show any toxic symptoms on tea crop and tea leaf yield was similar as under standard formulation used in the present study. Glyphosate 71% SG (ammonium salt) sprayed at 6 kg/ha gave highest tea leaf yield (1940 kg/ha) which was statistically similar to the Glyphosate 71% SG (ammonium salt) applied at the rate of 3 kg/ha (1895 kg/ha). It was also comparable to the market sample. Uncontrolled growth of weeds even for a one season reduced tea leaf yield by 48.5%. The bulk density, water holding capacity, moisture content, soil pH, electrical conductivity, available NPK and organic C were not influenced significantly at harvest. The test herbicide glyphosate 71% SG and the market sample glyphosate 41% SL had increased the population of total bacteria, fungi and actinomycetes at harvest over their initial population. However, there was a slight decrease in the population of this microflora immediately after the application of herbicide not due to the herbicide but owing to seasonal variation as the differences between treatments were not significant.

Abstract A field experiment was conducted in pre-monsoon season during 2017 and 2018 at National oil seed research program, Nawalpur, Sarlahi, Nepal, to study the impact of weed management practices in groundnut production. Pendimethalin as pre-emergence, while Metribuzin, Propaquizafop at 100 g per hectare, Quizalofop ethyl at 100 g per hectare, as post emergence was used along with integration with hand weeding and intercultural operation. The result revealed that supplement of the hand weeding after the application of the pre-emergence herbicides pendimethalin was found effective in  reducing  the weed severity and improves the growth and yield attributes and ultimately yielded 2101 kg ha^‑1. This treatment also recorded the highest gross and net return (NRs 168080 and 48470) and benefit cost ratio (1.4) thus, this integrated weed management practice could become effective and economic under southern belt terai agro climatic condition of Nepal.

Abstract Field experiments were conducted to identify the effective tank-mix combinations of HPPD (p-hydroxyphenylpyruvate dioxygenase) herbicides (Mesotrione, tembotrione and topramezone) with atrazine for post-emergence grass and broadleaf weeds control in maize crop during the three kharif seasons of 2013 to 2015. The dominant weeds infested the experimental plots were crow footgrass{Dactyloctenium aegyptium (L.) Willd.}; large crabgrass, Digitaria sanguinalis (L.) Scop; barnyard grass, Echinochloa crus-galli (L.) Beauv.; Digera arvensis Forsk. and Horse purslane(Trianthema portulacastrum L.). All the three HPPD herbicides showed good crop safety and among them, for grass weed control, mesotrione 120 g ha^-1 applied alone was inferior to topramezone 50 g ha^-1 and tembotrione 120 g ha^-1 applications. However, reduced doses of the HPPD herbicide (mesotrione 90 g or topramezone 37.5 g or tembotrione 90 g ha^-1) with atrazine 900 g ha^-1 as post-emergent tank-mixture gave better weed control and maize yield than their solo applications. The uncontrolled weed competition reduced the maize yields by 31.5 to 68.5%. Overall, topramezone + atrazine provided comparable or superior control of annual grass and broad-leaf weeds than mesotrione + atrazine or tembotrione + atrazine. Post applied (15-18 days after sowing) atrazine 1000 g ha^-1 was better to pre-emergence atrazine in weed control and producing maize yield. In another field study, replacement of maize with puddle rice completely reduced the Johnsongrass {Sorghum halepense (L.) Pers.} density and therefore, in areas having its infestation, rice can be an alternative to contain its problem. The synergistic interactions between HPPD-inhibiting herbicides, and atrazine, were also observed against three grass weeds in pot experimentation as higher weed control achieved than what was expected from Colby’s equation. The results show that tank-mixture of topramezone or tembotrione with atrazine can be effectively used for diverse weed flora control in maize.

Abstract The study was conducted with the aim of assessing the distribution and abundance of invasive alien plant species (IAPS) in two administrative Zones (1 and 3) of the Afar region. Data were collected using systematic sampling technique and regular intervals of 10 km were used during the field survey. The following weeds Calotropis procera, Cryptostegia grandiflora, Jatropha curcas, Lantana camara, Opuntia stricta, Parkinsonia aculeata, Parthenium hysterophorus, Prosopis juliflora, Senna occidentalis, and Solanum incanum were recorded in this study. Prosopis was found in 38% of the 91 sample waypoints in the altitude range of 347-1005 meters above sea level whereas C. procera was recorded in 28% of the interceptions between 347 m and 1010 meters above sea level. P. hysterophorus occurred in 15 % of the waypoints in the altitudes ranged from 603 to 1005 meters above sea level. C. grandiflora and P. aculeata were observed respectively in 3% and 6% of the interceptions while L. camara and O. stricta were recorded only at a single waypoint. Higher abundance levels were observed for P. juliflora and C. procera. The majority of the IAPS were found infesting diversified habitats such as road sides, cropland, grazing land, riversides, forest and habitation areas. Awash Fentale district had the highest IAPS richness by possessing all the recorded species. The detailed distribution maps of the identified IAPS were developed and prioritization and ranking of invasive species was made based on abundance levels. The results of this study can be used in invasive weed management or extension programs that aim to tackle major IAPS problems in the region.

Abstract Striga hermonthica (Del.) Benth., Orobanchaceae, is an obligate root parasite on important cereal crops. The aim of this study is to investigate variability and host specificity in the early developmental stages of S. hermonthica parasitism in response to in-situ root exudates of sorghum. Field surveys were conducted during the seasons 2013/14 in Striga endemic areas in Sudan to collect seeds from the parasite. Fifteen S. hermonthica populations were collected. An in vivo experiment was conducted at the University of Gezira, Sudan to study the effects of in-situ root exudates of three sorghum cultivars on percentage of seed germination, haustorium initiation, attachment and penetration. Treatments were arranged in a factorial completely randomized design with three replicates. Data were subjected to the analysis of variance (P £ 0.5). The results revealed the highest percentage of seed germination (46.9-57.5 %), haustorium initiation (73.8-77.9 %), attachment (38.4–40 %) and penetration (20.7–23.7 %) into sorghum root was induced by in-situ root exudates of sorghum cv. Abu-70 and by sorghum cv. Wad Ahmed. While, the lowest percentage of seed germination (53.5 %), haustorium initiation (45.2 %), attachment (5.8 %) and penetration (1.5 %) into sorghum root was induced by in-situ root exudates of Hakika. The results also revealed that percentage of seed germination, haustorium initiation, attachment and penetration of S. hermonthica populations collected from infected sorghum in response to sorghum in-situ root exudates was the highest. While, the percentage of seed germination, haustorium initiation, attachment and penetration of S. hermonthica populations collected from infected millet in response to sorghum in-situ root exudates was the lowest. This study confirms the existence of two levels of physiological specialization in S. hermonthica populations in Sudan. Moreover, two strains of S. hermonthica are one specific to sorghum and the other to millet. 

Abstract Oilseed rape (OSR) has one of the highest potential for gene flow through seed and pollen. Volunteer plants are one of the most important sources of contamination of OSR crop of different quality cultivars. The aim of this study was to estimate the abundance of soil seed bank after the harvest of high erucic (HE) cultivar Maplus and to determine biochemical and molecular characteristics of OSR volunteers. The investigation comprised volunteers of oilseed rape obtained from the soil seed bank in two localities in Poland: Dlon and Zielecin (Greater Poland Voivodeship). The seeds of volunteers and reference cultivars were analyzed using biochemical (erucic acid and glucosinolates [GLS]) and molecular biology methods. In seeds of volunteers, erucic acid content ranged from 0 to 57.4% of all fatty acids and glucosinolate content ranged from 5.2 to 105.0 µmol g⁻¹ of seeds. In sowing seeds of the cultivar Maplus, the erucic acid content was 57% and total glucosinolates were 12.6 µmol g⁻¹ of seeds. RAPD markers were used to determine genetic similarity coefficient and relationship between polymorphic RAPD markers and erucic acid and total GLS content. Twenty RAPD markers showed statistically significant association with erucic acid and GLS content in seeds. Volunteers originating from the investigated soil seed bank were characterized by different content of erucic acid and GLS in seeds typical for different types of oilseed rape cultivars: double low (00, canola type), cultivars with zero erucic acid and high GLS content (0HG) and traditional cultivars with high erucic acid and high GLS content (HEHG). The results of this study, especially the presence in soil seed bank the seeds of very old cultivars, confirm that seeds of rapeseed of different origin may persist for a long time at the stage of secondary dormancy.

Abstract A field experiment was undertaken to determine optimum combination of weed management practices and inter-row spacing levels for effective weed control in maize at Bako agricultural research center, Western Oromia, Ethiopia during 2018 main cropping season. The treatments included pre-emergence s-metolachlor 290 g/L + atrazine 370 g/L (1.0, 2.0 and 3.0 L ha^-1), hand pulling and hoeing 25 and 45 days after sowing (DAS) and weedy check in combination with inter-row spacing levels (65, 70, 75, and 80 cm). The experiment was laid out in a randomized complete block design with a factorial arrangement in three replications. The experimental field was infested with 22 weed species belonging to 12 families, out of which 77.3 %, 18.2 % and 4.5 % were broad leaved, grass and sedges, respectively. Weed management practices (WMP), inter-row spacing (IRS) and their interaction significantly influenced the weed density, dry weight and weed control efficiency at 25 and 70 DAS. All parameters of the crop were significantly affected by WMP and IRS. However, their interaction was non-significant except for number of ear per plant and grain yield. The highest grain yield was recorded in inter-row spacing of 65 cm treated with hand pulling and hoeing 25 and 45 DAS (10492.0 kg ha^-1). Whereas, the lowest grain yield (2237.0 kg ha^-1) was obtained from weedy check plot at 80 cm inter-row spacing. On the other hand, maize planted at 65 cm IRS in combination with 2 L ha^-1 s-metolachlor 290g/L + atrazine 370 g/L gave comparable grain yield which was statistically at par with that of hand pulling and hoeing 25 and 45 DAS and 3 L ha^-1 s-metolachlor 290g/l. + atrazine 370 g/L involving the same IRS. Hence, putting the environmental concern and scarce labor force under consideration, the use of reduced rate (2 L ha^-1) of herbicide in combination with narrower IRS would be the best option for effective weed management in maize. Furthermore, integration of narrower IRS with other weed management treatments enhance maize grain yield there by improving weed control efficiency.

Abstract Striga hermonthica is widespread in several regions of Burkina Faso. It attacks crops of agronomic interest, causing losses ranging from 20 to 100% of grain yield in sorghum varieties. This study carried out at the weed science laboratory from October 2022 to February 2023 aims to identify sorghum varieties resistant to Striga hermonthica and local plants that inhibit or stimulate its germination. Fifteen varieties of sorghum has been evaluated for their germination stimulant capacity production using the agar gel method. The roots of two seedlings of each variety were buried in the opposite position in the agar medium containing Striga seeds. The effect of nine local plants on Striga hermonthica seeds germination has been evaluated by preparing 10% aqueous extract for each plant by macerating a mass of 10 g of powder in 100 ml of sterile distilled water. The inhibitory effect was estimated by conditioning the Striga hermonthica seeds during 14 days in each of the plant aqueous extracts and the stimulatory effect by the application of aqueous extracts on the Striga hermonthica seeds. The results revealed Rsoe 38 (MGD=0.74cm), Icsv 1049 (MGD = 0.74cm), Ouédzouré (MGD = 0.81cm), Grinkan (MGD = 0.85cm), Rsoe 15(MGD = 0.85cm) and B 35 (MGD = 0.97cm) as resistant to Striga hermonthica germination. Parkia biglobosa and Tephrosia purpurea have proved effective in inhibition while Andira inermis and Albizia zygia stimulate it. The promotion of resistant sorghum varieties and plants with inhibitory or stimulatory effects could be an important asset for the biological control of Striga hermonthica in the most infested areas.

Abstract Tea is regarded as one of the most significant and affordable beverages consumed in more than 65 nations throughout the world. Its productivity is at risk because of the various pests infecting the tea plants. Among these, Mite pests in tea are highly damaging, tenacious, and difficult to eradicate. Oligonychus coffeae or Red spider mites are the most prevalent causing huge loss to the tea industry. The control measures using chemical pesticides have a negative impact on the quality of tea and make it unfit for human consumption. In this context, floral diversity can be explored for the effective control of pests. The present study envisages the comparative analysis of pesticidal efficacy of two common weeds in the tea garden of the Terai and Dooars region of North Bengal, India.The aqueous extracts of Justicia adhatoda and Polygonum hydropiper (L.) as biocide employed in this study demonstrated substantial acaricidal and oviposition deterrent action against the tea Red Spider Mite Oligonychus coffeae after 48 hours of application. The results of this study showed that aqueous extracts of the above-mentioned plans are promising biocontrol agents against the tea red spider mite Oligonychus coffeae. This aqueous extract may have the potential to be an effective acaricide in the future at a reasonably low cost.