Journal of Research in Weed Science
Volume:3 Issue: 2, Jun 2020

Coastal areas are famous for its diversity and abundance of marine flora and fauna. Several tonns of seaweeds grows annually and during low tide they are easily avaliable either in growing or drift form. The current investigation was focus to target these marine flora to provide an alternative to toxic colorants. The brown seaweed, Stoechospermum marginatum were collected form the coastal area of Arabian sea during low tide. Seaweed colorants can be used as sustainable and eco-friendly source to make a value added product. Extraction process were optimized by varying solvent medium (alkali, acidic and distilled water), solvent concentration and extraction time. Eco-friendly metal salt like ferrous and alumium sulphate were used to developed twenty-four soft shades on S/J 100% cotton. Dye exhaustion, color measurements and fastness properties such as wash, crock and light fastness of resultant fabric have been studied. The optimized condition of extraction process was 5g/L sodium hydroxide for 3hrs processing time. The dyed fabric having 5g/L sodium hydroxide extarcted dye and mordanted with ferrous sulphate shows maximum exhaustion percentage as well as good to very good fastness property while the Δa and Δb values of color measurements shows that the dyed fabric has reddish-yellow shade.

The rapid emergence of herbicide-resistant weeds has further added complexity to the management of weeds in Australian cotton farming systems. Fleabane (Conyza bonariensis L) has been identified by the cotton industry as being potentially resistant or at risk of developing resistance. Thirty-seven C. bonariensis populations were collected in the 2014-2015 cotton season from 9 cotton farming regions in Queensland and New South Wales. Glasshouse screening trials showed that 27 populations (73%) expressed resistance to glyphosate salt at rate of 0.68 kg a.i ha-1 applied at the rosette stage. Another 9 populations (24%) were categorised as developing resistance. A dose response study of 4 selected resistant populations using glyphosate rate of 0, 0.34, 0.68, 1.36, 2.72, and 5.44 Kg a.i ha-1 showed a high level of Resistance Index (RI) ranging from 3.5 to 7.0 and the dose-response model revealed that 3 to 4 times more glyphosate is required to control resistant C. bonariensis populations. These results further confirm the frequent reports of reduced efficacy of glyphosate against fleabane in northern cotton farming systems of Australia. To reduce the risk of resistance other non-glyphosate tactics are needed in the weed management toolbox.

Echinochloa colona (L) Link. is a problematic annual grass weed in summer fallows in northern Australian cropping regions where repeated use of glyphosate has resulted in the evolution of glyphosate resistance. Pot trials conducted on E. colona populations collected from northern Australia identified 34 glyphosate resistant populations out of 65 populations tested, with resistance levels varying between 2 and 11-fold. The technique of AFLP (amplified fragment length polymorphism) was used to investigate genetic diversity within and between two resistant and one susceptible population. Within these three populations, a total of 354 fragments were identified with 99.2% being polymorphic. The frequency of polymorphic fragments within the 30 individuals from each of the two resistant populations (81.0 and 83.9%) was similar to the susceptible population (80.8%), suggesting no apparent selection bottleneck associated with resistance evolution. The large genetic diversity present within populations suggests a significant level of outcrossing between individuals. A high level of genetic diversity among the individuals was identified across a single individual examined from each of 62 populations. These individuals clustered into four main groups with three isolated accessions. Individuals did not cluster geographically; additionally, individuals did not cluster by resistance or susceptibility to glyphosate either. The results of this study suggest glyphosate resistance evolved independently across a wide geographical region in northern Australia and the large genetic diversity within populations likely contributed to rapid resistance evolution.

Weeds are ubiquitous and eternal pests. In India, the total annual loss of agricultural produce by weeds, insects, diseases and other pests are estimated to be 37%, 29%, 22% and 12%, respectively. Weeds are, mainly, autotrophs, but few are heterotrophs/parasitic such as Orobanche/ Phelipanche sp (Broomrape). Several species that are dominant across the world are Orobanche cernua, Orobanche crenata, Phelipanche ramosa, Phelipanche aegyptiaca, Orobanche cumana, and Phelipanche muteli. Orobanche is an important holo-root parasitic weed and cause yield losses of many economically important crops. The damage by Orobanche can range from 0-100%. Studies highlighted annual crop losses due to Orobanche infestation was to the tune of $1.3 to 2.6 billion worldwide.A Orobanche plant can produce more than 500,000 seeds, whose longevity may vary from 2-20 years. The distribution, species diversity and biology of this weed have been discussed in this review. Sound management strategies involving physical, cultural, biological and chemical options, and above all, integrated Orobanche management have been contemplated as well. New bio-technological approach that must trigger to develop host plant’s resistance against Orobanche and recommended selective herbicides should be envisaged for better Orobanche management.

A field experiment was conducted to assess the growth, yield and profitability of wheat under different herbicides application in Kapilvastu and Rupandehi district, Nepal during winter season of 2018. The experiment was laid out in Randomized Complete Block Design (RCBD) with four treatments and five replications. The four treatments comprised of Pendimethalin 30 EC at 3.3 l ha-1 as a pre emergence herbicide, sulfosulfuron 75 WG at 33.3 g ha-1 as post emergence, pendimethalin 30 EC at 3.3 l ha-1 followed by sulfosulfuron 75 WG at 33.3 g ha-1 and weedy check (control treatment). Results revealed that application of pendimethalin 30 EC at 3.3 l ha-1 followed by sulfosulfuron 75 WG at 33.3 g ha-1 significantly reduced the weed population and produced higher wheat grain yield (4487 kg ha-1). Economic analysis of different herbicides application also showed the highest net returns (NPR. 50,940 ha-1) for application of pendimethalin followed by sulfosulfuron treatments. Among the tested herbicides, both pendimethalin and sulfosulfuron were found effective to weed management and profitable over weedy check.

Weeds are among the most harmful factors limiting sorghum production under Sudanian conditions of southern Senegal. Despite, the taxonomic structure of the flora is relatively well known, few studies have focused on crop-weed competition. Field experiment was carried out to determine the critical time for weed competition in grain sorghum. Ten treatments, weedy for initial 15, 30, 45 and 60 DAS and then weed-free, and weed-free for initial 15, 30, 45 and 60 DAS and then weedy, weed-free and weedy up to harvest were assigned in a randomized block design with four replications. The beginning and the end of critical period of weed competition were determined respectively under fertilized and unfertilized conditions. The results showed that more the weeds competition is longer, more sorghum parameters of growth and yield are reduced. Sorghum yield were significantly influenced by many factors such as year, nitrogenous fertilization and weeding periods. The highest plant height, dry matter, and yield were recorded in weed free treatment followed by weed free up to 60 DAS and weedy up to 15 DAS. Plant height, dry matter and yield decreased significantly with each increase in competition period. Therefore, the lowest growth parameters and yield were noticed in weedy check treatment followed by weedy up to 60 DAS and weed free up to 15 DAS. Moreover, our findings showed that sorghum height, dry matter and grain yield increased significantly under fertilized conditions compared to unfertilized conditions, which is widely used in traditional cropping system. The maximum competition between crop and weed was between 15-45 and 15-55 DAS under unfertilized conditions (F0) and 10-55 and 15-55 DAS under fertilized conditions (F1), which can be considered as critical period of crop-weed competition. The weeding practice should be adopted during these periods for getting optimum sorghum production under Sudanian conditions of Senegal.

Forests in Mauritius are facing an alarming rate of encroachment by alien plant species which are changing the ecosystem function, equilibrium and composition of species and richness. Mauritius being a small tropical island is one of the recently colonized areas of the world where only a few descriptions of species composition and diversity exist. Invasive plant species are controlled by mechanical, chemical and biological methods. Efficient herbicide and suitable application methods were assessed for the control of Tabebuia pallida (Tecoma) in a forest area managed by the National Parks and Conservation Services (Mauritius). Effectiveness of herbicides to ringed barks showed Round-up (100 %) to be most effective compared to Triclon (73%) and Tordon 101 (40%). Drastic changes were observed with Roundup, irrespective of the application methods used. Significant differences were found among cut stump, ring barking and drilling application methods. Cut stump method was much more effective compared to the other two treatments. Ring barking also proved to be successful to some extent. Application of herbicides through drilling was ineffective. The use of herbicides was a significant factor in the death rate of the invasive species.

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.

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.

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.