Journal of Research in Weed Science
Volume:4 Issue: 2, Jun 2021

The presence of monocotyledonous and dicotyledonous weeds resistant to glyphosate in the same area makes tank mixtures of herbicides necessary. However, mixtures containing latifolicides and graminicides may result in less effectiveness. This study aimed to evaluate the interactions of auxin-mimic herbicides with acetyl-CoA carboxylase (ACCase) inhibitors. Experiments were conducted in two consecutive years in an area with a high infestation of fleabane and sourgrass, with history of resistance to glyphosate. The average heights of fleabane and sourgrass plants were, respectively: 30 and 70 cm in the first year; 80 and 120 cm in the second year. Herbicides dicamba, 2,4-D, clethodim, quizalofop and glyphosate were applied alone or in combinations with each other, in a completely randomized design, with thirty treatments and four replications. The results obtained in the control evaluation at 35 days after application were analyzed by Colby’s method. For fleabane control, in the two years evaluated, there were no problems of antagonism of auxin mimics with ACCase inhibitors. However, mixtures of ACCase inhibitors with 2,4-D were more antagonistic than mixtures with dicamba in sourgrass control, since for double mixtures between auxin mimics and ACCase inhibitors, interactions with 2,4-D were antagonistic in 62.5% cases, while for dicamba was 12.5%. In addition, antagonism effects were more pronounced in larger plants of sourgrass, and in mixtures with quizalofop, compared with clethodim. Tank mixtures of glyphosate and clethodim or quizalofop were synergistic for the control of sourgrass.

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh from June to November 2018 to investigate the effect of application of lentil and grass pea crop residues on weed management and crop performance of T. aman rice. The experiment consisted of three variety i.e. BR11, BRRI dhan49 and Binadhan-7 and five treatments of crop residues such as no crop residues, lentil crop residue @ 2 t ha-1, grass pea crop residue @ 2 t ha-1, combination of lentil and grass pea @ 1 t ha-1 of each and hand weeding. The experiment was laid out in a randomized complete block design with three replications. The maximum weed growth was noticed with the no crop residues treatment, the minimum was found in hand weeding. The highest percent weed inhibition of 83.95%, 80.87%, 82.21% and 81.49% was obtained from Echinochloa crusgalli, Scirpus juncoides, Monochoria vaginalis and Marsilea quadrifolia L. respectively caused by hand weeding. The grain yield as well as the yield contributing characters produced by BRRI dhan49 was the highest among the studied varieties. The highest production of grain yield was obtained by hand weeding, however, the second highest was obtained from a combination of lentil and grass pea @ 1 t ha-1 of each was applied and the lowest production of grain yield was obtained in T1 (no crop residues). BRRI dhan49 under combination of lentil and grass pea @ 1 t ha-1 of each treatment produced the highest grain yield.

This study was conducted between 2013 and 2015 to determine the changes in the populations of wild oat (Avena sterilis L.) coverages, resistance and weed coverages based on the crop rotation applied at fields where wheat was being grown in Osmaniye Province and to reveal the relationship between the crop rotations and the resistance developed in wild oat by Clodinafop-propargyl with the Acetyl-CoA Carboxylase (ACCase) mode of action, Mesosulfuron-methyl + Iodosulfuron-methyl sodium and Pyroxsulam of the Acetolactate Synthetase (ALS) effect mechanism. By determining crop rotation systems for May and August in 103 fields selected in the year 2013, the coverage changes in the populations of wild oat and weeds and the resistance in wild oat poulations were determined. As a result, 48 different crop rotation systems were determined, wild oat resistance disappeared in the wheat + sunflower + sunflower rotation which was one of the most frequently preferred rotation, while the resistance index (RI) of wild oat against the ACCase inhibitor fell (RI<2.00) in the two-crop rotations involving maize as wheat/maize + maize + maize, wheat/maize + wheat/maize + wheat, wheat + wheat/maize + wheat and wheat/maize + wheat/maize + maize. In the three-crop rotation systems, resistance against ALS decreased in wheat/peanut + wheat/sesame + wheat, and resistance against ACCase decreased in wheat/maize + maize/peanut + peanut. It was revealed that the producers did not prefer four crop rotation much, and fallow did not change resistance indices. The wild oat resistant populations and coverages in the Osmaniye Province were determined for the first time, and the interactions of crop rotations are presented.

Pyroxasulfone is a new herbicidal molecule with residual activity to be used in Brazilian agricultural areas, it is necessary to gather information about its behavior in the soil, as well as its persistence in the environment and the risk of environmental contamination. The objective of this work was to evaluate the sensitivity of species to pyroxasulfone in order to select potential plants to be used as bioindicators in herbicide soil activity experiments. Greenhouse experiments were conducted with four species as potential bioindicators including lettuce (Lactuca sativa), cucumber (Cucumis sativus), sorghum (Sorghum bicolor), and tomato (Solanum lycopersicum). The preemergence pyroxasulfone treatments at 0, 3.125, 6.25, 12.5, 25, 50, and 100 g a.i. ha-1. The percentage of injury of the treated species was evaluated by a visual scale of 0-100% at 7 and 14 days after treatment (DAT). We also evaluated the effect of the herbicide on plant height, root length, shoot fresh biomass, root fresh biomass, and total fresh biomass. Using the non-linear regression models, was possible to estimate the dose of pyroxasulfone required to obtain 50% of the response for the analyzed variable (I50). I50 values ​​were used to determine the susceptibility of the species evaluated. The pyroxasulfone dose-response experiments revealed three species with potential for bioassay studies. Overall, Lettuce was the most sensitive to herbicide. Sorghum may be useful species to detect pyroxasulfone soil activity based on plant height measurements (I50 = 9.7 g a.i. ha-1). Cucumber also showed to be a potential candidate as bioindicators. Tomato was considered tolerant of pyroxasulfone doses evaluated.

Weeds are widely seen in a negative light, as being unsightly and possibly pulling resources away from crop plants. Traditional farming practices use selected beneficial "weeds", however, to provide floral resources to beneficial insects and support them through added biodiversity within farms. The global annual economic value of insect pollination is enormous, with more than a third of all crops dependent on pollinators worldwide. This free ecosystem service is steadily declining as we face a global pollinator decline crisis in areas of intensive agriculture. The loss of natural resources through land conversion has decimated insect populations; therefore, there has been interest in enhancing pollinator populations by providing alternative non-crop resources to increase food production. Weeds may be useful in this goal, as they provide resources that attract and may maintain populations of pollinators. In this review, the possibility of using weeds in agriculture to increase floral resources for pollinators and crop yield will be examined. Weeds can provide extensive, free resources to insects, and understanding their interactions in agriculture needs more focus now than ever in changing environments. Fallow lands have always been used by insects and are an important part of their diets in fragmented ecosystems. Understanding their utility could help shape agricultural practices and ameliorate global pollinator decline.

The composition of weed species and the distribution of weed seeds in the soil profile vary significantly and closely correlated to the previous cropping system. Information on the effect of tillage types, crop residue mulching and crop rotation on the soil weed seedbank is a useful tool for sustainable weed management in conservation agriculture (CA). With the view to studying the trend of weed seedbank in CA, a net-house experiment was conducted at the Department of Agronomy, Bangladesh Agricultural University during January - December, 2016. Soil samplings were done at 0 - 15 cm depth from four different sites after the end of CA trials at Mymensingh and Baliaknadi during 2012 - 2015 and Durgapur and Godagari in 2010-2015, in Bangladesh. At Mymensingh, conventional tillage (CT) and strip tillage (ST), while at Durgapur and Godagari, additional bed planting (BP) were practiced.  On the other hand, at Baliakandi additional Zero tillage (ZT) was included. At all sites 20% and 40 - 50% of standing mulches of previous crops were applied. A total of 290 samples replicated four times were placed in individual trays following a completely randomized design. The year-round headcount of emerged weed revealed that the smallest size of weed seedbank in terms of weed species composition and weed density was found in ST followed by CT, BP, and ZT with 40 - 50% crop mulch than 20% mulch. The ST, BP, and ZT produced a higher number of perennials weeds than annual weeds, but opposite in CT. Based on the results, it could be concluded that the continuous practice of ST with 40 - 50% residue mulch declined the size of weed seedbank with the proliferation of perennial weeds. Weed seedbank size in ST is even smaller than BP and ZT.

In the valley of the Senegal River, weeds represent one of the major constraints of irrigated rice cultivation. In that context, the development of efficient and adapted methods for better management of weeds is critical. This study aims at evaluating the efficacy of the combination of two formulations of herbicides (Eros Gold and Londax) and two sowing methods (direct sowing and transplanting) on rice weeds in a Split Plot design with three replicates. The weed flora was evaluated through phytosociological surveys with three observations: before heading, after heading and ripening stages of rice. Floristic surveys identified 16 families, 25 genera and 28 species of weeds. In addition, the results showed that Eros Gold had a significant effect with sowing methods on the decrease of sedges and grasses density but more specifically on the abundance-dominance of broadleaf weeds (dicotyledons) before and during heading stages of rice. On family groups, Cyperaceae (15.39 ind/ha), grasses (15.72 ind/ha) and dicotyledons (24.94 ind/ha) are more sensitive to Eros Gold in broadcast sowing than in transplanting mode with 26, 56 ind/ha, 26.50ind / ha and 27.94 ind/ha respectively.