Journal of Research in Weed Science

Abstract Herbicide efficacy could be enhanced by herbicide combinations and addition of surfactants. These substances improve absorption of herbicides by lowering the surface tension of spray droplets resulting in increased area of contact of the herbicide solution with the leaf surface. This experiment determined the tolerance of rice and efficacy of three post-emergence herbicides in varying combinations with surfactants against Echinochloa crus-galli (L.) Beauv., Cyperus iria L., and Ludwigia octovalvis (Jacq) Raven. The study was conducted at the Cambodian Agricultural Research and Development Institute (CARDI), in Cambodia from January to February 2019. Rice at 10 days after herbicide application (DAHA) showed some degree of susceptibility to Pyribenzoxim- and Quinclorac 50%+ Pyrazosulfuron-ethyl 7% + Fenoxaprop-P-ethyl 13% pre-mix-surfactant mixture but was fully recovered at 20 DAHA. Generally, rice was more tolerant at the 4-6 than at the 2-3 leaf stage. Phytotoxicity of the herbicides to Echinochloa crus-galli depended on the herbicide and surfactant concentration and the stage of growth of the weed at application time. Cyperus iria and Ludwigia octovalvis were relatively more sensitive to the pre-mix alone and where, in most instances, did not merit addition of surfactant.

Abstract Studies were conducted to ascertain the phytotoxic action of aqueous extracts and rhizospheric soils of wasteland weeds such as Parthenium hysterophorus L., Withania somnifera L., Lantana camara L., and Achyranthes aspera L. against four summer crops viz., Gossypium hirsutum L., Helianthus annuus L., Oryza sativa L. and Zea mays L. Experiment was carried out in Agronomy Laboratory, College of Agriculture, University of Sargodha, Punjab-Pakistan. In first experiment, the 5% (w/v) aqueous extract prepared from whole plant of each weed was applied to germinating crop seeds sown in petri plates. In the second experiment soils collected from rhizosphere of these weeds were filled in plastic pots and used as germination medium for seeds of these crops. A constant temperature of 30^oC was maintained in germinator throughout the germination period of 12 days. In first experiment, significantly lower germination percentages (31.7 and 38.3%) and germination indices (4.4 and 6.4) of crops were noted with application of A. aspera and P. hysterophorus extracts, respectively. All weed extracts except L. camara caused significant reduction in shoot length, root length, seedling length and seedling biomass of crops. Root growth of the crop seedlings was influenced more than their shoot growth. In second experiment, germination percentage, shoot dry weight, seedling biomass and seedling vigor index of crops were significantly inhibited by rhizospheric soil of all weeds. Among crops, H. annuus was more susceptible to the deleterious effect of the aqueous extracts as well as rhizospheric soils of weeds. It can be concluded that wasteland weeds especially P. hysterophorus and A. aspera imparted more negative impact on the germination and seedling growth of test crops. Therefore, crop fields and their surroundings should be kept free from these weeds by clean cultivation.

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 Microbes and their secondary metabolites offer a benign and eco-friendly alternative to manage weed. Mycoherbicide production for biological control of weeds requires a series steps, from selection of a suitable microbial strain to final formulation. Thus, this study aimed to select potential fungi for production of secondary metabolites with herbicidal activity for control of Parthenium weed. In the present study, phytopathogenic fungi namely Fusarium spp. were isolated from infected tissues of Parthenium and evaluated against Parthenium hysterophorus, a problematic monocotyledonous weed of open lands, Agriculture, Horticulture and Forests. Herbicidal potential of Cell Free Culture Filtrate (CFCF) of three strains of Fusarium spp. coded as FGCCW#16, FGCCW#43 and FGCCW#55, against Parthenium hysterophorus were evaluated by seedling and shoot cut bioassays.  Maximum mortalities of shoots, seedlings and phytotoxic damage were obtained from 21 days old cell free culture filtrate (CFCF) of FGCCW#16 at 100% concentration. Significant reduction in biological contents i.e. photosynthetic pigment and protein was observed in the host weed on treatment with the CFCF as determined by detached leaf bioassay. Phytotoxic damage such as severe wilting, chlorosis, necrosis and complete collapse of the entire parts of the weed were also noticed due to CFCF application.