In modern agriculture, with more emphasis on high input systems and the widespread application of herbicides has indubitably improved the crop production but has also resulted in inadvertent harm to the ecosystem. The increased awareness towards the adverse effects of herbicide residues on human health and environment resulted in a significant shift towards the mitigation strategies of herbicide residues in the soil as well as in the plants. Several approaches have been found to be utilized for mitigation of herbicide residues in the soil. The hazards from herbicide residues in the soil can be reduced by using low dosage chemicals, tillage operations, crop rotation, using proper nozzle and spraying technique and by using granular, foam, gel and encapsulated materials. Site specific application using variable rate applicator, enhancement of herbicide degradation through bio-stimulation, use of non-phytotoxic oil, adjuvants, surfactants, adsorbents, protectants, antidotes, safeners, biochar, etc. are various other effective ways for mitigation of herbicide residues in the soil. Biochar as an amendment to agricultural soils has been found to increase the bioavailable water, builds soil organic matter, enhances nutrient cycling, lowers bulk density, and can provide shelter for beneficial soil microorganisms. Biochar prevents the mobilization of herbicide residues in soil due to its sorption property and hence helps the crop to escape toxicity. Carbon based nano-absorbents such as carbon nanotubes (CNTs) represents a new class of nanomaterial and has been shown to have good potential in removal of various types of herbicide residues in the soil. Graphene is another carbon nanomaterial that has tremendous potential in water purification as well as in various fields due to its unique physical and chemical properties. Nanocrystalline metal oxides such as ferric oxides, manganese oxides, aluminium oxides, titanium oxides, magnesium oxides and cerium oxides are highly effective adsorbents for a broad range of herbicides. These nanocrystalline metal oxides do not only adsorb but also actually annihilate many chemical hazards by converting them to much safer by-products. The amalgamation of bio-augmentation and bio-stimulation along with organic matter addition might be a promising technology for biodegradation of herbicides in soil.

Biochar, Carbon nanotubes, Graphene, Herbicide residue and degradation, Mitigation, Soil decontamination

Field experiments were conducted to study the chemical and non-chemical weed management on weed spectrum, yield and economics of direct-seeded rice (DSR) under lowland irrigated condition at Regional Research Station, Tamil Nadu Agricultural University, Paiyur, Tamil Nadu, India in wet and dry seasons of 2013-14 and 2014-15. The results revealed that application of pyrazosulfuron-ethyl 10% WP at 20 g/ha at 3 DAS fb mechanical weeding with cono-weeder at 25 DAS recorded higher weed control efficiency (WCE) of 94% and higher grain yield of 6.45 t/ha, gross income of  82669/-, net income of  48767/- with the benefit : cost ratio of 2.45. It recorded 56% higher grain yield over weedy check and 14% higher yield over pyrazosulfuron-ethyl. Hence, pre-emergence application (3 DAS) of pyrazosulfuron-ethyl 10% WP at 20 g/ha followed by mechanical (cono-weeder) at 25 DAS was effective for weed management in DSR.

Bispyribac-sodium, Cono-weeder, Direct-seeded rice, Mechanical weeding, Weed control efficiency

Field experiment was conducted during rainy seasons of 2018 and 2019 to evaluate the efficacy of herbicide mixtures and nitrogen application scheduling to control grasses, sedges and broad-leaved weeds in transplanted rice. Post-emergence application of triafamone 20% + ethoxysulfuron 10% (ready-mix) 67.5 g/ha at 20 days after transplanting (DAT) was found comparable with two rounds of hand weeding at 20 and 40 DAT in controlling all categories of weeds. Among different nitrogen application schedules, application of 25% N at 10 DAT + 50% N at active tillering (AT) + 25% N at panicle initiation (PI) recorded higher weed control efficiency (73.4%) and grain yield (6.3 t/ha) of rice as compared to the recommended schedule of 25% N as basal + 50% N at AT + 25% N at PI (WCE of 66.9% and grain yield of 5.7 t/ha). Triafamone 20% + ethoxysulfuron 10% (ready-mix) 67.5 g/ha at 20 DAT recorded 81.7% WCE, improved crop growth and yield attributes and consequently increased grain yield (6.0 t/ha) as well as net return (69360 /ha) as compared to fenoxaprop-p-ethyl 9 EC 56.2 g/ha + ethoxysulfuron 15 WDG 18.7 g/ha (tank-mix) at 20 DAT. Tank-mix application of fenoxaprop-p-ethyl + ethoxysulfuron caused yellowing of rice leaves although it disappeared within 20 days after application, whereas no such phytotoxicity was recorded under ready-mix application of triafamone + ethoxysulfuron.

Herbicide mixture, Nitrogen application schedule, Transplanted rice, Weed control efficiency

A field experiment was conducted during Kharif (rainy season) 2016 and 2017 in sandy clay loam soils of experimental field at Banaras Hindu University, Varanasi, Uttar Pradesh India to find out the effect of leaf colour chart-based nitrogen and weed management practices on nutrient uptake and yield of direct-seeded rice. Minimum weed index, nutrient content and uptake by weeds and maximum weed control efficiency, yield and nutrient content and uptake by grain and straw were observed with application of nitrogen leaf colour chart LCC < 5. Application of pyrazosulfuron 20 g/ha (PE) fb bispyribac 25 g/ha at 15-20 DAS recorded minimum weed index, nutrient content and uptake by weeds and maximum weed control efficiency, rice yield and nutrient content and uptake by rice grain and straw, which was comparable with two hand weedings at 20 and 40 DAS.

Bispyribac-sodium, Direct-seeded rice, Leaf colour chart, Nutrient uptake, Pyrazosulfuron, Weed control efficiency

Vaucheria species from the coastal region of Karnataka were collected from a rice field during Kharif season from Kota hobli, Udupi Taluk, Coastal Karnataka. These were identified as V. sessilis (VAUCHER) DC and V.geminata (VAUCHER) DC. A field experiment was conducted during Kharif season of 2017 and 2018 at farmer’s field Kota, Udupi taluk, Coastal Karnataka, India for the management of these algal species. Among herbicide combinations, pre-emergence application of pendimethalin at 750 g/ha at 3 DAT fb post-emergence application of penoxsulam at 22.5 g/ha at 15, 30 and 45 DAT recorded lower dry weight (6.0, 5.6 and 4.8 g/m2 respectively) with higher weed control efficiency (92.37%). This treatment also recorded significantly higher plant height (95.18 cm), a higher number of tillers per hill (25.75), grain yield (5.33 t/ha), straw yield (6.24 t/ha) with B:C ratio (2.09-2.11).

Coastal Karnataka, Herbicide, Rice, Vaucheria, Yellow-green algae

A field study was conducted during 2016-17and 2017-18 to evaluate the impact of four tillage systems, viz. zero tillage (ZT) both in rice and wheat, conventional tillage (CT) both in rice and wheat, ZT in rice – CT in wheat and CT in rice –ZT in wheat with four weed management practices (recommended herbicide, recommended herbicide + one hand weeding, weed free and weedy check) in dry seeded rice–wheat cropping system on a lateritic soil of West Bengal. Among weed management practices, application of sulfosulfuron + metsulfuron at 0.032 kg/ha at 20 DAS followed by one hand weeding at 40 DAS in wheat was found to be the most effective. The yield of wheat under ZT-ZT was found to be the highest (3.78 t/ha), which was at par with CT-ZT. Advantages in ZT-ZT were to the extent of 23.6 and 21.8% over CT-CT in first and second year, respectively. Among weed management practices, recommended herbicide followed by one hand weeding registered higher yield (3.78 t/ha) and was comparable with the weed free treatment. The highest B:C ratio was recorded in zero tillage in wheat (ZT-ZT and CT-ZT) in combination with the sole application of recommended herbicide. The continuous ZT, especially in wheat with recommended herbicide alone was promising for higher productivity and profitability under dry-seeded rice–wheat system on lateritic soils of Eastern India.

Conventional tillage, Dry seeded rice, Recommended herbicides, Weed management, Wheat, Zero tillage

Field investigation was carried out at Akola, Maharashtra during three consecutive Rabi season of 2016-2017, 2017-18 and 2018-19 to assess the efficacy of herbicide combinations in wheat. Treatments comprised of twelve different pre-emergence and pre-mix combinations of post-emergence herbicides. Results revealed that pre-mix post-emergence application (PoE) of clodinafop propargyl + metsulfuron-methyl 0.06 + 0.004 kg/ha at 35 DAS and sulfosulfuron + metsulfuron-methyl 0.03 + 0.002 kg/ha at 35 DAS gave higher weed control efficiency (90 and 80%) and lower weed index (2.85 and 2.98%). These proved as effective as weed free treatment and recorded significantly higher grain yield of 4.37 and 4.36 t/ha, respectively over rest of the treatments. The highest net monetory returns and B:C ratio ( 64356/ha, 3.69) were registered with application clodinafop-propargyl + metsulfuron-methyl 0.06 + 0.004 kg/ha at 35 DAS followed by sulfosulfuron + metsulfuron-methyl 0.03 + 0.002 kg/ha at 35 DAS. ( 62162/ha and 3.40).

Clodinafop-propargyl, Metsulfuron-methyl, Post-emergence, Pre-mix, Wheat 

A field experiment was conducted to evaluate the bio-efficacy of dicamba 48% SL on the associated broad-leaf weeds of maize and to assess its phyto-toxicity on the crop in GBPUA&T, Pantnagar for two consecutive years during 2016 and 2017. The results revealed that application of dicamba 48% SL at 300 and 360 g/ha provided superior control of broad-leaved weeds as compared to 2,4-D Amine salt 58% SL 500 g/ha in maize. The same two treatments i.e. dicamba 48% SL at 300 and 360 g/ha also provided a total weed control efficiency of 100% in all the stages of crop growth. Maximum grain yield was recorded in the weed free plots to the tune of 5.45 t/ha and 5.22 t/ha in 2016 and 2017, respectively, which was at par with dicamba 48% SL at 300, 360 and 720 g/ha and the other yield attributing characters followed the same trend in both the years. However, numerically maximum yield was obtained in weed free plots, probably due to effectiveness of dicamba only against the broad-leaf weeds but hand weeding took care of broad spectrum of weeds. It was also revealed that, there were no symptoms of phytotoxicity on maize at any doses of dicamba 48% SL. Hence, it may be concluded that dicamba 48% SL at 300 g/ha was found to be effective against broad-leaved weeds in maize in Pantnagar region of Uttarakhand.

Bioefficacy, Dicamba, Maize, Phytotoxicity, Weeds

An investigation was carried out at Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu during 2015 and 2016 to study the effect of pre- and post-emergence application of herbicides on weed dynamics, microbial population and yield of summer blackgram. Thirteen weed management treatments was comprised of imazethapyr 70 g/ha as pre and post-emergence, imazethapyr 80 g/ha as pre- and post-emergence, imazethapyr + imazamox 70     g/ha as pre- and post-emergence, imazethapyr + imazamox 80 g/ha as pre- and post-emergence, pendimethalin 1000 g/ha as pre-emergence, imazethapyr + pendimethalin 1000 g/ha as pre-emergence, two hoeings at 15 and 30 DAS, weedy check and weed free were assessed. The results revealed that a significant reduction in total weed density and total weed biomass was observed with two hoeings at 15 and 30 DAS, imazethapyr + pendimethalin 1000 g/ha as pre-emergence and imazethapyr + imazamox 80 g/ha as post-emergence. Aapplication of imazethapyr + pendimethalin 1000 g/ha as pre-emergence recorded the highest seed yield and B:C ratio. Initially, after the herbicides treatment (15 and 30 DAS) microbial counts were slightly less in pre-emergence, reaching a maximum at 30 DAS.

Blackgram, Herbicies, Microbial population, Weeds, Yield

Effective weed management necessitates sound knowledge of weed seedbank dynamics. The experiment was laid out in split plot design with three replications. The main plots have three residue management treatments and sub-plots comprised seven weed management treatments. Results revealed that highest pod yield (1.47 t/ha) was recorded under wheat residue incorporation fb soil solarization. Among weed management, the highest pod yield (1.68 t/ha) and haulm yield (3.35 t/ha) was recorded with weed free and unweeded check registered lowest pod yield (722 kg/ha). The lowest dry weight of weeds was obtained under wheat residue incorporation fb soil solarization and weed free. Wheat residue incorporation fb soil solarization depleted correspondingly 54 (25.32%), 10 (5.29%) and 32 (16.16%) seeds per core from the initial weed seedbank in 2014, 2015 and pooled results, respectively. The highest seedbank depletion was observed with weed free by depletion of 147 (68.37%), 123 (68.20%) and 135 (68.29%) weed seeds per core. Pendimethalin 900 g/ha as pre-emergence fb IC and HW at 45 DAS depleted 129 (59.84%), 103 (57.09%) and 116 (58.59%) weed seeds per core. Pendimethalin 900 g/ha as pre-emergence fb pre-mix imazethapyr + imazamox 70 g/ha as post-emergence at 25 DAS depleted 126 (58.40%), 101 (55.86%) and 113 (57.24%) weed seeds per core and suicidal germination fb killing the weed flush by subsequent tillage fb IC and HW at 45 DAS depleted 116 (53.85%), 86 (47.64%) and 101 (51.01%) weed seeds per core in 2014, 2015 and pooled results, respectively as compared to the initial weed seedbank. While, unweeded check resulted in to addition of 609 (283.31%), 695 (384.16%) and 652 (329.41%) weed seeds per core sample (15 cm depth and 4 cm diameter) in the soil weed seedbank in comparison to initial weed seedbank.

Groundnut, Residue management, Weed seedbank dynamics, Weed management, Weed indices

A field experiment was conducted at Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India during 2017-2018 and 2018-19 to study the effect of different herbicide molecules in spring planted sugarcane. Cyperus rotundus, Cynodon dactylon and Alternanthera philoxeroides were dominant weed flora in the sugarcane field. Application of ametryn 1.0 kg/ha at 30 days after planting (DAP) followed by (fb) 2,4-D 1.0 kg/ha at 60 DAP effectively suppressed the grasses, sedges and broad-leaved weeds, improved yield attributes and registered higher cane yield (102.49 t/ha), juice recovery (52.80%) and B:C ratio (2.90) due to better weed control efficiency (71.05%). Next best treatments were atrazine 1.0 kg/ha at 30 DAP fb glyphosate 1.0 kg/ha at 60 DAP; and three hand weeding at 30, 60 and 90 DAP. Application of ametryn 1.0 kg/ha at 30 DAP + 2,4-D 1.0 kg/ha at 60 DAP proved to be a cost-effective option for getting higher cane yield in new alluvial zone of West Bengal.

Cane yield, Herbicides, Sugarcane, Weed biomass

Non-cropped areas are infested with diverse weed flora including annual and perennial grasses, sedges and broad-leaf weeds. The field efficacy of pre-mix of indaziflam plus glyphosate was evaluated for effective weed management in these areas. The field experiment was conducted over two years in Ludhiana (India). Seven treatments including pre-mix formulation of indaziflam-20 + glyphosate 400-420 SC (60 + 1200, 70 + 1400 and 80 + 1600 g/ha), glyphosate (1230 and 1600    g/ha) and indaziflam (80 g/ha) along with untreated control were evaluated. Major weed species at the experimental site were Cannabis sativa, Parthenium hysterophorus, Verbesina encelioides and Xanthium strumarium. All herbicidal treatments recorded complete mortality of C. sativa and P. hysterophorus till 30 days after application (DAA) while in case of V. encelioides and X. strumarium, complete mortality was recorded till 120 DAA. Pre-mix of indaziflam plus glyphosate at 80 + 1600 g/ha had >80% control of all weed species during both years till 60 DAA, and it was at par to its lower dose of 70 + 1400 g/ha; results with sole application of indaziflam and glyphosate were inconsistent.

Glyphosate, Herbicide, Indaziflam, Non-cropped area, Weed control

Pyrazosulfuron-ethyl is used in rice fields to manage a range of annual and perennial weeds. Its long-term herbicide residue dynamics in rice ecosystem and degradation pattern is poorly characterized.  Therefore, in the present study, field experiments were conducted for consecutive two years to investigate the residue dynamics and degradation of pyrazosulfuron-ethyl in the soil, rice plant, water and fishes in the rice field. Pyrazosulfuron-ethyl residues were found to be below the maximum residues levels (0.01 mg/kg) in the soil, rice grains, and straw. In the fishes, pyrazosulfuron-ethyl residues were in the range of 0.056- 0.013 µg/g. Half-life of pyrazosulfuron-ethyl in the soil of rice field was found to be 9.41 to 13.9 days. Results showed that pyrazosulfuron-ethyl at 25 g/ha application rate did not cause any environmental hazards and can be safely applied in the rice fields for management of annual and perennial weeds.

Degradation, Dissipation, Herbicide, Pyrazosulfuron-ethyl, Residues dynamics

Seedling traits of 60 weeds under 24 families of Magnoliopsida have been studied in some crop fields of Dakshin Dinajpur district of West Bengal. Conservative seedling characters emphasize that the studied taxa may be enlisted in four artificial groups i.e, Type I to IV, each having some families and/or genera. Artificial keys have been made for identification under field observations. The bearing of this study has also been addressed by camping seedling data with other botanical disciplines. Peculiar juvenile behaviors like heteroblastic developments have also been observed. Seedling study is very much significant for eradication of weeds at juvenile stage before display of variable weeds in crop fields.

Dicotyledonous, Morphological, Seedlings, Weeds identification

Three pre-mix herbicide combinations at two different times of application, viz. pendimethalin + penoxsulam at 5 and 10 DAS, cyhalofop-butyl + penoxsulam and florpyrauxifen-benzyl + cyhalofop-butyl both applied at 12 and 18 DAS were evaluated along with sequential spray of cyhalofop-butyl fb chlorimuron-ethyl 10% + metsulfuron-methyl 10% at 18 and 19 DAS, bispyribac-sodium at 18 DAS, hand weeding at 20 and 40 DAS and unweeded control. At 30 DAS, the lowest weed dry matter and highest weed control efficiency was obtained with application of florpyrauxifen-benzyl + cyhalofop-butyl (150 g/ha) at 12 DAS. The highest numbers of yield attributes and crop yields in rice were recorded in hand weeding followed by florpyrauxifen-benzyl + cyhalofop-butyl at 12 DAS and pendimethalin + penoxsulam (625 g/ha) at 5 DAS.

Herbicide combinations, Weed management, Wet seeded rice, Yield

A field experiment was conducted to assess the effect of tillage, seed rate and nitrogen levels on weed and yield of wheat at College of Agriculture, S.K. Rajasthan Agricultural University, Bikaner during Rabi (winter) seasons of 2015-16 and 2016-17. It was laid out in a split plot design with three replications with six main plots comprising three levels of tillage (conventional, minimum and zero tillage) and two levels of seed rate (100 and 125 kg/ha) and four levels of nitrogen (80, 100, 120 and 140 kg N/ha) as sub-plots and comprising a total of 24 treatment combinations.  The conventional tillage significantly increased the grain, straw and biological yields of wheat over zero and minimum tillage. Conventional tillage lowered the weed density and weed biomass as compared to zero and minimum tillage systems. Seed rate of 125 kg/ha and application of 120 kg N/ha significantly increased the grain, straw and biological yields over 100 kg/ha seed rate and 80 and 100 kg N.

Grain yield, Nitrogen, Tillage, Wheat

A field experiment was conducted during Kharif 2012 at Khrindwa research farm of CCS Haryana Agricultural University, Regional Research Station, Karnal, under the Bio-safety Research Trial Level-1 for transgenic maize hybrids to evaluate the bio-efficacy of glyphosate as post-emergence herbicide against weeds. There were 14 treatment combinations, including two transgenic hybrids of Monsanto, Hishell-NK603 and 900M Gold-NK603. Weed flora of the field included Echinochloa crus-galli, Dactyloctenium aegyptium, Brachiaria reptans and Eragrostis tenella among grassy weeds, Physalis minima and Phyllanthus niruri among broadleaf weeds and Cyperus rotundus among sedges along with few other minor weeds. Use of glyphosate 900-1800 g/ha in transgenic maize hybrids Hishell-NK603 and 900M Gold-NK603, provided 98.2-99.5% weed control efficiency, which was higher than the atrazine 750 g/ha treatments (62.1-68.6%); and resulted in improved grain yield of maize (7.7-8.7 t/ha) than unweeded checks (4.7-5.9 t/ha) and atrazine treatments (5.8-7.5 t/ha). At 60 DAT, minimum weed population (8.0-9.3/m2) was recorded in the glyphosate treatment at both the doses in transgenic maize hybrids, which was significantly lower than the atrazine treatments (19.3-21.3/m2) in transgenic/ conventional hybrids, as well as the non-weeded (37.3-41.3/m2) checks in conventional hybrids. Glyphosate 900-1800 g/ha in 900M Gold-NK603 produced maximum grain yield (8.6-8.7 t/ha) which was followed by glyphosate 900-1800 g/ha in Hishell-NK603 (7.7-7.8 t/ha). The growth, yield and yield attributes indicated superiority of 900M Gold-NK603 over Hishell-NK603, however, the differences in yield were not significant. Present study indicated the suitability of glyphosate use as post-emergence in transgenic maize hybrids Hishell-NK603 and 900M Gold-NK603. There was no phyto-toxicity of glyphosate 900-1800 g/ha on the transgenic crop.

Glyphosate, Maize , Transgenic, Weeds, Yield

Two years field study was conducted during 2010 and 2011 at research farm of SKRAU, Bikaner to evaluate the effect of different weed control measures on weed dynamics and yield in Kharif crops. Experiment was laid out in factorial randomized block design with three replications comprising different treatment combinations three Kharif crops as pearl millet, cluster bean, groundnut and three weed control measures- weedy check, mechanical method (two hand weeding) and chemical methods. The major weed species observed in the experimental plots were Digera arvensis L., Tribulus terrestris L., Cenchrus biflorus L., and Euphorbia microphylla L. with respect to their mean density at 30 DAS. The results of experiment showed that among Kharif crops, pearl millet recorded maximum density of weeds at 30 DAS whereas groundnut recorded maximum density of Digera arvensis and Euphorbia macrophylla at 30 DAS and maximum dry weight of all weed species at harvest. Two hand weeding significantly reduced the weed density at 30 DAS and weed dry weight at harvest. Application of atrazine 0.5 kg/ha in pearl millet and pendimethalin at 1.0 kg/ha in cluster bean and groundnut significantly reduced density and dry weight of weeds except that of Digera arvensis, which was not significantly controlled by pendimethalin in both cluster bean and groundnut. In pearl millet, cluster bean and groundnut, two hand weeding and chemical method increased the grain and straw yield over weedy check, on pooled mean basis.

Chemical method, Grain yield, Hand weeding, Kharif crops, Weedy check

Field experiments were conducted during winter, 2018-19 and summer, 2019 in groundnut and fodder sorghum, respectively at S.V. Agricultural College, Tirupati, Andhra Pradesh, India to know the performance of pre-emergence (pendimethalin 38.7% CS 725 g/ha and diclosulam 84% WDG 20 g/ha) and post-emergence (haloxyfop-p-ethyl 10.5% EC 135 g/ha and cycloxydim 20% EC 100 g/ha) herbicides on weed growth and yield of groundnut and their carryover effect on fodder sorghum. Significantly lower density and dry weight of weeds with higher WCE were recorded with pre-emergence application of diclosulam 20 g/ha + HW at 40 DAS and it was closely followed by pre-emergence application of diclosulam 20 g/ha fb cycloxydim 100 g/ha applied at 20 DAS in groundnut. The highest pod yield and benefit-cost ratio were registered with former weed management practice. All the herbicides tried did not show any inhibitory effect on germination, growth parameters and dry fodder yield of residual crop of fodder sorghum. Pre-emergence application of diclosulam 20 g/ha fb cycloxydim 100 g/ha applied at 20 DAS in groundnut showed its superiority in supressing weed growth at early stages of fodder sorghum due to extended herbicidal activity of diclosulam and reduced weed seed bank.

Cycloxydim, Diclosulam, Haloxyfop-p-ethyl, Fodder sorghum, Groundnut

A pot culture experiment was conducted in the nursery of Department of Silviculture, Forest College and Research Institute, Tamil Nadu Agricultural University, Mettupalayam, Tamil Nadu during summer season (February - April) 2016, to study the allelopathic effect of Lantana camara (L.) and Parthenium hysterophorus (L.) on germination and growth of Thespesia populnea (L.) tree species under greenhouse condition. Aqueous extracts of L. camara and P. hysterophorus at four concentration levels viz. 10, 20, 30 and 40% with absolute control (distilled water) were assigned as experimental treatments under completely randomized design and replicated thrice. Application of whole plant aqueous extract of P. hysterophorus and L. camara at 40% concentration recorded lower seed germination of 26.7% and 36.7% and germination value of 3.0 and 5.2 respectively than application of aqueous extracts of the weeds at 30, 20 and 10% concentration levels. Application of P. hysterophorus weed extract at 40% concentration recorded higher inhibition of shoot growth, root growth, total length and dry matter production of T. populnea seedlings than its application at lower concentrations and over L. camara weed extract at all concentrations.

Allelopathy, Germination and growth, Lantana camara, Parthenium hysterophorus, Thespesia populnea

Invasive alien weeds in Nepal have become a great problem. Many of them have been naturalized and threatening native ecosystems and biodiversity. This assessment was carried out to measure the density, frequency and coverage of four major invasive weeds in a historical place, Chobhar of Kathmandu, Nepal. It was found that Ageratina adenophora had the highest density, frequency, and cover in the Pine forest. Similarly, Ageratum conyzoides, Bidens pilosa, and Parthenium hysterophorus were dense and frequent with high cover along the roadside. The frequency of B. pilosa and P. hysterophorus was comparatively high in the fallow land. It shows that the ecological parameters of the particular invasive alien weeds vary with land-use types and aspects. These weeds should be regularly monitored and appropriate methods of controlling them should be implemented in the study area.

Alien plants, Biological invasion, Ecological impacts, Native species