Weed Science

Eichhornia crassipes or universally known as Water hyacinth (WH) is considered as one of the noxious and invasive plants with a high growth rate and vigorous reproductive capacity. Due to these characteristics, this plant causes severe ecological, economic and social problems in many tropical and subtropical countries. Currently, many countries like India, China, Vietnam etc., convert this aquatic invasive plant into a beneficial plant to solve serious environmental problems. WH is an excellent source in absorbing nutrients and pollutants from eutrophic/polluted waters. Moreover, WH biomass is used to produce bio-energy, feed and fertilizers. This review discusses the potential of using WH as a livestock feed in Sri Lanka. Sri Lanka is an agricultural country and livestock plays a major role in the society. The non-availability of quality pasture/fodder and shortage of improved pasture/fodder have been identified as one of the major causes for the poor production of milk and meat. But WH has been successfully utilized over the decades as a livestock feed by other countries for ruminants, swine, ducks, geese and fish due to its high crude protein content and progressive growth. Along with the relevant treatments and proper inclusion level to the main ration, this plant is a feasible alternative to rice straw and other low-quality roughages. WH shows an island-wide distribution in Sri Lanka inhabiting freshwater bodies such as tanks, canals, marshes, ponds etc. There is a greater opportunity of utilizing this plant to reduce the feed shortage in Sri Lanka ton livestock. Apart from biological, chemical and mechanical control methods, utilizing water hyacinth as a livestock feed is one of the better approaches out of many productive ways of controlling the growth of this plant.

Bio-efficacy of triafamone (20%) + ethoxysulfuron (10%) (ready-mix, 30% WG) was evaluated as early post-emergence (1-2 leaf stage of weeds, 15 days after transplanting) against complex weed flora in transplanted rice at CCS Haryana Agricultural University Regional Research Station, Karnal during Kharif 2011 and 2012, phyto-toxicity on transplanted rice during Kharif 2012 and 2013 and its residual phyto-toxicity on wheat during Rabi 2012-13 and 2013-14. Triafamone + ethoxysulfuron 60-67.5 g/ha proved superior or at par with other herbicidal treatments in reducing the dry weight of grassy and broad-leaf weeds to the extent of >99% and 85-94%, respectively, and provided almost complete control of sedges (Cyperus difformis and Fimbristylis miliaceae) during both the years. There was no significant effect of different treatments on the plant height and panicle length of the rice during both the years. Application of triafamone + ethoxysulfuron 60 g/ha resulted in number of effective tillers (58.7/mrl in 2011 and 78.2/mrl in 2012) at par with triafamone 45 g/ha, butachlor 1250 and 1500 g/ha, and also weed free check during both the years. The grain yield of rice (6.08 t/ha in 2011 and 7.06 t/ha in 2012) due to triafamone + ethoxysulfuron 60 g/ha was higher than its lower dose (52.5 g/ha) but at par with the higher dose (67.5 g/ha), triafamone 45 g/ha, butachlor 1500 g/ha and weed free check during 2011 and 2012; butachlor 1250 g/ha and pretilachlor 1000 g/ha during 2012; but superior to all other herbicidal treatments during both the years. There were no visual phyto-toxicity symptoms of triafamone + ethoxysulfuron on rice crop and also no residual phyto-toxicity on succeeding wheat crop even up to 120 g/ha.

A field experiment was conducted during rainy (Kharif) season of 2014 and 2015 at Zonal Agricultural Research Station, V. C. Farm, Mandya, Karnataka to study the efficacy of sequential application of herbicides on weed density, weed dry weight, yield and economics of dry direct-seeded rice. The results revealed that pre-emergence application of bensulfuron-methyl 0.6% + pretilachlor 6% GR at 10 kg/ha fb post-emergence application of bispyribac-sodium at 25 g/ha at 20 days after sowing (DAS) recorded significantly lower total weed population (39.4 and 43.1/m2) and weed dry weight (8.2 and 9.0 g/m2) with weed control efficiency of 77.8 and 77.2% during 2014 and 2015, respectively. As a consequence of effective weed control the same treatment recorded significantly higher grain yield (4.60 and 4.42 t/ha), net monetary returns (` 39,340 and 36,710/ha) and B: C ratio (2.32 and 2.23) during 2014 and 2015, respectively. This treatment was statistically comparable to hand weeding thrice at 20, 40 and 60 DAS. Uncontrolled weed growth caused 56% reduction in grain yield of dry direct-seeded rice.

Weeds in crop fields are largely influenced by crop rotations and management practices. A better understanding of response of various weed species to changing management practices is required to develop improved weed management systems.  A study was conducted to assess the effect of different tillage intensities and crop rotations on the weed population dynamics in rice-based cropping systems. In this study, three tillage practices viz. conventional tillage (CT), reduced tillage (RT) and RT with 30% crop residues (RTR30) were evaluated in three different crop rotations, viz. rice-wheat, rice-lentil and rice-winter maize for their effect on weeds. Results show that weed density and species composition differed with tillage and crop rotation. Interaction between various tillage intensities and cropping systems had significant effect on density and dry weight of total, broadleaved, grasses and sedges. Irrespective of the tillage systems rice-wheat crop rotation favoured the prevalence of weeds (a total weed population of 1670/m2 and weed dry biomass of 241.1 g/m2), whereas rice-winter maize rotation suppressed the weed growth (a total weed population of 403/m2 and weed dry biomass of 213.4 g/m2) in summer (pre-Kharif) season. Reduced tillage with 30% residues retention (RTR30) favoured the infestation of horse purslane (Trianthema portulacastrum L.) in rice-wheat cropping system, but suppressed the weed growth in rice-lentil system. Contrary to this, RTR30 favoured the infestation of black nightshade (Solanum nigrum L.) in rice-winter maize cropping system, but suppressed the weed growth in rice-lentil and rice-wheat systems during winter season. 

Evolution of multiple herbicide resistance in Phalaris minor in wheat has resulted from the repeated use of herbicides with a similar mode of action which could threaten the sustainability of the rice-wheat cropping system in North-West India. In this context, field studies were conducted at Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana during 2011-12, 2012-13 and 2013-14 in randomized block design replicated four times and at farmer’s field during 2016-17 and 2017-18 with the objective to evaluate the efficacy of herbicide with alternative mechanism of action for the control of resistant P. minor in wheat. The treatments included pyroxasulfone 85, 102, 127.5 g/ha, pendimethalin 750 g/ha as pre-emergence (PE), sulfosulfuron 25 g/ha, clodinafop 60 g/ha as post-emergence (PoE) and unsprayed control. However, the treatments during 2013-14 included pyroxasulfone 85, 102, 127.5 g/ha, pendimethalin 750 g/ha and unsprayed control with pendimethalin 1125 g/ha as PE at farmers’ field instead of pendimethalin 750 g/ha. The results indicated that pyroxasulfone at 127.5 g/ha recorded effective control of P. minor and its biomass and gave the highest wheat grain yield (4.87, 4.80 and 5.43 t/ha) during 2011-12, 2012-13 and 2013-14, respectively. At farmer’s field, pyroxasulfone 127.5 g/ha has been found effective against the resistant populations of Phalaris with 5.37 and 5.42 t/ha grain yield. The current study demonstrated that PE application of pyroxasulfone at 127.5 g/ha would be a suitable option for the control of resistant populations of Phalaris in wheat in Punjab.

A field experiment was conducted at Siswal, Hisar, Haryana during 2016-17 and 2017-18 to study the effect of different herbicides applied alone or mixtures on weeds and yield of wheat (Triticum aestivum). Significantly higher grain yield was obtained in weed free treatment, which was statistically similar with pinoxaden + metsulfuron and pendimethalin fb pinoxaden treatments, but significantly higher than all other treatments during both the years. Weed free, pinoxaden + metsufuron and pendimethalin fb pinoxaden treatments produced 70.9, 67.7 and 64.9; 69.4, 67.0 and 64.3% higher grain yield as compared to weedy check treatment, respectively during 2016-17 and 2017-18. Statistically similar grain yield was recorded in pyroxasulfone and pyroxasulfone + pendimethalin treatments, it was 54.1 and 51.1; 55.3 and 52.4% higher to weedy check treatment, respectively during 2016-17 and 2017-18. Application of flumioxazin and flumioxazin + pendimethalin provided effective weed control, but grain yield was lower due to crop phytotoxicity after first irrigation in light texture soils. Significant positive correlation between grain yield, growth and yield attributes, per cent control of weeds and weed control efficiency, but negative correlation was observed between grain yield and weed dry weight, panicle length, seeds/panicle, test weight of wild oat and weed index.

Littleseed canary grass (Phalaris minor) is the ubiquitous and pernicious grass weed of wheat in rice-wheat cropping system in north-western Indo- Gangetic plains of India. A field experiment was conducted during Rabi 2014-15 and 2015-16 in a farmers field infested with P. minor having history of poor control with acetyl-CoA-carboxylase inhibitors in village Nangla, district Fatehabad, Haryana, India with an objective to compare pre-emergence only, post-emergence only and pre-emergence followed by post-emergence herbicide treatments for control of P. minor in wheat. The sequential application of pre-emergence pendimethalin 1.5 kg/ha fb post-emergence pinoxaden + metsulfuron 64 g/ha and pre-emergence pendimethalin 1.5 kg/ha fb post-emergence mesosulfuron + iodosulfuron 14.4 g/ha provided 88-93% control of P. minor compared to alone pre- and post-emergence herbicide treatments. Grain yield of wheat increased significantly by 69-78% with pre-emergence pendimethalin 1.5 kg/ha fb post-emergence pinoxaden + metsulfuron 64 g/ha or pre-emergence pendimethalin 1.5 kg/ha fb post-emergence mesosulfuron + iodosulfuron 14.4      g/ha due to significant increase in yield attributes. Alone pre- or post-emergence herbicides provided ineffective control of P. minor (44-66%) and recorded lower grain yield. It was concluded that herbicide sequences having both pre- and post-emergence herbicides would be better option as compared to their alone applications in order to manage resistant populations of P. minor in wheat.   

The present communication pertains to major weeds of different crop ecosystems of Jorhat in India. The study was based on extensive and intensive fields surveys made during different months of rainy and dry season 2016-2018. Surveys were made in five important crops ecosystems of total eight developmental blocks of Jorhat district during both Kharif and Rabi seasons of the year. Vegetation data were collected followed by quadrat methods and analyzed for density, frequency, diversity and importance value index (IVI) for each crop ecosystems. Interspecific association was also analyzed for ten dominant weed species followed by Cole’s index.  During this period, a total of 82 weed species were reported of which 56 species were recorded from the transplanted Kharif rice fields, while 61 weed species were recorded from the Rabi crop fields. The five dominant weed families in the study area were Cyperaceae, Poaceae, Onagraceae, Asteraceae and Fabaceae.

Field and pot studies were conducted during two rainy (Kharif) seasons of 2013 and 2014 to identify the effectiveness and optimum dose of mesotrione and atrazine combination for diverse weed flora management in maize. The weed control treatments evaluated in field experiment were pre-emergence atrazine 1000 g/ha and post-emergence 2,4-D-Na 1000 g/ha, mesotrione 120 g/ha and ready mixture of mesotrione with atrazine in ratio of 1:10 w/w (Calaris Xtra 275 SC) at 750, 875 and 1000 g/ha. The major weeds infested were Dactyloctenium aegyptium, Digitaria sanguinalis, Echinochloa crus-galli, Trianthema portulacastrum, Digera arvensis and Phyllanthus niruri. The uncontrolled weed competition reduced the maize yield by 38.7 to 54.0%. Mesotrione 120 g/ha was effective in controlling the broad-leaved weeds but was poor in controlling grass weeds. The weed control with pre-emergence atrazine 1000 g/ha was also not consistent. However, in pot and field studies, ready or tank mixture of mesotrione with atrazine was synergistic and superior in controlling weeds than to sole mesotrione and atrazine applications. The weed control efficiencies with ready-mixture of mesotrione + atrazine (1:10 w/w) at 875 and 1000 g/ha ranged 89-99%. Mesotrione plus atrazine at 875 and 1000 g/ha yielded (7.74-8.11 t/ha) significantly higher as compared to mesotrione 120 g/ha (5.83-5.96 t/ha), atrazine 1000 g/ha (5.93-6.70 t/ha) and 2.4-D-Na 1000 g/ha (3.82-5.30 t/ha) applications, as well as, untreated weedy check (3.73-4.76 t/ha). The results showed that mesotrione and atrazine combination has synergistic effect, which can be used for managing diverse weed flora in maize.

The bio-efficiency of imazethapyr and its combination with imazamox or pendimethalin in comparison to hand weeding against weeds, their effect on growth, yield and phytotoxicity on black gram and residual effect on succeeding mustard crop were studied during 2014-15 and 2015-16. Hand weeding twice resulted in the highest overall weed control efficiency followed by pre-emergence application of imazethapyr + imazamox 80 g/ha, pre-emergence imazethapyr + imazamox 70 g/ha and pre-emergence imazethapyr + pendimethalin 1000 g/ha. Hand weeding twice and pre-emergence imazethapyr + pendimethalin 1000 g/ha were comparable to pre-emergence imazethapyr + imazamox 70 g/ha for seed yield. With every increase of one weed per square metre, the blackgram seed yield was reduced by 2.1 kg/ha. Similarly with every g/m2 increase in weed weight, the blackgram yield was subjected to fall by 5.1 kg/ha. The economic threshold levels i.e. No/m2 and g/m2 with the weed management practices studied varied between 8.3 – 42.0/m2 and 3.5-17.6 g/m2. Weed persistence index (WPI) was lowest and crop resistance index (CRI) was highest in the hand weeding twice treatment. Post-emergence application of imazethapyr 70 and 80 g/ha and imazethapyr + imazamox 70 and 80 g/ha caused mild toxicity during 2014 and had therefore lower crop resistance index. Efficiency index was the highest under hand weeding followed by pre-emergence application of imazethapyr + imazamox 80 g/ha, pre-emergence imazethapyr + pendimethalin 1000 g/ha and pre-emergence imazethapyr 80 g/ha. Weed index indicated 55.4% reduction in yield of blackgram due to weeds. Pre-emergence imazethapyr 80 g/ha, imazethapyr + imazamox 80 g/ha, imazethapyr 70 g/ha and imazethapyr + pendimethalin 1000 g/ha had higher overall impact index than hand weeding due to lower cost. Residual effect/phytotoxicity was not observed on succeeding crop of mustard during 2014 and 2015 as well.

To study the effect of selective and non-selective post-emergence herbicides on weeds and yield of cotton, a field experiment was conducted during two consecutive seasons of Kharif 2014 and 2015 at CCS Haryana Agricultural University, Hisar.The experimental field was pre-dominantly infested with natural population of jungle rice (Echinochloa colona L.) and carpet weed (Trianthema portulacastrum L.) to the extent of 79 and 21% in 2014 and 71 and 29% during 2015, respectively. Application of pendimethalin at 1.0 kg/ha supplemented with other two hoeings at 20 and 50 DAS or one hoeing and post-emergence application of quizalofop-p-ethyl at 60 g/ha or one hoeing and post-emergence application of propaquizafop-p-ethyl at 62.5 g/ha at 60 DAS caused significant reduction in density and dry wt. of weeds as compared to weedy check up to harvest in both the years. Protected spray of glyphosate (0.5%) integrated with pendimethalin or paraquat (0.3%) with  parthiobac Na fb quizalofop-p-ethyl being at par with three mechanical weedings (at 20,40 and 60 DAS) helped to significantly reduce the population and dry weight of weeds at 90 DAS over weedy check. Weeds throughout the crop growing season reduced seed yield by 49.9 and 47.2% during 2014 and 2015, respectively. During 2014, all the treatments involving directed spray of either glyphosate or paraquat caused 8.3 - 10% toxicity to cotton crop where in 2015 the toxicity in these treatments was 5-8%. In 2014, maximum WCE (96.9%) was obtained with use of pendimethalin fb directed spray of glyphosate but during 2015, it was 83.3 with application of parthiobac-Na fb quizalofop-p-ethyl fb directed spray of glyphosate.Pendimethalin fb parthiobac-sodium caused maximum uptake of nitrogen during 2014 and 2015, which was 23.37 kg/ha and 24.68 kg/ha, respectively.

Field experiments were conducted at the fodder farm of ICAR-IVRI, Izatnagar campus, Bareilly. Different doses of atrazine (0.50, 0.75, 1.00 and 2.00 kg/ha) as pre- and post-emergence were applied. The weedy check plots of fodder maize were largely infested by Trianthema portulacastrum, T. monogyna followed by other broad-leaved weeds during 1st year. However, during 2nd year, infestation of these weeds were considerably lower due to higher seed rate and use of ferti-seed-drill. In double-cut fodder sorghum, Trianthema sp. recorded the highest absolute density and absolute frequency followed by sedge (Cyperus esculentus), grasses (Digitaria ciliaris, Setaria glauca) and other broad-leaved weeds (Coccinia grandis, Celosia argentea and Cleome viscosa). The broad-leaved weeds Ageratum conyzoides and Sonchus oleraceus appeared after 1st cutting. In fodder maize, atrazine with all the doses as pre- and post-emergence showed effectiveness. Weeds in weedy check treatment caused a yield reduction of 22.6%, however, in 2nd year the value was 1.7% due to restricted weed growth. Most significant results were recorded in weedy check treatment in which 60.3% yield increment of green fodder maize was registered in 2nd year over 1st year and this resulted in the highest benefit: cost ratio of 3.15. ` 52,400/ha more profit was recorded over broadcasting method of sowing. Higher seed rate (63 kg/ha) along with the use of ferti-seed-drill was equally effective with atrazine treatments. In double-cut sorghum, pre-emergence treatments of atrazine 0.75 kg/ha and above recorded comparatively higher green fodder yield than post-emergence treatments. Weedy check treatment recorded the weed index value of 17.9%. Cumulative green fodder yield (1st and 2nd cut) was highest in weed-free treatment closely followed by atrazine 2.0 kg/ha as pre-emergence treatment. Additional investment of ` 2020/ha after 1st cutting registered the additional net returns of ` 43,100/ha. This indicated the benefits of growing double-cut sorghum and also shown the importance of growing multi-cut and perennial fodder crops. Both the green fodder crops contained atrazine residue at harvest.

This study was conducted at Research laboratory, Botany Department Amrit Campus, Kathmandu, Tribhuvan University, Nepal, in the year 2015-2016 to investigate the allelopathic effects of compost extract and soil amended with compost invasive weed Parthenium weed on seed germination and seedling growth of two crops Triticum aestivum, Brassica campestris and some common weeds (Ageratum conyzoides, Bidens pilosa, Galinsoga parviflora and Cyperus rotundus). Parthenium hysterophorus was collected before flowering and matured seeds of Bidens pilosa, Ageratum conyzoides, Galinsoga parviflora and Cyperus rotundus were collected from different sites around Kathmandu valley like Kirtipur and Bhaktapur areas. The compost extract of Parthenium of different concentration (control, 1, 2.5, 5 and 10%) and Parthenium compost (control, 10, 20, 40 and 50 g compost/kg soil) were used to determine its effect on seed germination, shoot and root length of T. aestivum and B. campestris and selected common weed seeds under laboratory condition. The compost extracts of Parthenium caused significant reduction in seed germination, seedling length (shoot and root length) of selected crops and weeds. The selected common weeds showed more reduction in germination and vegetative shoot and root length in comparison to crop plants (B. campestris and T. aestivum) in the soil amended with the compost of Parthenium. 

A field experiment was carried out during winter seasons of 2013-14 and 2014-15 at G.B. Pant University of Agriculture and Technology, Pantnagar to study the effect of pre- and post- emergence herbicides on weeds, fodder yield and quality of berseem (Trifolium alexandrinum L.). The experimental results indicated that pre emergence application of pendimethalin (1000 g/ha) followed by imazethapyr (100 g/ha) just after 1st cut produced significantly higher green and dry fodder yields, crude protein and net returns but alone application of pendimethalin at 1000 g/ha had the highest B:C ratio. The pooled values indicated that the lowest weed population was observed at application of pendimethalin + imazethapyr (1666 + 100 g/ha). The fresh and dry weight of weeds were recorded significantly lower under oxyflourfen + imazethapyr at 425 + 100 g/ha (just after 1st cut) in both the years, while pooled weed control efficiency was found significantly highest under oxyflourfen + imazethapyr at 425 + 100 g/ha (just after Ist cut). It is therefore, concluded that the application of pendimethalin + imazethapyr at 1000 + 100 g/ha may be recommended for effective weed control as well as higher fodder yield, its quality and net profit in berseem growing areas of lowland (Tarai) region of Western Himalayas.

Hormesis is a biphasic dose response to an environmental agent characterized by low dose stimulation and high dose inhibitory or toxic effect. In order to develop an effective weed management system, the stimulatory and/or inhibitory response of low doses of herbicides on germination and growth of weeds should be considered. Thus, a laboratory study was conducted to test the effect of low dosages of 2,4-D on wheat (Triticum aestivum L.) and associated dicotyledonous weeds. Low dosages of 2,4-D (0, 5, 10, 20, 40 and 50 g/ha) failed to accelerate either seed germination or seedling growth of T. aestivum and tested four weed species –Phalaris minor Retz., Avena ludoviciana Durieu., Medicago denticulata Willd. and Rumex dentatus L. under in vitro conditions  in Petri-dishes. The application of 2,4-D inhibited the seed germination and seedling growth of these weeds in a dose dependent manner with higher concentrations being more inhibitory. The sodium formulation of 2,4-D more adversely affected the germination of P. minor and A. ludoviciana as compared to its ethyl ester formulation. The results indicated that 2,4-D when used as a post-emergence herbicide in wheat fields can delay the emergence of new flushes of weeds like P. minor, A. ludoviciana, M. denticulata and R. dentatus due to its inhibitory effect on their germination. It could be concluded that low doses of 2,4-D did not enhance germination/seedling growth of wheat and associated weeds.

Dlapat sagar reservoir is one of the prominent aquatic bodies in Jagdalpur of Bastar region of Chhattisgarh state in India. The reservoir was severely infested by aquatic weeds for last many years. An experiment was done to evaluate the integration of herbicides and manual/mechanical approaches to reduce the cost in comparison to manual removal alone. The experiment comprised of 8 treatments, viz. glyphosate 2.0 and 1.0 kg/ha (41 SL), paraquat 2.0 and 1.0 kg/ha (24 SL) and 2,4-D (amine salt 58% SL) 2.0 and 1.0 kg/ha dissolving in 500 litre water, manual removal and control was laid out in randomized block design with three replications at reservoir located at 1905’41"N and 8200’43"E with elevation of 563 m MSL during 2016 and 2017. The aquatic body was covered with thick mat of different weeds entangled with each other. Herbicides were sprayed to loosen the entangled weed biomass followed by manual and mechanical removal after 25 to 30 days. Glyphostae, 2,4-D and paraquat were mixed with sticker (Latron AG-98) and were sprayed in three replications by power spray machine (1HP HTP MAK ASPEE) mounted on the boat. The pH of water was gradually increased from 6.79 to 7.09 while EC and TDS from 0.33 to 0.30 (mS/cm2) and 101 to 207 (mg/l), respectively. The minimum density and dry matter was recorded with manual/mechanical removal followed by application of glyphosate 2.0 kg/ha, which was significantly superior over control and lower dose of other two herbicides and found statistically at par with 2,4-D amine salt 58% SL and applied at higher dose (2.0 kg/ha) during both the years. Glyphosate (2.0 kg/ha) was found effective in controlling weeds with the cost of ` 19,660/- and ` 18080 per hectare during 2016 and 2017, respectively with weed control efficiency of 86.4, 84.3; 79.1, 82.2 and 83.8, 88.3 % for water hyacinth, lotus and alligator weeds during 2016 and 2017, respectively.

The phytoplasma-mediated witches’ broom disease in Parthenium hysterophorus L., a notorious weed, inhibits flower formation and percentage of seed setting. Even the seeds produced from infected plants showed poor viability and reduced rate of germination. Expression analysis of three orthologous genes in P. hysterophorus, namely, APETALA-1 (PhAP1), ubiquitin binding protein (PhDA1), and RING-type E3 ubiquitin ligase (PhATL80) showed significant variation in their transcription levels. Expression of PhAP1, PhDA1, and PhATL80 was higher in apical shoot bud and inflorescence than in other studied tissues. Infected plants showed suppressed expression of PhAP1 and PhATL80 in the inflorescences while no significant variation was observed in PhDA1 expression. This resulted in floral to vegetative transition, causing phyllody and virescence, and lesser seed setting.

These findings suggest that in naturally phytoplasma-infected P. hysterophorus, expression of gene(s) participating in floral development as well as seed setting at onset of the reproductive phase is suppressed.

A Rabi season (2012-13) field investigation was carried out at Directorate of Rice Research, Hyderabad to assess the impact of saturated moisture regime (SMR) with and without plastic mulching (black and transparent) in transplanted rice (TPR) on weed menace, water saving, productivity and economics as compared to 5 cm standing water regime (SWR) rice in RBD with six replications. Results revealed that no-mulch SMR rice has 37.3 and 80.2% higher weed count and thus 26.8 and 114.1% lower weed control efficiency than SWR rice culture at 20 and 40 days after transplanting. Plastic mulching (PM) with SMR has reduced the weed count and weed biomass in rice by over 90% as compared to no-mulch-SWR rice. Labour days required for weeding were enhanced by 50% under SMR (30 man days) as compared SWR (20 man days). SMR had 35% irrigation water (IW) economy but with 7.1% grain yield penalty (0.34 t/ha) as compared to SWR (100 cm IW use and 4.79 t/ha grain yield). When SMR was combined with plastic mulching (PM), there was aless yield depression (0.10-0.18 t/ha) when compared to SWR. SWR has more net returns (` 42,160/ha) than SMR (` 30,750). High cost of PM (` 23,000/ha) with SMR has masked gains in IW, weeding costs saving and higher yields. SMR can be adopted without any challenges but weed management through PM is desired with added advantage of water economy. Reducing cost of plastic mulches and evolving biodegradable plastics may make SMR rice culture a reality.

A field experiment was conducted during rainy season of (Kharif) 2018 at Tirupati, Andhra Pradesh to find out the effect of sequential application of pre-and post-emergence herbicides on weed growth and yield of rainfed lowland rice. The present study has revealed that pre-emergence application of pendimethalin 1000 g/ha fb florpyrauxifen-benzyl 25 g/ha or halosulfuron-methyl 65.7 g/ha applied at 20 DAS resulted in the highest grain yield and economic returns as well as broad-spectrum weed control in rainfed lowland rice.

A field experiment was conducted during Kharif seasons of 2015 to 2017 for three years at Agricultural Research Station, Vadgaon Maval, Pune, Maharashtra to find out the economical methods of weed control in transplanted rice. Post-emergence application of bispyribac-sodium 0.020 kg/ha (PoE) at 21 days after transplanting (DAT) followed by (fb) hand weeding at 45 DAT has effectively managed weeds in transplanted rice and produced the highest net returns (` 70107/ha) with higher B:C ratio (2.3) having lower weed index (2.83) and higher weed control efficiency (87.74 %).

The present study was carried out in a continuing experiment at the Bhadiarkhar farm of the CSK HPKV. Eight cropping systems were evaluated during 2016-17 for their effects on weed menace under mid hill conditions of Himachal Pradesh. There were 24 weed species, which invaded different cropping systems. During Kharif, Ageratum sp. (28%) Cynodon dactylon (20%) and Commelina benghalensis (19%) were the predominant weeds. In Rabi, Phalaris minor (63%) was the most dominating weed followed by Coronopus didymus (10%) and Spergula arvensis (6%). In traditional ‘rice-wheat’ system 14 species in Rabi and 8 in Kharif season were found associated and species richness varied with diversification of systems. In Rabi, the highest diversity of weed species was in rice-wheat system and in Kharif weed flora was more diverse in okra, turmeric and colocasia based systems and was lower in rice-based systems. During Kharif, Cynodon dactylon had the highest important value index (IVI) irrespective of the cropping system followed by C. benghalensis. Monochoria vaginalis was the important weed in rice-based cropping systems while Ageratum sp. was important in upland systems. Ageratum sp., Polygonum sp. and C. dactylon invaded the experimental field both during Kharif and Rabi. In Rabi, P. minor had the highest IVI in all the cropping systems.

A field experiment was conducted at Research Farm of College of Agriculture, Tikamgarh, Madhya Pradesh during Kharif, 2016 to find out the suitable herbicides for weed control in sesame. The experiment was laid out in a randomized block design with twelve treatments, viz. pre-emergence application of pendimethalin at 750 g/ha, post-emergence herbicides; quizalofop-ethyl at 40 and 50 g/ha, fenoxaprop-ethyl at 75 and 100 g/ha, pendimethalin at 750 g/ha fb quizalofop at 40 and 50 g/ha, pendimethalin at 750 g/ha fb fenoxaprop at 75 and 100 g/ha, pendimethalin fb one hand weeding at 20 DAS, two hand weeding at 15 and 30 DAS and weedy check. Hand weeding twice at 15 and 30 DAS recorded the lowest intensity and dry weight of total weeds (2.74 g/m2) followed by pendimethalin fb one hand weeding (3.35 g/m2) and these treatments significantly reduced the intensity and dry weight of total weeds over rest of the herbicidal treatments and weedy check. Pre-emergence application of pendimethalin fb post-emergence, quizalofop and fenoxaprop significantly reduced the weed dry weight over alone application of pendimethalin. The net profit was the highest under two hand weeding (` 35,099/ha) followed by pendimethalin 750 g/ha fb one hand weeding (` 30,365/ha) and pendimethalin fb fenoxaprop-ethyl at 100 g/ha (` 27,811/ha), whereas the B:C ratio was higher under the application of pendimethalin 750 g/ha fb fenoxaprop-ethyl 100 g/ha (2.72).

A field experiment was conducted during rainy season of  (Kharif) 2014 and 2015 at Main Research Station, Hebbal, Bengaluru to know the bio-efficacy of different herbicides against weeds and their effect on growth, yield of garlic and to study the integrated impact of mulching and herbicides on weed growth and to know phytotoxicity effect, if any. The experiment was laid out in a split-plot design with ten treatments, comprising with and without paddy straw mulch 5.0 t/ha in main-plot and weed management methods like pendimethalin at 1.0 kg/ha, oxyflurofen at 0.22 kg/ha, oxadiargyl at 0.14 kg/ha, manual weeding twice at 20 and 40 DAS and weedy check in sub-plot. Results revealed that among weed management practices, significantly higher bulb yield was obtained in oxadiargyl 0.14 kg/ha (6.6 t/ha in 2014 and 6.2 t/ha in 2015), at par with manual weeding (6.5 t/ha in 2014 and 6.0 t/ha in 2015), due to lower weed density and dry weight resulting in higher net returns and benefit:cost ratio.