Weed Science

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Field experiments were conducted in transplanted rice at Visva-Bharati, Sriniketan during Kharif seasons of 2012 and 2013. The predominant weed species were: Ludwigia parviflora, Cyanotis axillaris, Commelina diffusa and Spilanthes acmella. Pre-emergence application of pretilachlor + bensulfuron at 660 g/ha and post-emergence application of bispyribac-sodium + metsulfuron-methyl + chlorimuron-ethyl at 4 g/ha effectively controlled grassy weed population. Post-emergence application of bispyribac + metsulfuron-methyl + chlorimuron-ethyl was found to be most effective in controlling broad-leaved weeds and it was closely fb bispyribac + ethoxysulfuron applied as post-emergence. Application of bispyribac-sodium + metsulfuron-methyl + chlorimuron-ethyl as post-emergence and pyrazosulfuron-ethyl as pre-emergence were effective in controlling sedge population. Post-emergence application of bispyribac + ethoxysulfuron, pretilachlor fb metsulfuron-methyl + chlorimuron-ethyl, pyrazosulfuron fb manual weeding, pretilachlor + bensulfuron and weed-free check recorded more grain yield. The highest net returns and B:C ratio were recorded with bispyribac + metsulfuron-methyl + chlorimuron-ethyl and  pre-emergence application of pretilachlor fb metsulfuron-methyl + chlorimuron-ethyl. Herbicides applied in combination recorded more net returns and B:C ratio as compared to sole application of herbicides.

An experiment was carried out during 2008-09 and 2009-10 at Jagdalpur, Chhattisgarh to determine the influence of rice-based cropping system on the weed dynamics. The rice-fallow system had the higher density (1364 and 1435/m2) of Echinochloa colona, which was gradually reduced with increasing cropping intensity and the lowest density was under rice-garden pea system (20.0 - 20.9/m2). Increasing irrigation frequency increased the density of E. colona. In Rabi season, rice-wheat and rice-garden pea cropping systems were found highly infested with weeds as compared to rice-fallow, rice-chickpea and rice-summer maize systems. The highest rice equivalent yield was recorded under rice-chickpea (7.20-7.76 t/ha) cropping system.

The use of herbicides in direct-seeded rice may affect the biological equilibrium of the soil and thus influence the nutrient status, health and productivity of the soil. To study the effect of herbicides on soil microbial population of direct-seeded rice, field experiment was conducted at Punjab Agricultural University, Ludhiana (Punjab) during Kharif 2009 and 2010. Sixteen weed control treatments, viz. pendimethalin 0.75, butachlor 1.50, thiobencarb 1.50, anilofos 0.375, pretilachlor 0.75, oxadiargyl 0.09 and pyrazosulfuron-ethyl 0.015 kg/ha applied as pre-emergence and each followed by bispyribac 0.025 kg/ha at 30 days after sowing; two hand weedings and unweeded control were tested. The results revealed that viable microbial population was influenced to varying degrees with different weed control treatments during both the years. The herbicides, viz. pendimethalin, butachlor, thiobencarb, anilofos, pretilachlor, oxadiargyl and pyrazosulfuron-ethyl as pre-emergence and bispyribac as post-emergence were safe for soil microbial populations at recommended rate.

Sulfosulfuron at 33.3 g/ha recorded significantly lower weed intensity and biomass, higher weed control efficiency, which was at par with  hand weeding 30 DAS and superior to isoproturon and 2,4 D sodium salt. The maximum nutrient removal by wheat crop and response over weedy check towards grain yield of wheat (129.6%) were with weed free treatment followed by sulfosulfuron at 33.3 g/ha and minimum in   2,4-D of sodium salt at 0.80 kg/ha. The maximum net return and B: C ratio by wheat cultivation (` 31,475/ha and 1:1.80) was obtained with sulfosulfuron at 33.3 g/ha at par with weed free and weeding at 30 DAS than others treatments.

Little seed canary grass (Phalaris minor Retz.) is the dominant grass weed of wheat especially in rice-wheat cropping system in the North-Western Indo-Gangetic Plains of India. It developed resistance to isoproturon herbicide in early 1990’s. Alternate herbicides, viz. clodinafop, sulfosulfuron and fenoxaprop were recommended for its control and were widely adopted by the farmers. Complaints of poor efficacy of these alternate herbicides started appearing at farmers’ field, after decades of their use. Performance of these alternate herbicides was assessed, to study the occurrence of cross resistance in P. minor, through farmers’ field survey. The survey was conducted in 2011 at 73 farmers’ field in six districts viz. Patiala, Fatehgarh Sahib, Ludhiana, Moga, Jalandhar and Ropar in Punjab. The survey indicated that clodinafop and sulfosulfuron are widely used by the farmers. The farmers used to apply field rates of these herbicides till 2008-09 and were getting effective control of P. minor (>85%). During 2009-10, clodinafop started showing signs of reduced efficacy and >30% farmers used 1.5 times of field dose and control was still poor (<65%); few farmers (<10%) used 2 times the field dose with little success. In 2010-11, the farmers (<50%) used 2 times and <30% used 3 times or higher dose of clodinafop alone/tank mix of clodinafop + sulfosulfuron/both herbicides in sequence and control was still poor (0- <60%); re-growth recorded in Patiala, Fatehgarh Sahib, Ludhiana and Moga districts. Sulfosulfuron efficacy also showed declining trend (<60%) during 2010-11. Reduced efficacy of sulfosulfuron was more prevalent in fields having history of continuous use of sulfosulfuron but poor efficacy of clodinafop was even recorded in fields having continuous use of sulfosulfuron. The spray methodology adopted by the farmers was better than they were using in the previous years, hence cannot be related to the reduced herbicide efficacy. The survey results pointed towards the development of cross resistance in P. minor to clodinafop and indicated that sulfosulfuron was likely to meet the same fate in the near future. Proper and regular monitoring of all the existing herbicides is desirable before the situation comes out of control at farmers’ field.

Study was conducted at Punjab Agricultural Univeristy, Ludhiana to find the residual effect of sulphonylurea herbicdes, applied on wheat on the suceeding crops. The application of sulfonylurea herbicides proved quite effective against Phalaris minor in wheat crop without causing any toxicity to the crop. These herbicides being persistent in nature did not have same residual toxicity to most of the  crops grown in succession except in mung and maize where growth and development was adversely affected. The other crops like rice and cotton grew well and did not exhibit any toxicity due to various sulfonylurea herbicides viz., sulfosulfuron and mesosulfuron + iodosulfuron. fresh weight of maize was significantly more in normal pH soil than high pH soil which indicates that herbicides persist longer in high pH soil and cause 8.1% reduction in fresh weight of maize in high pH soil. 

An experiment was carried out during winter seasons of 2008-09 and 2009-10 at JNKVV, Jabalpur to study the response of post-emergence herbicides at variable available soil moisture (ASM) on weed biomass, yield attributing characters and yield of irrigated wheat. The weed control efficiency was higher at 100% ASM at the time of herbicides application and it was declined with every five per cent decrease in available soil moisture and was minimum under 80% ASM. The application of clodinafop fb 2,4-D registered significantly higher weed control efficiency over isoproturon and clodinafop alone.  Yield attributes, viz. number of effective tillers, length of ear head, weight of ear head, weight of grains per ear head, number of grains per ear head, test weight and grain and straw yields were significantly higher at 100% ASM  were at par with 95 and 90% ASM. Clodinafop fb 2,4-D proved significantly superior and produced 4.9, 5.8 and 18.4% higher grain yield over isoproturon, clodinafop and weedy check, respectively. 

The experiment comprising 10 weed management practices of different herbicidal combinations along with hand weeding were conducted on light textured soil of Jagdalpur as rainfed in Kharif season 2011 and 2012 on Tubers. Digitaria sangunalis, Eleusine indica, Setaria gluaca, Cyperus compressus and Echinochloa colona among monocots whereas broad leaved weeds, viz. Celosia argentea, Commelina  benghalensis, Spilanthus acmella and Euphorbia geniculata were found rampant weeds. Irrespective of weeds management practices, density and dry weight of weeds and weed control efficiency were significant under four hand weeding (1,2,3 and 4 month after planting). The growth and yield attributes of cassava over weedy check were also higher in same treatment over weedy check.

Field investigation were carried out during winter season of 2011-12 and 2012-13 at Kalimpong (1250 m asl), to evaluate the effect of different fertilizer levels and weed management practices on density and dry matter of weeds and crop-weed completion for nutrient in Indian mustard (Brassica juncea (L.) Czern and Coss.). Amongst various fertility levels minimum weed density and dry matter production was recorded with the application of 150% RDF, which was found to be significantly superior to all other main plot treatments. Amongst various chemical treatments, the minimum weed density and weed dry matter production was observed with  pendimethalin (0.75 kg/ha) + hand weeding (HW) at 35 DAS, and was at par with the hand weeding twice during both the years, and in second year this was statistically similar with pendimethalin (1.25 kg/ha) and alachlor (1.25 kg/ha).  More seed yield was recorded with 150% RDF (2.19 t/ha) in first year and in second year more yield was associated with the 125% RDF (2.07 t/ha). Amongst various herbicidal treatments, during the first year maximum seed yield was registered with pendimethalin (1.25 kg/ha), and was at par with all the treatments except weedy check, fluchloralin (0.75 kg/ha) and pendimethalin (0.75 kg/ha), and in second year highest seed yield was recorded with the hand weeding twice, and was statistically at par with the pendimethalin (1.25 kg/ha), pendimethalin  (0.75 kg/ha) + HW at 35 DAS and alachlor (1.25 kg/ha). Amongst various main plot treatments, least nutrient uptake by weed was recorded with the application of 150% RDF. Least nutrient depletion by weed was registered with the hand weeding twice during both the year of data recording, and was at par with the pendimethalin (0.75 kg/ha) + HW at 35 DAS. Economics revealed that application of 150% RDF gave maximum net return   (` 19,380). However highest benefit: cost ratio (2.03) was registered with the application of 125% RDF. With sub-plot treatment highest net return (` 19,950) was observed with the hand weeding twice (` 19,950/ha), and was followed by application of pendimethalin (0.75 kg/ha) + HW at 35 DAS (` 19,850/ha). Maximum benefit: cost ratio (2.06) was recorded with the application of pendimethalin (1.25 kg/ha) and was closely followed by pendimethalin  (0.75 kg/ha) + HW at 35 DAS (1.91).

Assessment of various physico-chemical and biological properties of seed powder of Sida cordifolia was done. This plant grows along roadsides and in open land in tropical climates. Mainly useful plant parts are seeds, leaves and roots. The loose bulk density, tapped bulk density, hausner ratio and angle of repose of sample were found to be 0.31g/cm3±0.1, 0.38 g/cm3± 0.2, 1.22%± 1.6 and 30.96o± 0.7, respectively. Moisture content of sample was found to be 10.00±1.6. Total ash, fat, total protein and non protein nitrogen was 3.80% ± 0.5, 10.56% ± 0.3, 22.00% ± 0.9 and 11.20% ± 0.4, respectively. Thermal stability of seeds was up to 200 oC. Low molecular weight protein bands ranging 10-60 kDa were identified. The demonstration of antimicrobial activity against microbes may be indicative of the presence of broad spectrum antimicrobial compounds. Amide I and amide II bands were two major bands of the infrared spectrum. This powder has very low water absorption capacity.

An experiment was conducted at Nadia, West Bengal during 2012 and 2013 to evaluate the effect of herbicides for weed control in transplanted chilli. The weed density, dry weed biomass, WCE and yield components of chillies such as number of fruits/plant, fruit length and economic yield were significantly affected in response to weed control treatments. Treatment receiving oxyfluorfen recorded lower weed biomass (6.01 and 17.57 g/m2) and higher WCE (81.7% and 75.0%) at 30 and 60 DAT, while hand weeding recorded the lowest weed biomass (4.87 and 17.32 g/m2) and highest WCE (85.5 and 75.4%). Hand weeding resulted in the highest number of fruits/plant (36.11), fruit length (6.75 cm) and yield of chilli (3.46 t/ha).

A field experiment was carried out to study the effect of pendimethalin, imazethapyr and paraquat on plant growth and seed yield of pigeonpea. It was found that  maximum increase in seed yield and B:C were obtained with pendimethalin as pre-emergence (PE) 1.0 kg/ha followed by (fb) paraquat 0.40 kg/ha at 8 weeks after sowing (WAS). The next best treatments were pendimethalin as PE 1.0 kg/ha fb paraquat 0.40 kg/ha 6 WAS, imazethapyr 0.075 kg at 20 days after sowing (DAS) fb paraquat 0.40 kg at 6 WAS and imazethapyr 0.075 kg at 20 DAS fb paraquat 0.40 kg at 8 WAS. Similar trend accrued with the economic returns, but B:C  was highest in  pendimethalin as pre-emergence 1.0 kg/ha fb paraquat 0.40 kg/ha at 8 WAS (2.50) followed by imazethapyr 0.075 kg/ha fb paraquat at 6 WAS (2.25) and 8 WAS (2.25) and pendimehalin as PE 1.0 kg/ha fb paraquat 6 WAS (2.20).

A field experiment was conducted at Bhubaneswar to evaluate the efficacy of halosulfuron-methyl for the control of weeds in bottle gourd. The treatments constituted of new herbicide formulation halosulfuron-methyl (75% WG) in different doses (52.5, 67.5, and 135 g/ha) at 3-4 leaf stages of Cyperus rotundus compared with recommended dose of metribuzin at 490 g/ha and two hand weeding on 20 and 40 DAS with unweeded control. The results revealed that the density of Cyperus rotundus was distinctly controlled by application of halosulfuron-methyl. But grasses and broad-leaved weeds were considerably lower in pre-emergence application of metribuzin at 490 g/ha. The lowest total weed dry weight, higher weed control efficiency and cane yield were recorded in metribuzin  490 g/ha followed by halosulfuron-methyl 135 g/ha. The herbicide tested in this study did not show any residual phytotoxic effect on succeeding crop of cowpea.

Biopolymer films have been regarded as potential replacements for synthetic petrochemical based polymers for different uses mainly in pharmaceuticals and packaging applications in view of strong awareness towards more environmental friendly materials. Polysaccharide-mucilage and lignin concentrate were isolated from the mint weed (Hyptis suaveolens). Potato starch was modified and starch-lignin-mucilage-polyvinyl alcohol was prepared in different composition from lignin and mucilage isolates of H. suaveolens. The physical properties like film appearance, opacity, swelling per cent and mechanical properties namely tensile strength and elongation per cent of polyfilms were measured. Acetylated starch with lignin isolates showed good elongation % (17.43±0.24) in comparison to native starch films (2.62±0.11). Acetylation increased the tensile strength while Hyptis lignin increased the elongation per cent of films. The tensile strength of mucilage and polyvinyl film blend was found to be decreased significantly. This  study revealed that lignin and mucilage blends are compatible with starch and synthetic polymers which could be advantageous for cost reduction with improved properties and enhanced increase range of application.

A pot culture experiment was conducted in Open Top Chambers during 2007-08. The plantlets (ramets) of water hyacinth were grown in pots with four different media (M1- tap water, M2- distilled water, M3- hoagland solution and M4- hoagland solution with added heavy metals) in three replications and the pots were kept in open top chambers (OTCs), maintained at ambient (360±20ppm) and elevated CO2 (550±30 ppm), and in open field conditions. Pots in three replications from each media-without plant-were kept under the above three conditions as control to measure the evaporation for WUE estimation. The growth of the plants grown in M1 and M2 was severely affected. The plants grown under elevated CO2 and nutrient rich media (M3 and M4) maintained higher green-leaf area over the growth period and recorded higher net assimilation rate (NAR). CO2 enrichment resulted into reduction of water loss (increased WUE) from plants grown in hoagland (M3) and heavy metal (M4) solutions. When the comparison was made in between M3 and M4 treatments, there was tremendous increase in WUE (reduced transpirational loss of water per gram of dry matter produced) in plants grown in M4. the elevated CO2 enhanced the uptake of heavy metals like Cu, Fe, Mn and Zn in both the media but it was higher in M4 than in M3 due to increased availability.

A field experiment was carried out at Punjab  Agricultural University, Regional Research Station, Bathinda during Kharif 2012. Pendimethalin 750 g/ha followed by imazethapyr 40 g/ha results minimum weed intensity and weed dry matter accumulation and maximum yield attributes and yield except weed free. The application of pendimethalin 750 g/ha followed by imazethapyr 40 g/ha resulted maximum net return (` 33,118/ha) and b:c ratio (2.07) which was more than other treatments of weed control. Imazethapyr, imazethapyr + imazamox, quizalofop-ethyl, fenoxaprop-p-ethyl and pendimethalin at all doses and combinations resulted no phytotoxicity symptoms on guar crop and no residual effect on succeeding wheat crop.

Experiment to evaluate the bioefficacy of pinoxaden 5 EC in combination with carfentrazone in wheat was conducted in sandy loam soil at CCS HAU Hisar during Rabi seasons of 2008-09 and 2009-10, at Agronomy Research Area of CCS Haryana Agricultural University, Hisar. The dominant weeds present in experimental field were little seed canary grass (Phalaris minor Retz.) among grassy weeds and Chenopodium album, Convolvulus arvensis and Melilotus indica among broadleaf weeds. Use of carfentrazone 25 g/ha at 35 DAS and pinoxaden 40 g/ha 7 days after carfentrazone use was not as effective against P.minor as pinoxaden use at 35 days after sowing. Post-emergence use of pinoxaden at 50 g/ha (35 DAS) with sequential use carfentrazone at 25 g/ha (42 DAS) with 1% ammonium sulphate provided complete control grassy and broadleaf weeds without any phytotoxic effect on wheat crop.

A field experiment was conducted during Rabi season of the year 2011-12 at Anand Agricultural University, Anand, Gujarat. The maximum grain yield, straw, grain, lower weed count , weed dry matter, weed index, higher weed control efficiency were obtained from treatment 1/3   as basal + 1/3 at CRI + 1/3 at FND. Different weed management practices significantly influenced yields and weed parameters. The higher grain yield, straw yield were recorded from treatment  pendimethalin 1.0 kg/ha (PE) fb metsulfuron-methyl 0.004 kg/ha (PoE at 25-30 DAS) (3882 kg/ha). While, treatment of hand weeding at 20 and 40 DAS recorded significantly minimum count, weed dry matter, weed index with higher weed control efficiency. Interaction effects time of nitrogen and weed management practices were significant in respect of plant height weed dry matter at 25, 50 and at harvest.

A field experiment was conducted during Rabi season of 2010-11 at Faizabad to assess the bio-efficacy of fenoxaprop and formulation of fenoxaprop available as Wipsuper in the market at various doses and clodinofop on weeds and productivity of late sown wheat. Fenoxaprop at higher doses effectively suppressed weeds and produced significantly lowest weed dry weight but it did not able to enhance nitrogen removal by crop as at lower doses. Post-emergence application of Whipsuper (fenoxaprop) 120 g, fenoxaprop 100 and 120 g and clodinofop 60 g/ha in late sown wheat eliminates crop weed competition at tillering and grant growth period which ultimately provides congenial conditions to crop for better harnessing of available crop growth resources and produced profitable grain yields.

Parthenium is an alien invasive species spreading very fast in natural and agricultural ecosystems of Pakistan. Besides having direct negative effects on many field crops and other economically important plants, this weed has also been reported to be an alternate host of a number of agricultural pests and diseases. This paper reports Parthenium weed being as an emerging host for cotton mealy bug in Pakistan. Efforts were needed to remove Parthenium weed from cotton growing belt to minimize the damages caused by this pest to cotton crop in the season.

A field experiment was carried out during 2012-13 in randomized block design with three replications at Weed Science Research Station, VNMKV, Parbhani with eight treatments. Results showed that metribuzin 0.7 kg/ha PE fb straw mulch 10 t/ha fb one HW recorded lowest dry weight of weeds, highest weed control efficiency, fresh rhizome yield (12.16 t/ha) net monitory returns (Rs 1,44,630/ha) and B:C ratio (1.47) as compared to other treatments.

Natural incidence of the oligophagous fly Phytomyza orobanchie was observed on Orobanche crenata in brinjal (egg plant: Solanum melongena) in the farmers’ field in Central India during a survey in January 2013. This natural incidence indicatesd that the bioagent is now established in India. The bioagent has been submitted to gene bank accession (No. KC732453.1, p. 658). It was concluded that if more intensive surveys are conducted in the Orobanche infested areas, there may be chances for more areas to be indentified and this insect may be used in the integrated management of Orobanche.  

Based on the data on the effect of nutrient management and crop spacing  on the growth and development of I. miliacea, it could be elucidated that application of enhanced nutrients exclusively as chemical fertilizers in combination with wider spacing  stimulated growth and vigour of the weed. Hence an integrated approach in nutrient management is suggested for efficient and economic management of the weed.  By altering nutrient management and adjusting the plant population, the competitive ability and productivity of rice crop can be improved and weed management made more efficient and economic. Considering the practical importance of the study, detailed investigation in similar lines needs to be conducted on such major weeds for the entire state under all systems of rice cultivation including upland rice.

Pendimethalin 1000 g/ha as pre-emergence effectively controlled C. album, M. denticulata and Phalaris minor. Pinoxaden 50 g/ha and clodinafop 60 g/ha as post-emergence were effective in controlling only P. minor. Pinoxaden and trifluralin were slightly phytotoxic to chickpea plants, which recovered later on. The highest grain yield was obtained in weed free treatment which was at par with two hand weeding, pre-emergence use of pendimethalin at 1000 g/ha fb pinoxaden at 50 g/ha applied at 45 DAS and pendimethalin at 1000 g/ha fb clodinafop at 60 g/ha applied at 45 DAS. Presence of weeds throughout crop season reduced the seed yield up to 68%.

An experiment was conducted during Kharif season of 2009 at BHU, Varanasi to evaluate the bio-efficacy of imazethapyr 10% SL + surfactant against important weeds of groundnut. Application of imazethapyr  200 g/ha + surfactant being at par with its lower rates of 100 and 125 g/ha, reduced the density of dominant weeds. Pre-emergence application of oxyfluorfen 250 g/ha effectively controlled the Dactyloctenium aegyptium and Trianthema portulacastrum whereas, it was least effective against Echinochloa colona and Cyperus rotundus. Imazethapyr  200 g/ha + surfactant recorded significantly the highest seed and haulm yield and weed control efficiency over imazethapyr 100 g/ha + surfactant (market sample), imazethapyr 75 g/ha + surfactant and oxyfluorfen 250 g/ha. There was no-phytotoxicity symptoms on crop even at higher rate (200 g/ha) of the herbicide.

The residual effects of pendimethalin, quizalofop, imazethapyr and imazamox, applied to soybean crop, on the succeeding winter season crops, viz. wheat, barley, spinach, pea, raya, canola and sugarbeet were determined through field bioassay at Ludhiana in 2013-14. Soybean was supplied with fifteen weed control treatments, viz. pendimethalin at 450 g/ha as pre-emergence alone and followed by (fb) hoeing, imazethapyr + imazamox at 60 and 70 g/ha each at 3 and 4 weeks after sowing (WAS), quizalofop 37.5 and 50.0 g/ha at 3 WAS, pendimethalin 450 g/ha fb imazethapyr + imazamox 60 and 70 g/ha at 4 WAS/quizalofop at 37.5 and 50.0 g/ha at 4 WAS, imazethapyr + imazamox 60 and 70 g/ha at 3 WAS fb quizalofop 37.5 g/ha at 6 WAS and unsprayed check. The emergence, plant height and dry matter accumulation of all the succeeding crops were similar among herbicidal and unsprayed plots indicating that all the herbicides are safe for raising of these winter crops in rotation with soybean.