Weeds In Wheat Research Articles

Weed seed bank dynamics responses to long-term chemical control in a rice-wheat cropping system.

It remains an open question if the long-term application of single chemical herbicides would inevitably lead to increased weed populations and result in out-of-control weeds. The annual dynamics of weed seed bank responses to different weeding measures (chemical herbicide, hand weeding and no weeding) in rice-wheat cropping systems were compared to observe the succession of weed communities under different weed selection pressures for 17 years. In unweeded rice-wheat cropping plots, the initially dominant broadleaf weeds were overtaken by grasses and eventually by sedges, while in plots subjected to chemical herbicide or hand weeding, broadleaf weeds remained dominant followed by grasses. The rice-wheat cropping system favoured the spread of paddy weed species; weeding had little effect on the composition of the dominant rice weeds but greatly influenced that of wheat weeds. Total seed density tended to decrease in both weeded and unweeded plots, but the species density and composition of the seed banks differed among plots treated differently. Weeding slightly increased weed species diversity and decreased weed community evenness and dominance in the first several years, but this scenario could have negative consequences in the long term; however, without weeding, stronger interspecific competition led to a decrease in weed species diversity whereas weed community evenness and dominance increased. Long-term and repeated application of pre-emergence chemical herbicides and hand weeding had similar effects on the weed community dynamics, indicating that exclusive application of pre-emergence herbicide could maintain the weed community at a durable relatively low infestation level. © 2019 Society of Chemical Industry.

Herbicidal Potential of Some Dry Land Plants Against Lathyrus aphaca (L.), Winter Season Weed

ABSTRACT: Dry land plants owing to their capability to grow under stressful environment have shown higher allelopathic potential as compared to cultivated plants. An experiment was conducted to investigate the herbicidal potential of aqueous extracts of four dry land plants viz. fruit and vine of Citrullus colocynthis, and above ground parts of Rhazya stricta; Crotalaria burhia and Calligonum polygonoides, with four concentrations (25, 50, 75 and 100%) of initially prepared extracts against Lathyrus aphaca, a common weed of wheat in the studied region. These plants were collected from dry land area (30.03° N and 70.38° E, 129 m above sea level, almost desert conditions) of Dera Ghazi Khan, Punjab, Pakistan. All the four plants exhibited pronounced herbicidal potential with 9 to 91% suppression of different parameters in L. aphaca). Maximum inhibition was recorded in germination (36-91%). Significant suppression in leaf count (9-65%), shoot length (12-59%), root length (4-62%), shoot fresh weight (17-71%), root fresh weight (10-60%), shoot dry weight (15-72%), root dry weight (13-64%), and nodule numbers (34-89%) was also observed. The highest inhibition was exhibited by R. stricta followed by C. colocynthis: fruit. However, in case of nodulation maximum suppression was produced by C. burhia extract. Least suppressant activity was observed for the C. polygonides extract. These results encourage the potential use of locally available dry land plants possessing strong allelochemical properties for nonchemical control of weeds ultimately reducing reliance on chemical control.

Allelopathic potential of the pea seed powder as natural herbicide for controlling weeds infested wheat plants

BackgroundAllelopathy is an alternative safe strategy for chemical herbicides in controlling weeds. So, two successive greenhouse experiments were conducted to determine the phytotoxicity of pea seed powder on two weeds chard- (broad leaf) and canary grass (grass weed)-infested wheat. Pea seed powder was added to the soil surface at successive rates 20, 40, 60, 80, and 100 g/pot. The pots were cultivated on time (at sowing application) or 1 week after the addition of the pea seed powder.ResultsThe results indicated that the pea seed powder at 100 g/pot controlled more than 70–80% of both weeds in comparison to the corresponding controls. On the other hand, the inhibitory effect of the pea seed powder on weeds was accompanied by increases in the growth as well as photosynthetic pigments content and consequently wheat yield especially at 80 g/pot.ConclusionThis study suggested that the pea seed powder has allelopathic and phytotoxic effects that controlled investigated weeds in wheat. Analysis of the allelopathic pea seed powder at the applied rates revealed the presence of phenolic compounds and flavonoids. Both allelopathic compounds showed high levels with increasing the pea seed powder rate. The mixing of pea seed powder with the soil surface at 80 g/pot 1 week before sowing was the most efficient treatment in controlling weeds under investigation that consequently achieved the highest wheat yield.

Devil's Thorn (Emex spinosa (L.) Campd.) Response to Tribenuron-methyl and 2,4-D in Ouazzane Region of Morocco

A soft wheat weed control trial was conducted during the 2016-2017 growing season. The aim of this study is to investigate the effect of two postemergence herbicides Tribenuron-methyl and 2,4 D on Emex spinosa infestation in a soft wheat crop. Treatments consist on two Tribenuron-methyl rates of application and two 2,4-D rates of application. The experimental design was a random block with tree repetitions and observations were made 60 days after application of herbicides. Results showed that treatment with Tribenuron-methyl at 9.50g/ha and 14.25g/ha widely decrease E. spinosa infestations. Tribenuron-methyl at 9.50g/ha recorded 87.8%, 86.1% and 90.5% respectively on E. spinosa density reduction, E. spinosa height reduction, and E. spinosa dry biomass reduction. Tribenuron-methyl at 14.25g/ha recorded 96.3%, 95.5% and 98.7% respectively on E. spinosa density reduction, E. spinosa height reduction, and E. spinosa dry biomass reduction. 2,4 D at 400g/ha and 600g/ha recorded the lowest efficacies that did not exceed 75.2% in all observed parameters.

Growth response of wheat and associated weeds to plant antagonistic rhizobacteria and fungi

Wheat is the staple cereal crop of Pakistan but its growth is rigorously affected by associated weeds. Present study evaluated the synergistic effect of plant antagonistic rhizobacteria and fungi on growth, yield and suppression of wheat-associated weeds. Wheat associated weeds Phalaris minor and Avena fatua were grown in pots containing wheat as well. Pseudomonas aeruginosa strain PAO1 and Trichoderma harzianum T-MN6 were used as amendments to check their effect on two major weeds of wheat. The combined application of PAO1 and T-MN6 reduced the shoot length of Phalaris minor up to 30% and Avena fatua 40%, root length 22% and 28%, fresh biomass 29% and 31% respectively over their sole application. Similarly, inoculation of PAO1 and T-MN6 alone and in combination considerably enhanced growth, yield and physiological parameters of wheat. It was inferred from this study that the synergistic application of PGPR and fungi is a promising option to suppress major weeds of wheat and to enhance growth and yield of wheat.

Age-stage, two-sex life table and food utilization efficiencies of Galerucella placida Baly (Coleoptera: Chrysomelidae) on two Polygonaceae weeds

Abstract Rumex dentatus L. and Polygonum glabrum Willd. (Polygonaceae) are important weeds of wheat and rice fields, respectively, in India and Pakistan. Adults and larvae of Galerucella placida Baly (Coleoptera: Chrysomelidae) feed both weeds. Therefore, we studied the biology of G. placida on two weed leaves using age-stage, two-sex life table at 21 °C, 65 ± 5% r.h. and 12L: 12D. We also studied food utilization indices of G. placida on these leaves. Further, we investigated the quantities of nutrients (total carbohydrates, proteins, lipids, amino acids and nitrogen) and antinutrients (total phenols, flavonols and tannins) of the leaves. Correlation analysis suggested that fecundity and the intrinsic rate of increase (rm) of G. placida were positively correlated with nutrients of leaves, while negatively correlated with antinutrients. Faster larval development, higher longevity of adults and greater fecundity of G. placida were recorded on R. dentatus than P. glabrum. The rm was higher on R. dentatus than P. glabrum. The nutrients were greater in R. dentatus than P. glabrum, while antinutrients were lower in R. dentatus than P. glabrum. The growth rate and consumption index were greater on R. dentatus than P. glabrum. The above results suggested that better nutritional quality of R. dentatus than P. glabrum influenced faster larval development, higher longevity of adults and greater fecundity of G. placida on R. dentatus. This study concluded that R. dentatus could be used for mass rearing of G. placida in biocontol program prior to release in fields for control of both these weeds.

Application of the Herbicides Wing P and Stratos Ultra for Weed Control in Newly-Planted Vineyard

At the Experimental Base of the Institute of Viticulture and Enology, Pleven, Bulgaria it was carried out a three-year planting (2014, 2015 and 2016) of a vineyard for chemicals testing for weed control. Each variant included 20 Cabernet Sauvignon vines grafted to Berlandieri X Riparia Selection Oppenheim 4 (SO 4) rootstock as it was repeated every year of the study. A single spray with Wing P (pendimethalin 250 g/l + dimethenamid P 212.5 g/l) at doses of 0.4 and 0.6 l/da was performed immediately after planting the vines and once with Stratos Ultra (100 g/l cycloxydim) at a dose of 0.2 l/da during the active vegetation stage of the wheat weeds. It was not found a negative impact on the bud germination and the shoot growth and maturation. Applied at a dose of 0.6 l/da, Wing P showed the best control over one-year weed vegetation in the vineyard as the treated vines had more intensive development and mature growth of greater length and mass.

Efficacy of Certain Tribenuron-Methyl Formulations for the Control of Broad-Leaved Weeds in Wheat under Field Conditions

Two field experiments were conducted during 2017-2018 and 2018-2019 seasons to evaluate the effect of eight tribenuron-methyl formulations (four as WG 75% and four as DF 75%) beside hand weeding (twice at 21 and 42 DAS) on broad-leaved weeds (BLWs) in wheat under field conditions. All the agricultural practices were carried out uniformly as recommended. All treatments were arranged in randomized complete block design and replicated four times each of 42 m2 (6×7 m). All formulations were applied at the rate of 8.0 gm fed.-1 in 200 L. water fed.-1 by Knapsack sprayer (CP3) at 30 days after sowing (DAS). After two months from sowing (2MAS) (one month after treatment, one MAT), weeds were collected from an area of 2m2 which was randomly selected from each plot (by using a square woody frame, 50 cm×50 cm). The removed annual BLWs were identified and counted for density as number m-2 and biomass [fresh weight gm m-2] in all treatments. In the untreated control, biomass, biomass%, density and density% for each BLW were recorded. The common prevailed annual BLWs in the experimental wheat field during both seasons were annual Sowthistle (Sonchus oleraceus L.), cheese weed, little mallow (Malva parviflora L.), chicory (Cichorium pumpilum Jacq.), dentated dock (Rumex dentatus L.), medic (Medicago intertexta (L.) Mill.), scarlet pimpernel (Anagallis arvensis L.), sea beet, wild beet (Beta vulgaris L.) and sweet clover, Indian melilot (Melilotus indica L.). The results clearly indicated that biomass and density were varied according to the dominant weed species and from season to another. The BLWs were the most dominant and also they were common in wheat fields and the biomass and density of BLWs were varied between years and weeds. The herbicidal treatments gave the minimum weed biomass and density and gave good weed control efficiency (WCE %) than hand weeding treatments. Granstar formulation completely controlled C. pumpilum weed (in the first season), A. arvensis, R. dentatus and S. oleraceus weeds (in the second season). Skylla formulation completely controlled M. parviflora and R. dentatus weeds in the first season. The tested tribenuron-methyl formulations did not cause complete control for B. vulgaris, M. intertexta and M. indica weeds in both seasons. In all cases, the herbicidal treatments increased significantly the biological yield, grain yield, straw yield, harvest index and thousand grain weight in comparison with untreated control. Also, Granstar, Skylla and Cash Cool herbicides were the most effective, while Ownostar was the least effective. We can concluded that, Granstar, Skylla and Cash Cool formulations are the most effective in controlling broad-leaved weeds in wheat field and consequently increased the grain yield.

Non–target site based resistance to the ALS-inhibiting herbicide mesosulfuron-methyl in American sloughgrass (Beckmannia syzigachne)

AbstractAmerican sloughgrass [Beckmannia syzigachne (Steud.) Fernald] is one of the most predominant and troublesome weeds in wheat (Triticum aestivum L.) fields rotated with rice (Oryza sativa L.) in China. Mesosulfuron-methyl is one of the main herbicides used to selectively control B. syzigachne in winter wheat fields in China. After many years of application, mesosulfuron-methyl failed to control B. syzigachne in Yutai County. The objectives of this study were to determine the resistance level to mesosulfuron-methyl and other acetolactate synthase (ALS) inhibitors in the B. syzigachne population collected from Yutai County (R) and identify the mechanism of resistance. The results indicated that the R population was 4.1-fold resistant to mesosulfuron-methyl and was cross-resistant to pyroxsulam (600-fold), imazethapyr (4.1-fold), flucarbazone (12-fold), and bispyribac-sodium (12-fold). In vitro assays revealed that ALS in the R population was as sensitive as that in a susceptible (S) population. Gene sequence analysis identified no known resistant mutations in the ALS gene of the R population. Furthermore, real-time quantitative reverse transcriptase PCR experiments indicated that the expression level of the ALS gene in the R population was not different from that of the S population. However, the cytochrome P450 inhibitor malathion reversed the R population's resistance to mesosulfuron-methyl. The result of ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS-MS) spectral analysis indicated that the metabolic rates of mesosulfuron-methyl in the R population were significantly faster than in the S population. Therefore, non-target resistance to mesosulfuron-methyl has been demonstrated in the R population. The resistance was very likely caused by enhanced herbicide metabolism.

IMPACT OF WHEAT ESTABLISHMENT METHODS AND WEED MANAGEMENT PRACTICES ON WEED FLORA, YIELD AND NUTRIENT UPTAKE OF WHEAT IN RICE-WHEAT CROPPING SYSTEM

A field experiment was conducted at the Crop Research Centre of Govind Ballabh Pant University of Agriculture and Technology Pantnagar, Udham Singh Nagar during continuous two years to study the weed flora, yield and nutrient uptake of wheat (Triticum aestivum L.) under different wheat establishment methods in main plots and seven weed management in sub plots. Phalaris minor was the most dominant weed at 60 DAS contributed 55.0 per cent of total weed population. Melilotusindica was the major non grassy weeds in wheat which contributed 11 per cent to total weed population during respective years. Sowing of wheat with zero tillage significantly reduced the Phalaris minor density as compared to conventionally tilled wheat after transplanted rice, 60 per cent Phalaris minor emerged from 0-3 cm in reduced and conventional tillage where as in zero tillage after transplanted rice there was 55 per cent emergence from 0-3 cm layer.The highest grain yield was obtained in two hand weedings done at 30 and 60 DAS and was at par with Isoproturon 1.0 kg ha-1 + Metsulfuron methyl 4 g ha-1 at 30 DAS and Clodinafop – Propargyl 60 g ha-1 at 30 DAS fb. Metsulfuron methyl 4 g ha-1 at 37 DAS. Zero tillage resulted in significantly higher uptake of NPK by wheat plants as compared to conventional tillage, whereas reduced tillage recorded minimum NPK, which was significantly lower over the other treatments of wheat establishment methods.

Flufenacet controls multiple herbicide resistant Phalaris minor Retz. in wheat

Phalaris minor Retz. is the major grass weed of wheat, which has developed resistance to multiple herbicides working through three modes of action. The identification of suitable herbicides with different modes of action will assist in the control of this weed in resistance affected areas. Keeping this in view, the efficacy of flufenacet, an oxyacetanilide herbicide, was investigated in 2013 and 2014 at Ludhiana, India. Three doses of flufenacet (200, 250 and 300 g ha−1) were tested at three application timings on Zadoks wheat stages (Z00, Z13 and Z21) and compared with clodinafop application and weedy check for the control of resistant P. minor biotype. Flufenacet 250 and 300 g ha−1, applied at Z00 and Z13 wheat stages, had more than 85% mortality and more than 90% growth reduction of P. minor compared to the unsprayed check (76–109 plants m−2; 60–69 g m−2) at 45 days after sowing in both years, whereas clodinafop just provided 26–37% reduction in density and 39–40% reduction in biomass of this weed. Flufenacet 250 g ha−1 at Z00 and Z13 produced better wheat grain yield (4.2–4.5 t ha−1) in both years, while weed competition in the unsprayed check reduced wheat grain yield by 54–67% (1.75–1.97 t ha-1). This study suggests that flufenacet could be used to control multiple herbicide resistant P. minor in northern Indian wheat production systems.

A Trp-574-Leu mutation in the acetolactate synthase (ALS) gene of Lithospermum arvense L. confers broad-spectrum resistance to ALS inhibitors

Lithospermum arvense is a troublesome dicotyledonous winter annual weed of wheat in China. A L. arvense population (HN01) suspected of being resistant to acetolactate synthase (ALS) inhibitors was found in Henan Province, China. This study aimed to testify the sensitivity of this HN01 population to eight herbicides from 3 different modes of action, and to explore the potential target-site-resistance mechanism to tribenuron-methyl. The whole-plant bioassays indicated that the population was highly resistant to tribenuron-methyl (SU, 350-fold), pyrithiobac sodium (PTB, 151-fold), pyroxsulam (TP, 62.7-fold), florasulam (TP, 80.6-fold), and imazethapyr (IMI, 136-fold), but was sensitive to carfentrazone-ethyl and fluroxypyr-meptyl. ALS gene sequencing revealed that the Trp (TGG) was substituted by Leu (TTG) at codon 574 in resistant plants. In in vitro ALS assays, the concentration of tribenuron-methyl required to inhibit 50% ALS activity (I50) for HN01 was 117-fold greater than that required to inhibit a susceptible population (HN05), indicating that resistance was due to reduced sensitivity of the ALS enzyme to tribenuron-methyl. To the best of our knowledge, this is the first report of ALS gene Trp-574-Leu amino acid mutation confer resistance to tribenuron-methyl in L. arvense.

Herbicidal weed control in drill sown spring wheat under Bangladesh condition

Weeds are considered as one of the major factors responsible for current low wheat yield in Bangladesh. Although chemical weed control is well established in many wheat growing countries, in Bangladesh, the herbicides are typically not used by farmers to manage weeds in wheat. Hence, to evaluate the efficacy of pre- and post-emergence herbicides in mechanized drilled sown wheat, a two-year field study was conducted in southwest Bangladesh. The study evaluated the performance of four pre-emergence herbicides (oxadiargyl 80g, pendimethalin 850 g, pyrazosulfuron 15 g, and mefenacet + bensulfuran methyl 550 g a.i. ha-1) applied at 2 days after sowing (DAS) and four post-emergence herbicides (2,4-D 1400 g, ethoxysulfuron18 g, penoxsulam22.5 g, and fenoxaprop 56 g a.i. ha-1) applied at 20 DAS, on weed control efficacy. A season long weed-free and a season long weedy plots were also maintained to compare the results. The weed control option using a single pre- or post-emergence herbicide was not adequate to control weed effectively when weed infestation was relatively higher. The best yield provided by pre-emergence (pendimethalin and oxadiargyl) and post-emergence (2,4-D and ethoxysulfuron) herbicide treatments were respectively 13-15% and 12-17% lower than the yield (4.1-4.2 t ha-1) of weed-free treatment. Post-emergence herbicides fenoxaprop was the best in controlling weeds; however, due to phytotoxic effects on wheat plants, the plots applied with fenoxaprop produced very low yield (2.6-2.8 t ha-1). Similarly, even after good weed control by the post-emergence application of penoxsulam, phytotoxicity on wheat resulting in low yield. The study suggested that the best weed control option for wheat is to use a pre-emergence (pendimethalin or oxadiargyl) followed by (fb) a post-emergence (2,4-D or ethoxysulfuron) herbicides depending upon weed species which would benefit the farmers by providing high weed control efficacy at lower cost compared to manual weeding.

Effect of herbicides to control weeds in wheat

Effect of herbicides to control weeds in wheat

Control of broad-leaved weeds in wheat under eastern sub-Himalayan plains

Control of broad-leaved weeds in wheat under eastern sub-Himalayan plains

Pre-and post-emergence herbicide sequences for management of multiple herbicide-resistant littleseed canary grass in wheat

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 201516 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, postemergence only and pre-emergence followed by post-emergence herbicide treatments for control of P. minor in wheat. The sequential application of preemergence 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 postemergence herbicides would be better option as compared to their alone applications in order to manage resistant populations of P minor in wheat.

Weed Population Assessment in Wheat at Central Highlands of Ethiopia

Study was conducted on Weed Population Assessment in Wheat at Adea, Gimbichu, Minjar shenkora, Akaki, Boro and Lume Districts in Central Highlands of Ethiopia during, 2014/15 main cropping season to determine the distribution of weed species in wheat growing areas of central highlands of Ethiopia and to record the weed infestation level on wheat crop production. Depending on the area coverage of Wheat in each Districts seven to three kebeles, again in each kebele six to four from Wheat fields samples were taken using 0.5 x 0.5m quderate and GPS instrument. The frequency, abundance and dominance regarding different aspects of weeds were calculated. The result revealed that 45 weed species belonging to 33 families as weeds of wheat for each species was calculated. The 5 major families based on number of taxa were: Poaceae (14), Asteraceae (7), three species each under Polygonaceae and Solanaceae, and Papilionaceae (2), totally they contain 66% of the total weed flora. The most frequent, abundant and dominant weed species were found to be setaria pumila, Plantago lanceolata, Bromus pecpectinatus, Cyperus rotudus, Xanthium strumarium L. and Snowdenia polystachya. Greater than 60% similarity index of weed communities was registered across all locations sampled.

Target-site and non-target-site-based resistance to tribenuron-methyl in multiply-resistant Myosoton aquaticum L.

Myosoton aquaticum L., a widespread and competitive winter weed of wheat in China, has evolved resistance to many classes of herbicides. In one M. aquaticum population (AH03), collected from Anhui Province, where tribenuron-methyl and florasulam had been used to control this weed resistance to both herbicides had evolved. Compared with the sensitive population, HN03(S), the resistant (R) population, AH03, was highly resistant to tribenuron-methyl, flucarbazone-Na and pyroxsulam, moderately resistant to pyrithiobac‑sodium, and florasulam, and had low resistance to diflufenican. AH03 was still controlled by imazethapyr, 2,4-D butylate, fluroxypyr-meptyl, and isoproturon. Pretreatment with the P450 inhibitor malathion reduced the GR50 value of tribenuron-methyl by 43% in the R population, and by 25% in the S population. This indicates that P450-mediated enhanced metabolism is one likely mechanism for tribenuron-methyl resistance in M. aquaticum. Glutathione-S-transferase (GST) activity could be induced by tribenuron-methyl in both the R and S populations. However, both the basal and induced GST activity of the R population was lower than that of the S population. The in vitro ALS assay confirmed that the ALS from the R plants showed a high resistance (52.93-fold) to tribenuron-methyl. ALS gene sequencing revealed a Pro197Ala substitution in the R plants. Based on the ALS gene sequence analysis, molecular markers were also developed to identify the specific Pro197Ala mutation. This population of M. aquaticum has multiple resistance and target-site (ALS Pro197Ala) and non-target-site resistance mechanisms contribute to tribenuron-methyl resistance.

Allelopathic Effects of Different Plant Water Extracts on Yield and Weeds of Wheat

ABSTRACT: Use of synthetic herbicides to control weeds poses serious threats to sustainable agricultural production around the globe. The phytotoxic effect of different plant water extracts (i.e., sorghum, sunflower and mulberry) against weeds has been previously studied; however, their combined effects at different rates are yet to be explored. In this study, mixtures of allelopathic water extracts of sorghum + sunflower and sorghum + sunflower + mulberry were sprayed each at 12, 15, 18 and 21 L ha-1 at 40 and 55 days after sowing in wheat to control wild oats (Avena fatua), little seed canary grass (Phalaris minor), lamb’s quarters (Chenopodium album) and swine cress (Coronopus didymus). A synthetic herbicide Affinity 50 WP (Carfentrazone-ethyl 0.75% + Isoproturon 50% applied at 1000 g a.i., ha-1) and a weedy check were kept as a control treatment. The increasing order of water extract dose 12-21 L ha-1 showed substantial reduction in total weed density and their dry biomass production of both narrow and broad-leaved weeds in all the treatment combinations. Mixture of sorghum + sunflower + mulberry water extracts each at 18 L ha-1 applied at 40+55 DAS resulted in an 87.14% decrease in total weed dry matter with a 19.5% increase in grain yield of wheat and higher net benefits of Rs. 100525 with 777.5% marginal rate of return. Nonetheless, application of sorghum + sunflower water extracts each at 12 L ha-1 at 40+55 DAS was more economical than the other treatments in terms of higher marginal rate of return of 799.82%. Based on this study, it can be suggested that the use of allelopathic plant water extracts in a mixture may act as a potential weed control strategy in wheat.

Bioherbicidal potential of rhizosphere bacteria for management of Phalaris minor weed

Phalaris minor is a problematic weed of wheat (Triticum aestivum L.). Repeated application of herbicides to control this weed causes environmental pollution and some of the weeds even develop herbicide resistance. Recently, phytohormones and allelochemicals produced by rhizosphere microorganisms have been found to suppress the growth of different weeds. Therefore, 32 bacterial isolates obtained from the rhizosphere of wheat were screened for the production of phytohormones indole-3-acetic acid (IAA) and 5-aminolevulinic acid (ALA). Rhizobacterial isolates, having variation in IAA and ALA production ability, were tested for their effect on seedling growth of P. minor on 0.8% water agar plates and four rhizobacterial isolates i. e. HWM 7, HWM 11, HWM 17 and CP 43 caused significant retardation of P. minor seedling growth on 5th and 10th day of seed germination. Under pot house conditions, seed inoculation with Bacillus subtilis strain SYB 101 caused 70.8 and 80.7% decrease in root and shoot dry weight of P. minor and its inoculation showed 136.8 and 316.6% increase in root and shoot dry weight of wheat at 75 days of wheat growth. P. minor growth was also suppressed in the pot house by inoculation of Providentia rettgeri strain CPS 67 and Pseudomonas isolate HWM 11. Maximum growth stimulation of wheat was observed by inoculation with rhizobacterial isolates SYB 101 and HWM 11. Maximum growth retardation of weed was observed by inoculation of B. subtilis strain SYB 101 having moderate level of IAA and ALA production, followed by high IAA and ALA producing P. rettgeri strain CPS 67, suggesting that besides phytohormones, some other metabolite was also involved in growth retardation of P. minor. These rhizobacterial isolates could be further tested for suppression of weed growth under field conditions for their subsequent application as bioherbicide.