Pyrithiobac Sodium Research Articles

Investigation on the Carry-over Effects of Various Pre- and Post-emergence Herbicides Applied Alone and in Combination to Cotton on Succeeding Chickpea Crop

A field experiment was conducted in kharif and rabi season during 2018-19 and 2019-20 at cotton research scheme farm, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (M.S) under irrigated condition (drip) and studied the effect of various pre- and post- emergence herbicide treatments used alone or in combination for weed control on cotton and subsequent chickpea (Cicer arietinum L.) crop. Without using any weed control techniques, chickpea was grown on the same field after the cotton crop had been harvested. Three replications of the randomized block design were used to evaluate seven different treatments. The crop was significantly affected by all herbicide applications, with the exception of hand weeding at 30, 60, and 90 DAS. From the current study, it can be concluded that crops like chickpeas cannot be grown in a safe order after cotton because using pyrithiobac sodium 62.5 g/ha as PE + quizalopfop ethyl 50 g/ha at 60 DAS as the weed management practice in cotton had a significant impact on growth, yield, and economics.

Effect of Herbigation on Weed Control and Yield of Drip Irrigated Cotton

A field experiment was conducted during Summer, 2023 at Anbil Dharmalingam Agricultural College and Research Institute, Tamil Nadu Agricultural University, Tiruchirappalli to study the effect of herbigation on weed control and yield of drip irrigated cotton. The experiment was laid out in randomized block design with nine treatments and replicated thrice. The treatments consisted of herbigation of pre emergence (PE) herbicides (Pendimethalin 1.0 kg ha-1 and Oxyfluorfen 0.2 kg ha-1) combined with hand weeding at 45 DAS or manual spray or herbigation of post emergence (PoE) herbicide (Pyrithiobac Sodium + Quizalofop Ethyl 75 g ha-1 on 25 DAS) compared with recommended practice of manual spray of PE pendimethalin 1.0 kg ha-1 + HW at 45 DAS, HW twice on 20 and 40 DAS and unweeded control. The results revealed that among the different weed management practices manual spray of PE pendimethalin 1.0 kg ha-1 + HW at 45 DAS registered significantly lower total weed density (12.63 m-2), total weed dry weight (8.23 g m-2) and higher weed control efficiency (77%) at 20 DAS. This was followed by herbigation of PE pendimethalin 1.0 kg ha-1 + manual spray of PoE pyrithiobac sodium + quizalofop ethyl 75 g ha-1 on 25 DAS. Among the herbigation treatments, herbigation of PE pendimethalin 1.0 kg ha-1 + manual spray of PoE pyrithiobac sodium + quizalofop ethyl 75 g ha-1 on 25 DAS obtained lower total weed density (12.13 m-2), total weed dry weight (9.19 g m-2) and higher WCE (86%) at 40 DAS. This was followed by herbigation of PE oxyfluorfen 0.2 kg ha-1 + manual spray of PoE pyrithiobac sodium + quizalofop ethyl 75 g ha-1 on 25 DAS. At 60 DAS, application of manual spray of PE pendimethalin 1.0 kg ha-1 + HW at 45 DAS recorded lower total weed density (18.07 m-2), total weed dry weight (16.03 g m-2) and higher weed control efficiency (85%). However, this was comparable with herbigation of PE pendimethalin 1.0 kg ha-1 + manual spray of PoE pyrithiobac sodium + quizalofop ethyl 75 g ha-1 on 25 DAS and HW on 20 and 40 DAS. The highest seed cotton yield (2109 kg ha-1) was obtained with manual spray of PE pendimethalin 1.0 kg ha-1 + HW at 45 DAS and it was on par with herbigation of PE pendimethalin 1.0 kg ha-1 + manual spray of PoE pyrithiobac sodium + quizalofop ethyl 75 g ha-1 on 25 DAS and HW on 20 and 40 DAS. Hence, considering the labour scarcity, herbigation of PE pendimethalin1.0 kg ha-1 on 3 DAS followed by manual spray of PoE pyrithiobac sodium + quizalofop ethyl 75 g ha-1 on 25 DAS could be recommended for better weed control in drip irrigated cotton.

Effects of Integrated Weed Management Practices on Weed Parameters and Yield of Bt Cotton (Gossypium hirsutum L.)

Aim: To know the effect of integrated weed management on weed parameters and yield of bt cotton.
 Study Design: Randomized complete block design.
 Place and Duration of Study: College of Agriculture Farm, Bheemaraynagudi between July 2021 and Feb 2022.
 Methodology: The field experiment was conducted during Kharif 2021 at Experimental block, College of Agriculture, Bheemarayanagudi. The soil of the experiment field was deep black clayey in texture. The experiment comprises 11 weed management practices viz., T1: Pendimethalin 38.7% CS @ 750 g a.i./ha as PE + Hand weeding @ 20-25 DAS and Intercultivation @ 55-60 DAS, T2: Pendimethalin 38.7 % CS @ 750 g a.i./ha as PE fb Pyrithiobac Sodium 10 EC @ 75g a.i./ha + Quizalofop ethyl 5 EC @ 37.5g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS. (Tank mix), T3 : Pendimethalin 38.7 % CS @ 750 g a.i./ha as PE fb Pyrithiobac Sodium 10 EC @ 50g a.i./ha + Quizalofop ethyl 5 EC @ 25 g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS, T4 :Pendimethalin 38.7 % CS @ 750 g a.i./ha as PE fb Pyrithiobac Sodium 10 EC @ 75g a.i./ha + Quizalofop ethyl 5 EC @ 37.5g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS, T5 : Pendimethalin 38.7 % CS @ 750 g a.i./ha as PE fb Pyrithiobac Sodium 10 EC @ 100g a.i./ha + Quizalofop ethyl 5 EC @ 50g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS, T6 : Pyrithiobac Sodium 10 EC @ 50g a.i./ha + Quizalofop ethyl 5 EC @ 25g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS, T7: Pyrithiobac Sodium 10 EC @ 75g a.i./ha + Quizalofop ethyl 5 EC @ 37.5g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS, T8: Pyrithiobac Sodium 10 EC @ 100g a.i./ha + Quizalofop ethyl 5 EC @ 50g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS, T9: Farmers practice (Hand weeding @ 25 DAS and 2 intercultivations @ 50 and 75 DAS), T10: Weedy check, T11: Weed free check.
 Results: Among the treatments, application of pendimethalin 38.7 % CS @ 750 g a.i./ha as PE fb pyrithiobac sodium 10 EC @ 100 g a.i./ha + quizalofop ethyl 5 EC @ 50 g a.i./ha as PoE (combi-product) @ 25 DAS and intercultivation @ 55-60 DAS recorded significantly lower weed density and higher weed control efficiency (82.39 %), also recorded higher seed cotton yield (2495 kg ha-1) and stalk yield (4056 kg ha-1) over other treatments.
 Conclusion: Application of Pendimethalin 38.7 % CS @ 750 g a.i./ha as PE fb Pyrithiobac Sodium 10 EC @ 100g a.i./ha + Quizalofop ethyl 5 EC @ 50g a.i./ha as PoE @ 25 DAS and Intercultivation @ 55-60 DAS was found effective in controlling the weeds with coupled with higher seed cotton yield .

Significance of Weed Flora Identification and its Management on Bt Cotton (Gossypium hirsutum L.) Growing Tract of Tungabhadra Command Area

Aims: To identify the weed species in Bt cotton under Tunga-bhadra project command area and to study the effect of sequential application of pre- emergent (PE) and post- emergent herbicides (PoE) on weed growth and to know the efficiency of different weed control practices on weed species.
 Study Design: The experiment was laid in RBD (Randomized Block Design).
 Place and Duration of Study: The experiment was conducted at ICAR- Krishi Vigyan Kendra farm, UAS, Raichur situated in TBP command area during kharif season of 2018-19.
 Methodology: The design was RBD with 11 treatments and replicated thrice. Gross plot size of the field was 7.2 m × 4.8 m and net plot size was 5.4 m ×3.6 m with spacing of 90 x 30 cm. The certified seeds of Jadoo Bt II Cotton with the test weight of 6.5 g was used for sowing. The crop duration was around 6 month
 Results: Weed flora present in the Bt cotton field were identified and classified based on their morphology. It was divulged that; dicotyledonous weeds were dominant in cotton field. The sequential applications of metolachlor 50 % EC @ 1000 g a.i. ha-1 as PE fb pyrithiobac sodium 10 EC @ 125 g a.i. ha-1 as PoE @ 2-5 leaf stage of weeds fb Inter cultivation (IC) @ 60 DAS reported lower weed count and weed dry matter and reported the highest weed control efficiency (90.22 %) at harvest than the application of diuron 80 % WP as PE fb @ 1500 g a.i. and pendimethalin Pendimethalin 30 EC @ 1250 g a.i. ha-1 as PE followed by pyrithiobac sodium 10 EC @ 125 g a.i. ha-1 as PoE @ 2-5 leaf stage of weeds fb Inter cultivation (IC) @ 60 DAS.
 Conclusion: Application of pre-emergent followed by post emergent herbicides control the early and later flush of weeds. It avoids the emergence of broad spectrum weed flushes and weed shift. Integrated herbicidal application along with intercultural operations was found better in keeping weeds under a threshold than following a single method.

Evaluation of Growth Rates of Bt. Cotton (Gossypium hirsutum L.) Hybrid NHH-44 as Influenced by High Density Planting and Weed Management Practices under Rainfed Conditions in Marathwada Region of Maharashtra, India

A field experiment was conducted at experimental farm, AICRP on Integrated Farming Systems, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (M.S.) during kharif seasons of 2020-21 on to study the “Impact of high density planting and weed management practice on growth and yield of Bt. cotton. (Gossypium hirsutum L.)” Treatment consist of Twelve treatment combinations comprising Three planting densities in main plot that is (S1-120 cm x 45 cm (18518 plants ha-1), S2- 80 cm x 60 cm (20833 plants ha-1) and S3- 90 cm x 45 cm (24691plants ha-1) and four weed management practices that is W1 - Stale seedbed technique + PoE Pyrithiobac Sodium 10% EC @ 62.5 g ha-1 + Quizolfop-ethyl 5% EC @ 50 g ha-1 + Straw mulching, W2 - Stale seed bed technique +PoE Glufosinate ammonium 13.5% SL @ 0.7 kg ha-1 + Hand weeding, W3 - Weed Free and W4 - Weedy Check.
 The mean maximum AGR for plant height were recorded under high density planting 90 cm x 45 cm. Among different growth intervals 61-90 DAS recorded maximum AGR for plant height (1.664 cm day-1 plant-1), while mean maximum AGR for dry matter (2.358 g day-1 plant-1) were recorded between 91-120 DAS under high density planting 120 cm x 45 cm. Among weed management practices, weed free treatment recorded mean maximum AGR for plant height (1.645 cm day-1 plant-1) 61-90 DAS interval, while mean maximum AGR for dry matter (2.441 g day-1 plant-1) were recorded between 91-120 DAS. The mean CGR, RGR and LAI were also maximum under weed free treatment.

Effect of Non-Chemical Weed Management Approaches on Yield and Nutrient Uptake in High Density Planting of Cotton in Vertisol of Northern Karnataka

In order to investigate the impact of non-chemical eco-friendly weed management strategies on the yield, nutrient uptake, and soil balance of high density planting cotton in deep vertisols, a field experiment was carried out in 2017 and 2018 at the Department of Agronomy, College of Agriculture, UAS, Raichur. Three replications were used in the experiment's Randomized Completely Block Design layout. There were 14 different interventions used, including polythene mulch, paddy straw mulch, cotton stalk mulch, intercropping with green manures at a 1:1 ratio (sunnhemp and cowpea), four different botanical extracts at 20% as PE (Eucalyptus sp., Prosopis juliflora extract, Cassia tora, and Parthenium hysterophorus), mechanical, cultural, and their combination, in comparison to weed-free check. Three replicated randomised complete block design was used to conduct the experiment. The two years pooled data showed that, compared to the other treatments, weed free check had a significantly higher seed cotton production (1,722 kg /ha). It was then followed by Cotton + Sunnhemp (1:1) in-situ mulching at 45 DAS (1299 kg /ha), pendimethalin 38.7 CS @ 680 g a.i./ha as PE fb pyrithiobac sodium 10 EC 75 g a.i./ha + quizolofop ethyl 37.5 g a.i./ha at 25 DAS as PoE (1274 kg /ha), The environmentally friendly treatments, such as cotton + sunnhemp (1:1) and in-situ mulching at 45 DAS, mulching with black polythene sheet, cotton + cowpea (1:1) and in-situ mulching at 45 DAS, and others, were on par with weed free check and may be suggested since they were the best options.

Impact of Chemical Weed Management Practices on Yield, Nutrient Uptake and Balance in Soil of High Density Planting Cotton in Deep Vertisols

In order to assess Clomazone 50 EC's effectiveness on seed cotton yield, nutrient uptake, and balance in HDPS cotton in deep Vertisols of the Northern Karnataka region, a field experiment was carried out in 2017–18 and 2018–19. The recommended course of treatment includes pre-emergence applications of Clomazone 50 EC at 250, 500, and 750 g a.i./ha compared to pendimethalin 37.5 CS@680 g a.i./ha, post-emergence applications of pyrithiobac sodium 10 EC and quizalofop ethyl hand weeding at 25 DAS and intercultivation at 50 and 75 days after sowing, as well as weed free. The experiment was set up using a randomised block design with triple replication. The application of Clomazone 50 EC @ 250 g a.i./ha was found to be effective in weed control and enhanced seed cotton yield (38.5%), according to the results. It led to excellent weed control, decreased nitrogen uptake by weeds, and increased nutrient uptake by the crop. Additionally, it leads to the least amount of nutrient losses in terms of uptake and losses. In order to effectively manage weeds in cotton, it was observed that Clomazone 50 EC @ 250 g a.i/ha, followed by pyrithiobac sodium 10 EC @ 75 g a.i./ha + Quizalofop ethyl 5 EC @ 75 g a.i./ha at 25 DAS, were the best applications.

Resistance to ALS inhibitors conferred by non-target-site resistance mechanisms in Myosoton aquaticum L.

Myosoton aquaticum L. is a competitive broadleaf weed commonly found in wheat fields in China and has become challenging due to its evolving herbicide resistance. In this study, one subpopulation, RF1 (derived from the tribenuron-methyl-resistant population HN10), with none of the known acetolactate synthase (ALS) resistance mutations was confirmed to exhibit resistance to tribenuron-methyl (SU), pyrithiobac‑sodium (PTB), florasulam (TP), flucarbazone-Na (SCT), and diflufenican (PDS). In vitro ALS activity assays showed that the total ALS activity of RF1 was lower than that of the susceptible (S) population. However, there was no difference in ALS gene expression induced by tribenuron-methyl between the two populations. The combination of the cytochrome P450 monooxygenase (P450) inhibitor malathion and tribenuron-methyl resulted in the RF1 population behaving like the S population. The rapid P450-mediated tribenuron-methyl metabolism in RF1 plants was also confirmed by liquid chromatography tandem mass spectrometry (LC–MS/MS) analysis. In addition, approximately equal glutathione S-transferase (GST) activity was observed in RF1 and S plants of untreated and tribenuron-methyl treated groups. This study reported one M. aquaticum L. population without ALS resistance mutations exhibiting resistance to ALS inhibitors and the PDS inhibitor diflufenican, and the non-target-site resistance mechanism played a vital role in herbicide resistance.

Effect of Plant Population Density and Methods of Weed Control on The Yield of Pepper (Capsicum annum L.) in Northeastern Nigeria

Field experiments were conducted at Yola and Garkida in Adamawa State, North-Eastern Nigeria during the 2017 rainy season. In the Yola location the experiment was conducted at the Teaching and Research Farm of the Department of Crop Production and Horticulture, Modibbo Adama University of Technology, Yola, and in Garkida it was conducted at Garkida village in Gombi Local Government Area of Adamawa State. The experiment was designed to study the effect of plant population density and methods of weed control on the yield of pepper (Capsicum annum L.). The treatments consist of three spacings, 25 x 30cm, 35 x 40cm and 45 x 50cm with four (4) different herbicides rates (No herbicide, pyrithiobac sodium 65.5kg a.i/ha, pendimethalin 1kg a.i/ha + pyrithiobac sodium 65.5kg a.i/ha and Haloxyfop 108g a.i/ha + hand hoe weeding. The experimental design was a split-plot design replicated three times. Spacing was assigned to the main plot while methods of weed control as subplots. Parameters measured were weed density, number of pepper fruits per plot, and fruit yield per hectare. All data were subjected to analysis of variance (ANOVA) appropriate to the split-plot design. The results of the experiment showed that herbicide pyrthiobac sodium 65.5kg a.i/ha recorded the highest number of fruit per plot of 72.4 while herbicide haloxyfop 108g a.i/ha followed by hand weeding recorded the least number of fruits of 50.1. The result of the experiment shows that there was a significant effect on spacing in both locations. Concerning yield per hectare spacing 25x30cm obtained the highest yield per hectare of 945kg in Garkida, while the least was from the Yola location which recorded 537kg. It was concluded that pepper yield depends on the proper spacing and proper use of herbicide which will suppress weed and increase yield significantly. 
 Keyword: Weed Density, Weed Control, Yield, Pepper

Residual effect of weed control methods on growth parameters of succeeding chickpea (Cicer arietinum L.) Crop

A field experiment was conducted in kharif and rabi season during 2018-19 and 2019-20 under irrigated condition (drip) at cotton research scheme farm, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (M.S) to study the residual effect of weed control methods on growth parameters on succeeding chickpea crop. The experiment was laid out in a randomized block design with seven treatments in three replications. After harvesting of Cotton, Chickpea was sown on the same field without practicing any weed control methods in field. It revealed that weed free treatment recorded the maximum plant height (39.4 cm and 43.0 cm), mean leaf area (20.2 dm2 and 10.4 dm2) and dry weight plant-1 (19.2 g and 18.7 g). Among herbicides treatment POE pyrithiobac sodium @ 62.5 g ai/ha + quizalofopethyl @ 50 g ai/ha at 30 DAS followed by one hand weeding at 60 DAS recorded the maximum plant height (cm), mean leaf area (dm2) and dry weight plant-1 during both the years of study.

Bioefficacy of sequential application of herbicides in cotton

A field experiment was conducted for two years during kharif 2011-12 and 2012-13 to study the bio-efficacy of sequential application of herbicides in Bt cotton. Ten weed control treatments were tested in randomised block design and they were replicated thrice. The mean of two years data indicated that, all the herbicide treatments significantly reduced dry weight of weeds over unweeded control. Among the herbicide treatments sequential application of Pyrithiobac sodium at 0.125 kg/ha as pre emergence followed by (fb) Pyrithiobac sodium at 0.125 kg/ha as post emergence, Butachlor at 1.5 kg/ha fb Butachlor at 1.5 kg/ha and Pendimethalin 38.7% CS 0.68 kg/ha fb Pendimethalin 38.7% CS 0.68 kg/ha were quite effective in controlling weeds which reflected in significantly decreased weed dry weight and increased weed control efficiency. These three herbicide treatments also recorded significantly higher yield (2863, 2830 and 2725 kg/ha, respectively). The growth and yield parameters followed similar trend as that of yield. The weed index was also lower in the above three treatments (11.43, 12.45 and 15.45 %, respectively) compared to un weeded control (76.56 %).

Chemical weed management in hybrid cotton under southern dry zone of Karnataka

A field experiment was conducted during Kharif season of 2015 & 2016 at Krishi Vignana Kendra Haradanahalli, Chamarajanagara, Karnataka to study the efficacy of herbicide for controlling weeds in hybrid Cotton. The trial was comprised of three herbicides viz., pendimethalin (38.75 EC) at 0.75 kg a.i.ha-1, Tank mixture of pyrithiobac sodium (10 SC) @ 62.5 g a.i.ha-1 + quizolofop ethyl (5 EC) @ 37.5 g a.i.ha-1, pendimethalin (38.75 EC) @ 0.75 kg a.i.ha-1, followed by Glyphosate (41% SL) @ 1.0 kg a.i.ha-1, were compared with weed free and weedy check and laid out in randomized complete block design and replicated four times. The results revealed that, tank mixture of pyrithiobac sodium (10 SC) @ 62.5 g a.i.ha-1 + quizolofop ethyl (5 EC) @ 37.5 g a.i.ha-1 at 2 to 4 leaf stages of weeds recorded higher weed index (16.6%), net monetary returns (48500/- Rs./ha) and returns per rupees spent (Rs.12.54) with kapas yield of 1702 Kg/ha as compare to other herbicides.

Energy Balance Studies of Weed Control Practices in Rainfed Cotton

Energy dynamics of the weed control options adopted in rainfed cotton was valuated in a study conducted at College farm, PJTSAU, Hyderabad, Telangana State during kharif, 2017 in red and black soils. Three doses of Diuron (0.5, 0.75 and 1.0 kg ha-1), pendimethalin 38.7% CS at 677 g ha-1 as PE followed by sequential application of pyrithiobac sodium 10% EC 62.5 g ha-1 + quizalofop p ethyl 5% EC 50 g ha-1, intercropping of cotton with green manure crop (Sunhemp), mechanical weeding thrice at 20, 40 and 60 DAS (weed free), polymulch and unweeded control were the treatments included in RBD design which was replicated thrice. The energy balance studies were determined by using direct and indirect energy. The results indicated that the maximum energy input was required for polymulch in both the soils. Highest kapas energy output (EOk) was observed in polymulch and mechanical weeding which was followed by diuron 1.0 kg ha-1PE fb pyrithiobac sodium + quizalofop p ethyl PoEin red soil, whereas in black soils, diuron 0.75 kg ha-1PE fb pyrithiobac sodium + quizalofop p ethyl PoE followed polymulch and mechanical weeding treatments. EUE of both kapas and total output was significantly higher in diuron 1.0 kg ha-1PE fb pyrithiobac sodium + quizalofop p ethyl PoE in red soil. While in black soil, significantly highest EUE of kapas and total output was recorded in diuron 0.75 kg ha-1PE fbpyrithiobac sodium + quizalofop p ethyl PoE.

Productivity of cotton as influenced by different weed control measures in red and black soils

A field experiment was conducted during kharif, 2018 to identify chemical weed control package in cotton with diuron as preemergence herbicide at Professor Jayashankar Telangana State Agricultural University, Rajendranagar. The experiment comprised of 7 treatments having varied doses of diuron 80% WP at 0.5 kg ha-1, 0.75 kg ha-1, 1.0 kg ha-1 and pendimethalin (1.0 kg ha-1) as preemergence application followed by postemergence application of pyrithiobac sodium (62.5 g ha-1) + quizalofop p ethyl 50.0 g ha-1. Non herbicidal treatments comprised of polyfilm, mechanical weeding (at 20 and 40 DAS) and unweeded control. The kapas and stalk yields were higher with polymulch and mechanical weeding in both red and black soils. Among the herbicidal treatments, diuron 0.75 kg ha-1 recorded highest kapas yield in both red and black soils while the higher stalk yield was recorded by pendimethalin in red soil and by diuron 0.5 kg ha-1 in black soil.

Field evaluation of preemergence and postemergence herbicides for control of protoporphyrinogen oxidase-resistant Palmer amaranth (Amaranthus palmeri S. Watson)

AbstractPalmer amaranth accessions resistant to protoporphyrinogen oxidase (PPO), 5-enolpyruvyl-shikimate-3-phosphate synthase, and acetolactate synthase (ALS)-inhibitor herbicides are widespread in the Midsouth, making control difficult. Field experiments were conducted in Marion and Crawfordsville, AR, in 2016 and 2017 to assess PRE and POST herbicides labeled for use in corn, cotton, or soybean for control of multiresistant Palmer amaranth. Accessions at both locations were resistant to glyphosate and ALS inhibitors and segregating for both the R128 and ΔG210 PPO resistance mechanisms. Of the 15 herbicide treatments tested, only atrazine (1,120 g ai ha−1), pyroxasulfone (149 g ha−1), and flumioxazin (144 g ha−1) provided 85% or greater Palmer amaranth control 14 days after treatment (DAT). Visible control ratings at 35 DAT declined sharply, with no treatment providing more than 84% control, suggesting POST applications should be made no later than 28 DAT. Glufosinate (594 and 818 g ha−1), dicamba (560 g ae ha−1), 2,4-D plus glyphosate (784 g ae ha−1 plus 834 g ae ha−1), and paraquat (700 g ha−1) applied POST to 7- to 10-cm plants reduced Palmer amaranth density 83% or more 14 DAT. Both glyphosate (1,266 g ha−1) and pyrithiobac sodium (73 g ha−1) provided less than 7% Palmer amaranth control. Although flumioxazin alone at a labeled rate controlled Palmer amaranth 82% in the PRE experiment, PPO inhibitors by themselves applied POST provided no more than 37% control at 14 DAT. Effective foliar herbicides applied POST, including residual herbicides, should be made when Palmer amaranth are less than 10-cm tall for optimal control of these multiresistant Palmer amaranth accessions.

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.

Nontarget site resistance in Palmer amaranth [Amaranthus palmeri(S.) Wats.] confers cross-resistance to protoporphyrinogen oxidase-inhibiting herbicides

AbstractPalmer amaranth is one of the most problematic weeds in cropping systems of North America, especially in midsouthern United States, because of its competitive ability and propensity to evolve resistance to several herbicide sites of action. Previously, we confirmed and characterized the first case of nontarget site resistance (NTSR) to fomesafen in a Palmer amaranth accession from Randolph County, AR (RCA). The primary basis of the present study was to evaluate the cross- and multiple-resistance profile of the RCA accession. The fomesafen dose-response assay in the presence of malathion revealed a lower level of RCA resistance when compared with fomesafen alone. The resistance index of the RCA accession, based on 50% biomass reduction, ranged from 63-fold (fomesafen alone) to 22-fold (malathion plus fomesafen), when compared with a 2007 susceptible, and 476-fold and 167-fold, respectively, relative to a 1986 susceptible check. The RCA accession was resistant to other protoporphyrinogen oxidase (PPO) inhibitors (i.e., flumioxazin, acifluorfen, saflufenacil) as well as the 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor tembotrione and acetolactate synthase (ALS) inhibitor pyrithiobac sodium. Sequencing of theALSgene revealed no point mutations, indicating that a target-site mechanism is not involved in conferring ALS-inhibitor resistance in the RCA accession. Of the three PPO-inhibiting herbicides tested in combination with the malathion, saflufenacil resulted in the greatest biomass reduction (80%;P< 0.05) and lowest survival rate (23%;P< 0.05) relative to nontreated plants. The application of cytochrome P450 or glutathioneS-transferase inhibitors with fomesafen did not lead to any adverse effects on soybean, suggesting a possible role for these compounds for management of NTSR under field conditions. These results shed light on the relative unpredictability of NTSR in conferring herbicide cross- and multiple resistance in Palmer amaranth.

Weed control in Bt (Bacillus thuringiensis) cotton with pre mix of pyrithiobac sodium plus quizalofop ethyl in north-west India

Cotton is the most important cash crop in North-west India. It is highly sensitive to weed competition during initial growth stages. Lack of selective post-emergence herbicides for broad spectrum weed control has been among major cotton production constraints in the region. Farmers had to rely on non-selective herbicides and or hand-weedings for post-emergence control of weeds. Efficacy of a new pre-mix of pyrithiobac sodium plus quizalofop ethyl for selective post-emergence weed control in cotton was evaluated in a field study conducted over two consecutive cropping seasons at Punjab Agricultural University (PAU), Ludhiana, India. Pyrithiobac sodium plus quizalofop ethyl at 100–125 g ha−1 significantly reduced density and dry biomass of annual grasses and broadleaved weeds in both years; it gave effective control (>88%) of Trianthema portulacastrum L., Dactyloctenium aegyptium, Digitaria sanguinalis and Acrachne racemosa, fair to good control (<80%) of Digera arvensis and no control of Cyperus rotundus. Pyrithiobac sodium plus quizalofop ethyl at 125 g ha−1 gave the highest seed cotton yield (2226–2367 kg ha−1) which was 42–45% higher than unsprayed control and equivalent to pyrithiobac sodium plus quizalofop ethyl at 100 g ha−1 and weed free check in both years. The study demonstrated that pre-mix of pyrithiobac sodium plus quizalofop ethyl at 100–125 g ha−1 could be a suitable option for post-emergence selective control of grass and broadleaved weeds in Bt cotton.

Weed management strategies in Bt cotton under Humid Southern Plain Zone of Rajasthan

A field experiment was conducted during two consecutive years of Kharif 2012 and 2013 at Agricultural Research Station, Banswara to find out suitable weed management strategies for Bt cotton. The experiment was laid-out in Randomized Block Design with three replications having nine treatments. Results revealed that, the application of pendimethalin 30% EC @ 0.75 kg a.i./ha PE fb quizalofop-P-ethyl 50 g a.i./ha at 20-30 DAS+one hoeing gave significantly higher bolls plant -1 (36.30), boll weight (4.22 g), seed cotton yield (2275 kg ha -1 ), net return (Rs.55581/- ha -1 ) and B:C (2.70) over rest of treatments, but it was found at par with weed free check and application of pyrithiobac sodium @ 62.5 g a.i./ha fb quizalofop-P-ethyl 50 g a.i./ha at 20-30 DAS+one hoeing bolls plant -1 (34.84), boll weight (4.19 g), seed cotton yield (2251 kg ha -1 ), net return (Rs.54669/- ha -1 ) and B:C (2.64). The maximum weed control efficiency (60.75%), lowest weed population (12.39 m -2 ) and weed dry matter accumulation (14.63 g m -2 ) at 60 DAS were observed under application of pendimethalin 30% EC @ 0.75 kg a.i./ha PE fb quizalofop-P-ethyl 50 g a.i./ha at 20-30 DAS+one hoeing over rest of treatments. However, it was found at par with weed free check and application of pyrithiobac sodium @ 62.5 g a.i./ha fb quizalofop-P-ethyl 50 g a.i./ha at 20-30 DAS+one hoeing.

Effect of Different Time of Sowing and Weed Management Methods on Weed Interference, Productivity and Profitability of Bt Cotton in Western Zone of Tamil Nadu

A field experiment was conducted at Tamil Nadu Agricultural University; Coimbatore during winter season of 2015-16 and 2016-17 to evaluates the influence of time of sowing and weed management on weed interference and productivity, profitability of Bt cotton hybrid. Result reveled that, Distinctive time of sowing in cotton impact the weeds and cotton growth. Advance sowing of cotton (1st August) with pre-emergence application of pendimethalin 38.7% CS followed by post-emergence pyrithiobac sodium 5% EC 62.5 g/ha significantly recorded lower total weed density and dry weight and better crop growth, higher seed cotton yield, net return and B: C ratio in both years of the experiment.