Early Postemergence Applications Research Articles

Herbicidal impact on density of Cuscuta campestris Yunck. emerged in berseem fodder crop

A field experiment was conducted at the research farm of RVSKVV Gwalior during Rabi 2018-19 and 2019-20 to assess the efficacy of different pre- and post- emergence herbicides to manage Cuscuta campestris Yunck. in berseem. C. campestris, well known as a dodder, is a serious problem in berseem. Eight treatments consisting of pre-emergence application (PE) of pendimethalin 1000 g/ha, early post-emergence application (EPoE) at 10 days after sowing (DAS) of pendimethalin 1000 g/ha, oxyfluorfen 250 g/ha PE, post-emergence application (PoE) of imazethapyr 40 g/ha after first cut at 60 DAS, imazethapyr 40 g/ha PoE after last cut at 120 DAS, imazethapyr 40 g/ha PoE after first cut + 40 g/ha after last cut, Cuscuta free and control plot (no herbicide application) were laid out in RBD with three replications. Imazethapyr 40 g/ha PoE after first cut at 60 DAS was found to be very effective in controlling the C. campestris resulting 43% and 16% higher fodder and seed yield, respectively with 43.6% higher profitability. The next best was imazethapyr 40 g/ha PoE after first cut + 40 g/ha after last cut. Pendimethalin PE and oxyfluorfen PE caused phytotoxicity to berseem due to the higher dose of both herbicides and reduced the fodder and seed yield drastically.

Evaluating herbicide programs for peanut response and weed control

AbstractField research evaluated peanut (Arachis hypogaea L.) tolerance and weed control with preemergence (PRE) followed by early postemergence (EPOST) herbicide programs: PRE pyroxasulfone, S‐metolachlor, flumioxazin, pendimethalin, ethalfluralin, diclosulam, or dimethenamid‐P, followed by EPOST application of paraquat + acetochlor + bentazon at 4 wk after PRE (WA‐PRE). The herbicides resulted in no differences in peanut injury at 2 WA‐PRE in 2019 but flumioxazin resulted in approximately two‐fold greater injury (>22%) than other treatments in 2020 because of heavy rainfall at peanut cracking. Palmer amaranth (Amaranthus palmeri S.Watson) control with diclosulam was lower than with other herbicides. Carpetweed (Mollugo verticillata L.) control with S‐metolachlor and dimethenamid‐P was at least 10% lower than with pendimethalin, flumioxazin, or pyroxasulfone at 4 WA‐PRE. Palmer amaranth control 2 wk after the EPOST (WA‐EPOST) application was >94% for all treatments except diclosulam. Peanut injury at 2 WA‐EPOST was ≤28% but was minimal by 8 WA‐EPOST. Overall, yield with herbicide treatments was similar to the weedfree control. A greenhouse experiment evaluated postemergence herbicide combinations for Palmer amaranth control, including 2,4‐DB, acifluorfen, imazapic, bentazon + acifluorfen, pyroxasulfone + carfentrazone, and various combinations of each. Palmer amaranth control (≥99%) was greater and biomass (≤0.3 g plant–1) was lower with acifluorfen treatments than with other treatments. The 2,4‐DB + pyroxasulfone + carfentrazone treatment provided similar control to acifluorfen treatments. The EPOST paraquat + acetochlor + bentazon combinations following an effective PRE program will effectively control Palmer amaranth in peanut. Additionally, greenhouse experiments supported the use of acifluorfen for postemergence Palmer amaranth control.

Effect of herbicide mixtures on weeds and yield of summer groundnut

Field experiment was carried during summer 2020 at Agronomy farm, B. A. College of Agriculture, Anand Agricultural University, Anand, Gujarat on loamy sand soil to study the effect of herbicide mixtures on weeds and yield of summer groundnut (Arachis hypogaea L.). The experiment was conducted in randomized block design with twelve treatments, replicated four times. Weed density decreased significantly with pre-emergence application (PE) of pendimethalin + oxyfluorfen (tank mix) 900 + 120 g/ha and intercultivation (IC) followed by (fb) hand weeding (HW) at 20 and 50 days after seeding (DAS), as compared to other treatments, which resulted in significant increase in growth and yield attributes viz., periodical plant height (cm), plant dry biomass (g/plant), nodule dry weight (mg/plant), number of pods/ plant, pod yield (kg/ha), haulm yield (kg/ha), seed index (g), harvest index (%) and shelling percentage (%). Maximum net returns (Rs. 125485/ha) and B:C (4.94) was achieved with pendimethalin + oxyfluorfen 900 + 120 g/ha PE which was closely followed by IC fb HW at 20 and 50 DAS and early post-emergence application of fluazifop-p-butyl (11.1%) + fomesafen (11.1%) SL (pre-mix) 250 g/ha.

Carfentrazone Plus Pyroxasulfone Combinations for Weed Control in Peanut (Arachis hypogaea L.)

Aims: To determine peanut response and weed control following the use of carfentrazone plus pyroxasulfone (C + P).
 Study Design: Randomized complete block design with 3-4 reps depending on location.
 Place and Duration of Study: Studies were conducted during the 2015 and 2016 growing seasons in south Texas near Yoakum (29.276o N, 97.123o W), the High Plains of Texas near Lamesa (32.769o N, 101.977o W) or Brownfield (33.104o N, 102.161o W), and southwestern Oklahoma near Ft. Cobb (35.091o N, 98.275o W).
 Methodology: Plots were infested with naturally occurring weed populations. Pendimethalin was applied either preplant incorporated (PPI) or preemergence (PRE). Early postemergence (EPOST) applications varied according to weather conditions and peanut growth at each location. Postemergence (POST) treatments were applied 26 to 58 days after planting. Weed control and peanut stunting were visually estimated on a scale of 0 to 100 (0 indicating no control or plant death and 100 indicating complete control or plant death).
 Results: Peanut stunting with C + P was only noted at the High Plains and Oklahoma locations in 2015 but not 2016. Urochloa texana (Buckl.) control with C + P (PRE) varied from 75 to 93%. POST applications provided inconsistent control. Amaranthus palmeri S. Wats. control with C + P (PRE) was at least 78% season-long while POST applications were inconsistent (24 to 100%). Pendimethalin plus C + P controlled Cucumis melo L. var. Dudaim Naud. at least 80% late-season. Ipomoea hederacea Jacq. control was excellent season-long (> 80%) in 2015 but poor (< 60%) in 2016. Reduced peanut yields were noted with C + P in Oklahoma in 2015 to excessive season-long injury. 
 Conclusion: The premix of C + P has potential for use in peanut especially for control of many small-seeded annual broadleaf weeds that continue to plague many peanut growers across the southwest. For effective broad-spectrum annual weed control season-long, the addition of pendimethalin to PRE applications will be required.

Efficacy of Herbicides in Controlling Wild Onion (Asphodelus tenuifolius L.) in Cumin Grown under Arid Climatic Conditions

A field experiment was conducted to investigate the effectiveness of different herbicides for controlling wild onion (Asphodelus tenuifolius) in cumin (Cuminum cyminum L.) during the rabi seasons (2018–2019 and 2019–2020) at Agricultural Research Station, Agriculture University, Jodhpur, Rajasthan. The experiment comprised eight herbicidal weed management treatments for wild onion applied to cumin in a three-replication randomized block design. Among the herbicidal weed management treatments, early post-emergence (8 DAS) application of oxyfluorfen 200 g/ha resulted in the lowest weed density and dry matter of Asphodilus tenuifolius, with maximum weed (Asphodilus tenuifolius) control efficiency at 40 days after sowing (DAS) during both experimental years. Likewise, the highest total efficiency of weed control was recorded with the application of oxyfluorfen 200 g/ha at 8 DAS. Oxyflourfen 200 g/ha used early post emergence (8 DAS) reduced the weed index more effectively than the other herbicides. It also recorded the highest number of branches/plant, plant height, umbels/plant, umbellates/umbel, seeds/umbellates, and seed yield. However, application of oxyflourfen @ 200 g/ha 8 DAS–early POE and pendimethalin 38.7 CS 500 g/ha + oxyfluorfen @ 150 g/ha 8 DAS–early POE were statistically similar in terms of plant growth, yield, and yield attributes. The net returns (366.49 USD/ha in 2018–2019 and 175.72 USD/ha in 2019–2020) and B:C ratio (1.70 and 1.33 in 2018–2019 and 2019–2020, respectively) were also superior, with oxyfluorfen 200 g/ha applied early post emergence.

Control of glyphosate‐ and mesotrione‐resistant Palmer amaranth in glyphosate‐ and glufosinate‐resistant corn

AbstractIncreasing reports of herbicide‐resistant Palmer amaranth (Amaranthus palmeri S. Watson) pose a serious management concern for Kansas corn (Zea mays L.) producers. The objectives of this study were to evaluate various herbicide programs, including preemergence (PRE) alone, PRE followed by (fb) early postemergence (EPOST), and PRE fb late POST (LPOST) for control of glyphosate‐ and mesotrione‐resistant (GMR) Palmer amaranth in glyphosate‐ and glufosinate‐resistant corn, and their effect on crop injury, yield, and net economic return. Field experiments were conducted in 2018 and 2019 in grower fields with natural infestations of GMR Palmer amaranth near Seward in Stafford County, KS. Preemergence programs, including dicamba + thiencarbazone‐methyl + atrazine and dicamba + [atrazine, bicyclopyrone, mesotrione, S‐metolachlor (ABMS)] or dicamba + ABMS in mixtures with atrazine, mesotrione, S‐metolachlor, and metribuzin provided 89–93% control of GMR Palmer amaranth 3 wk after PRE. Preemergence fb EPOST programs provided 87–96% control of GMR Palmer amaranth at 2 wk after EPOST through 7 wk after LPOST. In comparison, PRE‐only programs provided 62–82% and PRE fb LPOST programs provided 75–86% control. The various herbicide programs resulted in greater corn grain yield ranging from 9,207 to 10,508 kg ha–1 compared with 6,056 kg ha–1 in the nontreated control. The highest net return ($1,300 ha–1) was achieved from dicamba + ABMS + atrazine applied PRE fb EPOST application of ABMS + atrazine. These results suggest that effective PRE fb EPOST herbicide programs consisting of multiple sites of actions are available and provide effective control of GMR Palmer amaranth in glyphosate‐ and glufosinate‐resistant corn.

Injury potential of herbicide combinations on XtendFlex® cotton

AbstractXtendFlex® technology from Bayer allows growers to apply glyphosate, glufosinate, and dicamba POST to cotton. Since the evolution and spread of glyphosate-resistant weed species, early POST applications with several modes of action have become common. However, crop injury potential from these applications warrants further examination. Field studies were conducted from 2015 to 2017 at two locations in Mississippi to evaluate XtendFlex® cotton injury from herbicide application. Herbicide applications were made to XtendFlex® cotton at the three- to six-leaf stage with herbicide combinations composed of two-, three-, and four-way combinations of glyphosate, glufosinate,S-metolachlor, and three formulations of dicamba. Data collection included visual estimations of injury, stand counts, cotton height, total mainstem nodes, and nodes above whiteflower at first bloom. Data collection at the end of the season included cotton height, total mainstem nodes, and nodes above cracked boll. Visual estimations of injury from herbicide applications were highest at 3 d following applications containing glufosinate +S-metolachlor (36% to 41% injury) and glufosinate +S-metolachlor in combination with dicamba + glyphosate (39% to 41% injury), regardless of the dicamba formulation. Crop injury decreased at each rating interval and dissipated by 28 d following applications (P = 0.3748). Height reductions were present at first bloom and at the end of the season (P < 0.0001), although cotton yield was unaffected (P = 0.2089), even when injury at 3 d after application was greater than 30%. Results indicate that growers may apply a variety of herbicide tank mixtures to XtendFlex® cotton and expect no yield penalty. Furthermore, if growers are concerned with cotton injury after herbicide applications, the use of glufosinate in combination withS-metolachlor should be approached with caution in XtendFlex® cotton.

Spring-applied triclopyr mixtures for bermudagrass (Cynodon dactylon) suppression in Louisiana sugarcane

AbstractSugarcane infested with bermudagrass and harvested as seed cane introduces the potential for weedy propagules to reinfest fields. Research was conducted in 2018 and 2019 following sugarcane harvest for seed cane to evaluate bermudagrass management with photosystem II (PSII)- and 4-hydroxyphenylpyruvate dioxygenase (HPPD)–inhibiting herbicides applied alone or mixed with triclopyr. Combinations of diuron at 2.8 kg ha–1 with clomazone at 1.5 kg ha–1 or triclopyr at 1.1 kg ha–1 and hexazinone at 0.74 kg ha–1 with triclopyr applied early POST (EPOST) in mid-February injured bermudagrass 85% to 86%, and injury was greater than diuron or hexazinone alone (16% and 10%) in mid-March. Bermudagrass injury decreased to 45% to 56% for these combination treatments by April; however, injury differences were similar to the earlier rating. Late POST (LPOST) mid-March application of these treatments indicated similar bermudagrass injury trends when evaluated in early April. By mid-May, however, no treatment resulted in greater than 18% bermudagrass injury. Clomazone plus diuron applied LPOST resulted in 19% sugarcane injury by early April; however, all other treatments resulted in 7% sugarcane injury or less. In mid-May, a mid-April EPOST application of topramezone at 0.025 kg ha–1 plus triclopyr at 1.1 kg ha–1 resulted in 62% bermudagrass injury, which was equivalent to that observed with other topramezone rates in this combination (0.012 and 0.037 kg ha–1) (54% to 60%). Bermudagrass injury from triclopyr mixed with mesotrione (32%) or triclopyr mixed with atrazine, mesotrione, and S-metolachlor (47% to 55%) resulted in bermudagrass injury similar to that with topramezone plus triclopyr (54% to 62%). Data showed the flexibility of triclopyr when mixed with several HPPD- or PSII-inhibitor herbicides for bermudagrass management in a Louisiana sugarcane cropping system. Greater flexibility in application timing for HPPD-inhibitor herbicides than for PSII-inhibitor herbicides (diuron or hexazinone), and mixed with triclopyr, may suppress bermudagrass POST in April and May with minimal sugarcane injury.

Sesame (Sesamum indicum L.) Response to Delayed Applications of Preemergence Herbicides Applied 3 or 6 Day after Emergence

Aims: Field studies were conducted to determine sesame response to the pre-emergence herbicides (acetochlor at 1.7 kg ai ha-1; S-metolachlor at 0.72, 1.43, and 2.86 kg ai ha-1; dimethenamid-P at 0.84 kg ai ha-1; pethoxamid at 0.22 kg ai ha-1; pyroxasulfone at 0.09 kg ai ha-1and bicyclopyrone at 0.12 and 0.24 kg ai ha-1) applied 3 or 6 days after 50% emergence.
 Study Design: Randomized complete block design with 3-4 reps depending on location.
 Place and Duration of Study: Sesame growing areas of Alabama, Mississippi, and Texas during the 2016 through 2018 growing seasons.
 Methodology: Treatments consisted of a factorial arrangement of herbicide treatments at two early POST application timings. A non-treated control was included for comparison. Crop oil concentrate (Agridex®, Helena, Collierville, TN 38017) at 1.0% v/v was added to all herbicide treatments. Plot size was either five rows (76 cm apart) by 9.1 m or four rows (101 cm apart) by 7.3 m depending on location. Only the two middle rows were sprayed and the other rows were untreated and served as buffers. Sesame cultivars were seeded approximately 1.0 to 2.0 cm deep at 9 kg/ha at all locations. Injury was evaluated early-season, 7 to 27 days after herbicide application (DAA), and later, 28 to 147 DAA, based on a scale of 0 (no sesame injury) to 100 (complete sesame death). Injury consisted of stuntingand leaf chlorosis and/or necrosis.
 Results: All herbicides tested resulted in significant injury to sesame at some location and application timing. None of the herbicides evaluated are safe to use early POST on sesame without causing significant injury. 
 Conclusion: The ability of sesame to recover from significant injury and compensate for injury led to no yield loss in many instances. However, levels of injury observed are not acceptable by growers and will not allow the use of these herbicides soon after sesame emergence.

Crop Establishment and Weed Control Options for Sustaining Dry Direct Seeded Rice Production in Eastern India

Dry direct seeded rice (DSR) has emerged as an economically viable alternative to puddled transplanted rice to address emerging constraints of labor and water scarcity and the rising cost of cultivation. However, wide adoption of DSR is seriously constrained by weed management trade-off. Therefore, the availability of effective weed control options is critical for the success and wide-scale adoption of DSR. A field study was conducted at ICAR-National Rice Research Institute, Cuttack, India, in the dry seasons of 2015 and 2016 to evaluate the performance of three crop establishment methods and five weed control practices on weed management, productivity, profitability and energetics of dry DSR. The results demonstrated that weed density and weed dry weight was lower in drill seeding than broadcast seeding by 26–36% and manual line-seeding by 16–24%, respectively, at 30 and 60 days after crop emergence (DAE). Among herbicides, post-emergence application (17 DAE) of azimsulfuron was most effective in controlling weeds compared to early post application of bispyribac-sodium and bensulfuron-methyl+pretilachlor. Weed competition in the weedy check treatment resulted 58% reduction in rice yield. Among establishment methods, drill-seeding was most profitable with US $ 685 ha−1 higher net income than broadcast seeding primarily due to higher yield. Among weed control treatments, azimsulfuron was most profitable resulting in US $ 160 and 736 ha−1 higher net income than weed free and weedy check, respectively. The specific energy was lowest for drill seeding among establishment method and azimsulfuron among weed control practices, suggesting lowest energy consumed in producing per unit of grain yield.

Effect of weed management practices on weed dynamics in clusterbean [Cyamopsis tetragonoloba (L.) Taub

A field experiment was conducted to find out the effect of weed management practices on weed dynamics in clusterbean [Cyamopsis tetragonoloba (L.) Taub]. The experiment was carried out during kharif season of 2018 and ten treatment combination of different herbicides were replicated thrice in RBD. Results revealed that the early post-emergence application of imazethapyr + imazamox 50 g/ha + HW at 35 DAS was found the most effective treatment which recorded lowest density of narrow and broad leaved weeds and minimum weed dry matter at all growth stages. This treatment also recorded significantly higher seed yield (1180 kg/ha) with higher weed control efficiency (92.8%) and lowest weed competition index (4.6%). This practice of weed management was statistically at par with weed free season long plots and another treatment of application of imazethapyr 40 g/ha at 20 DAS + HW at 35 DAS.

Annual bluegrass control in bermudagrass using dimethenamid and pendimethalin

AbstractA 2‐yr field experiment was conducted at three locations across Tennessee during 2017–2018 to determine if early‐postemergence (EPOST) applications of FreeHand [pendimethalin (3,4‐dimethyl‐2,6‐dinitro‐N‐pentan‐3‐ylaniline) + dimethenamid (2‐chloro‐N‐[2,4‐dimethylthiophen‐3‐yl]‐N‐[1‐methoxypropan‐2‐yl]acetamide)] could control annual bluegrass (Poa annua L.)(ABG) similar to Kerb SC [pronamide (3,5‐dichloro‐N‐[2‐methylbut‐3‐yn‐2‐yl]benzamide)] and Princep [simazine (6‐chloro‐2‐N,4‐N‐diethyl‐1,3,5‐triazine‐2,4‐diamine)]. Across all locations and years, EPOST applications of FreeHand at 200 lb acre–1 controlled ABG by 88 to 100% 23 wk after the initial treatment, more than or equal to Kerb SC and Princep. Follow‐up research was conducted in Knoxville, TN, during 2018–2019 to compare the efficacy of FreeHand applied EPOST with Pendulum AquaCap (pendimethalin) and Tower (dimethenamid) applied individually. Sequential EPOST applications of Tower controlled ABG similar to FreeHand on all ratings dates, whereas single applications of Tower resulted in less control. Annual bluegrass control efficacy with EPOST applications of Pendulum AquaCap varied over years. Over the course of eight trials, EPOST applications of FreeHand at 200 lb acre–1 controlled ABG by 88 to 100%, suggesting that it is a new option turfgrass managers can use to control ABG in bermudagrass (Cynodon spp.).

EVALUATION OF EARLY POST-EMERGENCE HERBICIDE APPLICATION ON WEED CONTROL, CROP GROWTH AND NUTRIENT UPTAKE IN TRANSPLANTED RICE (ORYZA SATIVA)

A field experiment was conducted during Kuruvai season at the Experimental Farm, Department of Agronomy, Annamalai University to evaluate the performance of early post emergence application of herbicides on weed control in transplanted rice. The experiment was carried out in a Randomized Block Design with eight treatments and three replications. All the imposed treatments significantly influenced the weed parameters and crop parameters in rice. The experimental results revealed that, hand weeding twice at 20 and 40 DAT recorded the lowest total weed count (13.74), highest weed control efficiency (WCE) (92.79 per cent), highest plant height (85.76 cm), higher leaf area index (4.28), higher crop dry matter production (7689 kg ha-1 )and highest nutrient uptake by rice crop (134.79, 33.17, 99.41 kg of N, P2O5 , K2O ha-1, respectively) which was statistically on par with application of penoxsulam + cyhalofop butyl@135 g ha-1 (premix)(15 DAT) that recorded the total weed count (16.74), weed control efficiency (91.21 per cent), plant height (85.03cm), leaf area index (4.19), dry matter production (7567 kg ha-1), crop nutrient uptake (132.37 , 32.48, 97.25 kg of N, P2O5 , K2O ha-1, respectively). Highest total weed count, with lowest plant height, leaf area index, crop dry matter production and crop nutrient uptake were recorded with unweeded control.

Replace of the EPOST glyphosate with pre herbicides and application of different LPOST glyphosate rates for weed control in established vineyard

Two-year field trials were conducted at two winegrowing districts (Kavadarci and Skopje in 2016 and 2017) to evaluate wheather oxyfluorfen, pendimethalin and flazasulfuron can replace early post-emergence (EPOST) application of glyphosate in established vineyard until its application in early summer period. The weed vegetation in vineyards in both years was consisted mainly of Chenopodium album L., Setaria viridis (L). Beauv., Papaver rhoeas L., Xanthium strumarium L., Lolium multiflorum Lam., Sorghum halepense (L.) Pers. and Cynodon dactylon (L.) Pers. Pendimethalin, oxyfluorfen and flazasulfuron efficiently reduced predominant annual weeds and S. halepense seedlings in 2017, but not in 2016. PRE herbicides, regardless year, had no significant effect on C. dactylon. Opposite, the efficacy of EPOST applied glyphosate was significantly lower in 2017 compared to 2016. LPOST glyphosate applied at 2.0 l ha-1 provided at least 94 % control of dominant annual broadleaf and grass weeds. LPOST application of glyphosate at 2.0 l ha-1 and glyphosate at 2.0 and 4.0 l ha-1 resulted in unsatisfactory weed control of predominant perennial S. halepense, and C. dactylon, respectively. LPOST glyphosate applied at 4.0 l ha-1 provided control of S. halepense by 84 % or more. LPOST glyphosate applied at 8.0 l ha-1 reduced the amount of S. halepense and C. dactylon at least 97 %. Grapevine yield of both varieties was not lower in all herbicide treatments in 2016 compared with 2017. However, yield in the PRE herbicide treatments fb 2.0 and 4.0 l ha-1 glyphosate was collectively 15-19 % and 17-19 % lower compare to PRE herbicide treatments fb 8.0 l ha-1 glyphosate and standard two applications of glyphosate, respectively for both years and districts. No impacts to grapevine growth were observed from PRE herbicide treatments at either district

Studies on pre and post emergence herbicidal weed management in hybrid maize COH (M)6 (Zea mays)

In general, Maize is one of the most important cereal crops in the world’s agricultural economy both as food for human being and feed for animals. Among the cereals, maize is the important cereal crop next to rice and wheat. Weeds are generally vigorous growers and their nutrient requirements are often greater than that of crop plants. Major area of maize in India is during Kharif season in which weed is one of the important yield limiting factor and significantly reduces the yield. Hence this condition the research sub project is proposed to evaluate suitable recommendations and combination of pre and early post emergence application herbicide management for hybrid maize CO (MH) 6. A field experiment was conducted during 2016 (Aug –Sep), 2017 (Aug –Sep),& 2018 (Jan- Feb) at Agricultural Research Station, Vaigai Dam The treatment consisted that alachlor 1.25kg ha-1 with addition of one hand weeding on 30 DAS, alachlor 1.0 kg ha-1coupled with tembotrione 120g ha-1 on 30 DAS, atrazine 0.5 kg ha-1with addition of one hand weeding on 30 DAS, atrazine 0.5 kg ha-1coupled with early post emergence herbicide of Tembotrione 120 g ha-1, Tembotrione 120g ha-1alone, hand weeding twice on 20 and 40 DAS and control (Unweeded control). From the experiments it can be concluded that the pre-emergence application of Atrazine 0.5 kg ha-1 with addition with addition of early post emergence herbicide of Tembotrione 120g ha-1has recorded higher grain and stover yield.

Effect of Pre and Early Post Emergence Herbicides on Weed Control in Irrigated Blackgram (Vigna mungo L.)

Field experiment was conducted to find out the effect of pre-emergence(PE) and early post-emergence (EPoE) herbicides on weed control inirrigated blackgram at College of Agricultural Technology, Kullapuram- Theniduring 2015-2016. In this experiment, weed management practice of preemergenceapplication of Pendimethalin 30 EC 1.0 kg a.i. ha-1 at 3 daysafter sowing (DAS), early post-emergence application of Quizalofop ethyl@50 g a.i. ha-1 at 15 DAS, early post-emergence and Imazethapyr each @50 g a.i. ha-1 at 15 DAS and their combinations of Pendimethalin @ 1.0 kgha-1 at 3 DAS followed by either Quizalofop ethyl or Imazethapyr each @50 g a.i. ha-1 were tested against hand weeding twice at 20 and 40 DAS,weedy check and weed-free check as controls in randomized block designreplicated thrice. Among the different weed management practices, preemergenceapplication of Pendimethalin 1.0 kg a.i. ha-1 (3 DAS) followedby Imazethapyr @ 50g a.i. ha-1 as EPoE (15 DAS) recorded relatively lesserproportion of broad-leaved weeds (30.90 and 49.16%) and higher WeedControl Efficiency (WCE) of 91.27 at 60 DAS. Application of pendimethalin1.0 kg a.i. ha-1 PE (3 DAS) followed by Imazethapyr @ 50g a.i. ha-1 as EPoE(15 DAS) registered significantly taller plants (42.22 cm), higher dry matterproduction(2649 kg ha-1), more number of pods per plant (44.19), seedsper pod(5.57) and higher grain yield (1052 kg ha-1). Thus, pre-emergenceapplication of pendimethalin 1.0 kg a.i. ha-1 (3DAS) followed by Imazethapyr@ 50g a.i. ha-1 as EPoE (15DAS) recommended as effective and economicweed management practices on the basis of better weed control, crop growth,and yield of irrigated blackgram.

Early post-emergence application of penoxsulam for weed control in transplanted rice

Results of field experiments conducted during kharif 2016 and 2017 to study the effect of penoxsulam on weeds in transplanted rice are reported. The study comprised 7 treatments consisting of 3 doses of penoxsulam 2.5 per cent OD (20, 22.5 and 25 g ha−1), bispyribac-Na 10 per cent SC (20 g ha−1), pretilachlor 50 per cent EC (750 g ha−1), hand weeding (20 and 40 d after transplanting, DAT) and un-weeded control. Echinochloa crusgalli, Leptochloa chinensis, Caesulia axillaris and Cyperus iria were the major weeds. Application of herbicides reduced weed density and increased grain yield as compared to un-weeded control during both the growing seasons. Penoxsulam at 25 g ha−1 provided effective control of grasses and broad-leaved weeds and sedges with 88.24 and 87.05 per cent weed control efficiency at 45 and 60 DAT. The treatment recorded significantly more panicle length, though the grain yield was at par with penoxsulam @ 22.5 g ha−1 (7.14 and 7.12 t ha−1 and 7.23 and 7.37 t ha−1, during 2016 and 2017 respectively). Penoxsulam at 25 g ha−1 recorded 21.5 and 23.9 per cent increase in grain yield over unweeded control during 2016 and 2017 respectively.

Rapid metabolism increases the level of 2,4-D resistance at high temperature in common waterhemp (Amaranthus tuberculatus)

Common waterhemp emerges throughout the crop growing season in the Midwestern United States, and as a result, the seedlings are exposed to a wide range of temperature regimes. Typically, 2,4-D is used in the Midwest to control winter annual broad-leaf weeds before planting soybean and in an early post-emergence application in corn and sorghum; however, the evolution of 2,4-D-resistant common waterhemp in several Midwestern states may limit the use of 2.4-D for controlling this problem weed. Moreover, temperature is one of the crucial factors affecting weed control efficacy of 2,4-D. This research investigated the effect of temperature on efficacy of 2,4-D to control 2,4-D susceptible (WHS) and -resistant (WHR) common waterhemp. Do se-response of WHS and WHR to 2,4-D was assessed at two temperature regimes, high (HT; 34/20 °C, d/n) and low (LT; 24/10 °C, d/n). Whole plant dose response study indicated an increased level of 2,4-D resistance in WHR at HT compared to LT. Additional investigation of the physiological mechanism of this response indicated that both WHS and WHR common waterhemp plants rapidly metabolized 14C 2,4-D at HT compared to LT. In conclusion, a rapid metabolism of 2,4-D conferred increased level of resistance to 2,4-D in WHR at HT. Therefore, application of 2,4-D when temperatures are cooler can improve control of 2,4-D resistant common waterhemp.

Residual effect of pre-sowing weed management on the purple nutsedge (Cyperus rotundus) and succeeding maize germination and yield

A study was carried out to evaluate different pre-sowing weed management methods on Cyperus rotundus and on succeeding maize germination and yield at Chinnankuppam village in Dharmapuri district, Tamil Nadu. Pre-emergence, early post-emergence and post-emergence herbicides viz metribuzin, halosulfuron methyl, glyphosate and 2, 4-D were applied at different doses to select an optimum dose suitable for the management of purple nutsedge (C rotundus) as a pre-sowing weed management method. Pre-sowing weed management treatments did not influence the per cent germination of succeeding maize. Among the pre-sowing weed management treatments early postemergence application of halosulfuron methyl at 50 g/ha followed by post-emergence application of glyphosate at 1.00 g/ha resulted in reduced density and dry weight (2.2 and 4.1/m2, 0.37 and 0.70 g/m2) followed by early postemergence application of halosulfuron methyl at 75 g/ha (3.5 and 5.7/m2, 0.60 and 0.97 g/m2) at 15 and 30 DAS respectively. Simultaneously both the treatments increased the weed control efficiency of C rotundus (69.16 and 58.33%) and (50.00 and 42.26%) at 15 and 30 DAS respectively. Among the treatments pre-sowing application of early post-emergence halosulfuron methyl at 50 g/ha followed by post-emergence application of glyphosate at 1.00 kg/ha recorded the higher grain (9, 387 kg/ha)and stover (9, 500 kg/ha) yield of succeeding maize.

Influence of Formulation and Rate on Rice Tolerance to Early-Season Applications of Acetochlor

AbstractAcetochlor (WSSA Group 15) is a very-long-chain fatty acid–inhibiting herbicide used to control grass weed species in row crops and could potentially be effective when used in a rice herbicide program. A field study was conducted in 2016 and 2017 at four locations to determine the effects of acetochlor formulation and rate on rice tolerance. Overall, rice was more tolerant to the microencapsulated (ME) formulation of acetochlor than to the emulsifiable concentrate (EC) formulation, likely because of the potential for immediate absorption of acetochlor from the EC formulation following rainfall. Differences in rainfall among experimental sites and years caused variation in acetochlor activation and influenced crop injury. In all environments, PRE applications of either formulation resulted in the greatest injury at 2 WAT (61%), while injury following delayed PRE (DPRE) or early POST (EPOST) applications averaged 30% and 16%, respectively. When ME acetochlor was applied EPOST, rough rice yield was 97% of nontreated rice or 9,020 kg ha−1, indicating that applications should be delayed until this stage to minimize crop damage and maximize yield.