Combinations Of Metribuzin Research Articles

Impact of varying doses and application methods of metribuzin on productivity and profitability of wheat (Triticum aestivum) under different tillage systems

Addressing the imperative of aligning food production with the escalating global population necessitates the identification of sustainable land management strategies. In the Indo-Gangetic Plains of India, weed infestation causes a significant threat to wheat (Triticum aestivum L.) productivity. To address this concern, a field experiment was conducted during the winter (rabi) seasons of 2021–22 and 2022–23 at the research farm of CCS Haryana Agricultural University, Rice Research Station, Kaul, Haryana. The primary objective of this experiment was to assess the effects of varying doses and application methods of metribuzin on the productivity and profitability of wheat crop under zero and conventional tillage systems. Notably, the application of post-emergence (POE) metribuzin at a dose of 350 g/ha as a urea-mix broadcast at 35 days after sowing (DAS) in combination with pinoxaden (PDN) exhibited notablebenefits in terms of productivity and economic viability of wheat. This treatment yielded significantly higher number of effective tillers/mrl (111 in zero tillage; 112 in conventional tillage) and grain yield (5,573 kg/ha in zero tillage; 5,972 kg/ha in conventional tillage). Moreover, the treatment combination of metribuzin at 350 g/ha as a urea-mix broadcast and pinoxaden applied at 35 DAS resulted in the highest net returns and benefit-cost ratio under both tillage systems.

Herbicide Management for Sustainable Sugar Cane (Saccharum officinarum l.) Production in Sudan

Field investigations were carried out during 2018/19 at Sugarcane Research Center Farm El Guneid, Sudan, in two sites, to evaluate the effect of the combination of chemical herbicides, Ametryne (3.8 L/ha) + Atrazine (3.8 L/ha), Atrazine (3.0 L/ha) + Pendimethalin (2.9 L/ha) and Metribuzin (5.21 L/ha) + Pendimethalin (3.57 L/ha), on common weed control, sugar cane growth, yield and quality. Experimental design was a randomized complete block (RCBD) with three replications. Results revealed that the combination of Metribuzin (5.21 L/ha) + Pendimethalin (3.57 L/ha) recorded the best results in weed control efficiency percent (WCE%) for both grass and broadleaved weeds in sugarcane crop compared to the other treatmentsand the control in the two sites. On the other hand, significant difference of means between treatments was observed in growth parameters and yield of sugar cane at 3, 6 and 9-month ages. Among all treatments the combination of Metribuzin (5.21 L/ha)+Pendimethalin (3.57 L/ha) showed the best results, irrespective to parameters compared to the other treatments and the control in the two sites. The mixture of Metribuzin+pendimethalin sustained the highest WCE% for both, grass and broadleaved weeds in addition to increased cane yield and yield component compared to other treatments and the corresponding control. Based on this study, it can be concluded that the herbicide combination provided effective weed control and promoted sugarcane quality and yield. Therefore, the use of herbicides not only increases the net income of farmers, but also demise weeds seed bank.

Assessing varietal tolerance and weed control effectiveness of metribuzin-based herbicide mixtures in wheat (Triticum aestivum)

A field experiment was conducted during 2014–15 and 2015–16 at Research Farm of Department of Agronomy,CCSHAU, Hisar. The experiment comprised five wheat (Triticum aestivum L.) varieties (WH 1105, HD 2967, DPW621-50, WH 1124 and DBW 17) in main plots and six weed management practices, viz. metribuzin (210 g/ha),metribuzin + fenoxaprop (150 + 100 g/ha), metribuzin + pinoxaden (150 + 40 g/ha), metribuzin + clodinafop (150+ 45 g/ha), weed free and weedy check in sub-plots was conducted in split-plot design with three replications. Thepopulation and dry matter accumulation of weeds were not affected by wheat varieties. Wheat variety WH 1105resulted in maximum grain yield and remained at par with HD 2967 and DPW 621-50, but statistically superior toDBW 17 and WH 1124. Minimum population of grassy and total weeds and dry matter accumulation by them wasobserved with metribuzin + fenoxaprop, being at par with other two combinations of metribuzin. But, the densityand dry matter of broad leaved weeds was minimum with metribuzin alone (210 g/ha). Among herbicidal treatments, metribuzin + fenoxaprop (150 + 100 g/ha) remained superior with maximum grain yield.

Differences in selectivity between bermudagrass and goosegrass (Eleusine indica) to low-rate topramezone and metribuzin combinations

AbstractGoosegrass [Eleusine indica (L.) Gaertn.] remains problematic for bermudagrass [Cynodon dactylon (L.) Pers.] turf managers due to the ineffective, selective control of mature plants with available postemergence herbicides and lack of sufficient residual activity from those herbicides to control seedling plants. Topramezone controls mature E. indica, but past efforts to suppress potential injury to bermudagrass turf have been inconsistent. We hypothesized that metribuzin at 210 g ai ha−1 in admixture with topramezone would improve bermudagrass tolerance while conserving mature E. indica control. In preliminary field studies, metribuzin mixed with topramezone at 1.2 or 2.5 g ae ha−1 applied twice at a 3-wk interval reduced bermudagrass injury and white discoloration compared with topramezone applied alone, but metribuzin did not safen bermudagrass to mesotrione. Topramezone at 3.7 g ha−1 plus 210 g ha−1 metribuzin applied twice at a 3-wk interval offered improved bermudagrass tolerance while it still controlled mature E. indica during 15 field and 2 greenhouse studies in Virginia. This program offered a 10-fold decrease in suprathreshold duration of white discoloration compared with topramezone alone at 6.1 g ha−1. Bermudagrass absorbed three times less radioactivity than E. indica at timings up to 48 h after treatment with [14C]topramezone. Bermudagrass also metabolized twice as much topramezone compared with E. indica at 48 h after treatment. Metribuzin reduced 14C absorption by approximately 25% in both species. These studies confirm the performance of a novel, low-dose topramezone plus metribuzin program for mature E. indica control in bermudagrass turf and suggest that selectivity between bermudagrass and E. indica to topramezone is due to differential absorption and metabolism. The fact that metribuzin reduces topramezone absorption in both species suggests that it may help reduce bermudagrass phytotoxic response to topramezone, but its role in altering selectivity between bermudagrass and E. indica may be due to other factors.

Effect of Mechanical and Herbicide Treatments on Weed Densities and Biomass in Two Potato Cultivars

The effect of potato cultivar and mechanical or herbicide treatments on weed densities and biomass was determined in a research study on a field, conducted from 2007 to 2009 at the Institute of Plant Breeding and Acclimatization. Included in the study were two cultivars and different weed control treatments, including a mechanical method and metribuzin combined with various herbicides and application timings. Chemical methods of controlling weeds were more effective than mechanical methods to reduce weed densities and biomass. The combination of metribuzin with rimsulfuron + SN oil, applied before potato emergence (PRE), was more effective than the other metribuzin combinations. The weed infestation of potato cv. “Irga” was greater than that of cultivar “Fianna” due to differences in the type of growth.

Economic Feasibility of Chemical Weed Control in Soybean Production in Serbia

The aim of this study was to investigate the efficacy and phytotoxicity of herbicides in combinations and to determine their economic feasibility in the soybean crop. The trials were placed at two locations, Pobeda and Budisava (Serbia), during 2016 and 2018, organized in a randomized block design with four replicates of all herbicide combinations (metribuzin + S-metolachlor; imazamox + oxasulfuron + typhenesulfuron-methyl; metribuzin + S-metolachlor + imazamox + oxasulfuron + typhenesulfuron-methyl; and bentazon + imazamox + typhenesulfuron-methyl). At the first location, 16 weed species were determined, while in the second location, 14 were determined. The highest reduction in the number of weeds was achieved at the first location, using a combination of herbicides metribuzin + S-metolachlor + imazamox + oxasulfuron + typhenesulfuron-methyl with a total efficacy that ranged from 96.98% to 97.40%. Only on the second location bentazone + imazamox + tifensulfuron-methyl showed passable phytotoxicity on soybean, during both years. Based on the established economic justification, in the combinations of metribuzin + S-metolachlor + imazamox + oxasulfuron + typhenesulfuron-methyl, yield was increased for 2350 kg/ha or 1.91 times more, according to the untreated variant at first location. The economic injury level at the most effective combination of herbicides was 52.70 weeds/m2.

Competition, reproduction ability, and control possibilities of conventional and Clearfield® volunteer oilseed rape in winter wheat

Three plot field trials (2014–2017) were carried out in Prague. The aim of the study was to evaluate the efficacy of herbicides against volunteers from Clearfield® (CL) and conventional oilseed rape (Brassica napus L.) in winter wheat (Triticum aestivum L.) and to quantify the effect of herbicide and application time on wheat yield. Autumn control (diflufenican, isoproturon, flumioxazin, metribuzin, penoxsulam, florasulam, chlorsulfuron were tested) of volunteer oilseed rape (OSR) was more effective than using the spring herbicide treatments (2,4-D, iodosulfuron, amidosulfuron, tritosulfuron, florasulam), especially against the CL OSR variety. Full control of both CL and conventional OSR was recorded only on plots treated by the combination of metribuzin + diflufenican + flufenacet. The most effective spring herbicide was 2,4-D, but its efficacy (82–95%) depended on the growth stage of OSR and application rate. Efficacy of spring herbicides against CL OSR was lower compared to that against conventional OSR, but there were large differences among tested herbicides. Efficacy of tested ALS inhibitors against volunteer CL OSR ranged between 20% (chlorsulfuron) and 77% (tritosulfuron + florasulam). Seed production of volunteer OSR ranged between 0 and 37,000 seeds m−2 while depending strongly on time of sowing and weather conditions during the autumn and winter. No seed of CL OSR matured on plots treated by metribuzin in autumn or 2,4-D at application rate 377 g ha−1 in spring. Volunteer OSR in competition with winter wheat caused almost 50% wheat yield loss on the untreated check. Although the efficacy of most spring herbicide treatments on conventional OSR was good, the competition effect of OSR on wheat during winter and early spring caused about 0.52–0.86 t ha−1 greater yield loss compared to autumn herbicide treatments.

Quantifying Resistance to Isoxaflutole and Mesotrione and Investigating Their Interactions with Metribuzin POST in Waterhemp (Amaranthus tuberculatus)

AbstractGreenhouse experiments were conducted to quantify resistance levels to the 4-hydroxyphenyl-pyruvate dioxygenase (HPPD)-inhibiting herbicides mesotrione (MES) and isoxaflutole (IFT) in NEB (Nebraska HPPD- and atrazine-resistant) and SIR (Stanford, IL, HPPD- and atrazine-resistant) waterhemp [Amaranthus tuberculatus(Moq.) J. D. Sauer] populations. These populations differ in their field-use histories and resistance levels to MES. Foliar growth responses were compared with ACR (HPPD sensitive; metabolic atrazine-resistant) and SEN (sensitive to HPPD and photosystem II [PSII] inhibitors). A greenhouse dose–response study was conducted with each herbicide at two POST timings: early (EPOST) (5 cm; 4 to 5 true leaves) and POST (10 cm; 8 to 9 true leaves). At the EPOST timing, SIR was 10-fold resistant to IFT and 32-fold resistant to MES, while NEB was 4-fold resistant to IFT and 7-fold resistant to MES when compared with ACR. At the POST timing, SIR was 17-fold resistant to IFT and 21-fold resistant to MES, while NEB was 3-fold resistant to IFT and 7-fold resistant to MES when compared with ACR. Results overall indicated greater fold-resistance levels to MES relative to IFT at each timing. However, POST treatments to SIR showed contrasting effects on resistance levels relative to EPOST. To investigate potential management strategies for resistantA. tuberculatuspopulations, a POST interaction study was conducted using combinations of metribuzin and either IFT or MES. A metribuzin rate (191 g ai ha−1) causing an approximately 20% biomass reduction was chosen for interaction studies and combined with varying rates of either IFT or MES. Results indicated 52.5 g ai ha−1of MES combined with metribuzin displayed a synergistic effect on biomass reduction in SIR. However, other combinations of either MES or IFT and metribuzin resulted in additive effects on biomass reduction in both HPPD-resistant populations. These results provide insights into the joint activity between HPPD and PSII inhibitors for controlling metabolism-based, multiple herbicide–resistantA. tuberculatus.

Reduced Rates of Metribuzin and Time of Hilling Controlled Weeds in Potato

The current emphasis on reducing herbicide applications has led to an increase in alternative weed control measures. Field experiment was conducted in the spring of 2014 to examine the effect of hilling-time and reduced-rates of metribuzin and their combinations on weed infestation in potato, and to determine their impact on potato yield. Metribuzin at 0.35, 0.56, or 0.75 kg ai/ha with or without hilling 6, 7, and 8 weeks after planting (WAP) were used. Weed count, weed control visual rating, weed dry weight, potato plant height, number of shoots and leaves, root dry weight, and potato yield were collected. Results showed that metribuzin, at all tested rates, with or without hilling significantly reduced weed infestation after 50, 70, and 110 days after planting (DAP) compared to the check. Best results were obtained by a combination of metribuzin at all tested rates with hilling 6, 7, and 8 WAP. The results suggest that long season weed control and high marketable yield could be achieved by metribuzin at 0.35 kg ai/ha (53% reduction in metribuzin) supplemented with hilling (6 WAP). None of the treatments was toxic to potato plants compared to the hand-weeded plots.

Post-emergence herbicides for the control of resistant littleseed canarygrass in wheat

Farmers ’participatory field trials were conducted at village Kheri Raiwali in Kaithal district of Haryana during winter seasons of 2011–12 and 2012–13 to evaluate the bio-efficacy of post-emergence herbicides, their mixtures and sequential application for the control of the resistant littleseed canarygrass (Phalaris minor) and other weeds in wheat. Application of clodinafop 60 g/ha, fenoxaprop 120 g/ha and sulfosulfuron 25 g/ha at 35 days after sowing (DAS) did not provide satisfactory control of P. minor; however, mesosulfuron + iodosulfuron 14.4 g/ha provided better control (85–90%). Pinoxaden 50 g/ha resulted in 80% control of P. minor during first year but it provided only 55% control during second year. Ready-mix combination of metribuzin with fenoxaprop and clodinafop significantly improved the control of P. minor and broad-leaf weeds as compared to alone application of fenoxaprop and clodinafop. Maximum weed control efficiency (WCE) and highest grain yield (5.2 t/ha) was recorded with the application of sulfosulfuron + metsulfuron 32 g/ha during 2011–12, which was statistically at par with mesosulfuron + iodosulfuron and clodinafop + metribuzin; whereas during the second year, sulfosulfuron + metsulfuron 40 g/ha resulted in highest grain yield. Sequential application of sulfosulfuron + metsulfuron 32 g/ha at 25 DAS before irrigation fb sulfosulfuron + metsulfuron 32 g/ha at 40 DAS (after first irrigation) registered 97% WCE but its continuous adoption may lead to rapid development of resistance. The study indicates the need of new post-emergence herbicide with different mechanism of action (MOA), which can be integrated with non-chemical weed control strategies.

Multiple Resistance of Horseweed to Glyphosate and Paraquat and Its Control with Paraquat and Metribuzin Combinations

Greenhouse and field studies were conducted in 2007 and 2008 to investigate possible multiple-resistance of horseweed to paraquat and glyphosate, and to evaluate the effect of the addition of metribuzin to paraquat on control of paraquat-resistant horseweed. Results indicated that the GR50 (herbicide dose required to cause a 50% reduction in plant growth) value for the susceptible population S102 was 0.066 kg ae/ha glyphosate, and for the resistant population MDOT was 0.78 kg/ha glyphosate. The level of glyphosate resistance for MDOT was 12-fold compared with S102. The GR50 value for the susceptible population S102 was 0.078 kg ai/ha paraquat, and for the resistant population MDOT was 0.67 kg/ha paraquat. The level of paraquat resistance for MDOT was 9-fold compared to S102, suggesting multiple-resistance to glyphosate and paraquat in the MDOT population. In field studies the addition of metribuzin to paraquat improved horseweed control.

Common Lambsquarters and Hairy Nightshade Control in Potato with Dimethenamid-p Alone and in Tank Mixtures and Comparison of Control by Dimethenamid-p with S-metolachlor and Metolachlor

Dimethenamid-p was labeled for preemergence use in potatoes in 2005. The herbicide provides hairy nightshade control; however, a tank-mix partner targeting common lambsquarters must be used in order to provide satisfactory control of that weed. S-metolachlor and metolachlor, also labeled for use in potato, are in the same chemical family as dimethenamid-p and questions have arisen as to whether or not these herbicides provide the same or different levels of hairy nightshade control. The objectives of this study, therefore, were (1) to compare preemergence control of common lambsquarters and other weeds in potato with dimethenamid-p applied at 0.72, 0.94, or 1.12 kg ai ha−1alone or in two-way tank mixtures to determine appropriate tank-mix partners, and (2) to compare hairy nightshade control by dimethenamid-p with control by S-metolachlor or metolachlor. Two-way tank mixtures of dimethenamid-p with ethalfluralin, EPTC, flumioxazin, metribuzin, pendimethalin, or sulfentrazone generally improved season-long common lambsquarters control compared with dimethenamid-p applied alone at 0.72, 0.94, or 1.12 kg ha−1. When compared with control by dimethenamid-p alone at 0.72 or 0.94 kg ha−1, control by dimethenamid-p at either rate tank-mixed with ethalfluralin or EPTC was not improved as much as control by combinations of dimethenamid-p at those rates with the other tank-mix partners. Hairy nightshade control by three-way tank mixtures of S-metolachlor or metolachlor with various combinations of metribuzin, ethalfluralin, EPTC, or pendimethalin ranged from 60 to 86% and was not as great as the 93 to 98% control by dimethenamid-p at 0.72 kg ha−1combined with the same tank-mix partners. U.S. No. 1 and total tuber yields of comparative two- and three-way tank mixtures were generally increased when weed control was improved.

Efficacy of Reduced Sulfentrazone Rates Applied Preemergence with Metribuzin in Potato (Solanum tuberosum)1

Field trials were conducted with sulfentrazone at 53, 80, and 105 g ai/ha combined with 0, 420, and 560 g ai/ha metribuzin in a 3 by 3 factorial arrangement. Sulfentrazone and metribuzin combinations improved control of redroot pigweed, common lambsquarters, hairy nightshade, and volunteer oat compared with sulfentrazone applied alone. Kochia control was more than 90% regardless of metribuzin presence in the treatment. Sulfentrazone at 105 g/ha was needed for greater than 90% hairy nightshade control. Sulfentrazone alone or in combination with metribuzin did not provide greater than 89% volunteer oat control. Potato crop injury was less than 5% and total tuber yields increased as metribuzin rate increased from 0 to 560 g/ha, reflecting improved weed control as metribuzin rate increased.Nomenclature: Metribuzin; sulfentrazone; potato, Solanum tuberosum L. ‘Russet Burbank’; common lambsquarters, Chenopodium album L. #3CHEAL; hairy nightshade, Solanum sarrachoides Sendter # SOLSA; kochia, Kochia scoparia L. Shrad. # KCHSC; redroot pigweed, Amaranthus retroflexus L. # AMARE; volunteer oats, Avena sativa L. # AVESA.Additional index words: Crop safety, herbicide injury, reduced rates.Abbreviations: OM, organic matter; WAT, weeks after treatment.

Flufenacet and Metribuzin Combinations for Weed Control and Corn (Zea mays) Tolerance1

Field studies were conducted in 1999 and 2000 at seven locations in south Texas to evaluate flufenacet plus metribuzin for weed control and corn tolerance. Texas panicum control with flufenacet plus metribuzin was variable with less than 70% control in 1999 and greater than 75% control in 2000. Palmer amaranth and pitted morningglory control ranged from 41 to 100%. Corn stunting (4 to 13%) was noted in soils with greater than 75% sand. Corn yields with flufenacet and metribuzin combinations were increased up to 19% over the untreated check where stunting was not observed. Nomenclature: Flufenacet; metribuzin; Palmer amaranth, Amaranthus palmeri S. Wats. #3 AMAPA; pitted morningglory, Ipomoea lacunosa (L.) # IPOLA; Texas panicum, Panicum texanum Buckl. # PANTE; corn, Zea mays L. ‘AS986’, ‘Pioneer 3223’, ‘Pioneer 32K61’, ‘DK-668’. Additional index words: Corn tolerance, ivyleaf morningglory, weed management. Abbreviations: POST, postemergence; PRE, preemergence.

Evaluation of herbicides for control of tufted vetch ( Vicia cracca) and narrow-leaved vetch ( Vicia angustifolia)

Production of soyabeans ( Glycine max, L. Merr) in rotation with spring barley ( Hordeum vulgare L) in Prince Edward Island, Canada, has increased in recent years and in fields used for several years tufted vetch ( Vicia cracca L.) and narrow-leaved vetch ( Vicia angustifolia Reichard) have become more of a problem. Experiments were conducted in the field and glasshouse to evaluate herbicide treatments that would provide adequate vetch control. In field studies on soyabeans, combinations of metribuzin and metolachlor gave 94–100% control of tufted vetch, whereas, combinations of bentazon with imazethapyr, or aciflurofen, or thifensulfuron did not provide control. Imazethapyr or thifensulfuron applied alone post-emergence did not control tufted vetch. In glasshouse studies, metribuzin gave complete control of tufted vetch and narrow-leaf vetch when used at 500 and 1000 g/ha. Combinations of metribuzin and metolachlor at lower rates controlled tufted vetch and narrow-leaf vetch. In glasshouse studies using herbicides normally used in barley, tufted vetch and narrow-leaf vetch were controlled by the herbicides thifensulfuron methyl/tribenuron methyl when used in combination with MCPA amine. When thifensulfuron methyl/tribenuron methyl was used in combination with 2,4-D amine control of narrow-leaf vetch was less than that achieved with tufted vetch. Tufted vetch and narrow-leaf vetch were not controlled by thifensulfuron methyl/tribenuron methyl, MCPA amine, 2,4-D amine, or by bromoxynil. Dicamba/2,4-D gave 92% control of narrowleaf vetch but was not effective on tufted vetch.

Postemergence Control of Broadleaf Weeds in Tomato (Lycopersicon esculentum)

Greenhouse and field experiments were conducted to evaluate the control of eastern black nightshade and velvetleaf in tomato with bentazon, metribuzin, pyridate, and acifluorfen. Metribuzin controlled velvetleaf but not eastern black nightshade, whereas pyridate controlled eastern black nightshade but not velvetleaf. A combination of metribuzin + pyridate controlled both weeds, but caused tomato injury 4 wk after application. Bentazon neither controlled the weeds nor injured the crop. Acifluorfen controlled both eastern black nightshade and velvetleaf. Diammonium phosphate and oxysorbic (5 POE) improved bentazon and acifluorfen activity against velvetleaf. Although initial crop injury from some treatments applied prior to fruit initiation was severe, the crop recovered and there were no reductions in fruit weight compared with the control. However applying acifluorfen with oxysorbic (5 POE) during fruit development reduced yield 50%.

Bermudagrass (Cynodonspp.) Cultivar Response to Diclofop, MSMA and Metribuzin

Postemergence grass weed control in turf-type bermudagrass is currently available only with repeated applications of organic arsenicals and/or with combinations of metribuzin which decrease turf quality. Research was conducted to determine tolerance of the turf-type bermudagrass cultivars, Tifway, Ormond, and common, to diclofop rates ranging from 0.54 to 4.48 kg ai ha-1with and without MSMA (2.2 kg ai ha-1) and metribuzin (0.2 kg ai ha-1). Bermudagrass cultivars tolerated diclofop well. When injury was evident, a rate response was noted, with higher rates (3.4 and 4.5 kg ha-1) resulting in increased phytotoxicity. However, this level of phytotoxicity was acceptable and the turf soon recovered (3 to 14 d). The addition of crop oil concentrate (1.25% v/v) did not affect turf quality. Addition of MSMA resulted in slightly lower turf quality than diclofop alone. However, these responses were acceptable and usually the turf recovered by 14 d after treatment. Metribuzin applied alone or in combination with diclofop damaged turf to unacceptable levels and up to 21 d were required for turf recovery.

Controlled Release of Three Herbicides by the Kraft Lignin PC940C

A pine kraft lignin (PC940C) controlled the release of14C-chloramben (3-amino-2,5-dichlorobenzoic acid),14C-metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one], and14C-alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] as measured by water leaching in soil columns. As more PC940C was used, a concentration effect was found with more of the three herbicides being retained in the top portion of the soil columns. Combinations of alachlor and metribuzin applied with PC940C did not alter the retention in the top portion of the soil columns of either14C-metribuzin or14C-alachlor compared to each herbicide applied with PC940C alone. This would suggest that, at the rate of PC940C used, there was no competition between either herbicide for the controlled-release function of PC940C. The percentage of14C-chloramben,14C-metribuzin, and14C-alachlor retained by PC940C in the top portion of the columns was very similar. Combinations of metribuzin and alachlor without PC940C reduced the mobility of both14C-metribuzin and14C-alachlor. Finally,3H-PC940C was found to be immobile in soil columns leached with water.

Weed Competition, Yield and Tuber Size of Potato as Affected by Herbicides Under Sudanese Conditions

SUMMARYThe effects on the potato crop of the herbicides metribuzin, linuron and metobromuron, singly and in combination with each other and with hand weeding, were investigated and compared with cropped and uncropped weedy controls. Weed competition was determined by measuring weed dry weight. When the three herbicides were applied singly metribuzin gave the lowest weed dry weight, while the combination of metribuzin, metobromuron and hand weeding gave the lowest weed dry weight per unit area of all treatments in both seasons. However, the best potato yield was obtained from the combination of metribuzin and hand weeding. Metobromuron consistently reduced yield through reduction of tuber size irrespective of its effect on weed competition. Metribuzin was the best herbicide for the control of broad leaved weeds and many grasses.

Interaction of Selected Insecticide-Herbicide Combinations on Soybeans (Glycine max)

Phorate {O,O-diethylS-[(ethylthio)methyl] phosphorodithioate}, disulfoton {O,O-diethylS-[2-(ethylthio)ethyl] phosphorodithioate}, linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea], or metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] when used alone did not reduce soybean [Glycine max(L.) Merr. ‘Calland’] grain yield or plant population. However, combinations of metribuzin with either phorate or disulfoton interacted synergistically to reduce both soybean grain yield and plant population significantly even at recommended rates of both chemicals. Combinations of linuron with either phorate or disulfoton at recommended rates did not reduce soybean grain yield or plant population. Greenhouse studies further substantiated the synergistic interaction of phorate or disulfoton with metribuzin.