Phytotoxicity Of Herbicides Research Articles

Bioefficacy and phytotoxicity of pre-and post-emergence herbicides in grain sorghum

Bio-efficacy and phytotoxicity of pre-emergence tank mix application of atrazine + pendimethalin, pendimethalin + imazethapyr, ready mix application of pendimethalin+ imazethapyr (Velore), imazethpyr + imazamox (Odessey), penoxsulam, and post-emergence application of penoxsulam, atrazine, imazethapyr and imazethpyr + imazamox along with standard pre-emergence herbicide atrazine were evaluated at ICAR-Indian Institute of Millet Research, Hyderabad during rainy season of 2014. The field was dominated with broad-leaved weeds (65.8%) followed by grasses (26.3%) and sedges (7.9%). Infestation of weeds throughout the cropping season caused 37% reduction in grain yield. Post-emergence (15 DAS) application of imazethapyr and velore herbicides was highly phytotoxic and caused complete mortality of both sorghum plants and weeds at 2 weeks after herbicide application. Tank mix application of atrazine + pendimethalin (500 + 750 g/ha) as pre-emergence was safe and most effective in sorghum. Atrazine as post-emergence was less effective than its pre-emergence application. New herbicide molecules viz., penoxsulam, velore and odessey, though effectively controlled the weeds but reduced the grain yield due to reduction in number of grains/panicle.

Phytotoxicity of Alachlor, Bromacil and Diuron as single or mixed herbicides applied to wheat, melon, and molokhia.

This study investigated the phytotoxicity of herbicides applied singly or as mixtures to different crops under greenhouse conditions. Growth inhibition of the crops was taken as an indicator of phytotoxicity. Phytotoxicity of mixtures was estimated by calculating EC50 value in toxic units. EC50 (mg/kg soil) of Alachlor, Bromacil and/or Diuron were: 11.37, 4.77, 1.64, respectively, on melon; 0.11, 0.08, 0.24, respectively, on molokhia, and 3.91, 3.08, 1.83, respectively, on wheat. EC50 values of binary mixture tests of (Alachlor + Bromacil), (Alachlor + Diuron), and (Bromacil + Diuron) were 12.21, 5.84, 10.22 on melon, 0.982, 925.4, 38.1 on molokhia, and 0.673, 1.34, 0.644 on wheat. Tertiary mixture tests showed EC50 values (TU/kg soil) of (Alachlor + Bromacil + Diuron) was 633.9 on melon, 3.02 on molokhia and 32.174 on wheat. Diuron was more toxic than Alachlor and Bromacil to the tested crops based on individual tests. Molokhia was the most sensitive crop to herbicides. Binary mixtures showed a synergistic effect as compared to the tertiary mixtures.

Eficácia e fitotoxicidade de herbicidas aplicados para manejo de plantas daninhas infestantes do trigo

Objetivou-se com o trabalho identificar alternativas para o manejo químico de plantas daninhas infestante do trigo, bem como verificar a fitotoxicidade de herbicidas sobre a cultura. Instalou-se o experimento em blocos casualizados, arranjado em esquema fatorial 2 x 13, com quatro repetições. No fator A, alocou-se as cultivares de trigo (Quartzo e Pioneiro) e no B os herbicidas (iodosulfuron – 0,100 kg ha-1; imazapic + imazapyr – 0,140 kg ha-1; clomazone 0,800 L ha-1; imazethapyr + imazapic – 1,250 L ha-1; propanil – 6,000 kg ha-1; oxyfluorfen – 1,000 L ha-1; penoxsulam – 0,175 L ha-1; metsulfuron-methyl – 0,0033 kg ha-1; 2,4-D – 1,250 L ha-1; cyhalofop-p-buthyl – 1,380 L ha-1; pyroxsulam – 0,400 L ha-1), mais duas testemunhas uma capinada e outra infestada. O iodosulfuron, propanil, oxyfluorfen, metsulfuron-methyl, 2,4-D, cyhalofop-p-buthyl, penoxsulam e pyroxsulam ocasionaram valores inferiores a 5,5% de fitotoxicidade às cultivares de trigo e de modo geral não diferiram das testemunhas capinada e infestada. Os maiores efeitos fitotóxicos foram ocasionados pelo imazethapyr + imazapic, clomazone e imazapic + imazapyr sobre as cultivares de trigo. A aplicação de iodosulfuron, imazethapyr + imazapic, imazapic + imazapyr e o pyroxsulam apresentaram elevados percentuais de controle do azevém, com índices superiores a 95,5%. O imazethapyr + imazapic, clomazone e imazapic + imazapyr apresentaram as maiores fitotoxicidades sobre as cultivares de trigo. O iodosulfuron, imazethapyr + imazapic, clomazone e imazapic + imazapyr e o pyroxsulam demonstraram os melhores controles do azevém. O iodosulfuron apresentou a menor influência sobre os componentes do rendimento de grãos do trigo ao se comparar com os demais herbicidas.

Herbicide impact on the growth and reproduction of characteristic and rare arable weeds of winter cereal fields.

The decline of arable species characteristic of winter cereal fields has often been attributed to different factors related to agricultural intensification but most importantly to herbicide use. Herbicide phytotoxicity is most frequently assessed using short-term endpoints, primarily aboveground biomass. However, short-term sensitivity is usually not sufficient to detect actual effects because plants may or may not recover over time following sublethal herbicide exposures. Therefore, it is important to assess the long-term effects of herbicide applications. Annual species rely on renewable seed production to ensure their persistence; hence, assessment of herbicide sensitivity is more accurately estimated through effects on reproduction. Here we aim to assess the phytotoxicity of two commonly used herbicides: tribenuron and 2,4-D on eight plant species belonging to four families, each with one rare and one more common species. Specifically we examined the pattern of sensitivity using short-term and long-term endpoints (total aboveground biomass, total seed biomass and number of seeds) of these species; we determined the levels of and time to recovery in terms of stem length and fruit number, and assessed whether their rarity relates to their sensitivity to herbicide application. Our results suggest that although differences in herbicide sensitivity are not a direct cause of rarity for all species, it may be an important driver of declining arable plants.

Distribuição, diâmetro de gotas e fitoxicidade de herbicidas aplicados em mudas de eucalipto com pontas de indução de ar

As pontas de pulverização são responsáveis pela formação das gotas, sendo que cada tipo de ponta exerce uma função diferente, com características próprias relacionadas à deposição de gotas de acordo com alvo que se deseja atingir. Este trabalho teve como objetivo avaliar a distribuição, diâmetro de gotas e fitotoxicidade dos herbicidas glyphosate e isoxaflutole, aplicados em mudas de eucalipto com pontas de indução de ar (AIUB 04 e TTI 110 04). O espectro do diâmetro de gotas foi determinado em analisador de tamanho de partículas por difração de luz laser. Os perfis de distribuição volumétrica foram avaliados em mesa de deposição, para a coleta da calda pulverizada. As avaliações visuais da fitotoxicidade dos herbicidas foram realizadas aos 7, 14, 21 e 28 dias após a aplicação. Ao final do período experimental determinou-se a massa de matéria seca de caule e folhas. A ponta de TTI 110 04 teve maior diâmetro mediano volumétrico (DMV), menor percentual de gotas menores que 100 µm e menor coeficiente de uniformidade de gotas em comparação com a ponta AIUB 04, independentemente da calda utilizada. Para a ponta de pulverização modelo TTI 110 04, os espaçamentos de 0,45 e 0,75 cm apresentaram melhor uniformidade (coeficiente de variação menor que 10%). O modelo AIUB 04 não resultou em nenhum coeficiente de variação aceitável. A aplicação de glyphosate com a ponta AIUB 04 aumentou a fitointoxicação. O herbicida isoxaflutole mostrou-se seletivo ao eucalipto.

Influence of Application Timings and Sublethal Rates of Synthetic Auxin Herbicides on Soybean

Synthetic auxin herbicides have long been utilized for the selective control of broadleaf weeds in a variety of crop and noncrop environments. Recently, two agrochemical companies have begun to develop soybean with resistance to 2,4-D and dicamba which might lead to an increase in the application of these herbicides in soybean production areas in the near future. Additionally, little research has been published pertaining to the effects of a newly-discovered synthetic auxin herbicide, aminocyclopyrachlor, on soybean phytotoxicity. Two field trials were conducted in 2011 and 2012 to evaluate the effects of sublethal rates of 2,4-D amine, aminocyclopyrachlor, aminopyralid, clopyralid, dicamba, fluroxypyr, picloram, and triclopyr on visible estimates of soybean injury, height reduction, maturity, yield, and yield components. Each of these herbicides was applied to soybean at the V3 and R2 stages of growth at 0.028, 0.28, 2.8, and 28 g ae ha−1. Greater height reductions occurred with all herbicides, except 2,4-D amine and triclopyr when applied at the V3 compared to the R2 stage of growth. Greater soybean yield loss occurred with all herbicides except 2,4-D amine when applied at the R2 compared to the V3 stage of growth. The only herbicide applied that resulted in no yield loss at either stage was 2,4-D amine. When applied at 28 g ae ha−1at the V3 stage of growth, the general order of herbicide-induced yield reductions to soybean from greatest to least was aminopyralid > aminocyclopyrachlor = clopyralid = picloram > fluroxypyr > triclopyr > dicamba > 2,4-D amine. At the R2 stage of growth, the general order of herbicide-induced yield reductions from greatest to least was aminopyralid > aminocyclopyrachlor = picloram > clopyralid > dicamba > fluroxypyr = triclopyr > 2,4-D amine. Yield reductions appeared to be more correlated with seeds per pod than to pods per plant and seed weight. An 18- to 26-d delay in soybean maturity also occurred with R2 applications of all synthetic auxin herbicides at 28 g ae ha−1except 2,4-D. Results from this research indicate that there are vast differences in the relative phytotoxicity of these synthetic auxin herbicides to soybean, and that the timing of the synthetic auxin herbicide exposure will have a significant impact on the severity of soybean height and/or yield reductions.

Influence of Seeding System Disturbance on Preplant Incorporated Herbicide Control of Rigid Ryegrass (Lolium rigidum) in Wheat in Southern Australia

Field experiments were conducted in 2008, 2011, and 2012 to investigate the interaction between seeding system disturbance and PPI herbicides on rigid ryegrass control in wheat. Of the herbicides examined, prosulfocarb +S-metolachlor, and pyroxasulfone provided ≥ 70% control of rigid ryegrass, irrespective of seeding system. In contrast, trifluralin was the least-effective herbicide against rigid ryegrass and was particularly ineffective when used with single disc (10% control) relative to the triple-disc seeding system (80%) in 2012. Trifluralin consistently reduced wheat density when incorporated using single discs (46 to 59%) but not do so with the triple disc or double-shoot knife-point systems. Although there were large differences in crop establishment because of herbicide phytotoxicity, that did not always translate into large differences in yield because wheat was able to recover from reductions in plant density by increasing the spike number per plant. Pyroxasulfone caused no damage to wheat and appeared to be the most suitable PPI herbicide for use with single-disc seeding systems.

Ocena stosowania herbicydów z biostymulatorami i adiuwantami w uprawie marchwi (Daucus carota L.)

The studies were conducted in 2010–2011 at the Research Institute of Horticulture in Skierniewice. The aim of the research was to determine the impact of separate and combined application of biostimulants Asahi SL and AlfaMax, adjuvants Olbras 88 EC and Protector on efficacy of metribuzin and linuron and the growth and yield of carrot. Herbicides were used with split-application method. First treatment with metribuzin and linuron was applied at 1 leaf stage of carrot, the second treatment of linuron was performed 10–14 days after the first one, and metribuzin was applied at 2–3 leaves stage of carrot. Asahi SL, AlfaMax, Olbras 88 EC and Protector were applied in mixture with herbicides or separate – 1 day before or 1 day after herbicide treatment. The weed control, number and biomass of weeds, phytotoxicity of tested herbicides and the yield of carrot roots were determined during the experiments. Better weed control was achieved with metribuzin than linuron and the addition of biostimulants and adjuvants did not affect its effectiveness. The addition of adjuvants increased the efficacy of linuron. Applied substances did not increase the phytotoxicity of herbicides to carrot plants. The highest yield was obtained by using a mixture of metribuzin with Asahi SL and Protector at 1 day before metribuzin application. W latach 2010–2011, w Instytucie Ogrodnictwa prowadzono badania nad określeniem wpływu rozdzielnego i łącznego stosowania biostymulatorów Asahi SL i AlfaMax oraz adiuwantów Olbras 88 EC i Protector na skuteczność działania metrybuzyny i linuronu oraz wzrost i plonowanie marchwi. Herbicydy stosowano metodą dawek dzielonych. Pierwszy zabieg metrybuzyną i linuronem wykonywano w fazie 1 liścia właściwego marchwi, drugi zabieg linuronem po 10–14 dniach od pierwszego, a metrybuzyną w fazie 2–3 liści marchwi. Asahi SL, AlfaMax oraz Olbras 88 EC i Protector stosowano łącznie z herbicydami lub w zabiegach rozdzielnych – 1 dzień przed lub 1 dzień po zabiegu herbicydem. Przeprowadzano obserwacje stopnia zniszczenia chwastów, określano ich liczbę i świeżą masę, stopień fitotoksyczności badanych środków dla marchwi i wysokość plonów. Stwierdzono lepsze działanie chwastobójcze metrybuzyny stosowanej metodą dawek dzielonych niż linuronu, a biostymulatory i adiuwanty nie wpływały na jej skuteczność. Dodatek adiuwantów zwiększył skuteczność działania linuronu. Stosowane substancje nie powodowały wzrostu fitotoksyczności badanych herbicydów dla marchwi. Najwyższy plon uzyskano stosując mieszaninę metrybuzyny z Asahi SL oraz Protector na jeden dzień przed zastosowaniem metrybuzyny.

Implications of plant geometry and weed control options in designing a low-seeding seed-drill for dry-seeded rice systems

Farmers in many Asian countries are moving from puddled-transplanted rice to dry-seeded rice systems as they respond to increased costs or decreased availability of labor or water. Hybrid rice has the potential to grow in dry-seeded conditions and can perform well even if seeds can be planted at low seedling rates. A field study was conducted in the wet season of 2011 and dry season of 2012 to evaluate the effect of plant-to-plant spacing (10 or 20cm), the number of rice seeds planted per spacing (2 or 3), and weed control methods (42 days weedy, weed-free, and oxadiazon followed by penoxsulam+cyhalofop) on the growth and yield of rice under a dry-seeded rice system. The crop was planted at 20-cm row spacing. Herbicide-treated plots had fewer rice plants than the 42 days weedy and weed-free plots when rain occurred before crop emergence. However, the herbicide treatment provided 81–93% better weed control than the 42 days weedy treatment, which resulted in 54–125% yield advantages over no weeding for 42 days. Grain yield in the herbicide-treated plots was only 75–88% of the grain yield in the weed-free plots, suggesting further scope to improve rice yield in dry-seeded systems. Grain yield was similar across plant-to-plant spacing and the number of seeds planted per spacing. Our study suggests that hybrids can be grown at low seeding rates or at 20-cm plant-to-plant spacing, provided that there is no herbicide phytotoxicity on crop emergence and rice plant density is uniform. These results may help manufacturers in designing sowing drills with precise seed-metering systems for dry-seeded rice systems in Asia.

Application of luminescence method for estimation of herbicide phytotoxicity

Results of research on the applicability of the luminescence method for estimation of phytotoxicity of herbicides inhibiting photosynthesis (atrazine, terbutrine, linuron) are presented. This method was tested on wheat, barley and oat seedlings. Measurements of dry weight and photosynthesis intensity were done for comparison. The results show the possibility of replacing standard methods by the luminescence test since it is easier to perform and more precise than the standard ones.

Efficacy, phytotoxicity and economics of different herbicides in aerobic rice

Aerobic rice is a potential water-wise rice production system, but high weed infestation has threatened its sustainability, which demands an efficient and cost-effective weed management technique. Eight commercial herbicide products were applied singly or as tank-mix or in sequence to evaluate their efficacy, rice selectivity and cost-effectiveness in aerobic rice. The study was conducted under field conditions in Malaysia during 2010/2011 following a randomized complete block design. Most of the herbicide treatments provided excellent weed control, and produced much higher net benefit than weedy or weed-free check. None of the herbicides caused significant phytotoxicity to rice plants. Among the herbicide treatments, sequential application of Cyhalofop-butyl+Bensulfuron at early growth stage followed by Bentazon/MCPA at mid growth stage provided the highest weed control efficiency, productivity and net benefit. Application of Bispyribac-sodium at early growth stage followed by Bentazon/MCPA at mid growth stage performed very close to the above-mentioned treatments. Sequential application of Pretilachlor/safener just after seeding followed by Propanil/Thiobencarb at early growth stage also provided satisfactory results in terms of efficacy and economic return. Since manual weeding was not economic, herbicide rotation using the above chemicals may be recommended for effective weed management in aerobic rice.

The effectiveness and the selectivity of herbicides applied in tillage blue lupinSkuteczność i selektywność herbicydów stosowanych w uprawie łubinu wąskolistnego

Summary In 2008–2010 at the qualification of influence was the aim of investigations tillage systems and weed control methods on effectiveness of destruction of the weed air‐dry mass as well as the influence of damage herbicides applied in the blue lupine tillage. In 2008–2010 a field experiment was carried out at the Agricultural Experimental Farm Zawady of the University of Natural Sciences and Hummanities in Siedlce. The experiment was set up in split‐plot design with four replications. The aim of the study was to evaluate the efficacy of weed regulation in blue lupin crops with the use of: I – different tillage systems (conventional and simplified) and II – five weed control methods. Phytotoxicity of applied herbicides to the plants of blue lupin was also taken into consideration. The best results in weed controlling were obtained after the use of the herbicide mixture: Afalon Dyspersyjny 450 SC + Metron 700 SL + Fusilade Forte 150 EC at both dates of observations, and its efficacy amounted to 81.7 and 53.3% respectively. The results the studies revealed that the efficacy of weed regulation in blue lupin crops depended on such factors as tillage systems, applied herbicides and their mixtures and weather conditions.

Response to imazapyr and dominance relationships of two imidazolinone-tolerant alleles at the Ahasl1 locus of sunflower

Imisun and CLPlus are two imidazolinone (IMI) tolerance traits in sunflower (Helianthus annuus L.) determined by the expression of different alleles at the same locus, Ahasl1-1 and Ahasl1-3, respectively. This paper reports the level of tolerance expressed by plants containing both alleles in a homozygous, heterozygous and in a heterozygous stacked state to increasing doses of IMI at the enzyme and whole plant levels. Six genotypes of the Ahasl1 gene were compared with each other in three different genetic backgrounds. These materials were treated at the V2-V4 stage with increasing doses of imazapyr (from 0 to 480g a.i. ha(-1)) followed by an assessment of the aboveground biomass and herbicide phytotoxicity. The estimated dose of imazapyr required to reduce biomass accumulation by 50% (GR(50)) differed statistically for the six genotypes of the Ahasl1 gene. Homozygous CLPlus (Ahasl1-3/Ahasl1-3) genotypes and materials containing a combination of both tolerant alleles (Imisun/CLPlus heterozygous stack, Ahasl1-1/Ahasl1-3) showed the highest values of GR(50), 300 times higher than the susceptible genotypes and more than 2.5 times higher than homozygous Imisun materials (Ahasl1-1/Ahasl1-1). In vitro AHAS enzyme activity assays using increasing doses of herbicide (from 0 to 100μM) showed similar trends, where homozygous CLPlus materials and those containing heterozygous stacks of Imisun/CLPlus were statistically similar and showed the least level of inhibition of enzyme activity to increasing doses of herbicide. The degree of dominance for the accumulation of biomass after herbicide application calculated for the Ahasl1-1 allele indicated that it is co-dominant to recessive depending on the imazapyr dose used. By the contrary, the Ahasl1-3 allele showed dominance to semi dominance according to the applied dose. This last allele is dominant over Ahasl1-1 over the entire range of herbicide rates tested. At the level of enzymatic activity, however, both alleles showed recessivity to semi-recessivity with respect to the wild-type allele, even though the Ahasl1-3 allele is dominant over Ahasl1-1 at all the herbicides rates used.

Manejo de plantas daninhas em milho safrinha em cultivo solteiro ou consorciado à braquiária ruziziensis

O objetivo deste trabalho foi avaliar a eficiência de herbicidas pós-emergentes no controle das plantas daninhas, e sua seletividade à braquiária (Urochloa ruziziensis) e ao milho safrinha, em cultivo solteiro ou consorciado. O experimento foi conduzido em delineamento de blocos ao acaso, com quatro repetições, em esquema fatorial 2x14: cultivo do milho consorciado ou não à braquiária e 14 tratamentos químicos, além de duas testemunhas, com ou sem controle das plantas daninhas. Avaliou-se o controle das plantas daninhas, a fitotoxicidade para braquiária e a produtividade do milho. Todos os tratamentos com herbicidas proporcionaram controle acima de 80% das plantas daninhas aos 14 dias após a aplicação. As misturas formuladas de atrazina+óleo, a 800 e a 1.200 g ha-1, compuseram o grupo de herbicidas mais seletivos a U. ruziziensis; o grupo de menor seletividade consistiu da aplicação isolada de tembotrione ou de suas associações com atrazina. A competição com a braquiária reduziu a produtividade do milho em até 45,3%. Contudo, não houve diferença entre os tratamentos nas parcelas tratadas com herbicidas.

Sulfometuron methyl influences seedling growth and leaf function of three conifer species

Seedling growth and gas exchange responses were measured for two potted seedling trials testing herbicide phytotoxicity to three important tree species of the Inland Northwest, USA. Media-filled pots were treated with sulfometuron methyl (Oust®) in varying concentrations and planted with seedlings of Larix occidentalis Nutt., Pseudotsuga menziesii var. glauca (Beissn.) Franco, and Pinus monticola Dougl. ex D. Don. Seedlings were grown in two trials to determine the effects of two important residue breakdown factors, substrate moisture and pH, relative to that of herbicide application rate on seedling health. Changes in seedling height, root-collar diameter, and root volume were morphologic variables of interest, and physiological variables measured were net photosynthetic assimilation, stomatal conductance, and transpiration rate. While three levels of media moisture and four levels of media pH had no effect on seedling performance, most growth and leaf function variables were hindered across application rate treatments of all three species. Label-recommended dosages resulted in growth suppression levels potentially detrimental to seedling establishment for all three species. This was most pronounced for Pinus monticola, in particular for root growth, where untreated control seedlings showed 109% more root volume growth than treated seedlings. We conclude that when possible, a species-specific application rate might be found that balances the benefits of vegetation control with the phytotoxicity to promote optimal growth gains.

Growth Response of Direct-Seeded Rice to Oxadiazon and Bispyribac-Sodium in Aerobic and Saturated Soils

Studies were conducted to determine the growth responses of rice to PRE application of oxadiazon and POST application of bispyribac-sodium. Oxadiazon at 1.0 and 1.5 kg ha−1and bispyribac-sodium at 0.030 and 0.045 kg ha−1were applied to four rice varieties (‘IR64’, ‘IR72’, ‘RC09’, and ‘RC18’), which were grown in saturated and aerobic (30% of saturation) soils. Control treatments, where no herbicides were applied, were also included in the study. Shoot and root biomass, and height of rice plants were measured 14 d after application. Phytotoxic effects for both herbicides, including reduced shoot and root biomass, were consistent in all varieties. Rice phytotoxicity symptoms were greater when herbicides were applied to saturated than to aerobic soils. Oxadiazon at 1.0 kg ha−1reduced rice shoot biomass by 22 to 36% in aerobic condition, and 43 to 56% in saturated condition when compared with the control. Bispyribac-sodium reduced rice shoot biomass by 9 to 17% at 0.030 kg ha−1in aerobic soil and 23 to 37% in saturated soil. The results of this study suggest that soil water content is an important factor influencing herbicide phytotoxicity in rice, and its influence warrants further research to improve understanding of physiology of phytotoxicity to minimize the effects of these herbicides on crop production.

Evaluation of the Efficacy of Mesotrione Plus Nicosulfuron with Additives as Tank Mixtures Used for Weed Control in Maize (Zea Mays L.)

The evaluation of the effects of grass and broadleaf weed control with different mixture rates of mesotrione plus nicosulfu- ron with methylated rapeseed oil and urea-ammonium nitrate liquid fertilizer (UAN) applied postemergence in maize was conducted in field experiments during the agricultural seasons of 2006, 2007 and 2008. Contact angle and surface tension were measured for all tank-mix solutions. There was no phytotoxicity observed on maize following the application of the herbicide-plus-additives treat- ment. Reduced rates of herbicide with additives provided similar control levels of Echinochloa crus-galli (L.) Beauv. as mesotrione used alone. The tank-mix of herbicides and adjuvants gave no antagonistic effect and it increased weed control. Plots treated with a reduced rate of tank-mix with additives, were always among the highest yielding as compared to untreated plots. Any reductions in cob and grain yield were associated with high weed fresh matter yields, indicating that it was the competition with weeds that led to a reduc- tion in the maize grain yield and not the herbicide phytotoxicity.

Yield of herbicide tolerant sunflower hybrids due to the different herbicide treatments

Sunflower is our most important oil-plant grown on the largest area in Hungary. In Europe sunflower has been grown since the 16th century. In recent years sunflower growing area is between 450-500 thousand hectares. Weed management in sunflower production is getting more and more difficult in case of annual and perennial dicotyledonous weeds, especially in dry springs. Two active ingredients, imazamox and tribenuron-methyl could be a solution for farmers for the control of these weeds in herbicide tolerant sunflower hybrids (Christensen-Reisinger 2000, Hódi-Torma 2004, Nagy et al. 2006). Most of the farmers choose the Clearfield technology and the use of tribenuron-methyl herbicides. In 2009 imazamox- (IMI) and tribenuron-methyl- (SU) tolerant sunflower hybrids were produced on 200 hectares in Hungary, of which 150 hectares was IMI, while 50 hectares was SU-hybrids. Small plot experiments were carried out to investigate the phytotoxicity of herbicides on imazamox (IMI) and tribenuron-methyl (SU) tolerant sunflower hybrids under field conditions. At harvest we measured the moisture content of achenes and average yield.

Sensitivity of Winter Wheat Cultivars to Selected Herbicides

Sensitivity of Winter Wheat Cultivars to Selected HerbicidesThe experiments on tolerance of winter wheat cultivars to herbicides were performed under field conditions during 2003-2005 in the region of Wrocław (South-West of Poland). Five cultivars were examined (Zyta, Tonacja, Sukces, Clever, Kobra). Two herbicide mixtures: isoproturon + pendimethalin and diflufenican + flurtamon were applied in the autumn, in stage of 3-4 leaves. In the spring, when wheat reached stage of full tillering, the following herbicides were used: florasulam + 2.4-D and fluroxypyr + 2.4-D. Phytotoxicity of herbicides was determined on the base of plants vigour assessment, plants counting, yield and some yield components. During the experimental period, impact of the mixture pendimethalin + isoproturon on grain yield of Clever cultivar was observed only in the season with hard winter conditions (2002/2003). The remaining varieties: Zyta, Tonacja, Sukces and Kobra were completely tolerant to this herbicide mixture. Mild winter seasons did not show a negative influence of herbicides on grain yield of tested varieties. All cultivars showed a complete tolerance to diflufenican + flurfamon and florasulam + 2.4-D. The mixture fluroxypyr + 2.4-D caused ear deformation of all tested wheat cultivars, but did not affect negatively grain yield.

Phosphate-Solubilizing and Plant-Growth-Promoting Pseudomonas aeruginosa PS1 Improves Greengram Performance in Quizalafop-p-ethyl and Clodinafop Amended Soil

The quizalafop-p-ethyl- and clodinafop-tolerant phosphate-solubilizing and plant-growth-promoting Pseudomonas aeruginosa PS1 isolated from the rhizospheric soils of mustard was used to determine its phosphate-solubilizing activity and other plant-growth-promoting traits both in the presence and absence of technical grade quizalafop-p-ethyl and clodinafop under in vitro conditions. Quizalafop-p-ethyl (at 40, 80, and 120 ppb) and clodinafop (at 400, 800, and 1200 ppb) reduced the P-solubilizing activity, synthesis of indole-3-acetic acid, and siderophores progressively with increasing concentrations of each herbicide. Hydrogen cyanide and ammonia synthesisized by this strain, however, did not change. Furthermore, the effects of three concentrations each of quizalafop-p-ethyl [40 (recommended dose), 80, and 120 ppb] and clodinafop [400 (recommended dose), 800, and 1200 ppb] were evaluated on plant-growth-promoting Pseudomonas aeruginosa strain PS1 inoculated greengram plants, grown in sandy clay loam soil. Generally, all of the concentrations of both quizalafop-p-ethyl and clodinafop showed phytotoxicity and severely affected the growth, symbiosis, grain yield, and nutrient uptake by greengram plants. The toxicity of quizalafop-p-ethyl and clodinafop enhanced gradually with the increase in the dose rate of herbicides. Quizalafop-p-ethyl was more toxic than clodinafop. In contrast, herbicide-tolerant P. aeruginosa strain PS1 when used with herbicides increased the measured parameters at all concentrations. Both quizalafop-p-ethyl at 120 ppb and clodinafop at 400 ppb increased total chlorophyll content, leghemoglobin, root N, shoot N, root P, shoot P, seed yield, and seed protein, relative to the uninoculated control. The study suggests that the phytotoxicity of herbicides to legumes could be reduced by applying the growth-promoting herbicide-tolerant strain of Pseudomonas aeruginosa PS1.