Combined effects of wheat competition and 2,4-D amine on phenoxy herbicide resistant Raphanus raphanistrum populations

Phenoxy herbicides are integral to the control of Raphanus raphanistrum populations in Australian crop production systems, but the development of phenoxy resistant R. raphanistrum populations poses a major threat to the sustainability of these systems. In dose–response pot studies, phenoxy herbicide resistant R. raphanistrum populations, WARR12 and WARR20, suffered large biomass reductions following treatment with recommended or higher application rates of phenoxy herbicides. This indicates the presence of a weak resistance mechanism where treated plants, although surviving, are affected by these herbicides. Subsequently, the competitive ability of 2,4-D amine treated or untreated WARR12 and WARR20 populations with wheat was assessed using a target-neighbourhood experiment. The combination of wheat competition and 2,4-D amine application resulted in control of the resistant WARR12 population, but not the WARR20 population. Wheat crop competition alone resulted in large (>40%) biomass reductions of WARR12 and WARR20 populations. However, the application of the recommended rate of 2,4-D amine caused a large (>75%) reduction in WARR12 biomass, but had a reduced effect on WARR20 biomass. These studies possibly explain the largely successful control of R. raphanistrum populations being achieved with phenoxy herbicides in cropping systems across the Western Australia wheatbelt. However, the results also indicated that the strategy of combining crop competition with phenoxy herbicides for the control of this weed is likely to be an effective option in the short-term only.     

Effects of alcohols,glycols and monodisperse ethoxylated alcohols on mobility of 2,4-D in isolated plant cuticles

Effects of n-alcohols, ethoxylated alcohols and glycols on mobility of 2,4-dichlorophenoxy acetic acid (2,4-D) in cuticular membranes (CM) isolated from bitter orange (Citrus aurantium L.) leaves were studied. 1-Heptanol, 1-octanol and 1-nonanol had the highest effects, as they increased solute (2,4-D) mobility by 25- to 30-fold. Increasing the number of carbon atoms in the alcohols decreased their effectiveness. Ethoxylation of alcohols did not increase 2,4-D mobility and effectiveness decreased with increasing ethoxylation. Free glycols had no effect on solute mobility in isolated cuticles. The results show that ethoxylation is not required for increasing solute mobility in cuticles. It is suggested that alcohols and ethoxylated alcohols are sorbed in cuticular waxes and plasticize them. The data show that alcohols and ethoxylated alcohols having between seven and ten carbon atoms are powerful accelerator adjuvants, as long as the degree of ethoxylation is not too high. Free short-chain alcohols synthesized by leaves may act as endogenous plasticizers and modulate permeabilities of cuticles, depending on environmental and growing conditions.     

The determination of residues of 2,4-D in post-emergence-treated triticale

A gas chromatographic method, using electrolytic conductivity detection, is presented for the determination of 2,4-0 as its methyl ester in triticale (X Triticosecale Wittmack). The method was used to monitor the dissipation of 2,4-0 residues in triticale over a growing season at two sites following post-emergence application of the dimethylamine salt of 2,4-D at 0.56 kkg ha^?1. Initial residues, in the order of30 mg kg^?1. on the day afer application (3- to 4-leaf stage of the crop), decreased to non-detectable levels in the mature straw and seed. Recoveries of 2,4-D were greater than 90% fiom green tissue fortified at 0.1 mg k^?1., and in the order of 75% from seed fortified at 0.05 mg kg^?1.     

2,4-滴异辛酯的水解及光解特性

为明确2,4-滴异辛酯的环境行为规律,采用室内模拟试验方法,研究了2,4-滴异辛酯在不同温度、pH值、水体及初始浓度下的水解特性及其在不同pH值、水体、光源和初始浓度下的光解特性。结果表明:中性 (pH = 7) 条件下,初始质量浓度为5 mg/L的2,4-滴异辛酯在15、25 和35 ℃ 下的水解半衰期分别为346.6、231.0和173.3 h;25 ℃下,5 mg/L的2,4-滴异辛酯在pH值分别为4、7 和9 的缓冲溶液中的水解半衰期分别为77.0、231.0 和138.6 h;2,4-滴异辛酯在稻田水、自来水和河水中的水解速率高于其在蒸馏水中的水解速率,4 种条件下的半衰期分别为23.1、25.7、40.8 和63.0 h;初始质量浓度分别为1、3和5 mg/L的2,4-滴异辛酯在pH值为7的缓冲溶液中的水解半衰期分别为231.0、173.3和138.6 h。300 W汞灯照射下,2,4-滴异辛酯在酸性条件下的光解速率大于其在中性和碱性条件下,半衰期分别为49.5、77.0 和138.6 h;2,4-滴异辛酯在河水和稻田水中的光解速率高于其在自来水和蒸馏水中的光解速率,4 种条件下的半衰期分别为6.7、7.6、43.3 和46.2 h;2,4-滴异辛酯在不同光源下的光解速率依次为500 W汞灯 > 300 W汞灯 > 500 W氙灯;初始质量浓度分别为1、3和5 mg/L的2,4-滴异辛酯在pH值为7的缓冲溶液中的光解半衰期分别为63.0、43.3和40.8 h。2,4-滴异辛酯水解及光解的主要产物是2,4-滴,其降解机制主要是酯水解反应。研究结果可为2,4-滴异辛酯的合理使用及其环境风险评估提供参考。     

The effect of repeated applications of 2,4-D and MCPA on their breakdown in soil

The effect of repeated applications of 2,4-D and MCPA in a long-term field experiment on their subsequent degradation was investigated. The herbicides had been applied annually since 1954, Comparisons were made with plots treated once and then retreated the following year. Repealed applications of the two herbicides resulted in a reduction in degradation lime from 10 weeks for 2,4-D and 20 weeks for MCPA after one application to 4 and 7 weeks respectively after 19 years of annual application. In spite of an increased capability of the soil microflora lo degrade 2,4-D and MCPA 9 months after a previous treatment. no change in numbers of organisms capable of utilizing the substances as carbon sources were found in treated plots as compared with the control. It is obvious that there is a cross adaptation between 2,4-D and MCPA. It seems most likely that two different ‘enrichment’ been induced, each capable of decomposing both herbicides, but with different efficiencies. Effet d'applications répétée de 2,4-D et de MCPA sur leur degradation dans le sol L'effet d'applications répétée de 2.4-D et de MCPA sur leur degradation uléerieure a étéétudié dans une expérience au champ de longue durée. Les herbicides ont été appliqués chaque année depuis 1954. Des comparaisons ont été effectuées avec des parcelles traiées une fois et traitées à nouveau l'année suivante. Les applications répétées des deux herbicides ont provoqué une réduction du temps de dégradation qui est passé de 10 semaines pour le 2,4-D et 20 semaines pour le MCPA après une seule application, à 4 et 7 semaines respectivement, après 19 années d'applications annuelles. En dépit d'une capacité accrue de la microflore du sol à dégrader le 2.4-D et le MCPA, neuf mois après un traitement préalable, aucun changement n'a été constaté dans le nombre des organismes capables d'utiliser les produits comme sources de carbone dans les parcelles traitées, par rapport au témoin. II est évident qu'il y a une adaptation croisée entre le 2,4-D et le MCPA. II apparait très probable que deux ‘enrichissements’ de Hores ont été induits, chacun d'eux étant capable de décomposer les deux herbicides mais avec des efficacités différentes. Die Wirkung wiederholter Behandlungen von 2.4- D und MCPA auf ihren Abbau im Boden Die Wirkung wiederholter Anwendungen von 2,4-D und MCPA auf ihren Abbau wurden in einem Freiland-Versuch untersucht. Die Herbizide wurden jährlich, sell 1954 ange-wendet. Es wurden Vergleiche mil Parzellen angcstellt, die zum erstenmal und im folgenden Jahr nochrnaK bchandelt worden waren. Die widerholien Behandlungen mit den beiden Herbiziden bewirkte elne Verringerung der Ab-bauzeit von 10 Wochen fur 2,4-D und 20 Wochen fiir MCPA nach einer Behandlung, auf 4 bzw. 7 Wochen nach 19 Jahren jahrlicher Anwendung. Trotz der erhohten Ffihigkeit der Bodenmikroflora 2,4-D und MCPA neun Monate nach einer vorhergehenden Behandlung abzubauen, war die Zahl der Organismen, die diese Herbizide als Kohlensloffquelle verwerten konnen, in den behandelten und unbehandelten Parzellen gleich gross. Zwischen 2.4-D und MCPA existiert ofVensichtlich elne Kreuz-Adaplalion. Sehr wahrscheinlich wurden zwei versehiedene ‘enrichment’-Floren induziert, von der jede in der Lage ist beide Herbizide, aber mit unterschiedlicher Effizienz, Hbzubauen.     

Effect of low temperatures on 2,4-D behaviour in maize plants

The foliar surface of 4-leaf maize plants was found to be poorly wettable and retained 106 μl g^?1 dry matter when sprayed with a U46D (2,4-D formulation) blank. The third leaf retained 141 μl g^?1. A 7-day cold spell (17/9°C) increased retention per unit dry matter by 53% (135% on the third leaf). Cold stress lowered epicuticular wax quantity by 29% on the third leaf. Contact angles of formulated 2,4-D lay between 115 and 125° and were not significantly affected by cold stress. 2,4-D rapidly entered into maize third leaf (66% in 24 h) but migration from it was less than 1.5%. 2,4-D was readily degraded in maize (80% in 72 h). The most abundant metabolite was probably an ester conjugate; little of the hydroxy derivatives were found. Cold stress reduced 2,4-D degradation, and 72 h after treatment the amount of undegraded 2,4-D was 78% higher in cold-stressed maize plants. It was concluded that 2,4-D selectivity in maize results from low spray retention per unit dry matter and active degradation of penetrated herbicide. Cold stress affects both factors.     

秸秆覆盖全程节水对小麦病害发生的影响

通过秸秆覆盖全程节水对小麦病害发生影响调查,发现其主要病害有:小麦条锈病(Puccinia striiformis West)、小麦白粉病[Blumeria graminis(DC.) Speer]和小麦散黑穗病[Ustalago tritici(Pers)Jens.],免耕和秸秆覆盖处理对这3种病害的发生几乎没有影响;随冬季灌水量的增加,小麦条锈病发病减轻,小麦散黑穗病发病加重,对小麦白粉病影响不大。     

Spray application factors and plant growth regulator performance: II. Foliar uptake of gibberellic acid and 2,4-D

Effects of droplet size and carrier volume on foliar uptake and translocation of gibberellic acid (GA₃) and 2,4-D were investigated. Simulated spray droplets were applied to primary leaves of 10-day-old Phaseolus vulgaris (cv Nerina) in droplet sizes and carrier volumes ranging from 0.5 to 10 μl and 10 to 200 μl per leaf, respectively. Doses of GA₃ (2 μg per leaf) and 2,4-D (100 μg per leaf) were held constant. Total uptake of GA₃ approached a penetration equilibrium within 24 h after application, but uptake of 2,4-D continued to increase. Decreasing droplet size and/or increasing carrier volume increased GA₃ and 2,4-D uptake. Translocation to stem and roots was positively related to total uptake. A positive linear relationship between the logarithm of the total droplet/leaf surface interface area and 2,4-D uptake or translocation was found, but for GA₃ this relationship was quadratic. Potential mechanisms of the effects of spray application factors on foliar uptake are discussed. © 1999 Society of Chemical Industry     

Translocation of 2,4-D, asulam and amitrole in water hyacinth

In glasshouse experiments foliar application or ¹⁴C-labelled herbicides to water hyacinth plants at the 4-leaf stage indicated that amilroie transport from the treated leaf blade was faster and greater than 2.4-D. but a little less than asulam. From the treated leaf 14·2, 25·9. 39·7. 44·5 and 51·8% of the recovered ¹⁴CNamitrole was translocated at intervals of 6 h. and 1. 3. 6 and 12 day., respectively. Both xylem and phloem transport of asulam and amitrole was evident, whereas 2.4-D moved only from ‘source to sink’. Movement of the herbicides from the mother to the connected daughter plant or vice versa was dependent upon the size of the latter. Maximum transport of these herbicides in either direction took place at the 2-leaf stage of daughter plants. With any increase or decrease in the number of leaves on daughter plants, the transport of herbicides was reduced. As an exception, daughter plant to mother plant movement of amilroie was maximum at the 1-leaf stage. After extraction, fractionation and TLC separation of foliage applied ¹⁴C-2.4-D 76–4 and 72·1% of the radioactivity was detected in the chloroform phase of the leaf extract at 3 and 6 day intervals, respectively. In another pot culture experiment, it was observed that after spraying the mother plants with 2.4-D-amine at 0–75 kg/ha the connected daughter plants at 1 to 4-leaf stages werckilled if the culture solution was contaminated while spraying, or by dying leaves. When contamination was totally avoided, the connected but unsprayed daughter plants at 3 to 4-feaf stages survived.     

The influence of water solubility on the movement and degradation of simazine in a fallow soil

The movement and degradation of simazine in the field during winter and summer were measured and compared with simulations using a simple model. The model only simulated simazine behaviour closely when water solubility was taken into account. Relationships between water solubility, melting point, soil adsorption and octan-1-ol/water partition coefficient indicate that, at agricultural rates of application, water solubility will only have an important influence on behaviour for relatively polar chemicals with high melting points.     

2,4-滴丁酯土壤处理对大豆产量的影响

以黑龙江不同积温带的3个大豆主栽品种‘东农52’、‘合丰55’、‘黑河48’为材料,运用盆栽试验方法,在大豆播后苗前施用不同剂量的2,4-滴丁酯进行土壤处理,探讨了2,4-滴丁酯对不同大豆品种的产量及产量构成因素的影响。结果表明：2,4-滴丁酯对供试3个大豆品种的百粒重均无影响;2,4-滴丁酯造成大豆减产的处理,大豆单株粒数必然减少,而单株荚数、有效荚数不一定减少,造成大豆减产的主要原因是大豆单株粒数减少。可见,施用2,4-滴丁酯是否造成大豆减产可通过调查大豆单株粒数进行评判;供试3个大豆品种对2,4-滴丁酯的敏感性不同,2,4-滴丁酯施药量达1 080 g/hm2时引起‘黑河48’减产,达1 620 g/hm2时引起‘东农52’减产,达2 160 g/hm2时才引起‘合丰55’减产。供试大豆品种对2,4-滴丁酯的敏感性顺序为：‘黑河48’>‘东农52’>‘合丰55’。     

复合改性粘土对除草剂2,4-D的控制释放作用研究

采用无机/有机复合改性粘土作制剂载体,探讨了其对阴离子型除草剂2,4-D的控制释放作用,目的在于延长2,4-D的持效期,同时减轻其污染。利用无机和有机改性的结合优势,复合改性粘土具有更强的吸附性能,能够显著延缓2,4-D在水中和土壤中的释放。分析其水中释放动力学数据得出,2,4-D释放50%所需时间(t50)长达73.8 h,远大于有机改性粘土作载体时的1 h。土壤层释放实验表明,当2,4-D载药量在20~80 mg/g之间时,复合改性粘土均能保持良好的控制释放效果。     

植物疫情截获相关影响因素分析

文章从植物疫情截获途径、检验检疫工作内容和流程等方面入手,对植物疫情截获评价指标体系构建过程中应重点考虑的影响因素进行了分析与梳理,提出了影响植物疫情截获评价的直接和间接因素,并对其他可能影响评价效果的因素进行了讨论。     

复合改性粘土对除草剂2,4-D的控制释放作用研究

采用无机/有机复合改性粘土作制剂载体,探讨了其对阴离子型除草剂2,4-D的控制释放作用,目的在于延长2,4-D的持效期,同时减轻其污染.利用无机和有机改性的结合优势,复合改性粘土具有更强的吸附性能,能够显著延缓2,4-D在水中和土壤中的释放.分析其水中释放动力学数据得出,2,4-D释放50%所需时间(t_(50))长达73.8 h,远大于有机改性粘土作载体时的1 h.土壤层释放实验表明,当2,4-D载药量在20～80 mg/g之间时,复合改性粘土均能保持良好的控制释放效果.     

Response of winter wheat (Triticum aestivum L.) and weeds to tank mixtures of 2,4-D plus MCPA with clodinafop propargyl

Field and greenhouse experiments were conducted in 2004 and 2005 to study weed control and the response of winter wheat to tank mixtures of 2,4-D plus MCPA with clodinafop propargyl. The field experiments were conducted at Yazd and Oroumieh, Iran, with factorial combinations of 2,4-D plus MCPA at 0, 975, and 1300 g ai ha⁻¹ and with clodinafop propargyl at 0, 64, 80, 96, and 112 g ai ha⁻¹ in four replications. The greenhouse experiments further evaluated the effect of these tank mixtures on weed control, where each herbicide mixture was considered as one treatment and the experiment was established in a randomized complete block design with four replications. In the field experiments, the herbicides were applied at wheat tillering, while in the greenhouse experiments they were applied at the beginning of the tillering stage and at the four-leaf stage of the grass and broadleaf weeds, respectively. The results indicated antagonistic effects between 2,4-D plus MCPA and clodinafop propargyl. The best tank mixture with regard to weed control efficacy was 2,4-D plus MCPA at 975 g ai ha⁻¹ with clodinafop propargyl at 96 g ai ha⁻¹. The wheat grain yield was also increased by the tank mixture of clodinafop propargyl with 2,4-D plus MCPA. Generally, to inhibit clodinafop propargyl efficacy reduction due to tank-mixing with 2,4-D plus MCPA, it is recommended that the application dose of 64 g ai ha⁻¹ should be increased to 96 g ai ha⁻¹.     

石羊河流域植物类型对其水坝修建的响应

石羊河流域作为我国开发利用程度较高,生态环境问题较突出的内陆河流域,备受国内外研究者关注。通过整理参考前人考察研究结论及实地调查分析发现:石羊河流域修建水坝,水资源分配方式及利用模式因此发生了根本性的改变,强烈影响其中下游的植物种及群落变化。主要表现在:1)自上世纪五十年代以来,石羊河流域中下游植被面积、植被盖度、生物量等均有不同程度减少;植物类型发生了从湿生系列向旱生系列的转变,柽柳、盐爪爪、芦苇等植被逐渐退出,白刺、红砂、黑果枸杞等更耐旱植被逐渐占据优势地位,尤其是白刺在大部分地方都成为建群种。2)在石羊河流域中下游,植物为了适应风沙大、温差高、降水稀少、蒸发强等不利的生长环境,形成了多种旱生特征和适应方式;在人为干扰相对较重的区域植物叶片结构逐渐变化为以环栅型为主;在人为干扰相对较轻区域的植物逐渐向正常型和全栅型方向发展;在地下水位下降较剧烈的区域,植物叶片类型发生了由正常型、环栅型向不规则型的完全转变。水坝建设引起的大面积开荒种田、水资源利用不均衡、下游地下水严重超采、水质恶化等是植物类型和面积发生变化的主要影响因素。     

小麦田不同杂草群落及防除时间对小麦产量的影响

为明确小麦田不同杂草群落及防除时间对小麦产量的影响,于2013—2015连续两年在山东省聊城市高唐县小麦田中设无草对照区、禾本科杂草区、阔叶杂草区以及混合杂草自然发生区4种不同杂草群落以及不同的杂草防除时间,测定在不同条件下小麦产量及各项产量构成指标的情况。结果表明,阔叶杂草对小麦产量的影响大于禾本科杂草,冬小麦田杂草的最佳防除时间为4月1日之前,在此期间除草对小麦产量影响均不大,但之后防除或不除草会造成小麦严重减产甚至绝产,2014年4月15日除草可造成在阔叶杂草区和杂草混合生长区的小麦减产30.5%和32.6%,不除草可造成在禾本科杂草区、阔叶杂草区和杂草混生区的小麦减产8.6%、91.4%和94.3%,2015年趋势和2014年一致。从构成小麦产量的3个指标来看,杂草危害主要影响小麦的总穗数,其次为穗粒数,对千粒重影响最小。