Herbicide resistance in Aster squamatus conferred by a less sensitive form of acetolactate synthase

A biotype of Aster squamatus (Sprengel) Hieronymus with suspected resistance to the ALS-inhibiting herbicide imazapyr was detected in a chicken farm in the province of Seville, Spain, which had been treated once a year with imazapyr for 10 years. Resistance to imazapyr in this biotype was studied using dose-response experiments, absorption and translocation assays, metabolism studies and ALS activity assays. The rate of imazapyr required to inhibit A squamatus growth by 50% (ED50) was 15 times higher for the R (resistant) than for the S (susceptible) biotype. Cross-resistance existed for the ALS-inhibitors imazamox, imazethapyr, amidosulfuron, nicosulfuron, rimsulfuron, triasulfuron and tribenuron, but not for bensulfuron. Control of A squamatus using alternative herbicides was poor with clopyralid, intermediate with quinclorac, amitrole and MCPA, and excellent with 2,4-D, glufosinate and glyphosate. Absorption of [14C]imazapyr increased over time for both the R and S biotypes, and translocation from the treated leaf to shoots and roots was similar in both biotypes, with most of the radioactivity remaining in the treated leaf. No metabolites of imazapyr were detected in either biotype. Sensitivity of the ALS enzyme (target site) to imazapyr was lower for the R biotype (I50(R) = 4.28 x I50(S)). The mechanism of imazapyr resistance in this R biotype appears to be an altered ALS conferring decreased sensitivity to imazapyr at the whole-plant level.     

不同施肥措施对稻田土壤氮素矿化的影响

以甘蔗品种新台糖22和粤糖93-159的愈伤组织和刚分化4周的小苗为试验材料,初步确定了灭草烟在愈伤组织分化阶段和刚分化4周小苗的筛选浓度.结果发现,不同基因型甘蔗的愈伤组织和刚分化小苗对灭草烟的耐受浓度均有差异.综合试验结果,适合灭草烟在新台糖22和粤糖93-159愈伤组织分化阶段的筛选浓度为0.3 μmol/L;适合灭草烟对新台糖22刚分化4周小苗的筛选浓度为0.5 μmol/L,适合灭草烟对粤糖93-159刚分化4周小苗的筛选浓度为1.0μmol/L.     

Research and Development of High and Ultra-low volume Sprays to Control Tomato Leaf Diseases at Samaru,Nigeria

Abstract

Fungicide spray trials showed that high volume applications (1121 lha) of mancozeb, captafol and vondozeb reduced foliage and stem disease and substantially increased marketable yields of rain-fed tomatoes in northern Nigeria. The results suggest that captafol had a more persistent fungicidal action as there was no yield difference between the 7 and 14 day frequencies of application. U.I.v. methods (<12 l/ha) using three fungicides were compared with high volume treatments. The u.I.v. captafol treatment was particularly effective. An assessment was made of droplet distribution in relation to atomiser disc rotation speed and the height of carriage of the sprayer.     

除草剂咪唑烟酸高效降解菌的筛选及其降解性能的研究

经过瓶培养法富集培养,从长期使用咪唑烟酸的非耕地土壤中,分离出两株该除草剂的高效降解菌ZJX-5和ZJX-9,经VITEK-AMS细菌自动鉴定仪对上述两菌株分别进行鉴定为:ZJX-5为荧光假单胞菌Ⅱ型(pseudomonasfluorescenesbiotypeⅡ);ZJX-9为腊状芽孢杆菌(Bacilluscereus)。当原始浓度为100mg·L-1时,其在5d内的降解率分别可达89.40%和95.56%,并研究了单一菌株和混合菌株对咪唑烟酸的降解能力。结果表明,混合菌的降解能力明显优于单一菌株,尤其在咪唑烟酸浓度较高时,混合菌在降解率及耐性方面均比单一菌株明显提高。     

Influence of metal salts on the photodegradation of imazapyr, an imidazolinone pesticide

The behaviour of imazapyr (2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid), a broad spectrum herbicide of the imidazolinone family, has been studied under UV radiation in the presence of metal salts. Complexation interactions between imazapyr and metal ions decreased imazapyr photolysis. A chemometric study compared the photodegradation of imazapyr in aqueous solutions in the presence of Na+, Ca2+ or Cu2+ and their concomitant anionic species (Cl-, NO3-) at various pesticide/metal ion molar ratios. The study showed the major role of metal ions in the degradation of imazapyr and its main photoproducts. The molecules were strongly stabilised on complexation with metal ions, leading to an increase in persistence of the pesticide.     

The Build-up of the Present Desert Locust Plague

Abstract

Imperata cylindrica is one of the most noxious weeds in South East Asia. Over the past two decades significant advances have been made in the understanding of its biology and control. This paper reviews work over this period and concludes that despite such advances, there remains much scope for improvement of control, particularly in development of methods appropriate for small scale farmers with limited resources.     

Herbicide efficacy for aquatic Alternanthera philoxeroides management in an early stage of invasion: integrating above‐ground biomass,below‐ground biomass and viable stem fragmentation

Alternanthera philoxeroides is a problematic invasive plant in many regions of the world that is difficult to control once naturalised. It poses a threat to agricultural productivity, biodiversity and social amenity values of aquatic environments. Significant research has been conducted internationally, regarding the efficacy of different herbicides for control of A. philoxeroides. However, no studies have looked at key aspects of control for effective management in an early stage of invasion of aquatic environments, hindering eradication and control programmes. This study evaluates the efficacy of herbicides and surfactants on key A. philoxeroides response metrics, including control of above‐ground biomass, below‐ground biomass and production of viable stem fragments. This study concluded that glyphosate (isopropylamine salt) minimises viable stem fragment production post‐herbicide application, compared with imazapyr and metsulfuron, thus reducing the potential for dispersal throughout catchments and waterways. In contrast, imazapyr and metsulfuron provided more effective control than glyphosate for A. philoxeroides growing on exposed embankments. We propose that an effective management strategy for early invasion of aquatic A. philoxeroides, using herbicides, would be to conduct initial applications of glyphosate to control overwater biomass and limit dispersal of viable stem fragments. Once infestations have been forced back to the embankment, imazapyr or metsulfuron treatments will provide longer term control.     

林业除草剂咪唑烟酸在土壤、水及杂草植株中的残留检测

采用HPLC建立了一种林业常用除草剂咪唑烟酸在土壤、水及杂草植株中的残留检测方法。土壤及杂草植株样品用甲醇+0.1mol/L的NH4HCO3水溶液(体积比70∶30)提取,水溶液样品直接用二氯甲烷萃取。 添加法测定结果表明:当添加水平为0.1~5 mg/kg时,平均回收率为86.9%~103.5% 。在土壤及杂草植株中的最小检知浓度分别为0.05、0.1 mg/kg;水中最小检知浓度为0.01 mg/L。     

咪唑烟酸在土壤表面光解动力学及深度的研究

运用模拟太阳光,探讨了咪唑烟酸在浙江4种典型土壤表面的光解动力学特征,分析了不同添加浓度,不同光强对其降解动力学的影响。结果表明,4种土壤的光解快慢顺序为:黄筋泥>黄红壤>海涂土>小粉土,其中最快的降解速率是最慢的1.38倍;影响光解半衰期最主要的因素为土壤的酸碱度,呈正相关,即土壤的pH值越高,其半衰期越长;而在光照强度较高,添加浓度相对较低的情况下,咪唑烟酸的降解较快。咪唑烟酸在不同湿度土壤中的光解深度明显不同,在风干土壤中,4种土壤的光解深度分别在0.07～0.14mm之间;而在60%田间持水量的土壤中,4种土壤的光解深度比风干土壤平均提高2～3倍。     

Forest herbicide influences on floristic diversity seven years after broadcast pine release treatments in central Georgia,USA

Maintenance of biodiversity is becoming a goal of forest management. This study determined effects of broadcast pine release herbicide treatments on plant species richness, diversity, and structural proportions seven years after treatment. Three study blocks were established in central Georgia. Plots 0.6–0.8 ha in size were planted to loblolly pine (Pinus taeda L.) in the Winter of 1982–83 and then treated with imazapyr (Arsenal), glyphosate (Roundup), and hexazinone (Velpar L. and Pronone 10G) in 1985. In 1992, overstory and understory (<1.5 m height) layers were examined utilizing stem and rootstock counts and basal area of overstory species and cover of understory species. ANOVA's were used to test for significance using a randomized complete block model. We found no effect of treatments on species richness. Diversity, measured separately for overstory and understory layers by Shannon-Wiener and Simpson indices, also was not influenced significantly by treatments. Arsenal significantly decreased Diospyros virginiana L. and increased Rubus argutus Link and legumes. Hexazinone treatments generally decreased Quercus nigra L., and Roundup significantly reduced Vaccinium spp. compared to the Check. We concluded that herbicide release treatments did not decrease overstory or understory plant species richness and diversity seven years post-treatment.