森泰除草剂防除香椿幼林地杂草的试验研究

使用25%森泰水剂和5%森泰颗粒剂防除香椿幼林地的杂草研究试验结果表明:25%森泰水剂和5%森泰颗粒剂均能够有效防除香椿幼林地的五节芒、苦竹、刚竹、芒萁骨等多年生恶性杂草,防除效果均可达93%以上。使用25%森泰水剂除草比人工除草可减少用工56 1%～92 2%,降低除草成本36 1%～61%。同时,可根据幼林地杂草的种类、高度、盖度和水源等因素选择合适的森泰除草剂的剂型和剂量组合,以达到理想的防除杂草效果。     

Incorporating forage grasses in riparian buffers for bioremediation of atrazine, isoxaflutole and nitrate in Missouri

Multi-species tree-shrub-grass riparian buffer systems have been recognized as one of the most cost-effective bioremediation approaches to alleviate nonpoint source agricultural pollution in heavily fertilized systems. However, highly concentrated herbicides in surface and subsurface water and shade cast by trees along the stream bank usually compromise the effectiveness of these systems. Greenhouse trials and field lysimeter studies were conducted to evaluate the tolerance of orchard grass (Dactylis glomerata), smooth bromegrass (Bromus inermis), tall fescue (Festuca arundinacea), timothy (Phleum pratense), and switchgrass (Panicum virgatum) ground covers to atrazine and Balance™ (isoxaflutole) plus their capacity to sequester and degrade these herbicides and their metabolites. Their ability to remove soil nitrate was also quantified. Concentrations of atrazine, Balance™ and their metabolites in the leachate, soil and plant samples were determined by solid phase extraction followed by high performance liquid or gas chromatographic analyses. Distribution of the herbicides and metabolites in the system was calculated using a mass balance approach. Herbicide bioremediation capacity of each lysimeter treatment was determined by the ratio of metabolites to parent herbicide plus metabolites. Bioremediation of nitrate was quantified by comparing nitrate reduction rates in grass treatments to the bare ground control. Based on this herbicide tolerance, bioremediation data and shade tolerance determined in a previous study, it was established that switch grass, tall fescue and smooth bromegrass are good candidates for incorporation into tree-shrub-grass riparian buffer systems designed for the bioremediation of atrazine, Balance™ and nitrate.     

42%氟啶草酮复配33%二甲戊灵乳油对棉田杂草的防效、杀草谱及安全性评价

【目的】研究复配33%二甲戊灵乳油(200 mL/667m²)的42%氟啶草酮悬浮剂的最佳剂量,杂草的杀草谱以及对棉花安全评价。【方法】采用田间与室内结合方法,在不同浓度42%氟啶草酮悬浮剂复配33%二甲戊灵乳油(200 mL/667m²)条件下,分析其对棉田杂草防效、杀草谱以及对棉花出苗率、株高、产量等的影响。【结果】42%氟啶草酮悬浮剂对龙葵、反枝苋、灰藜、马齿苋有较高的杀草活性,EC₅₀分别为17.58、17.68、16.87和16.44 mL/667m²。药剂的最佳组合为42%氟啶草酮悬浮剂(35~40 mL/667m²)+33%二甲戊灵乳油(200 mL/667m²);42%氟啶草酮悬浮剂用量高于35 mL/667m²时对阔叶杂草的防效达到90%以上,且要优于禾本科杂草,该组合对苘麻和田旋花的防效低于59%;42%氟啶草酮悬浮剂复配33%二甲戊灵乳油(200 mL/667m²)对棉花的株高、鲜重、果枝数、单铃重、籽棉产量没有影响,出苗率在42%氟啶草酮悬浮剂(40~200) mL/667m²+33%二甲戊灵乳油的药剂下下降到90%以下。【结论】复配药剂的最佳浓度是42%氟啶草酮悬浮剂(35~40 mL/667m²)复配33%二甲戊灵乳油(200 mL/667m²);42%氟啶草酮悬浮剂单剂用量高于35 mL/667m²时对棉田主要阔叶杂草龙葵,反枝苋、灰藜、马齿苋具有良好的防效,有较高的杀草活性,防效达到90%以上;复配药剂中42%氟啶草酮悬浮剂浓度在40 mL/667m²以上时棉花出苗率下降到90%以下,但是对棉花产量,株高、鲜重没有影响。     

5%硝磺草酮.丙草胺.五氟磺草胺颗粒剂防除水稻移栽田一年生杂草的效果

为了明确5%硝磺草酮. 丙草胺.五氟磺草胺颗粒剂在水稻移栽田对一年生杂草的防除效果及对水稻的安全性,进行田间杂草防除试验,为高效防除水稻田杂草提供依据。结果表明：施药后40d,5%硝磺草酮.丙草胺.五氟磺草胺颗粒剂700,800,900,1600g/667m²对稗草的防效为93.2%～99.2%,对异型莎草的防效为92.3%～98.1%,对野慈姑的防效为88.5%～97.6%,对雨久花的防效为90.3%～97.5%,对泽泻的防效为87.0%～95.9%,对狼把草的防效为90.0%～98.3%。5%硝磺草酮.丙草胺.五氟磺草胺颗粒剂700,800,900,1600g/667m²处理对水稻均无药害表现,水稻生长发育正常。对稗草、异型莎草、野慈姑、雨久花、泽泻、狼把草有较好防效。     

吡啶甲酸类除草剂应用研究进展

吡啶甲酸类除草剂属合成激素类, 目前登记使用的有效成分包括氨氯吡啶酸、二氯吡啶酸和氯氨吡啶酸, 分别于1963年、1977年和2005年上市, 主要用于阔叶杂草和灌木的茎叶处理防控, 其中氯氨吡啶酸具有土壤封闭活性。吡啶甲酸类除草剂的作用靶标仍未明确, 有可能来自生长素结合蛋白家族。全世界报道的抗吡啶甲酸类除草剂杂草共涉及7种8个生物型。目前, 我国登记的除草剂品种中共有13个复配剂含氨氯吡啶酸和二氯吡啶酸, 1个含氨氯吡啶酸、氯氨吡啶酸和二氯吡啶酸;国外登记的吡啶甲酸类除草剂复配剂主要为与其他激素型除草剂、ALS(乙酰乳酸合酶)抑制剂、ACCase(乙酰辅酶A羧化酶)抑制剂的组合。该类除草剂仍然具有较好的应用前景, 在主要应用场景下常见杂草对氨氯吡啶酸、二氯吡啶酸、氯氨吡啶酸的敏感性仍需系统研究, 该类除草剂主要靶标杂草种群的抗药性水平也亟须检测。     

Vertical distribution, size and composition of the weed seedbank under various tillage and herbicide treatments in a sequence of industrial crops

Investigations were conducted during the 2003, 2004 and 2005 growing seasons in northern Greece to evaluate effects of tillage regime (mouldboard plough, chisel plough and rotary tiller), cropping sequence (continuous cotton, cotton–sugar beet rotation and continuous tobacco) and herbicide treatment on weed seedbank dynamics. Amaranthus spp. and Portulaca oleracea were the most abundant species, ranging from 76% to 89% of total weed seeds found in 0–15 and 15–30 cm soil depths during the 3 years. With the mouldboard plough, 48% and 52% of the weed seedbank was found in the 0–15 and 15–30 cm soil horizons, while approximately 60% was concentrated in the upper 15 cm soil horizon for chisel plough and rotary tillage. Mouldboard ploughing significantly buried more Echinochloa crus‐galli seeds in the 15–30 cm soil horizon compared with the other tillage regimes. Total seedbank (0–30 cm) of P. oleracea was significantly reduced in cotton–sugar beet rotation compared with cotton and tobacco monocultures, while the opposite occurred for E. crus‐galli. Total seed densities of most annual broad‐leaved weed species (Amaranthus spp., P. oleracea, Solanum nigrum) and E. crus‐galli were lower in herbicide treated than in untreated plots. The results suggest that in light textured soils, conventional tillage with herbicide use gradually reduces seed density of small seeded weed species in the top 15 cm over several years. In contrast, crop rotation with the early established sugar beet favours spring‐germinating grass weed species, but also prevents establishment of summer‐germinating weed species by the early developing crop canopy.     

Root exudation of diclofop-methyl and triasulfuron from foliar-treated durum wheat and ryegrass

In this study, we evaluated the release of diclofop-methyl and triasulfuron from the roots of foliar-treated ryegrass and wheat. The study with ¹⁴C-diclofop-methyl indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass. No root exudation from ¹⁴C-diclofop-methyl-treated wheat plants was observed, while 20 days after treatment (DAT) 0.2–0.9% of radioactivity absorbed by ryegrass was found exuded in the growing medium. Root exudation was stimulated three to six times by the presence of untreated wheat or ryegrass sharing the growing medium with diclofop-methyl-treated ryegrass. No subsequent uptake of exuded radiolabel by untreated plants (ryegrass or wheat) in the same pot with ¹⁴C-diclofop-methyl-treated ryegrass was observed. The study with ¹⁴C-triasulfuron indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass and also into the growing medium. By 20 DAT, 0.5–4.2% of radioactivity absorbed by wheat or ryegrass was found exuded in the growing medium. The presence of untreated plants (wheat or ryegrass) in the same pot as triasulfuron-treated ryegrass or wheat induced exudation seven to 32 times more. The study also revealed a subsequent uptake of exuded compounds by untreated wheat or ryegrass sharing the medium of ¹⁴C-triasulfuron-treated plants. This study has demonstrated for the first time that the root exudation of exogenous compounds can be related to plant arrangement in pots. The implication is that herbicide root exudation and transfer, a form of allelopathy, could be significant in the field. A precise estimation of environmental fate, unexpected ecological side effects and residual activity of herbicides may require quantification of such exudation.     

Inheritance of sethoxydim resistance in foxtail millet, Setaria italica (L.) Beauv.

Interspecific hybridization between foxtail millet cultivars (Setaria italica) and a green foxtail (S. viridis) resistant to the herbicide sethoxydim were undertaken to breed foxtail millet for improved herbicide resistance. Parents, reciprocal F₁ hybrids, F₂ selfed derived populations and BC₁ backcross progeny were produced and analysed for mortality and fresh weight over a range of dosages. All resistant progeny were 700 times more resistant than susceptible cultivars and was symptom free under current field dosages. Segregations of resistant and susceptible progeny (3:1 in F₂ and 1:1 in BC₁) were not dependent upon dosage. Heterozygous individuals displayed the same magnitude of resistance as homozygous plants at twelve times the recommended field dosage. Results suggested that sethoxydim resistance in foxtail millet was controlled by a single, completely dominant, nuclear gene. This revised version was published online in July 2006 with corrections to the Cover Date.     

Out-crossing frequency and genetic analysis of hybrids between transgenic glufosinate herbicide-resistant rice and the weed, red rice

The potential of transferring herbicide resistance from transgenic rice (Oryza sativa L.) varieties to sexually compatible weeds is of paramount importance for development of effective weed control strategies. The objective of this research was to determine the genetic control and frequency of natural outcrossing between a transgenic, glufosinate-resistant rice line and a Louisiana biotype of red rice (Oryza sativa L.). Molecular and phenotypic data showed that outcrossing in field plots between a non-transgenic purple marker line and red rice did occur within one field season, but at a low rate of <1%. Similarly, molecular and phenotypic data demonstrated that glufosinate resistance was transferred from the transgenic line to the red rice biotype in the field within one year at a low frequency of 0.3%. Compared to parental lines, the transgenic-red rice hybrids were extremely late, tall, and never set seed during the normal field season. Genetic analyses in all F₂ populations showed glufosinate resistance behaved in a Mendelian fashion as a single, dominant gene. Presence of the bar gene for glufosinate resistance did not increase fitness or seed fecundity in hybrids or subsequent progeny. The genetic analyses and outcrossing results from this study suggest that an effective management program can be developed to prolong the usefulness of transgenic, glufosinate herbicide technology. This revised version was published online in July 2006 with corrections to the Cover Date.     

Herbicide-tolerant crops in agriculture: oilseed rape as a case study

Oilseed rape has been modified extensively by conventional breeding for the production of varieties useful for human consumption (blended vegetable oil and margarine) and industrial processes (rubber additives and high‐temperature lubricants). Because much is now known about its genetic and biochemical composition, it has been an obvious choice for genetic modification and is now at the forefront of the commercial development of genetically modified (GM) or transgenic crops. Around the world, the increase in commercial plantings of all transgenic crops has been rapid. In 1996, 1.7 million hectares were planted, but by 1998 this figure had jumped to 27.8 million ha. The area in the year 2001 is likely to be about 50 million ha. With the possible introduction of transgenic varieties into European agriculture, it is essential that the associated farming practices employed are appropriate for their growth, both from a commercial and an environmental viewpoint. Some of the first transgenic crops are those carrying agronomic traits, e.g. herbicide tolerance transgenes. However, before full commercialization occurs, important agronomic and environmental questions need to be answered. How are these new crops to be incorporated into existing cropping practices? How will this change the current herbicide use profile for a given crop? Do herbicide‐tolerant varieties enhance or impede integrated pest management schemes? What is the likely uptake of such crops in agriculture? What are the ecological implications of their introduction? Are there effective measures to control the spread of transgenes to wild relatives? This paper addresses these questions, with special emphasis on oilseed rape production in the UK, but includes examples from other crops and countries where appropriate.