A method for mapping the distribution of willow at a catchment scale using bi-seasonal SPOT5 imagery

This study showed that seasonal imagery acquired at specific stages of phenology can be used to improve the mapping accuracy of invasive willow at a catchment scale. SPOT5 XI (10 m) satellite imagery was acquired for early autumn and winter to represent the phenological stages of leaf cover and leaf fall respectively. Four classification regimes were evaluated using single‐ and bi‐seasonal composite imagery to determine the most accurate method. Significant spectral noise was found in willow populations, especially in the winter image, due to the effects of undergrowth exposure, shadowing, topography and boundary‐mixed pixels. Two noise reduction techniques were applied to the bi‐seasonal composite image to improve the classification results. The noise‐reduced bi‐seasonal composite image was classified using the spectral angle mapper (SAM) algorithm before importation into a geographical information system. Aerial photography was used to reduce the errors of commission associated with misclassification of pastures. The class accuracy achieved for willow using the method described in this study was 77.5% (Kappa =0.87). The high cost of eradicating willow means that managers must establish priorities for control; this technique can provide a powerful tool for prioritizing control programmes and for monitoring results at a catchment scale.     

Can the occurrence of Senecio jacobaea be influenced by management practice?

Senecio jacobaea is a poisonous weed in grasslands of various countries (e.g. Great Britain, New Zealand, Central European states) and the further spread of the species into farmland must be prevented. To assess the influence of management practice and site conditions on the occurrence of S. jacobaea, we conducted a survey in the northern and central part of Switzerland. Botanical assessments were carried out on grassland plots with S. jacobaea occurrence and on neighbour plots without S. jacobaea. For these plots, we analysed the soil nutrients and the details of management practice, such as type and intensity of management and fertiliser application. The most important factors influencing the occurrence of S. jacobaea were related to management: There was a high risk for the occurrence of the species on parcels with low nitrogen fertilisation, continuous‐extensive grazing (set stocking) and a very open sward. Senecio jacobaea was not present in intensively managed meadows cut more than twice per year. As an exception, with a high propagule pressure from the vicinity, S. jacobaea was also found in intensively grazed pastures and in meadows of moderate management intensity (two cuts). We conclude that long‐term control of S. jacobaea can best be achieved by avoiding sward damage and by preventing the species’ seed formation in the pasture and local vicinity.     

Herbicide research and development: challenges and opportunities

The high adoption of chemical weed control and the broad range of solutions already available to manage most weed problems are significant hurdles to the development and launch of new herbicides. Business potentials are influenced by the high technical and biological standards provided by existing herbicides, as well as the intense competition in the marketplace. Other factors adding complexity are agronomic, structural and technological changes, including the introduction of herbicide‐tolerant crops, and the high costs of development for new active ingredients, mainly due to increasing regulatory requirements. In the light of increasing weed resistance to widely used herbicides, securing diversity in agronomy as well as weed management is a key to efficient crop production in future. In order to support this objective, new herbicides, preferably with new modes‐of‐action, will need to be discovered and developed.     

A review of non-chemical weed control on hard surfaces

Weed control research to date has mainly focused on arable land, especially regarding herbicides, but also regarding non‐chemical methods. Some of these experiences can be applied to hard surface areas. However, weeds on hard surface areas cause problems that are different from those on arable land. Additionally, crop tolerance does not need to be considered when choosing an appropriate weed control method on these areas. The aim of this review is to describe current knowledge of weeds and weed control methods on hard surface areas and reveal potential ways of advancement. One of the shortcomings of non‐chemical weed control on hard surfaces thus far, is a lack of proper definition of efficiency of the weed control methods. To obtain effective control, more frequently repeated treatments are required than chemical weed management, thereby increasing the costs of labour and fuel. One way to reduce costs can be by adjusting the level of control to the required visual street quality. Weeds are adapted to the hard surface environment and may be less susceptible to certain control methods. This review indicates that for efficient weed control on hard surfaces there is a need for combining weed control techniques, applying sensors for detecting weeds, adapting the energy dose to type of weed flora and prevention of weeds by improved construction of new surfaces.     

害草薇甘菊生防因子——安婀珍蝶的自然种群生命表研究

室外设立隔离网笼，在自然气候条件下，饲养、释放薇甘菊重要生防因子——安婀珍蝶，研究了安婀珍蝶野外释放后对广东地区环境的适应能力；利用庞雄飞作用因子组配的生命表方法，组建安婀珍蝶自然种群生命表，量化分析评价各因子对安婀珍蝶的影响。结果表明：释放安婀珍蝶两代的自然种群趋势指数分别为0．0872和0．0939，都非常低，安婀珍蝶野外增殖能力较差。第一代和第二代中“捕食与其他”的控制作用指数分别为190．0191和84．8973，均高于其他因子的控制作用，“捕食与其他”为影响安婀珍蝶生长发育的重要因子。综合上述结果认为，需通过大量饲养人工释放、补充幼虫数量的方法，逐步提高安婀珍蝶在野外建立自然种群的能力。     

240克/升烯草酮乳油防除夏大豆田杂草田间药效试验

田间试验结果表明,夏大豆田播后苗期使用240克/升烯草酮乳油30～40克/667m2,对禾本科杂草有较好的防除效果,并且有较长的持效期,对大豆生长安全。     

贵州马铃薯田杂草群落调查

贵州是我国马铃薯主产区之一,然而尚未有当地马铃薯Solanum tuberosum田杂草发生情况的研究报道。我们在贵州省修文县、开阳县、息烽县、习水县、水城县等5个典型马铃薯种植区展开田间调查。在所调查的19块马铃薯田间共发现64种杂草,其中重要值位列前10的杂草依次为:粗毛牛膝菊Galinsogaquadriradiata、卷茎蓼Fallopia convolvulus、繁缕Stellaria media、尼泊尔蓼Polygonum nepalense、马唐Digitaria sanguinalis、酸模叶蓼Polygonum lapathifolium、藜Chenopodium album、野艾蒿Artemisia lavandulaefolia、凹头苋Amaranthus lividus、鸭跖草Commelina communis。平均每块样田中杂草种类数为12.05种,Shannon多样性指数平均值为9.88,Pielou均匀度指数平均值为0.87;样地两两之间的Jaccard差异性指数平均值为0.76,Bray-Curtis差异性指数的平均值为0.72。通过主成分分析对所调查的19块马铃薯田杂草群落进行分析,结果表明所调查的19块田可分为4个类群,类群1优势种为粗毛牛膝菊、卷茎蓼、马唐,类群2以马兰为单优势种,类群3以繁缕、看麦娘、猪殃殃、酸模叶蓼为优势种,类群4以粗毛牛膝菊、卷茎蓼、马唐、尼泊尔蓼为优势种。结论:贵州马铃薯田杂草群落的α和β多样性均较高,不同马铃薯种植地区杂草群落结构差异较大,一些具有贵州地区特色的杂草例如粗毛牛膝菊、尼泊尔蓼等在当地马铃薯田危害严重。     

Effect of soil moisture during stratification on dormancy release in seeds of five common weed species

Although the effects of cold stratification on the release of physiological dormancy in seeds have been studied extensively, knowledge of the role of soil moisture content on seed dormancy release during cold stratification is limited. Our study determined seed dormancy characteristics and the effect of soil moisture content on seed dormancy breakage during cold stratification in the five common weed species Amaranthus retroflexus, Chenopodium album, Chenopodium hybridum, Plantago lanceolata and Setaria glauca. Seeds of all five species were dormant at the time of harvest and their germination response to light and temperature varied. Soil moisture content had a significant effect on seed dormancy release of all species except P. lanceolata. Germination percentage of A. retroflexus, C. album, C. hybridum increased and then decreased as soil moisture content increased, regardless of germination test temperature. The optimal soil moisture content and seed moisture content for dormancy breakage of A. retroflexus, C. album, C. hybridum were 8%, 12%, 8% and 22.0%, 37.7%, 25.7% respectively. Dry storage (after‐ripening) significantly increased germination of S. glauca. Moreover, increasing soil moisture content first slowed and then increased dormancy breakage in S. glauca. These results suggest that data on soil moisture content should be incorporated into models that predict weed seed dormancy breakage and timing of seedling emergence as well as those for weed management.     

You cannot fight fire with fire: a demographic model suggests alternative approaches to manage multiple herbicide‐resistant Avena fatua

Multiple herbicide‐resistant (MHR ) weed populations pose significant agronomic and economic threats and demand the development and implementation of ecologically based tactics for sustainable management. We investigated the influence of nitrogen fertiliser rate (56, 112, 168, or 224 kg N ha^?1) and spring wheat seeding density (67.3 kg ha^?1 or 101 kg ha^?1) on the demography of one herbicide susceptible and two MHR Avena fatua populations under two cropping systems (continuous cropping and crop‐fallow rotation). To represent a wide range of environmental conditions, data were obtained in field conditions over 3 years (2013–2015). A stochastic density‐dependent population dynamics model was constructed using the demographic data to project A. fatua populations. Elasticity analysis was used to identify demographic processes with negative impacts on population growth. In both cropping systems, MHR seedbank densities were negatively impacted by increasing nitrogen fertilisation rate and wheat density. Overall, MHR seedbank densities were larger in the wheat‐ fallow compared with the continuous wheat cropping system and seedbank densities stabilised near zero in the high nitrogen and high spring wheat seeding rate treatment. In both cropping systems, density‐dependent seed production was the most influential parameter impacting population growth rate. This study demonstrated that while the short‐term impact of weed management tactics can be investigated by field experiments, evaluation of long‐term consequences requires the use of population dynamics models. Demographic models, such as the one constructed here, will aid in selecting ecologically based weed management tactics, such as appropriate resource availability and modification to crop competitive ability to reduce the impact of MHR .     

入侵杂草虉草在云南的发生、危害和防除状况调查

采用倒置"W"九点取样法和5级目测法,调查了云南冬季作物田杂草虉草的发生和危害状况。结果表明,截至2017年在云南有7个地州33个区县发现有虉草危害,其中保山地区危害最为严重,占全省受害面积的92%,其次是大理白族自治州。虉草在冬季作物田大麦、小麦、油菜和蚕豆田均有发生。危害的虉草有两个种,分别是小籽虉草Phalaris minor和奇异虉草P.paradoxa。其中小籽虉草的发生较为普遍,奇异虉草为零星发生。虉草造成的危害指数在6%~50%之间,对农作物造成的产量损失在40~110kg/667m2之间。虉草的防除以化学防除为主,人工防除为辅,但目前尚缺乏经济有效的防除农田虉草的除草剂。