Inducing competition: intensive grassland seeding to control Ambrosia artemisiifolia

The invasion of Ambrosia artemisiifolia across European countries has been favoured by its ecological amplitude and by its ability to colonise and dominate disturbed/ruderal areas that have lost competition from native species. We supposed that a strong competition for habitat resources may inhibit A. artemisiifolia growth, generating a negative feedback to its establishment. Based on this hypothesis, in this study, we undertook a 1‐year field experiment to assess the effect of mixtures of grassland species on A. artemisiifolia growth and fitness in bare soils. We applied three different treatments within an abandoned quarry area invaded by A. artemisiifolia: (i) spontaneous succession, (ii) hayseed and (iii) a commercial seed mixture. Within plots, we recorded vegetation parameters, A. artemisiifolia abundance and traits. Results obtained after one growing season showed that the commercial seed resulted in the strongest reduction of A. artemisiifolia growth rate in terms of plant height, lateral spread and leaf size. This was ascribed to higher density of plants that play a key role in reducing biomass and fitness of A. artemisiifolia. However, hayseed should be preferred, as it preserves local biodiversity. Seeding mixtures of grassland species can successfully suppress A. artemisiifolia in the first year of establishment on a vegetation‐free soil derived from quarry activities. This study indicated that inducing dominance of different native species in a newly developing plant community should enhance competition for resources, reducing the success of early coloniser non‐native species.     

豚草和三裂叶豚草在新疆伊犁河谷的入侵及扩散特征

豚草(Ambrosia artemisiifolia)和三裂叶豚草(Ambrosia trifida)分别是我国公布的首批/第二批危害严重的外来入侵物种,目前已经在新疆伊犁河谷呈快速扩散趋势。文中通过对比分析2010~2016年的两个物种的分布状况,研究这两个物种在伊犁河谷的入侵及扩散特征。结果表明:(1)在入侵速度上,2010年豚草和三裂叶豚草开始入侵伊犁河谷,新源县是两个物种的主要分布区,2011年至2013年呈点状分布,2014年后大面积爆发。2016年豚草和三裂叶豚草面积分别是1015km~2、215 km~2,是2010年的10150倍、2150倍;2016年在100个调查样点的分布频度分别为0.52、0.38,是2010年的52倍、38倍,两个物种的分布频度是意大利苍耳和刺苍耳的5~9倍。(2)种子传播是两个物种的主要扩散方式。长距离扩散主要沿道路和河流,主要传播方式为人畜活动(车辆、人员往来,牛羊转场等)和流水(巩乃斯河);局部扩散主要以道路和河流为中心向周围扩散,主要传播方式为山间、田间、路边流水,人畜活动(农牧活动,车辆、人员往来等),地势(种子从高处向低处传播)等。     

豚草的生物防除现状与展望

文章综述了豚草的分布和危害,介绍了豚草的生物防除研究现状,重点讨论了目前豚草生物防除中存在的问题,并对豚草的生物防除前景进行了展望。     

Management of roadside populations of invasive Ambrosia artemisiifolia by mowing

Ambrosia artemisiifolia (common ragweed) is a highly allergenic alien weed in Europe, which spreads rapidly along roadsides. Road verges are subject to frequent mowing, which further increases the spreading of the plants' seeds. Ambrosia artemisiifolia reacts to cutting by producing new shoots, which are able to develop flowers and ultimately new seeds. An effective mowing regime that would decrease the production of seeds and their dispersal is desirable to control the spread of the plant, but an appropriate way of mowing has yet to be found. In this study, we explored how the reproductive traits of A. artemisiifolia plants in seven spontaneous roadside populations reacted to the application of different mowing regimes over 3 years. The mowing regimes that were applied differed in the timing and frequency of cuttings. We found that the cutting regime, if appropriately timed, can strongly influence the production of male inflorescences (i.e. allergenic pollen), of female flowers (i.e. seeds) and had an impact on the phenological development of the plant. Based on our findings, we suggest that the optimal management of the plant along roadsides must be adjusted to its phenological development. The most effective mowing method of control consists of a first cut shortly before male flowering, to limit the quantities of released pollen, followed by subsequent cuts before the onset of new flowers on the resprouting lateral shoots.     

Hierarchical models for white mould in snap bean

Limitations on the acceptable proportion (incidence) of pods with white mould may lead to the rejection of entire fields of processing snap bean. The low tolerances (no more than 2% to 6% of pods with white mould) are difficult to estimate with sufficient precision in the field when time is limited. These constraints motivated this study of white mould across three spatial hierarchical levels: pods, plants and quadrats consisting of two adjacent plants within rows. Hierarchical relationships are required when designing formal rules for estimating the incidence of pods with white mould from units higher in the spatial hierarchy. Disease assessments were made on all pods from 38 within‐row transects of 40 plants each of the snap bean cultivar Hystyle. Using probability‐based principles, equations were derived and fitted to data on the incidence of white mould on pods (i_pod), plants (i_pad) and quadrats (i_q(2)), which led to a function directly linking i_pod to i_q(2). The variance of i_pod increased with i_q(2), but that may be of little consequence at the lower values of i_q(2) likely to be associated with i_pod values at processor‐set tolerances. For example, at i_q(2) = 0.1 there was a 92% probability that i_pod was less than 0.02. Assessing i_q(2) may be more efficient than directly estimating i_pod because i_q(2) was about an order of magnitude higher than i_pod. Results suggest it may be feasible to design sampling plans for estimating the proportion of pods with white mould from an assessment of the proportion of diseased quadrats.     

利用天敌昆虫治理豚草的研究进展

豚草Ambrosia artemisiifolia L.起源于北美洲,一年生草本植物,靠种子繁殖。豚草在入侵地逃离了天敌等生物因子的制约,种群得以快速发展,并暴发成灾,对人类健康、农牧业生产、生态环境等均造成严重的影响。从20世纪60年代开始,许多国家从原产地寻找天敌,开始豚草生物防治。我国从20世纪80年代,先后从国外引进了5种植食性昆虫,对其生物学、生态学特性及其应用等开展了研究,最终确认豚草条纹叶甲和豚草卷蛾是2种具有应用前景的天敌昆虫。这两种天敌昆虫在野外释放后,仅有豚草卷蛾能在野外成功建立种群,一定程度上延缓了豚草种群的蔓延。随后,2001年,在南京市郊的豚草上发现一种来自北美的广聚萤叶甲,经过寄主专一性测定后,发现其具有严格的寄主专一性。同时,这种叶甲气候适应能力、繁殖力和对豚草控制潜力均较强。在中国,广聚萤叶甲和豚草卷蛾生态位互补的生物防治技术已被提出,并在南方各省市大面积推广应用,取了非常理想的控制效果。然而,广聚萤叶甲尚未能在北方建立种群,这给北方豚草的生物防治带来了许多困难。因此,通过野外创造有利于广聚萤叶甲成虫越冬的人工保护生境,或通过人工冷驯化和筛选获取高产耐寒种群,将有助于这些问题的解决。     

广州市花都区豚草种群监测调查

豚草是近年入侵广州市的外来入侵植物。对广州市花都区的一个野外种群进行了一年的生物学特性和种群监测。结果表明,大部分豚草为一年生植物,但也有少量个体冬季不枯死,能成功越冬,表现出二年生的习性。总体来看,广州花都区的豚草种群适应性强,花量大,花期长,扩散能力强,存在大面积暴发的可能。     

豚草（Ambrosia artemisiifoliaL）种群控制研究概况

豚草是世界性重要有害杂草之一,对农业生产和人类健康均造成严重危害。为抑制其种群蔓延,前人开展了化学防治、物理防治、植物替代和生物防治等对豚草的防控研究。文章阐述了各项措施在豚草种群控制中的作用和优缺点。提出以生物防治为主体,结合植物替代控制和物理防治,尽可能地不实施化学防治的的综合治理体系是未来豚草防治的一个主要途径。     

6种除草剂对豚草的田间防治效果

化学防治是一种对恶性入侵杂草豚草有效的防治措施,可在IPM中作为应急手段.为筛选出对豚草具高效的除草剂品种,采用茎叶喷雾法,在田间测定了草甘膦、百草枯、氟磺胺草醚、乳氟禾草灵、氯氟吡氧乙酸、双氟磺草胺·唑嘧磺草胺6种除草刘对豚草的防治效果.结果表明,无论是苗期(株高30 cm)还是成株期(株高60 cm),除双氟磺草胺·唑嘧磺草胺,参试除草剂均对豚草表现出良好的防治效果.可见,草甘膦、百草枯、氟磺胺草醚、乳氟禾草灵、氯氟吡氧乙酸均可应用于防治野外发生的豚草.     

豚草叶面积测定与回归分析

用扫描图像及photoshop相结合的方法测定了豚草叶面积,与坐标纸计数法比较无显著性差异。将叶面积与叶长、叶宽、叶片长宽积、长宽比等因子进行相关与回归分析,建立了叶长、叶宽与叶面积的线性回归方程Y=1．149x1＋2．750x2—9．042,长宽积与叶面积的幂函数方程Y=0．371x^0.935。     

Spray retention, foliar uptake and translocation of glufosinate and glyphosate in Ambrosia artemisiifolia

Ambrosia artemisiifolia plants exhibit stomata on both leaf surfaces and three types of trichomes: (i) small (<50 μm) spherical or ovoid, (ii) medium‐sized (50–100 μm) and (iii) long (100–200 μm) and sharp. Only the long and sharp trichomes were stained with AgNO₃, indicating the presence of hydrophilic domains. Epicuticular waxes appeared amorphous, consistent with high levels of spray retention. Glufosinate was readily taken up by A. artemisiifolia leaves, with maximum uptake of >80% of the applied label, and half maximum uptake being reached within 6 h. The foliar uptake of glyphosate was nearly complete and half of it was attained after 3 h. Glufosinate and glyphosate were ambimobile and their translocation out of the treated leaves amounted to 13–16% and 11–15% of the absorbed radioactive label respectively. Glufosinate was mainly directed to the apical developing tissues, with less amounts reaching the tissues below the treated leaves. Glyphosate was directed towards the sink tissues (apical developing tissues and roots). The sensitivity of A. artemisiifolia to glufosinate and glyphosate can be explained by high spray retention, rapid and important foliar uptake, and appreciable migration out of the parts of the plant hit by the spray.     

Fine‐tuned ability to predict future competitive environment in Ambrosia artemisiifolia seeds

Competition from native species is a key mechanism for biotic resistance to invasion. Accelerated germination to pre‐empt resources or delayed germination and induced dormancy until the next growing season are two alternative strategies for annual invasive plants to avoid the drawbacks of competition at the seed stage. In Ambrosia artemisiifolia, both of these tactics could theoretically increase its long‐term fitness. However, their relative importance has never been tested. We studied the germination pattern of A. artemisiifolia seeds in various competitive environments by experimentally modifying the life stage (seed, seedling, adult), density (low, high) and also the identity (intraspecific and 3 interspecific competitors) of neighbours in controlled conditions. When facing competition of seeds and seedlings at high densities or of particular identity, A. artemisiifolia accelerated its germination. In contrast, A. artemisiifolia followed a competition avoidance strategy in the presence of established adult heterospecific neighbours by delaying germination and reducing the germination fraction through induction of secondary dormancy. By testing the seedlings' performance in the same competition situations as those of seeds, we showed that the germination responses were beneficial in the case of heterospecific, but not of conspecific neighbours.     

外来入侵植物豚草在中国东北潜在分布区预测

文中利用最大熵生态位模型(MaxEnt)与地理信息系统(Arc GIS),结合豚草地理分布数据及19个环境因子,对入侵植物豚草在我国东北地区潜在分布和适生等级进行预测。结果表明:豚草的潜在分布区大致呈现以辽河平原腹地为中心,其适生等级向外辐射状递减趋势分布。根据豚草适生系数,确定赤峰-阿荣旗-伊春-黑河一线为豚草扩散风险的分界线。ROC曲线中AUC值为0.986,表明预测结果"非常好"。应用刀割法计算各环境变量对最大熵模型建立贡献率,结果表明影响豚草分布的主要环境因子为最暖季度平均温度和最湿季度平均温度。豚草在不同适生等级分布区域的比较分析,表明豚草在低海拔地区比在高海拔地区分布多。本研究为监测与控制外来入侵植物豚草的扩散提供了依据。     

30种除草剂对豚草和薇甘菊的防效初步评价

为了筛选出防除豚草和薇甘菊的新型高效除草剂品种,采用茎叶喷雾法,测定30种除草剂对盆栽豚草和薇甘菊的防除效果。辛酰溴苯腈375 g /hm2、麦草畏216 g /hm2、百草枯600 g /hm2、草铵膦540 g /hm2、草甘膦异丙胺盐922.5 g /hm2、乙羧氟草醚90 g /hm2、三氟羧草醚540 g /hm2、氟磺胺草醚427 g /hm2、莠去津1 140 g /hm2、莠灭净3 000 g /hm2和灭草松1 440 g /hm2对豚草防除效果好,药后30 d鲜重防效达100%;对薇甘菊防效较好的有辛酰溴苯腈375 g /hm2、麦草畏216 g /hm2、2,4-滴钠盐125 g /hm2、氯氟吡氧乙酸180 g /hm2、氯氟吡氧乙酸异辛酯150 g/hm2、草铵膦540 g /hm 2、草甘膦异丙胺盐922.5 g /hm2、灭草松1 440 g /hm2和百草枯600 g/hm2,药后30天鲜重防效达98%以上。本试验结果将为豚草和薇甘菊的化学防控提供有益参考。     

豚草提取物对4种植物病原真菌的抑制活性

采用生长速率法测定了豚草石油醚、乙酸乙酯、正己烷、乙醇提取物对4种植物病原真菌的抑制活性。结果表明,不同溶剂提取物的抑菌活性有差异,其中乙酸乙酯的抑制效果最好,在浸液浓度为4 mg/mL时,对小麦赤霉病菌的抑制作用为100%,对辣椒白绢病菌的抑制作用最低也达76.07%。而石油醚的抑制效果最差,均在30%左右。     

Discrimination of Ambrosia artemisiifolia and Artemisia vulgaris by hyperspectral image analysis during the growing season

Ambrosia artemisiifolia (ragweed) is an invasive plant in Europe. An optical detection system for effective monitoring requires differences in the spectral reflectance properties compared with other plant species. A. artemisiifolia often occurs together with Artemisia vulgaris (mugwort). Both plant species are of the Asteraceae family and they are almost indistinguishable in appearance. With the help of hyperspectral image analysis, a method was developed to determine characteristic wavelengths for their classification. High‐resolution hyperspectral images (400–1000 nm) were generated indoors. The factors measured were two weed species, two tissue classes (leaf and stem) and three growth stages (rosette growth, inflorescence emergence and fruit development). Only the stems of A. artemisiifolia in the fruit development stage showed different reflectance behaviour compared with its leaves and with the stems and leaves of A. vulgaris. At wavelengths ranging from 550 to 650 nm, the reflectance increased, and then at wavelengths up to 680 nm, the reflectance decreased. The other tissue classes showed constantly decreasing spectral reflectance from 550 to 680 nm. In the two other early growth stages, the reflectance of all four tissue classes decreased similarly. Thus, using two wavelengths of 550 and 650 nm, classification between A. artemisiifolia and A. vulgaris at fruit development was achieved. The findings could be a first step to develop an optical outdoor detection system to identify hot spots of A. artemisiifolia.     

Microsatellite DNA variation within and among invasive populations of Ambrosia artemisiifolia from the southern Pannonian Plain

Although the Pannonian Plain presents one of the areas in Europe most highly infested by Ambrosia artemisiifolia, previously reported population genetic studies of the invasive species have included only a few populations from this region. Our goal was to determine the level of genetic diversity and genetic structure of A. artemisiifolia populations from the southern Pannonian Plain using microsatellite DNA markers. We documented a high level of genetic diversity within the Pannonian populations, as compared with the genetic diversity parameters previously published for the other invasive populations of A. artemisiifolia in Europe. The mean number of alleles per locus (N_A) ranged between 6.8 and 9.4, allelic richness (r) between 6.59 and 8.53 and mean number of rare alleles per locus (N_R) ranged between 3.4 and 6.4 per analysed population. A low level of among‐population differentiation was detected, with percentage of variation between populations of 3.3%, generally low pairwise F_ST values (ranged from ?0.007 to 0.152) and also according to principal coordinate analysis. A Bayesian approach revealed that most individuals did not strongly associate with any single genetic cluster, confirming a lack of genetic structuring in the analysed region. Together with the results of quantification of the level of gene flow (N_m = 5.671), these observations indicated a presence of extensive gene exchange and admixture between the populations. Therefore, A. artemisiifolia in the Pannonian Plain region has the potential for rapid expansion.