Natural Weed Research Articles

Interregional features in the taxonomic composition of the Russian segetal floras

The article contains a comparative analysis of the taxonomical structure of the weedy species composition (segetal flora) in eight regions of Russian Federation: Leningrad, Novgorod, Vologda, Rostov and Sverdlovsk Provinces, Udmurt Republic, Republic of Bashkortostan, and Altai Territory. The segetal flora comprised weeds of cereals, root crops and perennial grasses. The comparison was made separately for the native and alien weeds. The number of native species was higher than that of alien species and varied from 137 to 209 species. The number of alien weeds varied from 99 to 179 species. Vologda Province had the lowest diversity of both native and alien plant species. Udmurt Republic had the greatest native species diversity and Altai Territory had the greatest alien species diversity. The Asteraceae, Poaceae, Brassicaceae, Fabaceae, Lamiaceae, Caryophyllaceae and Scrophulariaceae families dominated in both the native and alien fractions. The authors compared the compositions of species, families and genera of native and alien weeds. Native and alien weedy species showed the greatest similarity in their composition in geographically close regions: European Russia and the Urals. As for geographically remote regions – Altai Territory and Rostov Province – native and alien weedy species compositions were distant. At the same time, the levels of similarity among the native species were lower than among the alien ones. This attests to greater variability in the species composition among native weeds than among alien ones.

Natural Salicylaldehyde for Fungal and Pre- and Post-Emergent Weed Control

A sustainable, alternative weed control strategy is developed using salicylaldehyde (SA; 2-hydroxybenzaldehyde) as an active ingredient. SA is a natural, redox-active small molecule listed as a Generally Recognized As Safe food additive by the European Food Safety Authority and the United States Food and Drug Administration. The repurposing of SA determined that SA possesses both pre- and post-emergent herbicidal, fumigant activity, where the emitted SA from the source completely prevented the germination of plant seeds and/or the growth of the germinated plants. As a proof-of-concept, we developed agricultural byproducts (tree nutshell particles) as SA delivery vehicles to the soil, thus helping the growers’ sustainable byproduct recycling program, necessary for carbon sequestration. In plate assays, SA emitted from the nutshell vehicles (0.15 to 1.6 M) completely prevented the germination of six invasive or native weed seeds (monocots, dicots). In Magenta vessel assays, SA emitted from the nutshell vehicles (0.8 to 1.6 M) not only prevented the germination (pre-emergent) of Lagurus ovatus (Bunny Tails Grass) seeds but also inhibited the growth (post-emergent) of the germinated weeds. We determined further that soil covering (soil pasteurization) could be one of the practices to effectively deliver SA to the soil, whereby 1.6 M of SA emitted from the nutshell vehicles prevented the germination of the L. ovatus seeds maintained in soil trays covered with plastic tarp at 22 °C, while 0.8 M SA allowed partial (15%) germination of the weed seeds. Of note, SA also possesses an intrinsic antifungal activity that overcomes the tolerance of the stress signaling mutants of filamentous fungal pathogens (Aspergillus fumigatus, Penicillium expansum) to the phenylpyrrole fungicide fludioxonil. Environmental degradation data available in the public database indicate that, once released to the environment, SA will be broken down in the air by sunlight or microorganisms and, thus, is not built up in aquatic organisms. Altogether, SA can serve as a safe, potent pesticide (herbicidal, fungicidal) ingredient that promotes sustainable crop production by lowering the pesticide burden in fields.

Notes on the distribution of an alien weed Hyptis brevipes (Lamiaceae) in India

Hyptis brevipes Poit. is a native weed species of South and Central America and has been introduced and naturalized in many parts of SE Asia. It was reported from India for the first time in 1940 from Andaman and Nicobar Islands and then in 2012 from Darjeeling Himalaya. In the present study the authors have noticed the occurrence of the species in the wild in the Dima Hasao district of Assam and the Dampa Tiger Reserve of Mizoram. The study reveals that the species has naturalized in India in some parts of the Northeast region in cultivated lands along roadsides. The detailed taxonomic account of the species along with its distribution, phenology, uses and photographs is provided to confirm its identity and to take stock on its control from its further spread to some other regions, because due to the invasive nature it may affect the growth of crop plants.

Mixture of N2-fixing tree species promotes organic phosphorus accumulation and transformation in topsoil aggregates in a degraded karst region of subtropical China

Many studies have shown that introducing N2-fixing tree species into plantations can increase soil nitrogen (N) availability, via biological N2 fixation and faster N cycling. However, the effects and regulatory mechanisms of N2-fixing tree species in planting single species vs a combination of two species on phosphorus (P) accumulation and transformation in degraded karst soils remain poorly understood and appear site-dependent. This study aimed to determine the effects of introducing N2-fixing tree species (via single species vs a combination of two species) into a degraded karst region on organic phosphorus (Po) accumulation and transformation in topsoil aggregates. A comparative experiment was performed involving 8-year-old pure plantations of Dalbergia odorifera (PD) and Acrocarpus fraxinifolius (PA), a mixed plantation of Dalbergia odorifera and Acrocarpus fraxinifolius (MP), and an adjacent natural weed field (no trees, CK) in Mashan, Guangxi, subtropical China. The results showed that the contents of soil organic carbon (SOC), nitrate nitrogen (NO3−-N), available phosphorus (AP) and C:N ratios in bulk soil and aggregates, increased significantly (P < 0.05) in MP compared to CK. The levels of soil microbial biomass N (MBN) and microbial biomass P (MBP) in bulk and aggregate soils increased significantly (P < 0.05), except for micro-aggregates (<0.25 mm) in MP samples. In contrast, no significant differences of MBN or MBP were found among PD, PA and CK plots in bulk and most aggregate soils. The phospholipid fatty acid (PLFA) contents of all microbes, bacteria, fungi, arbuscular mycorrhizal (AM) fungi and actinomycetes were also significantly higher (P < 0.05) in MP than those in CK and PD in bulk and most aggregate soils. Labile Po and highly resistant Po, and the activities of all tested N and P hydrolytic enzymes, improved in bulk soil and most aggregate size classes in all forest types, especially in MP samples. Finally, redundancy analysis (RDA) indicated that Po fractions were primarily driven by alkaline phosphatase (ALP), MBN and AM. Our findings suggest that introducing N2-fixing tree species (especially MP) may be an effective method for increasing N availability and AM colonization of roots, and thereby promoting Po accumulation and transformation in degraded karst regions of southwest China.

EVALUATING THE PHYTOTOXIC EFFECTS OF SOME PLANT SPECIES OF SEMI-ARID REGIONS

The most effective method for weed control is the use of herbicides. However, the scope of this method is narrowing down due to herbicide-resistant weeds and the non-availability of new chemistry herbicides. Hence, to explore natural weed management options, the herbicidal potential of three weed species extracts namely Opuntia ficus-indica, Murraya koenigii and Dryopteris felix-mas were evaluated in lab and wirehouse experiments. A completely randomized design with factorial arrangements was used for lab and completely randomized design was used for wirehouse experiments. Each experiment was repeated twice with four replications each time. Data pertaining to seed germination, seedling growth and physiological traits of crops and weeds were recorded using standard procedures. Data indicated that aqueous extracts of tested species depicted more phytotoxicity than N-hexane extracts against germination and seedling growth of lettuce in the lab experiment. Aqueous extract of Opuntia ficus-indica completely inhibited lettuce seed germination whereas, N-hexane extract of the same species has least effect on germination and germination traits like mean germination time, time taken to 50% germination, germination index. The aqueous extract of O. ficus-indica resulted in minimum lentil, mashbean, mungbean, parthenium and Trianthema portuclacastrum seedling leaf area, chlorophyll content, shoot, root length, dry weight and maximum electrolyte leakage. The foliar application of O. ficus-indica, M. koenigii and D. felix-mas water extracts on seedlings of lentil, mashbean, mungbean, parthenium and T. portuclacastrum followed the phyto-toxicity order O. ficus-indica aqueous extract ˃ D. felix-mas aqueous extract ˃ M. koenigii aqueous extract. The growth-inhibitory demonstrations of O. ficus-indica extract suggest that active substances with herbicidal properties are present in this plant which could be exploited as natural weedicide.

入侵植物藿香蓟与常见伴生杂草的生态位特征

PDF HTML阅读 XML下载 导出引用 引用提醒 入侵植物藿香蓟与常见伴生杂草的生态位特征 DOI: 10.5846/stxb202104060881 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 浙江省自然科学基金项目(LY20C030002);浙江省教育厅一般项目(Y202045218) Niche characteristics of the invasive plant Ageratum conyzoides and its commonly associated weeds Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于传统生态位理论的生物入侵机制假说认为外来种和土著种生态位的差异是决定入侵成功与否和危害程度的关键。藿香蓟(Ageratum conyzoides L.)是一种在我国南方快速蔓延的恶性入侵种。为了了解藿香蓟与其他杂草在群落中的生态关系,探究造成藿香蓟成功入侵的可能机制及危害,在浙西南的丽水市开展了杂草群落调查,计算了藿香蓟和16种常见本地杂草的生态位宽度、生态位重叠和种间相关系数,并对主要物种进行典范对应分析(CCA)排序。结果表明(1)藿香蓟与常见本地杂草间的生态位重叠度显著高于本地杂草间的生态位重叠度,这与藿香蓟具有最大的生态位宽度有关;(2)藿香蓟与常见本地杂草的Pianka生态位重叠指数介于0.04-0.296之间,重叠度处于中下水平;(3)常见本地杂草对于藿香蓟的n-维超体积生态位重叠值显著高于藿香蓟对于常见本地杂草的n-维超体积生态位重叠值;(4)藿香蓟在CCA排序图上处于较中心的位置,说明其具有较高的中生性;不仅如此,外来杂草和本地杂草在排序图上充分混杂,说明外来种相对于本地种并无明显特化;(5)群落中大多数常见杂草间未出现显著种间负相关,仅7个种对显著正相关,大多数种对不相关。总的来说,丽水农村的杂草群落稳定较差,资源相对充足,种间生态位重叠较低,本地植物对于藿香蓟的竞争阻抗较小,加上藿香蓟本身较大的生态位宽度,导致了藿香蓟在本地区广泛而严重的入侵。 Abstract:According to the hypothesized mechanism of biological invasion, which is based on traditional niche theory, niche differentiation between alien species and native species is the key to the success of invasion and the damage it causes. Ageratum conyzoides L. is a malignant invasive species that is spreading rapidly in southern China. In order to understand the ecological relationships between A. conyzoides and native weeds in the community and to explore the possible mechanism of A. conyzoides invasion and its harmfulness, an investigation of the weed community was carried out in southwestern Zhejiang Province (28°06'-28°44'N, 119°32'-120°08'E) from 2014 to 2016. A total of 109 plots (1 m×1 m) and 286 plant species were investigated in the following habitats: roadside, abandoned farmland, streamside, and open forest. For each plot, all aboveground plant material was harvested, classified, and weighed according to species. In addition, slope, aspect, and altitude of the plot as well as the rate of sunshine arriving at the plot were measured. Moreover, pH value and the contents of total nitrogen, alkaline nitrogen, effective phosphorus, available potassium, and organic material in superficial soil (0-10 cm depth) of each plot were tested. Levin's niche breadth, Pianka's niche overlap, probability of n-dimensional niche overlap, and interspecific correlation coefficients of A. conyzoides and 16 common native weeds were calculated, and a canonical correspondence analysis (CCA) was conducted. The results showed that (1) the degree of niche overlap between A. conyzoides and common native weeds was significantly higher than that between any two native weeds, due to the largest niche breadth of A. conyzoides. (2) The Pianka niche overlap index between A. conyzoides and common native weeds was in the middle or lower level of 0.04-0.296. (3) The probabilities of n-dimensional niche overlap of common native weeds with A. conyzoides were significantly higher than those of A. conyzoides with common native weeds. (4) A. conyzoides was distributed in the central region of a CCA ordination chart, which indicated that A. conyzoides was a mesophilic species; moreover, exotic weeds (including A. conyzoides) and native weeds were fully mixed in the ordination chart, which indicated that there was no obvious specialization of exotic species relative to native species; and (5) there were no significantly interspecific negative correlations among the 17 common weed species; only 7 species pairs showed significantly positive correlation, and most species did not correlate with each other. In general, the weed community in the rural areas of southwestern Zhejiang Province is unstable, with relatively sufficient resources and low niche overlap among species. Low competition resistance from native plants and large niche width of A. conyzoides lead to extensive and serious invasion of A. conyzoides in the rural area of southwestern Zhejiang Province. 参考文献 相似文献 引证文献

引种降香黄檀和顶果木对石漠化山区土壤磷素转化及其有效性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 引种降香黄檀和顶果木对石漠化山区土壤磷素转化及其有效性的影响 DOI: 10.5846/stxb202012223252 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31960240）；广西自然科学基金项目（2017GXNSFAA198207，2018GXNSFAA294139，2019GXNSFAA185023） Effects of introducing Dalbergia odorifera and Acricarpus fraxinifolius on soil phosphorus transformation and availability in rocky desertification mountainous regions Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:我国西南岩溶区石漠化严重，植被覆盖率低，土壤贫瘠。植被恢复作为一项重要的生态治理措施，在提高土壤养分有效性，增加生物多样性和改善生态环境等方面发挥着极其重要的作用。以广西马山县经过8年植被恢复的4种样地类型（降香黄檀纯林；顶果木纯林；降香黄檀/顶果木混交林；相邻的天然灌草丛作为对照组）为研究对象，探讨了引进固氮树种（降香黄檀和顶果木）及其种植模式对石漠化山区土壤磷素转化及其有效性的影响。研究结果表明：（1）降香黄檀/顶果木混交林土壤的有机质（SOM）、硝态氮（NO3--N）、有效磷（AP）、微生物生物量碳（MBC）、微生物生物量氮（MBN）和微生物生物量磷（MBP）含量均显著高于对照（P<0.05）；降香黄檀/顶果木混交林、顶果木纯林和降香黄檀纯林的全磷（TP）相比于对照组更易转化为AP，其中以降香黄檀/顶果木混交林的效果最佳。（2）相关分析结果表明，土壤NH4+-N、NO3--N和MBN与AP分别呈显著线性正相关（P<0.05），MBN与MBP呈极显著线性正相关（P<0.01）。（3）引种降香黄檀和顶果木后，各林分的土壤无机磷组分均发生变化，其中降香黄檀/顶果木混交林和顶果木纯林的各种无机磷含量显著增加（P<0.05）。（4）最后，冗余分析表明MBP、SOM和MBN可能是影响土壤无机磷组分变化的最主要因素（P<0.05）。研究表明降香黄檀和顶果木在一定程度上能改善石漠化山区土壤的养分状况和提高土壤磷的有效性，其中以二者混交种植模式的效果最显著，以期为珍贵固氮树种在石漠化生态恢复与重建中的推广应用提供理论依据和实践支持。 Abstract:Rocky desertification is serious in karst areas in southwest China, with low vegetation coverage and poor soil. As an important ecological management measure, vegetation restoration plays an extremely important role in improving the availability of soil nutrients, increasing biodiversity, and improving the ecological environment. In this study, four types of site (the pure plantation of Dalbergia odorifera; the pure plantation of Acricarpus fraxinifolius; the mixed plantation of D. odorifera and A. fraxinifolius; the adjacent natural weed field as the control) in Mashan, Guangxi were selected as the research objects after 8 years of vegetation restoration. The effects of introducing N2-fixing tree species (D. odorifera and A. fraxinifolius) and their planting patterns on the soil phosphorus transformation and availability in rocky desertification mountainous regions were discussed. The results showed that:(1) the contents of soil organic matter (SOM), nitrate nitrogen (NO3--N), available phosphorus (AP), soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), and soil microbial biomass phosphorus (MBP) in the mixed plantation of D. odorifera and A. fraxinifolius were significantly higher than those of the control (P<0.05). The total phosphorus (TP) of the mixed plantation of D. odorifera and A. fraxinifolius, the pure plantation of A. fraxinifolius and the pure plantation of D. odorifera could be easily transformed into AP than control, among which the mixed plantation of D. odorifera and A. fraxinifolius had the best effect. (2) The results of correlation analysis showed that NH4+-N, NO3--N, and MBN had significant linear positive correlation with AP respectively (P<0.05), while MBN and MBP had extremely significant linear positive correlation (P<0.01). (3) After introducing D. odorifera and A. fraxinifolius, the soil inorganic phosphorus fractions in all sites changed, and the contents of various inorganic phosphorus in the mixed plantation of D. odorifera and A. fraxinifolius and the pure plantation of A. fraxinifolius increased significantly (P<0.05). (4) Finally, the redundancy analysis (RDA) indicated that MBP, SOM, and MBN would be the main factors affecting the changes of soil inorganic phosphorus fractions (P<0.05). Overall, D. odorifera and A. fraxinifolius could improve soil nutrient and phosphorus availability in rocky desertification mountain regions to a certain extent, among which the mixed planting pattern (the mixed plantation of D. odorifera and A. fraxinifolius) had the most significant effect. The purpose of the study could provide theoretical basis and practical support for the application of N2-fixing tree species in the ecological restoration and reconstruction of rocky desertification. 参考文献 相似文献 引证文献

Tomato Yellow Leaf Curl Virus Infection in a Monocotyledonous Weed (Eleusine indica).

Tomato yellow leaf curl virus (TYLCV) is one of the most important plant viruses belonging to the genus Begomovirus of the family Geminiviridae. To identify natural weed hosts that could act as reservoirs of TYLCV, 100 samples were collected at a TYLCV-affected tomato farm in Iksan from 2013 to 2014. The sample weeds were identified as belonging to 40 species from 18 families. TYLCV was detected in 57 samples belonging to 28 species through polymerase chain reaction using root samples including five species (Eleusine indica, Digitaria ciliaris, Echinochloa crus-galli, Panicum dichotomiflorum, and Setaria faberi) from the family Poaceae. Whitefly Bemisia tabaci-mediated TYLCV transmission from TYLCV-infected E. indica plants to healthy tomatoes was confirmed, and inoculated tomatoes showed typical symptoms, such as leaf curling and yellowing. In addition, TYLCV was detected in leaf and root samples of E. indica plants inoculated by both whitefly-mediated transmission using TYLCV-viruliferous whitefly and agro-inoculation using a TYLCV infectious clone. The majority of mastreviruses infect monocotyledonous plants, but there have also been reports of mastreviruses that can infect dicotyledonous plants, such as the chickpea chlorotic dwarf virus. No exception was reported among begomoviruses known as infecting dicots only. This is the first report of TYLCV as a member of the genus Begomovirus infecting monocotyledonous plants.

Horsenettle (Solanum carolinense) fruit bacterial communities are not variable across fine spatial scales.

Fruit house microbial communities that are unique from the rest of the plant. While symbiotic microbial communities complete important functions for their hosts, the fruit microbiome is often understudied compared to other plant organs. Fruits are reproductive tissues that house, protect, and facilitate the dispersal of seeds, and thus they are directly tied to plant fitness. Fruit microbial communities may, therefore, also impact plant fitness. In this study, we assessed how bacterial communities associated with fruit of Solanum carolinense, a native herbaceous perennial weed, vary at fine spatial scales (<0.5 km). A majority of the studies conducted on plant microbial communities have been done at large spatial scales and have observed microbial community variation across these large spatial scales. However, both the environment and pollinators play a role in shaping plant microbial communities and likely have impacts on the plant microbiome at fine scales. We collected fruit samples from eight sampling locations, ranging from 2 to 450 m apart, and assessed the fruit bacterial communities using 16S rRNA gene amplicon sequencing. Overall, we found no differences in observed richness or microbial community composition among sampling locations. Bacterial community structure of fruits collected near one another were not more different than those that were farther apart at the scales we examined. These fine spatial scales are important to obligate out-crossing plant species such as S. carolinense because they are ecologically relevant to pollinators. Thus, our results could imply that pollinators serve to homogenize fruit bacterial communities across these smaller scales.

Assessing Competitiveness of Fine Fescues (Festuca L. spp.) and Tall Fescue (Schedonorus arundinaceous (Schreb.) Dumort) Established with White Clover (Trifolium repens L., WC), Daisy (Bellis perennis L.) and Yarrow (Achillea millefolium L.)

Regulatory restrictions on herbicide use for managing turfgrass weeds has prompted the search for alternative control strategies. Fescue (Festuca) species were identified for their potential to interfere with growth of annual and perennial weeds. In a study conducted in 2018 and 2019, six fescue cultivars were tested from five different species for interference with the growth of three common turfgrass weeds: white clover (Trifolium repens L., WC), daisy (Bellis perennis L.) and yarrow (Achillea millefolium L.). Fine (Festuca L. spp.) and tall fescues (Schedonorus arundinaceus (Schreb.) Dumort.) were sown and grown in a field trial for 14 days before overseeding with different weeds. vigor and visual quality of grasses, weed cover, and vegetation cover was recorded regularly for 84 days. Differences in mean temperatures and precipitation between the two years of the study resulted in differences in growth of grasses and weeds, as well as in the extent of weed interference of fescue cultivars. Cultivars Musica (F. rubra L. ssp. commutata Gaudin) and Barpearl (F. rubra L. ssp. littoralis) were least affected by weed growth during both years, but there was overlap with other cultivars for the measured parameters. Melyane (tall fescue) was deemed unsuitable for natural weed suppression because growth and vigor declined after first mowing, ultimately leading to unacceptable visual quality. Turfgrass visual scores were moderately negatively correlated to weed cover in both years. Future research should focus on F. rubra L. ssp. rubra Gaudin and F. rubra L. ssp. littoralis subspecies and identify the mechanisms used to interfere with weed growth.

A non‐native earthworm shifts seed predation dynamics of a native weed

Abstract Introduced seed dispersers can shift seed predation dynamics in native species, impacting native plant establishment and spread. We studied the effect of the non‐native earthworm, Lumbricus terrestris, on seed loss dynamics in the large‐seeded native annual, Ambrosia trifida (giant ragweed), an expanding agricultural weed whose seeds are heavily predated by mice. Lumbricus terrestris may protect seeds against rodent predation by caching them in its burrows from which seedlings can emerge unharmed; however, little is known about the ability of earthworms to compete with rodents for seeds. We investigated this interaction and how environmental factors affected the competitive outcome. In a 2‐year field study, we analysed relative rates of seed removal by earthworms and mice for seeds dispersed at various times in habitats that varied in vegetative cover. Species‐specific responses to environmental conditions drove variation in the share of seeds taken by earthworms versus mice, with earthworms gaining relatively more seeds under warmer, wetter conditions and in low plant cover habitats, and mice obtaining more seeds under colder, drier conditions and in high cover habitats. Environmental factors also determined which competitor accessed seeds first, and this conferred a competitive advantage that was compounded over time. Earthworms cached some seeds under all experimental conditions, suggesting that L. terrestris can act mutualistically with giant ragweed in diverse environments. Synthesis and applications. Our results support the hypothesis that the non‐native earthworm Lumbricus terrestris behaves as a seed dispersal mutualist for the native annual giant ragweed by caching its seeds in its burrows, thereby reducing their availability to rodent seed predators. The data also support the view that interactions among the environment and competing seed predators determine the fate of seed pools in response to species‐specific environmental preferences. In crop fields where L. terrestris is abundant, additional efforts to prevent giant ragweed seed return may be warranted due to the likelihood that earthworms will increase giant ragweed soil seed pools. Lumbricus terrestris is expanding its range throughout temperate regions and may similarly affect secondary seed dispersal and seed predation dynamics of large‐seeded species in other plant communities.

Microhabitats Utilization by Solitary Parasitoids and Predatory Insects as Indicators of Oil Palm Agroecosystem’s Capacity to Support Insect Species Diversity

Microhabitats capacity to support insect species diversity and persistence were evaluated implementing solitary parasitoids and predatory insects according to different phases of herbicide and chemical fertilizer applications. Two species of the genus Xanthopimpla (Ichneumonidae) and one species of the genus Pompilus (Pompilidae) showed relationships on vegetation-type microhabitats, notably natural weeds, leguminous cover crops, and the beneficial plant Turnera subulata, while two species of the genus Evania (Evaniidae) showed relationships with chipped oil palm trunks. One species from the genus Odontomachus (Formicidae) as an exclusive predatory ant was related to both chipped oil palm trunks and the beneficial plant T. subulata. Xanthopimpla parasitoids exhibited abundance fluctuations difference around natural weeds during herbicide application phases between three- and six-years old oil palm stands, with decreased and increased abundance patterns of the former and the latter, respectively. 18 years old oil palm stand showed increased abundance patterns only along with the different phases of chemical fertilizer applications. The importance of natural weeds diversity, restrictions of leguminous cover crops, frequency of herbicide applications, and the arrangements between beneficial plants and wood-based microhabitats that benefited insect parasitoids and predators were discussed.

Effects of Sod-culture on Soil Nutrients and Microbial Abundance in Zanthoxylum bungeanum Plantation

In order to study the impacts of sod-culture on soil nutrients and soil microorganisms under Zanthoxylum bungeanum plantation, white clover was planted and natural weeds were cultivated, and the changes of soil nutrients and soil microorganisms were studied with clear tillage as control. The results showed that the effect of grass on soil nutrients and microbial abundance was mainly in 0~20 cm soil layer in Zanthoxylum bungeanum plantation. Grass increased the content of soil organic matter, some nutrient elements, the microbial abundance in soil, and changed the population structure of microorganisms. At the early stage of grass growing, the consumption of soil water and nitrogen fertilizer may be great, so scientific management combined with agricultural measures should be carried out according to the growth characteristics of Zanthoxylum bungeanum.

Plant Species Composition and Interactions within Communities Invaded by Persicaria perfoliata (Polygonaceae)

Persicaria perfoliata (Mile-a-Minute Weed), an invasive vine, forms monocultural patches of various sizes within infested landscapes among patches also containing other plants. We compared the species composition of P. perfoliata-dominated patches and adjacent nondominated patches in 2 topographically homogeneous sites using 20 paired plots, nonmetric multidimensional scaling, multi-response permutation procedure, and indicator species analyses. Richness and diversity were lower in the P. perfoliata-dominated patches but both patch types had uncommon native plants present. The patch types differed significantly in composition, and the nondominated patches were dominated by another nonnative invader, Microstegium vimineum (Japanese Stiltgrass), or a native weed, Ambrosia artemisiifolia (Common Ragweed). Documenting potentially interacting native and exotic species within an invaded landscape will help predict likely restoration success in response to targeted nonnative-invasive plant removal.

​RCA-based Detection of Begomoviruses in Weed Genera Associated with Legumes in Southern Karnataka

Background: Yellow mosaic disease (YMD) caused by begomoviruses transmitted through the insect vector Bemisia tabaci poses a serious threat to the production of legume crops. Methods: Season-long surveys were carried out for YMD occurrence in six different legume crops and associated natural weeds both symptomatic and asymptomatic across the districts of southern Karnataka, India. The samples were analyzed through RCA PCR using specific primer pairs. Result: Up to 94.1 per cent YMD incidence was recorded and nine weed species were commonly found associated with legume crops. The weeds viz., Ageratum conyzoides, Alternanthera sessilis, Commelina benghalensis and Euphorbia geniculata were abundantly found in the surveyed regions. The weeds were both symptomatic and asymptomatic. Rolling circle amplification coupled polymerase chain reaction method was employed to detect yellow mosaic virus in asymptomatic weeds. Phylogenetic analysis based on the sequences of PCR amplified products of weeds and symptomatic legumes revealed a close clustering of the weed samples with horsegram yellow mosaic virus, legume yellow mosaic virus and mungbean yellow mosaic virus. Overall, our data suggests the role of weed species associated with legume crops as alternative/collateral hosts of begomoviruses and their role in the epidemiology of yellow mosaic disease.

​RCA-based Detection of Begomoviruses in Weed Genera Associated with Legumes in Southern Karnataka

Background: Yellow mosaic disease (YMD) caused by begomoviruses transmitted through the insect vector Bemisia tabaci poses a serious threat to the production of legume crops. Methods: Season-long surveys were carried out for YMD occurrence in six different legume crops and associated natural weeds both symptomatic and asymptomatic across the districts of southern Karnataka, India. The samples were analyzed through RCA PCR using specific primer pairs. Result: Up to 94.1 per cent YMD incidence was recorded and nine weed species were commonly found associated with legume crops. The weeds viz., Ageratum conyzoides, Alternanthera sessilis, Commelina benghalensis and Euphorbia geniculata were abundantly found in the surveyed regions. The weeds were both symptomatic and asymptomatic. Rolling circle amplification coupled polymerase chain reaction method was employed to detect yellow mosaic virus in asymptomatic weeds. Phylogenetic analysis based on the sequences of PCR amplified products of weeds and symptomatic legumes revealed a close clustering of the weed samples with horsegram yellow mosaic virus, legume yellow mosaic virus and mungbean yellow mosaic virus. Overall, our data suggests the role of weed species associated with legume crops as alternative/collateral hosts of begomoviruses and their role in the epidemiology of yellow mosaic disease.

Spontaneous outbreak of Pascalia glauca poisoning in sheep in Argentina

Pascalia glauca is a native weed and one of the most common hepatotoxic plant affecting cattle in Argentina. Although experimental P. glauca poisoning have been reported in sheep, no spontaneous cases have been reported in this species. This work describes an outbreak of intoxication after spontaneous consumption of P. glauca, affecting 20% (6/30) sheep of a commercial flock. Affected sheep were ataxic, depressive, with mucous nasal discharge, cough and abdominal breathing. During post mortem examination, liver was swollen and a diffuse enhancement of the reticular pattern (“nutmeg liver”) was visible. Histopathological examination reveals severe and extensive acute diffuse centrilobular hepatic necrosis with hemorrhage. The presence of the toxic plant, the clinical and pathological findings allows us to confirm the etiology of this outbreak.

The Attractiveness of Five Common Mediterranean Weeds to Pollinators

Concerns about a global decline in pollinators have called for more knowledge about the factors influencing wild pollinator abundance and diversity in agroecosystems. Agricultural intensification has been identified as the main cause of this “global pollinator crisis”, particularly due to reductions in natural areas holding critical floral and nesting resources. Maintaining native wild plants in agricultural landscapes (e.g., in field margins) is often recommended as a cost-effective and efficient method for pollinator conservation. In this study, the role of common wild flowers, often considered weeds, in supporting pollinators in a Mediterranean agroecosystem was investigated. This work involved a two-year field trial to compare five native weed species common in Mediterranean cereal agroecosystems: Convolvulus arvensis L., Daucus carota L., Malva sylvestris L., Papaver rhoeas L., and Sonchus oleraceus L. The goal was to compare the attractiveness of these species, and a mixture of all five, to different flower-visiting insect groups in order to assess their value in supporting wild pollinators. Overall, D. carota had the highest number of insect visits, followed by P. rhoeas. C. arvensis, M. sylvestris, and S. oleraceus, which had lower numbers of visits. On the basis of their overall attractiveness to pollinators and low risk for invasiveness, D. carota, P. rhoeas, and M. sylvestris are the most likely to contribute positively to the conservation of pollinators in agroecosystems. Our results also suggest that it is advantageous for wild flowers sown for the purpose of pollinator conservation to be grown in clumps, rather than highly intermingled, for improved visitation rates.

Exotic forage grasses in the Brazilian semi-arid region: Forage mass, competitiveness, and botanical similarities of non-native pastures

This study evaluated the competitiveness and productivity of four non-native grass species from Africa introduced in the Brazilian semi-arid region. The experiment had a randomized block design with four replications. The grasses evaluated were Cenchrus ciliaris L., Digitaria pentzii Stent, Urochloa mosambicensis Hackel Dandy, and Megathyrsus maximus (Jacq.) B. K. Simon & S. W. L. Jacobs. Megathyrsus maximus and Urochloa mosambicensis showed the best combination of greater forage mass per harvesting (1818 and 1141 kg dry matter (DM) ha−1 per 35-day, respectively) and lesser herbage accumulation of weeds (453 and 156 kg DM ha−1 per 35-day, respectively). Despite the differences in suppressing the weed mass between different non-native grass species, all grasses showed a considerable level of similarity between their floristic composition (family-level 70%, species-level 60%). All pastures were characterized by a higher number of herb weeds than shrubs and trees, however, there was more mass accumulation from shrubs. The tallest grass in the study (Megathyrsus maximus), and the one with the best dispersing capacity (Urochloa mosambicensis), showed advantages in outcompeting the native weeds and accumulate forage mass. The intense incidence of broad-leaf shrub species must be taken as a signal of the initial stages of pasture degradation and ecological succession.

Assessing herbivorous insects as potential biological controls for the invasive species Miconia calvescens (Myrtales: Melastomataceae)

ABSTRACT Biological control methods may provide efficient and environmentally sustainable methods for curbing invasive weeds. Miconia calvescens DC (Melastomataceae) is an invasive weed of forest ecosystems on oceanic islands and one of the most invasive alien species. Therefore, the present study aimed to identify and assess the population dynamics of herbivorous insects that feed on M. calvescens in Brazil. The following species were found on M. calvescens plants at our three study locations: Apion sp. (Brentidae), Agrilus sp. (Buprestidae), Cryptorhynchus sp., Naupactus spp. (Curculionidae), Brasilaphthona sp., Cerotoma sp., Chrysodina sp., Colaspis sp., Diabrotica speciosa, and one unidentified species of the subfamily Cassidinae (Chrysomelidae). According to host specificity and impact caused to M. calvescens, the fruit-feeding Apion sp. and the stem-boring Cryptorhynchus sp. have high potential for this weed's biological control. Thus, our results provide useful information for potential biological control programmes for M. calvescens using herbivorous insects and will be helpful for companies working on natural weed control for this species.