Plant Host Range of Verticillium longisporum and Microsclerotia Density in Swedish Soils

Verticillium longisporum is a soil-borne fungal pathogen causing vascular wilt of Brassica crops. This study was conducted to enhance our knowledge on the host range of V. longisporum. Seven crop species (barley, oat, oilseed rape, pea, red clover, sugar beet and wheat) and five weed species (barren brome, black-grass, charlock, cleavers and scentless mayweed) all common in southern Sweden were evaluated for infection by response to V. longisporum. Oat, spring wheat, oilseed rape, scentless mayweed and charlock inoculated with V. longisporum in a greenhouse showed stunting to various degrees close to the fully ripe stage. Based on the extent of microsclerotia formation, explants were separated into four groups: for pea and wheat, <5% of the samples had formed microsclerotia; for scentless mayweed, 5–10%; for oat, 10–20%; and for charlock and oilseed rape >80%. The results suggest that plant species outside the Brassicaceae can act as reservoirs of V. longisporum inoculum. Soil inoculum densities in nine fields were monitored over a period of 12 months, which ranged from 1 to 48 cfu g⁻¹ soil. Density of microsclerotia was lowest just after harvest, reaching its maximum six months later. No significant correlation between inoculum density in soil and disease incidence on oilseed rape plants was found. However, the data suggest that a threshold of 1 cfu g⁻¹ soil is needed to cause disease on oilseed rape. Species identification based on microsclerotia morphology and PCR analysis showed that V. longisporum dominated in soil of seven, and V. dahliae in two of the nine fields studied.     

进口粮谷中携带杂草种子种植存活率的研究

将进口粮食中截获的杂草种子种植于隔离的自然环境中,观察自然环境下外来杂草的存活情况:在一个生长季种植的21科97种9152粒杂草种子中,有13科85种640粒种子最终存活,种类存活率达到87.6%,种子数量存活率达到7.0%;有超过一半种类的杂草种子存活率在0%~50%之间,处于中低存活水平。在此基础上,提出进口粮食的监管过程中,在严防撒漏的同时,要特别注意加强监测,尤其在杂草成熟前采取防除措施,是防止疫情扩散的关键环节。     

A diagnostic survey of shifting cultivation in northern Laos: targeting research to improve sustainability and productivity

About 25% of Laos' four million people practise shifting cultivation (mainly of rice) on a third of the country's cropped area. Official policy is to eliminate shifting cultivation by the year 2000. Diagnostic surveys of shifting cultivation were conducted in Luang Prabang and Oudomsay Provinces in northern Laos to understand the practice from a farmer's perspective, to observe fields, and to identify and give priority to problems and research to address problems. Weeds, low and possibly declining soil fertility, intensification of the cropping cycle, rats (plus birds, wild pigs), and insects lowered rice yields or reduced system sustainability. The forest ecosystem has been degraded by logging, burning, and rice monocropping; and potentials for environmental rehabilitation through natural succession are minimal. Farmers cannot adopt high labor and cash cost innovations; and improved fallow is needed as an intermediate step prior to crop diversification, adoption of agroforestry technologies, and sedentary agriculture.     

Benefits of a maize–bean–weeds mixed cropping system in Urubamba Valley,Peruvian Andes

Abstract

In the Urubamba Valley, Peruvian Andes, we evaluated the abundance of insect pests and natural enemies in experimental plots where maize was grown either as monoculture, intercropped with beans, or intercropped with beans plus associated weeds. We also assessed the consequences of the cropping system for maize yield. The main insect pests recorded were Diabrotica spp. (Coleoptera: Chrysomelidae), Carpophilus sp. (Coleoptera: Nitidulidae) and Pagiocerus frontalis (Coleoptera: Scolytidae), and their overall abundance did not differ among crop diversity treatments. However, there was a significant adverse effect of crop diversity on the maximum abundance of both Carpophilus and Pagiocerus. The main beneficial arthropods were Paratriphleps sp. (Hemiptera: Anthocoridae), ladybirds and spiders, and their density did not differ among treatments. Maize yield did not decrease with increasing plant diversity. The reported benefits of intercropping, together with the associated efficiency in land use, make this traditional agricultural practice a valuable alternative to the use of pesticides, particularly for resource-poor Andean farmers.     

广东主要茶区春季杂草群落调查与区域差异分析

探明广东茶园春季杂草基本情况,为茶园杂草防控提供基础数据.2020年3-5月,在广东省粤东、粤西、粤北3个茶叶主产区31个茶园共620块样方开展茶园杂草群落调查,采用七级目测法,记录样方杂草种类及生长优势等级.调查共发现杂草313种,出现频度高于10％的杂草有126种,其中菊科杂草23种、禾本科12种、茜草科8种、蔷薇...     

唑草·苯磺隆24%可湿性粉剂小麦田间药效试验

田间试验表明唑草·苯磺隆24%可湿性粉剂28.8～43.2g/hm2能有效防除小麦田一年生阔叶杂草,药后45d,对猪殃殃、泽漆、麦家公、播娘蒿的株防效在90.5%～94.2%,鲜重防效在92.1%～96.4%。在推荐剂量下,对小麦生长安全。     

Interactions between rodents and weeds in a lowland rice agro‐ecosystem: the need for an integrated approach to management

Rodents and weeds are important pests to rice crops in Southeast Asia. The interaction between these 2 major pests is poorly documented. In temperate cereal systems, seeds of grass weeds can be an important food source for rodents and weed cover along crop margins provides important refuge for rodents. In 2012 and 2013, a replicated study (n = 4) in Bago, Myanmar compared 4 treatments (rodents and weeds; no rodents and weeds; rodents and no weeds; no rodents and no weeds) each of 0.25 ha in transplanted rice. Weeds were managed with hand weeding in the wet season, and hand weeding and herbicides in the dry season. Plastic fences were installed to exclude rodents. We examined the weed cover and relative abundance of weed species, rodent damage, rodent population dynamics and rice yield loss caused by rodents and weeds. The dominant rodent species was Bandicota bengalensis. In the dry season, Cyperus difformis was dominant at the tillering stage and Echinochloa crus‐galli was the dominant weed species at the booting stage. In the wet season E. crus‐galli was a dominant weed throughout the season. Damage by rodents was higher in the dry season. There were larger economic benefits for best weed management and effective rodent control in the dry season (258 US$/ha) than in the wet season (30 US$/ha). Concurrent control of weeds in and around rice fields combined with coordinated community trapping of rodents during the early tillering stage and ripening stage of rice are recommended management options.     

Combining competition from Lolium perenne and an insect–fungus combination to control Rumex obtusifolius seedlings

Although adult Rumex obtusifolius are problematic weeds, their seedlings are poor competitors against Lolium perenne, particularly in established swards. We investigated the possibility of using this weakness to augment control of R. obtusifolius seedlings with combinations of Gastrophysa viridula (Coleoptera: Chrysomelidae) and the rust fungus Uromyces rumicis. Rumex obtusifolius seedlings were grown in competition with L. perenne sown at different rates and times after R. obtusifolius: they competed successfully with L. perenne when sown 21 days before the grass. Sowing both species at the same time resulted in a dominant grass sward, with R. obtusifolius becoming dominant when sown 42 days prior to L. perenne. Grass sowing rate had no effect on R. obtusifolius growth or biomass. A second experiment investigated how competition from L. perenne sown 21 days after R. obtusifolius combined with damage from G. viridula and/or U. rumicis (applied at either the 3–4‐ or 10–13‐leaf stage, or at both stages) affected the growth and final biomass of R. obtusifolius. Beetle grazing at the latter leaf stage was the only treatment that reduced R. obtusifolius biomass, although rust infection at the earlier application led to an increase in shoot and root weight. The results are discussed in terms of the potential for use of these agents in the field.     

玉米田养鹅对土壤理化性状、杂草多样性及玉米生长的影响

为探究"玉米田养鹅"对农田生态系统杂草多样性、土壤理化性质及玉米生长状况的影响,以林芝市八一镇章麦村试验田为研究对象,运用对比方法,研究玉米田养鹅(Raising geese in cornfield,RGC)和对照(Control,CK)土壤理化性质、杂草多样性及玉米生长的异同,旨在通过田间状态的描述和中间状态的研究,为以后优化玉米田调控措施提供依据。结果表明:1)RGC处理有19种杂草,其中以菊科植物最多,对照组仅有9种。不同功能群杂草密度相差很大,双子叶一年生或越年生被子植物功能群杂草密度远远高于其他5种功能群;RGC处理提高了杂草群落Shannon-Wiener和Simpson多样性指数,但降低了Pielou均匀度指数和Margalef物种丰富度指数;2)RGC处理土壤含水率较对照高1.27%,与对照相比差异不显著(P0.05);3)随着土层加深,RGC和对照土壤紧实度均呈逐渐增加趋势,且RGC对紧实度影响显著;4)对照土壤碱解氮含量为86.48mg/kg,略高于RGC处理2.67mg/kg(P0.05),速效钾含量为161.07mg/kg,略高于RGC处理28.66mg/kg(P0.05),而RGC的土壤中速效磷含量为120.98mg/kg,是对照(106.25mg/kg)的1.14倍(P0.05)。结论:RGC处理增加了农田系统杂草数量、种类和生物量,提高了生物多样性,使土壤紧实度明显减小、土壤含水率增加及土壤养分含量出现差异,且玉米各项农艺性状低于对照。     

依据干扰理论优化入侵植物控制体系的研究进展

入侵植物控制行为可被视为对生态系统的干扰,因而以成熟的干扰理论指导入侵植物控制体系的构建,可为提高控制入侵植物的效率提供参考。文章对构成控制体系的6个技术因子(包括类型、频次、时令、强度、面积和程度等)进行分析,并对优化目标和优化方法进行综述。最后,提出了依据干扰理论构建入侵植物控制体系的步骤。