Evaluating field‐scale sampling methods for the estimation of mean plant densities of weeds

The weed flora (comprising seven species) of a field continuously grown with soyabean was simulated for 4 years, using semivariograms established from previous field observations. Various sampling methods were applied and compared for accurately estimating mean plant densities, for differing weed species and years. The tested methods were based on (a) random selection wherein samples were chosen either entirely randomly, randomly with at least 10 or 20 m between samples, or randomly after stratifying the field; (b) systematic selection where samples were placed along diagonals or along zig‐zagged lines across the field; (c) predicted Setaria viridis (L.) P. Beauv seedling maps which were used to divide the field into low‐ and high‐density areas and to choose the largest sample proportion in the high‐density area. For each method, sampling was performed with 5–40 samples. Systematic methods generally resulted in the lowest estimation error, followed by the random methods and finally by the predicted‐map methods. In case of species over‐ or under‐represented along the diagonals or the zig‐zag sampling line, the systematic methods performed badly, especially with low sample numbers. In those instances, random methods were best, especially those imposing a minimal distance between samples. Even for S. viridis, the methods based on predicted S. viridis maps were not satisfactory, except with low sample numbers. The relationships between sampling error and species characteristics (mean density, variability, spatial structures) were also studied.     

新疆莫索湾南缘沙漠四种灌木空间异质性的对比

应用地统计学原理和方法,以莫索湾南缘沙漠为研究区,对心叶驼绒藜(Ceratoides ewersmanniana)、梭梭(Haloxylon ammodendron)、琵琶柴(Reaumuria soongorica)、沙拐枣(Calligonum leucocladum)4种优势灌木的空间分布格局进行定量研究。结果表明:心叶驼绒藜主要分布于丘底和丘坡,分布介于集群分布和均匀分布,变程31.44 m,各向同性;梭梭主要分布于丘坡和丘顶,呈自相关性很强的集群分布,变程89.03 m;琵琶柴主要分布在丘底,为中等程度的集群分布;沙拐枣在该区分布频度较低,各向异性,属于随机分布。该地区灌木分布受沙漠与绿洲环境的共同作用,心叶驼绒藜和梭梭在该地区适应良好,分布环境的互补性强,搭配建植防风固沙的生态效益明显。     

基于克里金插值的耕地表层土壤有机质空间预测

基于环境变量与耕地表层土壤有机质的相关分析,分别采用普通克里金(OK)、逐步回归克里金(SWRK)和地理加权回归克里金(GWRK),对吉林省扶余市耕地表层土壤有机质进行了空间预测。结果表明:扶余市耕地表层土壤有机质分布存在中等空间自相关性,受资源开发、耕作方式等随机因素影响较小;受曲率和植被长势影响大,受一阶微观地形、复合宏观地形及汇流和沉积物运移影响小;在海拔高、植被少且土壤水分不足的阳面通风山丘区含量低;空间分布以西南部为低值中心向四周升高,高值区出现在东部边界。GWRK中环境变量参与了局部回归,其模拟精度最高且揭示了更多空间变化细节。本研究的结果可为较大空间尺度的耕地表层土壤有机质空间变异与预测研究提供可靠的方法借鉴。     

Effects of mutations in Drosophila nicotinic acetylcholine receptor subunits on sensitivity to insecticides targeting nicotinic acetylcholine receptors

Several strains of Drosophila melanogaster possess mutant alleles in nicotinic acetylcholine receptor (nAChR) subunits, Dα1 and Dβ2 that confer resistance to neonicotinoids such as imidacloprid and nitenpyram, and Dα6, that confers resistance to spinosyns. These mutant strains were bioassayed with a selected set of nAChR active insecticides including neonicotinoids, spinosad, and sulfoxaflor, a new sulfoximine insecticide. All of the neonicotinoids examined, except dinotefuran showed reduced insecticidal efficacy on larvae of the Dα1 mutant, suggesting that this subunit may be important in the action of these insecticides. All of the neonicotinoids, including dinotefuran, showed reduced insecticidal efficacy on larvae possessing the Dβ2 mutation. A similar pattern of broad neonicotinoid resistance to that of Dβ2 alone was also observed for larvae with both the mutations (Dα1 + Dβ2). The Dβ2 mutation exhibited a lower level of cross-resistance to sulfoxaflor (<3-fold) than to any of the neonicotinoids (>13-fold). In contrast, there was no cross-resistance for any of the neonicotinoids or sulfoxaflor in adult flies with the Dα6 mutation, which confers high levels of resistance to spinosad. Thus in the D. melanogaster strains studied, target site resistance observed for the neonicotinoids and the spinosyns does not translate directly to resistance towards sulfoxaflor.     

A review of the pest management situation in mango agroecosystems

Integrated pest management programs for mango must be based on sampling and on economic thresholds, and must take into account the effects of cultural practices, horticultural sprays and disease control on pest and natural enemy interactions. An analysis of the mass of information available on the different mango pests,viz., fruit flies(Bactrocera sp.,Ceratitis sp.,Anastrepha sp.), mango seed weevil(Sternochetus mangiferae), thrips(Frankliniella spp.), gall midges(Procontarinia sp.), scales, mites and mealybugs is given, as well as different examples for future entomological research.     

棉田捕食性天敌空间分布型及抽样技术研究

了解天敌的空间分布型对于利用天敌控制害虫以及天敌试验研究工作均有重要意义。它不仅关系到天敌的调查取样设计技术的精确程度与保护利用效果,而且还可借以看出天敌的生活习性以及对不同环境的适应程度,从而有助于种群消长的分析。     

柑橘全爪螨空间格局与抽样技术的研究

应用空间分布型统计参数IwaoM—X模型中α,β及6个聚集指标分析柑橘全爪螨的空间格局,结果表明,柑橘全爪螨的空间格局为聚集型。在此基础上,研究提出了估算柑橘全爪螨在不同虫口密度情况下的理论抽样数。     

七星瓢虫的空间分布型研究

本文报道了七星瓢虫的空间分布调查结果。通过分析,七星瓢虫在包菜地内的空间分布属聚集分布,最适于Poisson-binomial分布,其次适于负二项分布和核心分布,不适于Poisson分布。但就本调查结果而言,七星瓢虫在包菜地的聚集行为可能是由于环境而引起的。分析结果还表明,七星瓢虫种群扩散亦属于聚集型扩散。     

稻瘿蚊综合防治新技术与示范

20世纪80年代后,稻瘿蚊发生危害明显回升,损失相当严重。以大田试验示范为主,系统研究了新耕作条件下稻瘿蚊综合防治,首次总结提出“喷药除草、压低虫源、抓住晚秧、做好测报、挑治本田”的综合防治新技术体系。室内外试验和大田示范表明,应用草甘膦杀死越冬寄主游草,可显著减少虫源基数;灭线磷(商品名益舒宝)、氯唑磷(商品名米乐尔)是防治稻瘿蚊的高效药剂,抗蚊青占品种高抗稻瘿蚊。此外,合理利用杀虫植物、性引诱剂和天敌等亦是防治稻瘿蚊的重要措施。在面积达12．46万hm^2的示范推广实践中,本田防治效果均达80％以上。     

甘肃旅游资源开发的空间布局选择

运用区域经济空间结构理论和资源空间开发模式理论,针对甘肃旅游资源空间分布特征,提出甘肃旅游资源空间开发模式应有所创新。由于甘肃旅游资源空间分布分散和旅游经济发展水平不高,甘肃旅游资源空间开发模式应以旅游中心城市为核心,旅游城镇为节点,重要旅游景区为支点,专题和特色旅游热线为纽带,按照"12356910"的总体布局与发展模式选择来实现空间开发格局,牵引式、分层次、有步骤地推进旅游资源开发。     

Control of potato virus Y (PVY) in seed potatoes by oil spraying,straw mulching and intercropping

Potato virus Y (PVY) is the potato virus with the highest economic impact on seed potato production. Insecticides are efficient in controlling aphids, which are the vectors of this virus, but rarely limit virus spread in the field. Straw mulching and mineral oil spraying are known as alternatives to insecticides to reduce PVY incidence, but important year‐to‐year variation in efficacy has been observed with both of these techniques. Preliminary studies revealed the efficacy of intercropping in controlling PVY spread, but more data are needed to validate this observation. A four‐year field trial was conducted in Switzerland to assess the potential synergistic effect of combining mineral oil spraying with straw mulching to increase the protection of seed potato crops against PVY spread. Furthermore, the efficacy of intercropping with oat and hairy vetch was examined as a novel way to control in‐field PVY spread. The present work demonstrates that the modes of action of mineral oil and straw mulching are complementary and reduce the year‐to‐year variation observed with oil and straw when used alone as PVY control agents. The results also demonstrate the efficacy of intercropping for the control of PVY, and the mode of action of this novel control method is discussed. Overall, this work shows that it is possible to increase the protection of potato fields against PVY spread by combining control strategies with different modes of action that complement each other, such as mulching, oil spraying and intercropping.     

烟草赤星病防治研究进展

在烟草赤星病综合防治研究中 ,国内外对烟草进行了诱导寄主抗病性、生物防治、化学药剂防治、转基因抗病育种等方面的研究。本文综述了近年烟草赤星病综合防治的研究成果 ,提出利用生物技术获得抗病品种 ,及采用生物防治、诱导抗病性进行烟草赤星病综合治理     

农业害虫抗药性及其治理

对农业害虫抗药性的定义、害虫抗药性现状、抗药性的发展因素、抗性产生的机理等方面进行了阐述,并介绍几种害虫抗药性治理方案。     

豆野螟发生为害及综合防治研究进展

从豆野螟分布、发生为害及综合防治等几方面综述了该虫的研究进展。气候因子、豆类品种、栽培耕作制度及天敌是影响豆野螟发生的主要因素。在防治方面，主要是化学防治，生物防治开始受到重视。在综述基础上，探讨了豆野螟今后研究的内容和重点。     

诱虫作物在害虫治理中的应用

诱虫作物主要从物理特性和化学特性两个方面形成比主栽作物更强的引诱力,使主栽作物得以保护。诱虫作物在生产中主要用来诱集害虫、给天敌提供避难和繁殖场所,其作用效果与诱虫作物的品种、播期和田间管理、害虫行为、对天敌的调控、与其他害虫防治方法的有机配合等有重要关系。采用引诱-排斥多策略相结合的方法,研究利用对害虫同时具有诱集和杀灭作用的植物作为诱虫作物,将大大增强诱虫作物在害虫治理中应用的可行性。