Mosquito repellents: a review of chemical structure diversity and olfaction

Research on mosquito chemical repellents continues to advance, along with knowledge of mosquito olfaction and behavior, mosquito–host interactions and chemical structure. New tools and technologies have revealed information about insect olfactory mechanisms and processing, providing a more complex approach for the interpretation of how chemical repellents influence host‐seeking and feeding behavior. Even with these advances, there is still a large amount of information contained in the early works on insect repellents. Many of the standard test methods and chemicals that are still used for evaluating active repellents were developed in the 1940s. These studies contain valuable references to the activity of different structural classes of chemicals, and serve as a guide to optimization of select compounds for insect repellency effects. Copyright © 2010 Society of Chemical Industry     

Effects of dieldrin (HEOD) and some of its metabolites on synaptic transmission in the frog motor end-plate

The effects of HEOD and some of its metabolites on synaptic transmission in the frog motor end-plate were studied by means of intracellular microelectrodes. HEOD itself and the metabolites 9-syn-hydroxy-HEOD and the aldrin-derived dicarboxilic acid had no significant effect on frequency and amplitude of miniature end-plate potentials, nor on end-plate membrane potential. In sharp contrast with this aldrin-transdiol (6,7-trans-dihydroxy-dihydro-aldrin) was very potent in exerting both pre- and postsynaptic actions. This metabolite caused a rapid and marked increase in miniature end-plate potential frequency, together with a decrease in their amplitude. Evidence is presented suggesting that the spontaneous transmitter release is enhanced by two prejunctional mechanisms: partly by a calcium-dependent effect, probably a depolarization of the nerve terminal, and partly by a calcium-independent action. Another typical prejunctional action of aldrin-transdiol is the reduction of the amount of transmitter released in response to high external potassium concentration. Aldrin-transdiol also affected the evoked transmitter release and caused a marked increase in end-plate potential amplitude followed by a decrease, and finally a complete blockade of neuromuscular transmission was observed. This transient increase in transmitter release was shown to be due to a transient increase in quantal content. The subsequent fall in end-plate potential amplitude and the fall in miniature end-plate potential amplitude are probably the result of a reduction of the sensitivity of the postsynaptic membrane to acetylcholine as demonstrated by ionophoretic application of this transmitter. There was no aldrin-transdiol-effect on the end-plate membrane potential. The present results strongly support the hypothesis that HEOD must be converted to aldrin-transdiol before it can exert its neurotoxic action.     

The effects of dieldrin and isomeric aldrin diols on synaptic transmission in the American cockroach and their relevance to the dieldrin poisoning syndrome

Dieldrin and two of its metabolites, 6,7-trans-dihydroaldrindiol, and 6,7-cis-dihydroaldrindiol, were studied with regard to their toxicity to the American cockroach, effects on ganglia of the ventral nerve cord, and penetration into the ventral nerve cord of poisoned cockroaches. An approximate LD₅₀ for injected doses of dieldrin was 0.45 mg/kg. After injection at 115 mg/kg, the trans isomer of aldrin diol caused about 70%, and the cis isomer about 50% mortality. Injected doses of 40 mg/kg of the three compounds appeared in the ventral nerve cord to the extent of 0.13–0.26% of the doses. Dieldrin was more potent, but slower acting than the diols in causing synaptic after-discharge and elevated spontaneous activity in isolated nerve cords. The results are discussed in relation to other studies on these compounds. It was concluded that, in the American cockroach, dieldrin, rather than either of the diols, is the insecticidal agent in dieldrin poisoning, and that metabolic conversion of dieldrin to the cis and/or trans aldrindiol constitutes a detoxification.     

拟松材线虫尾部形态多样性研究

本文对14个拟松材线虫群体和2个松材线虫群体进行了研究,研究表明拟松材线虫群体尾尖突平均长度为3.28～5.82μm,尾形有6种,主要为亚洲型和欧洲型两种。拟松材线虫和松材线虫的交合伞复杂多样,共有12种类型,两者的交合伞没有明显差别,都由2种或2种以上形态构成。交合伞的多样性和不确定性表明,以此作为一个主要分类特征是不恰当的。     

吡啶甲酸类除草剂应用研究进展

吡啶甲酸类除草剂属合成激素类, 目前登记使用的有效成分包括氨氯吡啶酸、二氯吡啶酸和氯氨吡啶酸, 分别于1963年、1977年和2005年上市, 主要用于阔叶杂草和灌木的茎叶处理防控, 其中氯氨吡啶酸具有土壤封闭活性。吡啶甲酸类除草剂的作用靶标仍未明确, 有可能来自生长素结合蛋白家族。全世界报道的抗吡啶甲酸类除草剂杂草共涉及7种8个生物型。目前, 我国登记的除草剂品种中共有13个复配剂含氨氯吡啶酸和二氯吡啶酸, 1个含氨氯吡啶酸、氯氨吡啶酸和二氯吡啶酸;国外登记的吡啶甲酸类除草剂复配剂主要为与其他激素型除草剂、ALS(乙酰乳酸合酶)抑制剂、ACCase(乙酰辅酶A羧化酶)抑制剂的组合。该类除草剂仍然具有较好的应用前景, 在主要应用场景下常见杂草对氨氯吡啶酸、二氯吡啶酸、氯氨吡啶酸的敏感性仍需系统研究, 该类除草剂主要靶标杂草种群的抗药性水平也亟须检测。     

荒漠化监测与评价指标研究进展

适宜的指标体系是高效开展荒漠化监测与评价工作的关键。文中从地面调查和遥感监测两个方面综述了荒漠化监测与评价的指标体系。地面调查的指标体系一般从三个层次上构建:以单一植被盖度指示荒漠化,综合植被、气候、土壤、土地类型等监测荒漠化状态,基于"压力-状态-响应"理论框架系统构建荒漠化监测与评价体系。遥感监测与评价指标主要包括多期影像分类指标、植被参数和土壤参数三个方面。最后总结当前研究中存在的问题,并提出了"多类型-多尺度-多维度"的荒漠化监测与评价指标框架,可为遥感与地面相结合的多类型和多尺度荒漠化过程监测与评价提供科学参考。     

新型吡唑酰胺类农药吡噻菌胺的研究进展

为明确露地和大棚条件下手性杀菌剂吡噻菌胺对映体在番茄中的对映选择性降解行为,本试验采用优化的QuEChERS前处理方法,建立了番茄中吡噻菌胺对映体的超高效液相色谱-串联质谱(UPLC-MS/MS)分析方法,研究了在两种种植模式下,吡噻菌胺对映体在番茄体系中的残留、消解及累积行为。结果表明：在0.002~1 mg/L范围内,吡噻菌胺对映体线性关系良好,R² > 0.99;在0.005、0.1和1 mg/kg添加水平下,R体和S体在各基质中的添加回收率分别为77%~98%和81%~101%,相对标准偏差(RSDs)为1.6%~5.1%和1.6%~4.2%。定量限(LOQ)为0.005 mg/kg。在−20 ℃条件下吡噻菌胺对映体在番茄中100 d降解率 < 30%,且在露地和大棚条件下的降解均符合一级动力学方程,相关系数(r)为0.9315~0.9400,R体和S体的半衰期分别为：露地5.43和5.10 d,大棚8.09 和7.80 d,S体降解均快于R体;在番茄上反复喷施会造成吡噻菌胺对映体累积。喷施后分布结果表明其主要残留在叶片中,大棚中番茄叶、茎和果实中浓度均高于露地。在末次施药后5 d,吡噻菌胺残留量均低于我国最大残留限量(MRL),其代谢物(PAM)的残留量低于LOQ。结果表明,按推荐方法在番茄上施用吡噻菌胺符合我国良好农业规范,满足食品安全的基本要求。     

A review on the potential effects of temperature on fungicide effectiveness

Fungicides are one possible way to manage fungal and oomycete plant pathogens in order to safeguard yield and quality of crops and to improve shelf-life of produce in agriculture and horticulture. However, global warming and the resulting temperature increase may affect the effectiveness of some important fungicides, including efficacy and duration of plant disease control. Nevertheless, according to our literature survey, there is little specific information available on whether and how temperature influences the effectiveness of fungicides. The very few publications that show specific data are summarized herein. Specific data are mainly gained under controlled conditions, both based on in vitro and in planta experiments. Field data are more or less missing. Most researchers assume that indirect effects of temperature on fungicide efficacy are particularly important. For example, temperature effects on pathogen spore germination and hyphal growth (optimal versus sub- and supra-optimal), whereby optimal temperature conditions can improve pathogen fitness, thereby increasing the tolerance of pathogens to fungicides. Presumably, these indirect effects are often more important than the direct effects of temperature on fungicide performance. However, the data needed to prove this assumption are lacking. Therefore, it would be beneficial to conduct more in-depth laboratory, greenhouse and field experiments in order to investigate the potential direct and indirect influence of temperature on the effectiveness of important fungicides. This would enable the establishment of appropriate recommendations for fungicide use in an increasingly warmer world and would assist the development of future fungicide solutions, based on improved knowledge.     

土壤种子库的研究方法综述

主要从取样方法、取样时间和种类鉴定等方面对土壤种子库研究方法进行综述,重点介绍了种子萌发法,并且提出了要采取长期定位观测的方法对土壤种子库的长期完整动态进行较系统的研究,而且最好在种子库长期的定位研究中搞清楚研究区内植物种的物种特性并且建立一个幼苗标本库,以增加土壤种子库研究的准确性。     

Cowpea aphid-borne mosaic potyvirus: A review

Cowpea aphid-borne mosaic potyvirus (CABMV) is a cosmopolitan, economically significant seed-borne virus of cowpea. It can cause a yield loss of 13 - 87% under field conditions depending upon crop susceptibility, virus strain and the environmental conditions. CABMV has spread world-wide through the exchange of virus-infected germplasm material. The virus-infected seed provides the initial inoculum and aphids are responsible for the secondary spread of the disease under field conditions. The virus symptoms vary with the cowpea genotype and virus strain. Excellent sources of resistance are available for the breeding of resistant cultivars. Resistance in cowpea is conferred by either a dominant or a recessive gene. Enzyme-linked immunosorbent assay (ELISA) is the most appropriate method for the detection of the virus in the seed or plant tissue for seed certification programmes. Production of virus-free seed is another control option. Given the significance of the disease and the large area under cowpea cultivation in the world, we review knowledge of various aspects of the disease.     

检疫杂草菟丝子生物防治研究的进展

本文对菟丝子的生物防治的研究成果进行了综述,已有4种真菌和12种昆虫用于菟丝子的生物防除.     

机油乳剂对香蕉交脉蚜的控制作用研究

应用室内生物测定与田间防治试验相结合的方法 ,研究了机油乳剂对香蕉交脉蚜的控制作用。室内生物测定结果表明 ,机油乳剂对不同龄期交脉蚜均有较强的致死作用 ,LC₅₀随龄期增大而减小 ;在田间用2mg/ml的机油乳剂喷施,24、48h香蕉交脉蚜的虫口减退率达90%以上。机油乳剂对交脉蚜各龄期混合种群忌避作用明显 ,其作用随时间延长而有降低的趋势     

Factors that influence the level of weed seed predation: A review

Herbicides applied alone have failed to reduce weed populations in agricultural ecosystems. The use of this management strategy has followed other problems such as damage to ecosystems and organisms that live in it. Herbicide resistance in weeds has also occurred more quickly based on the application of herbicides. Today, most scientists are looking for new integrated weed management programs in agricultural ecosystems. Biological control is one of the most effective ways of weed management. In this way, living organisms are used to reduce and control weed species in arable lands. Weed seed predators, including predispersal and postdispersal predators as biological control agents, can be primary factors of weed seed mortality in agricultural ecosystems. This review has discussed factors influencing seed predator populations, activity, and granivory. Knowledge of the interrelations between factors and seed predators can contribute to designing future strategies that augment weed seed predator activity and enhance weed seed consumption as a component of an integrated weed management system.     

A theoretical assessment of the effects of vector-virus transmission mechanism on plant virus disease epidemics

ABSTRACT A continuous-time and deterministic model was used to characterize plant virus disease epidemics in relation to virus transmission mechanism and population dynamics of the insect vectors. The model can be written as a set of linked differential equations for healthy (virus-free), latently infected, infectious, and removed (postinfectious) plant categories, and virus-free, latent, and infective insects, with parameters based on the transmission classes, vector population dynamics, immigration/emigration rates, and virus-plant interactions. The rate of change in diseased plants is a function of the density of infective insects, the number of plants visited per time, and the probability of transmitting the virus per plant visit. The rate of change in infective insects is a function of the density of infectious plants, the number of plants visited per time by an insect, and the probability of acquiring the virus per plant visit. Numerical solutions of the differential equations were used to determine transitional and steady-state levels of disease incidence (d*); d* was also determined directly from the model parameters. Clear differences were found in disease development among the four transmission classes: nonpersistently transmitted (stylet-borne [NP]); semipersistently transmitted (foregut-borne [SP]); circulative, persistently transmitted (CP); and propagative, persistently transmitted (PP), with the highest disease incidence (d) for the SP and CP classes relative to the others, especially at low insect density when there was no insect migration or when the vector status of emigrating insects was the same as that of immigrating ones. The PP and CP viruses were most affected by changes in vector longevity, rates of acquisition, and inoculation of the virus by vectors, whereas the PP viruses were least affected by changes in insect mobility. When vector migration was explicitly considered, results depended on the fraction of infective insects in the immigration pool and the fraction of dying and emigrating vectors replaced by immigrants. The PP and CP viruses were most sensitive to changes in these factors. Based on model parameters, the basic reproductive number (R(0))-number of new infected plants resulting, from an infected plant introduced into a susceptible plant population-was derived for some circumstances and used to determine the steady-state level of disease incidence and an approximate exponential rate of disease increase early in the epidemic. Results can be used to evaluate disease management strategies.     

Metabolomics - A robust bioanalytical approach for the discovery of the modes-of-action of pesticides: A review

The agrochemical industry is facing great undertaking that includes increasing demand for the development of new crop protection agents that are safe for the environment and the consumers, and at the same time combat the issue of the emergence of resistance pest strains. The mode-of-action (MoA) is among the features of a bioactive compound that largely determine whether the abovementioned issues are addressed or not, and subsequently whether its commercial development will be addressed. The early discovery of the MoA of bioactive compounds could accelerate pesticide research and development by reducing the required time and costs. Based on advances in synthetic and natural product chemistry, scientists have access to a vast number of compounds that could potentially be developed as crop protection agents. The screening of such compounds with respect to their MoA requires accurate and robust bioanalytical tools. Metabolomics is a powerful bioanalytical tool that will likely play a significant role in the acceleration of the discovery of MoA of bioactive compounds. In the present review, the capabilities and principles and applications of metabolomics for the study of the MoA of herbicides, insecticides, acaricides, fungicides, and antibiotics are discussed.     

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。     

A review on the occurrence of begomoviruses in ornamental plant families

Journal of Plant Diseases and Protection - The genus begomovirus is the prominent viral group among field crops transmitted by the (whitefly) vector, Bemisia tabaci. Begomoviruses are cosmopolitan...     

农田杂草种子库研究方法

杂草种子库作为潜在的杂草群落，是未来地上部杂草发生的源泉，研究杂草种子库有其基本方法体系。本文从土样获取方法开始，介绍比较了目前最常用的杂草种子库研究方法-诱萌法、淘洗法、漂浮法，以及各种方法的综合运用，为开展对农田杂草种子库的研究提供参考。