The use of tracers to estimate the exposure of beneficial insects to direct pesticide spraying in cereals

A fluorescent spray tracer was used to measure the profile of spray deposits through winter-wheat crop canopies and upon beneficial insects, placed in fixed positions which approximated to their natural distributions. Tracer deposition profiles were recorded on a series of occasions between G.S. 47 to G.S. 90. Deposition levels declined through the canopy on each occasion but the proportion of the spray reaching the ground varied between growth stages. Deposition rates upon insects followed the same trends but insects on the aerial parts of the plant received a higher volume of tracer per unit area than the part of the crop that they were placed upon. Insects placed on the ground received a dose equivalent to their ground area. For a given distribution of insects, these data permit direct spray exposure to be estimated. The general application of the method to a wide range of crops, to the calculation of risk indices, to the standardisation of field tests and to the development of selective spray placement methods are discussed.     

Genetic improvement of a parasitoid: Response of Trioxys pallidus to laboratory selection with azinphosmethyl

Colonies of Trioxys pallidus Haliday (Hymenoptera: Aphidiidae) were collected from California walnut orchards during 1985–86 and screened for variability of responses to azinphosmethyl. Variability was found and laboratory selection was initiated with four colonies. All colonies responded to selection; after seven to 12 selections, three colonies were combined (Select colony) and selection was conducted an additional 27 times. The corresponding base colonies were also combined and maintained for comparisons (Base). Concentration/mortality lines obtained for the Select and Base colonies after five and 27 selections indicated seven‐ and 9.2‐fold differences in LC₅₀ values respectively. Survival of the resistant strain varied with bioassay method and decreased in the order: clip cages on treated foliage > treated plastic cups with untreated mesh tops > treated plastic cups with treated mesh tops> treated cups with treated solid lids. The initial bioassay results with treated plastic cups suggested that the selection response was inadequate to allow the resistant strain to survive field rats of azinphosmethyl. When the resistant strain's survival was evaluated with bioassay methods more closely mimicking field conditions (clip cages on field‐treated foliage), we concluded the selected strain could survive field rates of azinphosmethyl.     

Ecological studies of Cladocera in the ricefields of Tanjung Karang,Malaysia, subjected to pesticide treatment

Temporal changes in the population densities of four dominant Cladocera (Moina micrura, Diaphanosoma excisum, Alona guttata and Macrothrix spinosa) were studied in untreated and pesticide treated rice plots over a growing season. M. micrura was the first dominant species to occur in all the plots which were initially devoid of vegetation except for the newly transplanted rice seedlings. With the growth of the rice seedlings and the appearance of aquatic macrophytes, open water ricefields were transformed into vegetated littoral conditions precipitating the disappearance of M. micrura and the appearance of the littoral A. guttata and M. spinosa, and the eurytopic D. excisum. The cladoceran community was affected by spraying of the pesticide FMC35001, an analogue of Furadan®. The response of the four dominant species to the pesticide treatment is discussed.     

麦长管蚜的抗药性研究

麦蚜在我国分布广、为害重,又传播病毒病,是小麦的重要害虫。近年麦蚜的发生为害有增长的趋势,有些地方反映农药防效下降、用药次数增加。本文介绍1983—1987年5年中采用6个省市的8个地区麦蚜种群对6种农药进行了点滴法毒力测定。探明了张掖和高台麦长管蚜[sitobion avenae (Fab.)]对氧化乐果产生10—15倍抗药性。用英国Rothamsted试验站的比色板试验法进行生化测定,结果同生物测定一致。作者认为该法是一种探测蚜虫抗药性简便可行的定性方法。用北京室内饲养的麦长管蚜以16种新老农药品种用点滴法进行了敏感水平测定,建立了麦长管蚜对16种供试农药的毒力基线。这对探测麦蚜抗药性、监测其抗药性动态变化打下一定基础。通过室内毒力测定、田间药效试验和20多万亩的大面积示范推广,作者提出杀螟松是防治麦蚜较理想的候选农药品种,以替换当前使用的药效已下降的乐果和氧化乐果、替换当前使用的毒性很高的杀虫剂甲胺磷。     

The post-registration monitoring of glyphosate-treated plants using anecic earthworms

Glyphosate N-(phosphonomethyl) glycine is a widely-used herbicide in agriculture. The anecic earthworm, Lumbricus terrestris feeds and forages for surface plant materials meaning that this species has a unique and direct exposure to agrichemicals. At the recommended product rates, significantly (F_1,44 = 8.67, p = .005) higher numbers of L. terrestris middens were found in the glyphosate treated areas of an arable crop field. Laboratory feeding assays using field aged plant materials indicated that previous glyphosate treatment was a statistically significant factor affecting earthworm L. terrestris biomass (F₁,₁₂ = 5.75, p = .03). Negligible glyphosate residues were detectable, and the field aged plant materials were encrusted with fungal hyphae. This suggests that glyphosate influences the colonisation of plant material by a litter-fungus complex which improves the food quality to earthworms. Concentrations of epoxiconazole, a fungicide, were detected in some plant materials and may influence overall food quality to earthworms. Glyphosate treatment on fresh volunteer plant leaves (unwanted crop seedlings) was not a statistically significant factor affecting earthworm L. terrestris biomass (F₁,₆ = 0.16, p = .92). These results indicate fungal communities influence feeding behaviours, and plant materials are a direct source of agrichemicals to anecic earthworms.     

Chronic sublethal stress causes bee colony failure

Current bee population declines and colony failures are well documented yet poorly understood and no single factor has been identified as a leading cause. The evidence is equivocal and puzzling: for instance, many pathogens and parasites can be found in both failing and surviving colonies and field pesticide exposure is typically sublethal. Here, we investigate how these results can be due to sublethal stress impairing colony function. We mathematically modelled stress on individual bees which impairs colony function and found how positive density dependence can cause multiple dynamic outcomes: some colonies fail while others thrive. We then exposed bumblebee colonies to sublethal levels of a neonicotinoid pesticide. The dynamics of colony failure, which we observed, were most accurately described by our model. We argue that our model can explain the enigmatic aspects of bee colony failures, highlighting an important role for sublethal stress in colony declines.     

Isolation and functional characteristics of the fungus Hypoxylon spp. Sj18 with biocontrol potential

A fungus with biocontrol potential was isolated from the roots of hickory trees. The strain named sj18 was classified as a member of the genus Hypoxylon (Hypoxylaceae) after multigene phylogenetic analysis (beta-tubulin gene, internal transcribed spacer, 28S large subunit ribosomal RNA gene, and RNA polymerase II subunit gene). The strain grew well on a PDA with an optimum temperature range between 32 and 34 °C. The fungus had obvious inhibitory effects on Botryosphaeria dothidea, Colletotrichum gloeosporioides, and Gibberella moniliformis in fumigation experiments on solid agar plates. In an inoculation experiment of Chinese cabbage, the fungus was also found to have an obvious repellent effect on cabbage caterpillars. In vitro experiments on Petri dishes showed that the fermentation broth of the sj18 strain could kill 100% of Bursaphelenchus xylophilus within 8 h even if the fermentation broth was diluted 8 times. The inoculation test of Arabidopsis thaliana showed that the fungus could promote the lateral root formation of plants and significantly increase their aboveground biomass. Through the analysis of solid phase microextraction (SPME), it was found that the main volatile components of the fermentation products were azulene 65.39% (61.77% + 3.62%), caryophyllene 7.41%, and eucalyptol 6.83% according to the peak area ratio. Therefore, sj18 can be used as a candidate for the further research and development of biocontrol agents.     

利用人工湿地去除农业径流中农药的研究进展

人工湿地对农业径流污染物去除效果显著,已成为控制农业径流污染的有效措施.本文结合国内外研究,介绍了当前水体农药污染的现状;从物理、化学及生物角度阐述了人工湿地对农药的去除机理和关键过程;归纳总结了人工湿地对农药的去除效率,指出人工湿地对农药的去除效率随农药类型的不同而差异较大:农药的平均去除率,按农药用途分为杀虫剂＞杀菌剂＞除草剂,按农药化学结构分为拟除虫菊酯类>有机磷类>三唑类＞酰胺类＞三嗪类＞脲类;综合考虑,潜流人工湿地在农药去除方面的效果优于表面流人工湿地.在此基础上分析了农药理化性质、人工湿地工艺类型及运行参数、进水中农药浓度、湿地植物等因素对农药在人工湿地中去除的影响.最后指出了当前研究中存在的问题,并提出了研究展望.     

西南喀斯特石漠化地区旱季土壤水分对裸岩的响应

大量岩石出露于地表是中国西南喀斯特地区石漠化典型的表观特征之一.为了揭示裸露岩石周围土壤水分对裸岩的响应,于西南地区发生特大干旱期间(2009年9月-2010年2月),研究了裸岩周围土壤水分的动态变化.结果表明:干旱期间,岩石北方土壤表层含水量高于东方、西方、南方(P＜0.01),且表层土壤含水量随岩石高度增加而增加;岩石出露面积与其西方、北方土壤含水量极显著相关(P＜0.01),与东方土壤含水量显著相关(P＜0.05);岩石的尖削程度越大,东、西、北方土壤含水量越低;岩石周围北、东、西方土壤含水量表现出随距离增加先升高后降低趋势,而岩石南方表现为随距离增加而增加的趋势;岩石周围土壤含水量均随土壤深度增加而增加.裸岩在干旱期间表现出遮荫作用,导致岩石北方土壤含水量高于其他方向,并在距离岩石15 cm处形成逆境背景下相对有利的人工恢复植被位点,对指导石漠化生态治理过程中植被恢复工作具有重要意义.     

韭菜和土壤中毒死蜱的残留与降解动态

在大棚和露地栽培条件下,研究了不同浓度的毒死蜱灌根施药后土壤和韭菜中毒死蜱的残留与降解动态.结果表明:韭菜中毒死蜱的降解速度比土壤中快,平均半衰期分别为3.41 d和7.40 d;在大棚和露地栽培条件下,韭菜中毒死蜱的降解速率差异不大,平均降解半衰期分别为3.37和3.44 d.施药灌根后第21天,韭菜中毒死蜱的残留量(0.021 ～0.102mg·kg-1)基本低于GB 2763-2005规定的最大残留限量标准(≤0.1 mg·kg-1).新生韭菜中仍残留少量毒死蜱,但明显低于药后第一次刈割.土壤中残留的毒死蜱对韭菜中的农药残留量有显著影响.