天敌竹盲走螨在纯竹林中种群数量锐减的原因研究

本项研究针对我国南方毛竹林,近年害螨突发性成灾的现象,进行调查与研究,结果表明：纯竹林害螨总量平均高于混交林289．28％,混交林天敌竹盲走螨(Typhlodromus bambusae Ehara)总量平均高于纯竹林263．56％;混交林益、害螨比例为1：13,而纯竹林益、害螨比例是1：118。研究表明纯竹林地面垦复、劈草,使得以芒草为生的芒草裂爪螨(Schizotetranychus mistanthi Saito)种群数量急剧下降,导致乡土优势种竹盲走螨缺乏中间食物,难以维持种群。在毛竹——芒草混生的毛竹林(含其它树种)由于毛竹上害螨和林下芒草裂爪螨受到共同天敌——竹盲走螨的控制维持着稳定的益、害种群数量,虽然有害螨,但不成灾,在纯竹林由于地面垦复、劈草破坏原有已形成的生物链,导致毛竹害螨失去天敌控制而突发性成灾,证明纯竹林中天敌锐减是导致毛竹害螨暴发成灾的重要因素。     

竹缺爪螨生态学初步研究

本报道严重危害毛竹生长和害螨－－竹缺爪螨在不同温度下生长,发育历期以及在竹林间种群动态。结果表明：在20－35℃范围内随着温度升高其发育历期缩短,温度与发育历期呈直线回归关系：Y全代＝651573-1.6250X（=-0.98);光照是影响竹缺爪螨的卵,幼螨存活及成螨产卵量的重要因素。在竹林间,毛竹换叶,降雨量,天敌数量是影响竹缺爪螨种群消长的和重要因素,最后提出综合防治的措施。     

毛竹叶螨的重要天敌竹盲走螨生态学研究

本文报道了毛竹害螨-南京裂爪螨Schizotetranychus nanjingensis Ma＆Yuan和竹缺爪螨Aponychus corpuzae Rimando的重要天敌竹盲走螨Typhlodromus bambusae Ehara的研究:在22～30℃室温下以南京裂爪螨为食料,卵期1.7天,幼螨期1.7天,Ⅰ若螨期0.8天,Ⅱ若螨期0.8天,产卵前期3.2天.林间雌:雄为2.78:1,总产卵量35～40粒.毛竹换叶、降雨量是影响林间竹盲走螨种群动态的主要因素.猎物的质量、数量是影响竹盲走螨存活的重要因素.最后对竹盲走螨的作用进行了评价.     

竹裂爪螨自然种群消长及空间格局研究

本文对毛竹害螨优势种竹裂爪螨Schizotetranychus bambusae Reck自然种群在主要发生季节的消长情况进行了调查。结果表明,竹裂爪螨在林间发生的高峰期为5—6月份。发生的严重度与林份条件有密切关系,在土壤瘠薄、林相较差的林区发生重;海拔较高、人为干扰度大的林区的发生重且高峰有所延后。竹裂爪螨在林间不同年龄竹株上存在转移危害,即4—5月,3年生竹上(当年不换叶)的有螨叶率与平均每叶螨量大于2年生竹;5月下旬以后,2年生竹换叶完成、新竹开始上林,竹裂爪螨逐渐转移到新叶上为害,使得在1年生竹、2年生竹上的发生量逐渐超过3年生竹上的发生量。通过对5、6月发生高峰期的空间格局研究表明,竹裂爪螨在毛竹林间呈聚集分布,且密度越高,聚集度越大。利用Iwao的m-m回归分析表明,竹裂爪螨是以个体群的方式存在。从空间格局的动态规律上看,5月份的聚集度大于6月份的聚集度,其中5、6月份的m'-m回归式分别为：m＝2．265 2．342m(R＝0．853,5月份)、m＝1．612 2．171m(R＝0．952,6月份)。     

从实验种群生命表参数评价胡瓜钝绥螨控制毛竹害的能力

本文报道胡瓜钝绥螨Amblyseius cucumeris Oudemans在25℃条件下以毛竹4种害螨南京裂爪螨chizotetranychus nanjingensis Ma&Yuan、竹裂爪螨S.bambusae Reck、竹缺爪螨Aponychus corpuzae Rimando、竹刺瘿螨Aculus bambusae Kuang为猎物的实验种群生命表,并进行比较结果表明:①胡瓜钝绥螨能取食上述4种害螨,其世代存活率依次为90.4%、77.55%、87.93%、81.63%;②每雌总产卵量依次为38.12粒、45.77粒、35.59粒、30.76;③胡瓜钝绥螨以南京裂爪螨为猎物其净增殖率R0=16.74低于南京裂爪螨(R0=20.84),但是内禀增长率rm=0.154是猎物的1.73倍(rm=0.089),世代周期T=18.31和种群倍增时间t=4.5088均低于南京裂爪螨(T=33.35,t=7.704),因此在林间当南京裂爪螨离巢、破巢或大量迁移时能有效地控制其种群增长;④胡瓜钝绥螨以竹裂爪螨为猎物其净增殖率R0=25.81,内禀增长率rm=0.152,周限增长率λ=1.164均低于竹裂爪螨(R0=39.28、rm=0.192、λ=1.212),而世代周期T=21.35种群倍增时间t=4.552均高于竹裂爪螨(T=19.08,t=3.603)因此必须在竹裂爪螨处于低密度时释放胡瓜犯绥螨才能有效地控制其种群密度的增长;⑤胡瓜钝绥螨以竹裂爪螨为猎物时,其净殖率R0=20.80,内禀增长率rm=0.175,周限增长率λ=1.191均略低于竹裂爪螨(R0=21.54、rm=0.185、λ=1.202),而世代周期T=17.30种群倍增时间t=3.958均略高于竹裂爪螨(T=16.62,t=3.753)因此必须在竹裂爪螨处于低密度时释放胡瓜钝绥螨才能有效地控制其种群密度的增长;⑥胡瓜钝绥螨以竹刺瘿螨为猎物时其净增殖率R0=16.82与取食南京裂爪螨相近,但内禀增长率rm=0.144,周限增长率λ=1.155均低于取食上述三种叶螨,但产卵量高于其乡土天敌竹盲走螨(Tylodromus bambusae),林间在竹刺瘿螨低密度时仍能控制竹刺瘿螨的种群密度.模拟试验表明当毛竹长至1米高时释放胡瓜钝绥螨16小时后,能在12米高的竹冠上发现大量的胡瓜钝绥螨.研究结果表明胡瓜钝绥螨能有效地控制毛竹害的危害.     

食物对竹裂爪螨生长发育及繁殖的影响

根据笔竹生长特性,用1年生竹、2年生竹、3年生竹和4年生竹的离体叶片作为食料,研究食用对竹爪螨（Schizoterranchus bambusae Peck)生长发育及繁殖的影响。试验结果表明,该螨各螨态的发育历期在4种食料组间存在显著差异或极显著差异,其中幼螨至成螨历期（雌螨）分别为5．00、5．10、6．31和5．03d;取食3年生竹叶片时,幼螨－成螨的存活率、单雌平均产卵量显著小于其余3组,分别为70．81％和14．71粒／雌。试验进一步研究了不同受害程度的毛竹叶片对竹裂爪生长发育及繁裂的影响,结果表明该螨各螨态的发育历期、雌成螨的寿命及敏殖力都因叶片的受害和蔼不同而存在显著差异或极显著差异,这表明了该螨种群在发展过程中,因对叶片的取食危害,通过对自身营养条件的恶化而存在着较强的负反馈作用。     

竹裂爪螨毛竹种群与慈竹种群对不同寄主植物的适应性及其生殖隔离

对危害毛竹(Phyllostachys pubescens)和慈竹(Neosinocalamus affinis)的竹裂爪螨(Schizotetranychus bambusae)两个种群进行相互间的食性选择和生殖隔离试验．结果表明,由于两种竹子叶片在物理结构上差异较大。尤其是慈竹叶片背面具有成排细茸毛,导致竹裂爪螨毛竹种群不能在慈竹叶上完成世代发育;竹裂爪螨慈竹种群能取食,危害毛竹叶片,但由于寄主转换后,对其生长发育不利,导致存活率低,繁殖力弱．两种群取食各自嗜食的寄主植物时,基本生物学特性存在差异,27℃条件下,当毛竹种群以毛竹为食时,种群的内禀增长率(rm)、周限增长率(λ)、净增殖率(Ro)分别为0．1415、1．1520和15．6298;慈竹种群以慈竹为食时,rm、λ、Ro分别为0．0993、1．1044、10．0622;慈竹种群取食毛竹叶片时,rm、λ、Ro分别为0．0391、1．0399和2．5542．生殖隔离试验表明,两种群间能互相正常交配,且互相交配的时间与两种群自交时的交配时间(1次)差异不明显．同一种群交配产生的后代,其性比均在2：1左右,而不同种群杂交产生的后代全部为雄性(竹裂爪螨为孤雌产雄),这表明两种群在长期的寄主植物选择压力下已形成一定的生殖隔现象．     

南京裂爪螨危害对毛竹生理生化的影响研究

本文首次报道毛竹上重要害螨——南京裂爪螨Schizotetranychus nanjinensis Ma et Yan的危害对毛竹生理生化影响。研究结果表明：毛竹叶片受害程度与叶绿素含量,还原糖含量,总糖含量,含水量呈明显直线负相关关系,其模型分别：Y叶绿素2.10-0.268x(r=-0.96),Y总量=5.2721-0.2788x(r=-0.87),Y还原糖=-2.778-0.1766x(r=-0.99),Y含水量=2.472-2.783x(r=-0.81)。最后对毛竹叶螨暴发成灾及综合治理作了简述。     

毛竹害螨的损失估测和防治指标

采用均匀分布、典型整群抽样调查法对福建省南平市延平区毛竹林毛竹害螨为害进行调查。结果表明,毛竹害螨为害对毛竹竹杆重量和出笋量都有一定的影响,使得竹林蓄积量下降,出笋量大大下降。建立了毛竹害螨对毛竹竹杆重量和出笋量损失的估测模型,并以此推导出了相应的经济危害允许水平和防治指标。     

福建省竹林益害螨名录( I)

本文首次报道福建省竹林益害螨名录,它们分别隶属于蜱螨亚纲的６ 个总科７ 科１９ 属３４ 种。其中有致使竹林大量落叶的叶螨类群。导致毛竹生长衰退的瘿螨,跗线螨类群,也有对竹林害螨,小型昆虫有重要控制作用的捕食性螨类。     

Ambulatory migration in mites (Acari: Tetranychidae, Phytoseiidae) to new leaves of moso bamboo shoots

The migratory behaviour of two tetranychid pest species, Aponychus corpuzae and Schizotetranychus nanjingensis, and one phytoseiid, Typhlodromus bambusae, was studied in several monocultural bamboo forests in Fujian Province, China. The aim of the study was to assess how the ambulatory immigration of tetranychid and phytoseiid mites from the ground to new leaves is affected by a sticky barrier around the stem, by the age of bamboo shoots or by shoot density. The results show that while the sticky barrier is particularly effective at disrupting the ambulatory immigration from the ground to new leaves of S. nanjinigensis to 1-year-old shoots and of A. corpuzae to 3-year-old shoots, it has no significant effect on the immigration of the phytoseiid mite.     

Population dynamics of phytophagous and predatory mites (Acari: Tetranychidae, Eriophyidae, Phytoseiidae) on bamboo plants in Fujian, China

The seasonal cycle and population dynamics of Schizotetranychus nanjingensis Ma and Yuan, Aponychus corpuzae Rimando (Tetranychidae), Aculus bambusae Kuang (Eriophyidae) and their natural enemy Typhlodromus bambusae Ehara (Phytoseiidae) were studied during 1996–1998 in moso bamboo forests in Nanping, Fujian, China. Damage to bamboo leaves was often caused by mixed populations of the three phytophagous species, which displayed different seasonal dynamics: S. nanjingensis fed actively and reproduced in May and from late July to late October (aestivating from June to mid July), Ap. corpuzae was active and reproduced from mid July to late November, and Ac. bambusae from July to next February. During Spring S. nanjingensis was the dominant species with the greatest niche width, but in Summer Ac. bambusae and Ap. corpuzae became dominant and had greater niche widths. In Autumn, Ac. bambusae decreased but both S. nanjingensis and Ap. corpuzae mites increased and the latter became dominant. In winter all species decreased sharply in number. The two spider mite species (S. nanjingensis and Ap. corpuzae) had high niche overlaps in all four seasons. Niche overlaps between the eriophyid Ac. bambusae and the two spider mites were similarly high except during the spring when Ac. bambusae was absent. The predatory mite (T. bambusae) had higher niche overlap with Ap. corpuzae than with others during Autumn and Winter, but during Spring and Summer niche overlap was higher with S. nanjingensis.     

Spider Mites Avoid Plants with Predators

While searching for food, prey can use cues associated with their predators to select patches with a reduced predation risk. In many cases, odours indicate the presence of both food and predators. Spider mites are known to use odours to locate food and mates, but also to avoid interspecific competitors. We studied the response of the two-spotted spider mite, Tetranychus urticae, to cues associated with the presence of their predators, the phytoseiid Phytoseiulus persimilis. We found that the spider mites strongly avoid plants defended by this predator, but do not avoid plants with another predatory mite, Neoseiulus californicus. Since P. persimilis is commonly used in the greenhouse where our strain of T. urticae was collected and strains of this pest are known to adapt to greenhouse environments, we hypothesize that there has been selection on the pest to recognize its enemy. We further hypothesize that there has been no selection to recognize N. californicus, as it has not been used against two-spotted spider mites in the greenhouse where our spider mites were collected. We discuss the implications of avoidance of predation by spider mites and non-lethal effects of predators for biological control of this pest in greenhouses.     

Pest species diversity enhances control of spider mites and whiteflies by a generalist phytoseiid predator

To test the hypothesis that pest species diversity enhances biological pest control with generalist predators, we studied the dynamics of three major pest species on greenhouse cucumber: Western flower thrips, Frankliniella occidentalis (Pergande), greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and two-spotted spider mites, Tetranychus urticae Koch in combination with the predator species Amblyseius swirskii Athias-Henriot. When spider mites infested plants prior to predator release, predatory mites were not capable of controlling spider mite populations in the absence of other pest species. A laboratory experiment showed that predators were hindered by the webbing of spider mites. In a greenhouse experiment, spider mite leaf damage was lower in the presence of thrips and predators than in the presence of whiteflies and predators, but damage was lowest in the presence of thrips, whiteflies and predators. Whitefly control was also improved in the presence of thrips. The lower levels of spider mite leaf damage probably resulted from (1) a strong numerical response of the predator (up to 50 times higher densities) when a second and third pest species were present in addition to spider mites, and (2) from A. swirskii attacking mobile spider mite stages outside or near the edges of the spider mite webbing. Interactions of spider mites with thrips and whiteflies might also result in suppression of spider mites. However, when predators were released prior to spider mite infestations in the absence of other pest species, but with pollen as food for the predators, we found increased suppression of spider mites with increased numbers of predators released, confirming the role of predators in spider mite control. Thus, our study provides evidence that diversity of pest species can enhance biological control through increased predator densities.     

The impact of eriophyoids on crops: recent issues on Aculus schlechtendali, Calepitrimerus vitis and Aculops lycopersici

The nature of the damage caused by eriophyoid mites and the assessment of yield losses still require detailed studies if appropriate control and risk mitigation strategies are to be planned. The economic importance of eriophyoid mites is increasing worldwide and a lot of species have reached a permanent pest status in certain crops, while others represent a quarantine threat for several countries. Due to their relevant role in Europe and elsewhere, three eriophyoid mites that have been frequently reported in recent research, are here considered as case studies: two of them (the apple rust mite, Aculus schlechtendali, and the grape rust mite, Calepitrimerus vitis) colonise temperate fruits, while one (the tomato russet mite, Aculops lycopersici) affects vegetables. The damage assessment related to the apple rust mite has been evaluated on different apple varieties with implications for pest control. Some factors affecting the spread and economic importance of the grape rust mite have been identified. The complexity and difficulty in controlling the tomato russet mite by chemicals enhances the interest in biological control agents. Considerations on interactions between eriophyoids and host plants (e.g. resistance, varietal susceptibility), on pest management regimes (e.g. impact of fungicides, resistance to acaricides, perspectives on biological control) are presented.     

Moso bamboo and Japanese cedar seedlings differently affected soil N2O emissions

毛竹和日本柳杉幼苗对土壤氧化亚氮排放的影响及微生物机制 毛竹(Phyllostachys edulis)向日本柳杉(Cryptomeria japonica)林的扩张现象越发普遍,其扩张对大 气重要温室气体氧化亚氮(N₂O)排放的影响也引起了更多的关注,而其微生物机制尚不明确。本研究通过添加微生物抑制剂链霉素和扑海因分别抑制细菌和真菌活性,连续观测土壤N₂O排放速率以及相关土壤养分和植物生物量。研究结果表明：(i)毛竹土壤N₂O的排放速率显著高于日本柳杉;与对照相比,细菌抑制剂、真菌抑制剂及其交互作用均对N₂O排放速率具有显著抑制效应,但三者之间无显著差异;(ii)毛竹生物量显著高于日本柳杉;(iii)日本柳杉土壤有机质、全氮和铵态氮显著高于毛竹土壤,日本柳杉土壤pH和全磷显著低于毛竹土壤。真菌抑制剂降低了土壤有机质含量,细菌抑制剂降低了土壤硝态氮含量。真菌抑制剂与物种在影响土壤pH、全磷和铵态氮方面具有显著交互作用。细菌抑制剂与物种在影响土壤全氮方面有显著交互作用。综上所述,毛竹和日本柳杉在生长过程中土壤N₂O排放速率不同,毛竹幼苗土壤N₂O排放及生物量均高于日本柳杉。细菌抑制剂和真菌抑制剂对N₂O的排放速率均具有一定抑制作用。因而,在全球气候变化背景下,应进一步深入了解森林生态系统物种组成和变化对N₂O排放的影响,以有效评估毛竹扩张等导致的生物多样性变化对全球N₂O排放的贡献。     

A tale of three acaropathogenic fungi in Israel: Hirsutella, Meira and Acaromyces

We review published and unpublished studies conducted in Israel with six acaropathogenic fungi, assayed in order to control the citrus rust mite, Phyllocoptruta oleivora (Ashmead) (CRM). Hirsutella thompsonii Fisher was introduced twice, killed 80-90% of the exposed mites, but due to its requirements for near-saturation humidities was deemed unsuitable for local outdoors conditions. Hirsutella kirchneri (Rostrup) Minter et al. and Hirsutella necatrix Minter et al. were also introduced and assayed against CRM and spider mites, but their efficacy was unsatisfactory. Three indigenous fungi found to be associated with mites, Meira geulakonigii, Meira argovae and Acaromyces ingoldii--all three recently described by Boekhout, Gerson, Scorzetti & Sztejnberg--were assayed against several mites. Meira geulakonigii killed 80-90% of several spider mites and of the CRM, and caused some mortality of Iphiseius degenerans (Berlese), one out of three phytoseiid predators assayed. Mortality was not due to parasitization; extracts from the media in which the fungi had developed caused considerable mite death, suggesting that it was a result of fungal toxins. Data from a field study indicated that spraying blastoconidia of M. geulakonigii on grapefruits infested by CRM significantly reduced pest-incurred damage from 23 to 13%. Applying qRT-PCR methodology indicated that M. geulakonigii was endophytic within sealed grapefruit flowers and in the flavedo of the fruits' peel. Neither in the laboratory nor in the field was any evidence ever obtained that this fungus damaged the plants, leading us to hypothesize that M. geulakonigii serves as a "body guard" of grapefruits (and perhaps other plants as well). All three fungi suffered very little mortality after being exposed to various insecticides and acaricides that are in current local use (with the exception of sulfur). The ability of M. geulakonigii to reduce mite numbers without affecting the host plant, the minimal fungal effect on some predatory mites, its endophytic nature along with the apparent tolerance of M. geulakonigii to many insecticides and acaricides, suggest that this fungus could be suitable for integrated pest management (IPM) program.