低温贮藏对加州新小绥螨生物学特性和捕食能力的影响

为探究加州新小绥螨国内种群的最佳贮藏方法,在4、7、10℃下,以叶片+叶螨和花粉2种冷藏基质及不同冷藏时间为参试因子,研究了低温贮藏对其雌成螨存活、产卵和捕食的影响,并测试了其卵冷藏后的存活及发育情况。结果显示,温度、基质和时间3个因子均显著影响冷藏处理后加州新小绥螨雌成螨的存活率、产卵量和捕食率。在4、7、10℃下,以花粉为基质冷藏超过10 d后雌成螨存活率均低于50%,不适宜长期贮藏;以叶片+叶螨为基质冷藏分别超过20、25、30 d后雌成螨存活率显著降低,超过30 d后产卵前期较对照的1.05 d显著延长,分别达到3.07、3.14、2.29 d。在2种基质中,所有冷藏处理的单雌1周日均产卵量为1.55~2.96粒,均低于对照的2.97粒,且随冷藏时间的增加呈下降趋势;冷藏后雌成螨产卵期捕食率为每12 h 11.60~15.84头,均高于对照的11.60头。冷藏温度和时间显著影响卵的孵化率和发育历期,短期冷藏后孵化的雌螨比例与对照差异不显著。表明加州新小绥螨雌成螨适宜以叶片+叶螨为冷藏基质,短期冷藏的最适温度为4~7℃,长期冷藏最适温度为10℃;卵以4℃冷藏7 d最佳,在10℃下冷藏不宜超过2周。     

巴氏新小绥螨在马铃薯腐烂茎线虫上的实验种群生命表及其捕食作用

为明确巴氏新小绥螨Neoseiulus barkeri对马铃薯腐烂茎线虫Ditylenchus destructor的捕食能力,以马铃薯腐烂茎线虫和椭圆食粉螨Aleuroglyphus ovatus为猎物饲养巴氏新小绥螨,构建了巴氏新小绥螨的实验种群生命表,并构建了雌成螨对马铃薯腐烂茎线虫的捕食功能反应模型。结果显示,巴氏新小绥螨取食马铃薯腐烂茎线虫后能完成整个生活史,平均世代为6.71 d,产卵前期、产卵期、日产卵量以及雌成螨寿命分别为2.89 d、19.13 d、1.79粒和26.44 d,与取食椭圆食粉螨后的各参数间均无显著差异。巴氏新小绥螨雌成螨对马铃薯腐烂茎线虫的捕食功能反应为Holling Ⅱ型,在温度16~28℃范围内,其攻击系数(a)、捕食能力(a/T_h)、最大日捕食量(1/T_h)均随温度升高而升高,处理时间(T_h)缩短;在28℃时日捕食量达到最高,为52.69条,处理时间最短,为0.019 d;当温度高于32℃时捕食量开始下降。表明巴氏新小绥螨具有防治马铃薯腐烂茎线虫的潜力。     

三种杀螨剂对双尾新小绥螨后代生长发育和繁殖的影响

为明确杀螨剂对双尾新小绥螨Neoseiulus bicaudus后代生长发育及繁殖的影响,采用联苯肼酯、三唑锡和哒螨灵对土耳其斯坦叶螨Tetranychus turkestani的致死中浓度处理双尾新小绥螨雌成螨,测定其后代各发育阶段的存活率、发育历期、寿命、雌性比例及繁殖力,构建亚致死条件下双尾新小绥螨后代的年龄-龄期两性生命表并模拟其种群增长模型,分析不同杀螨剂亚致死效应对捕食螨后代的影响。结果表明,联苯肼酯处理能显著缩短双尾新小绥螨后代的未成熟期（4.81 d）,显著延长双尾新小绥螨后代雌成螨的寿命（45.43 d）,且对存活率、产卵前期、雌性比例和净增殖率无显著影响。三唑锡处理降低了双尾新小绥螨后代雌性比例（0.37）并显著降低了其后代净增殖率（15.91）,对未成熟期、产卵前期和雌雄成螨寿命均无显著影响。哒螨灵处理对双尾新小绥螨后代的未成熟期、存活率、雌成螨寿命、产卵前期、和雌性比例均未产生显著影响,仅显著延长了雌雄成螨寿命（51.22 d和44.23 d）。经所建Timing种群模型模拟,3种杀螨剂处理后双尾新小绥螨后代种群均可以继续增殖,经过60 d无限制增殖后,联苯肼脂处理的双尾新小绥螨后代种群数量是对照的1.62倍,达4 976头;哒螨灵处理（2 101头）和三唑锡处理（983头）的种群数量较对照分别减少了31.43%和67.92%。表明联苯肼脂对双尾新小绥螨后代影响较小,是较为安全的杀螨剂。     

食物对兹沃尔新小绥螨生长发育和繁殖的影响

为探究不同食物对兹沃尔新小绥螨Neoseiulus zwoelferi种群生长、发育和繁殖的影响,采用年龄-龄期两性生命表分析测定兹沃尔新小绥螨取食卢氏叶螨Tetranychus ludeni、甜果螨Carpoglyphus lactis和香蒲Typha orientalis花粉后的存活率、发育历期、寿命及繁殖情况。结果显示,3种食物均能满足兹沃尔新小绥螨生长发育和繁殖的需求。卢氏叶螨处理组的净增殖率和总繁殖率分别是28.99和36.99,均显著高于其他2个处理组;以甜果螨、卢氏叶螨和香蒲花粉为食的兹沃尔新小绥螨从卵发育至成螨所需时间分别为5.28、7.34和6.87 d,种群倍增时间分别3.35、4.22和11.77 d,前者显著短于其他2个处理;甜果螨处理组和卢氏叶螨处理组的雌成螨平均寿命分别比香蒲花粉处理组长2.75 d和4.92 d,但两者之间无显著差异;卢氏叶螨处理组雌成螨产卵天数最长,为17.84 d,产卵前期时间最短,为2.75 d,产卵量最大,为38.15粒/雌;香蒲花粉处理组雌成螨产卵天数最短,仅1.82 d,产卵前期时间最长,为5.89 d,产卵量最少,为3.36粒/雌。甜果螨处理组的内禀增长率、周限增长率分别为0.21 d-1和1.23 d-1,均显著高于其他处理组,但平均世代周期为14.65 d,显著低于其他处理组。表明3种食物均可使兹沃尔新小绥螨完成整个世代,其中甜果螨是室内饲养兹沃尔新小绥螨的最佳食物,香蒲花粉可以作为短期饲养的食物。     

双尾新小绥螨对花蓟马的捕食控害评价

双尾新小绥螨Neoseiulusbicaudus是一种重要的捕食性天敌。为明确双尾新小绥螨对花蓟马Franklinilla intonsa的捕食控害作用以及寄主花粉对其取食花蓟马的影响。本研究通过室内测定不同螨态双尾新小绥螨对不同密度花蓟马若虫的捕食量;在棉花新鲜花粉影响下捕食螨对花蓟马1龄若虫捕食能力,进而在棉田花期时测定捕食螨对花蓟马的实际控制效果。结果表明,双尾新小绥螨各螨态对花蓟马若虫的捕食量随着猎物密度的增加而升高,对1龄若虫捕食量显著高于2龄若虫,其捕食量最高可达6.1头/日。加入花粉后,双尾新小绥螨成螨对花蓟马的捕食量随着花粉数量的增加而降低,足量的花粉处理使其捕食量显著低于不加花粉处理,其捕食功能反应类型也由Holling-Ⅱ型变为Holling-Ⅲ型。将捕食螨以1:1的益害比释放至棉田中对花蓟马的防治效果相对最好。综上,双尾新小绥螨对花蓟马1龄若虫有较好的捕食能力,可用于花蓟马的生物防治。     

巴氏新小绥螨的新特性——捕食植物线虫及其发育繁殖

在实验室条件下评价了巴氏新小绥螨捕食南方根结线虫时的发育和繁殖情况,观察了其捕食行为,并测定了其对几种线虫的捕食量。该螨对线虫的捕食行为可分为猎物的寻找、固定、捕食、清理和静息等步骤,对水稻干尖线虫和南方根结线虫二龄幼虫（Mi-J2）的捕食量显著大于对虫体较大和活动性较强的腐烂茎线虫和自由生活的小杆线虫的捕食量;每头雌螨日捕食Mi-J2不少于25条。以Mi-J2为食的巴氏新小绥螨能发育完成生活史,并具有较强的繁殖能力,其卵期、幼螨期、前若螨期、后若螨期、产卵期、雌螨寿命、平均每头雌螨产卵量和日均产卵量分别为1．1d、0．71d、2．06d、1．98d、22-31d、35．13d、41．08粒和1．85粒,其内禀增长率、周限增长率均大于以腐食酪螨为食的巴氏新小绥螨,而平均世代周期和种群倍增时间均小于后者。     

双尾新小绥螨对烟粉虱和土耳其斯坦叶螨的捕食选择性

为了明确双尾新小绥螨Neoseiulus bicaudus Wainstein对不同密度下烟粉虱Bemisia tabaci（Gennadius）和土耳其斯坦叶螨Tetranychus turkestani（Ugarov&Nikolskii）的捕食选择性,在实验室条件下,测定24 h内双尾新小绥螨对不同比例下猎物的捕食情况（烟粉虱和土耳其斯坦叶螨数量比为20：10、15：10、10：10、10：15、10：20和10：40）。结果表明双尾新小绥螨雌成螨对猎物的捕食量随猎物数量的升高而增加,其中对土耳其斯坦叶螨幼螨的捕食量最高。双尾新小绥螨除对烟粉虱1龄若虫和叶螨卵在10：10的相同密度下选择指数无差异外,其他各密度下,双尾新小绥螨对土耳其斯坦叶螨的选择性均显著高于烟粉虱。当烟粉虱和土耳其斯坦叶螨同时发生时,双尾新小绥螨对土耳其斯坦叶螨的选择性高于烟粉虱,对土耳其斯坦叶螨控制效果更好。     

基于两性生命表的以朱砂叶螨为猎物的加州新小绥螨四川种群生长发育、繁殖及捕食率

为全面掌握加州新小绥螨四川种群的种群特征,本试验运用两性生命表开展了以朱砂叶螨为猎物的加州新小绥螨四川种群的生长发育、繁殖与捕食率研究。结果表明,加州新小绥螨四川种群不同发育阶段重叠,在雌成螨产卵期结束前雌成螨特定年龄-阶段存活率S_xj明显高于雄成螨。单位时间（12 h）特定年龄-阶段繁殖力f_x5、特定年龄繁殖力m_x最大值分别为1.74和1.12粒/雌,单雌总产卵量为49.28粒。种群内禀增长率为0.27/d、周限增长率为1.31/d、净增殖率为26.61粒/个体、世代平均周期为12.34 d。在未成熟阶段,加州新小绥螨各螨态特定年龄-阶段捕食率C_xj均呈双峰型,雌成螨和雄成螨捕食率均随时间明显波动。加州新小绥螨取食朱砂叶螨的转化率为4.55、内禀捕食率为0.54、周限捕食率为1.72头。以朱砂叶螨为猎物时,加州新小绥螨四川种群表现出较好的个体发育、种群增长和捕食能力,可作为控制朱砂叶螨的生防资源,值得进一步研究和开发利用;同时朱砂叶螨可作为加州新小绥螨四川种群人工繁殖选择的猎物之一。     

胡瓜新小绥螨对荔枝叶螨的控制潜力

荔枝叶螨Oligonychus litchii Lo et Ho是一种重要的农业害螨,寄主范围广,在荔枝产区为害严重。为明确胡瓜新小绥螨Neoseiulus cucumeris Oudemans对荔枝叶螨的潜在控制能力,采用功能反应和数值反应,分析了胡瓜新小绥螨在不同温度下对荔枝叶螨卵和若螨的捕食效应以及胡瓜新小绥螨对荔枝叶螨种群密度效应的影响。结果表明:胡瓜新小绥螨对荔枝叶螨卵和若螨均有较强的嗜食性,但对雌成螨几乎不取食。在20.5~32.5℃时,胡瓜新小绥螨对荔枝叶螨若螨和卵的捕食功能反应均拟合HollingⅡ型方程,20~29℃时,胡瓜新小绥螨对荔枝叶螨卵和若螨的处理时间、瞬间攻击系数随着温度的升高而降低,对卵和若螨的最大日捕食量则随着温度升高而增大。在28~29℃时,胡瓜新小绥螨对荔枝叶螨若螨和卵捕食能力最强、捕食量最大,处理时间最短,但当温度达到32℃以上时捕食量开始减小。另外,胡瓜新小绥螨对荔枝叶螨种群的控制能力,随着益害比的增加,荔枝叶螨种群数量明显下降,当益害比为5:10时荔枝叶螨种群数量在第9 d下降了40.78%。综合分析表明,胡瓜新小绥螨对荔枝叶螨卵和若螨具有一定的捕食作用,捕食的最适温度为28~32℃,在荔枝叶螨种群密度较低时释放胡瓜新小绥螨可起到一定的控害效果。     

阿维菌素亚致死剂量对虚伪新小绥螨的影响

阿维菌素是目前常用的杀虫杀螨剂。本研究利用生命表技术,室内评价了阿维菌素亚致死剂量对虚伪新小绥螨成螨生长发育及生殖的影响。通过阿维菌素亚致死剂量(LC30、LC20和LC10)处理虚伪新小绥螨成螨后,平均每雌产卵量分别为29.11、34.25、45.81粒;每雌日均产卵量分别为0.73、0.99、1.50粒,平均每雌产卵量LC20和LC30与对照(53.89粒)有显著差别,每雌日均产卵量3个处理与对照(2.43粒)均有显著差别,而对后代的雌雄性比影响没有显著差异。阿维菌素亚致死剂量对次代的发育历期影响主要表现为产卵前期的延长,产卵期和产卵后期缩短,但对整体平均寿命影响不显著。生殖生命表的结果显示,阿维菌素会降低虚伪新小绥螨的发育速率,其净增殖率(R0)和内禀增长率(rm)下降,而平均世代周期(T)和种群加倍时间(Dt)增长。通过对次代存活率和种群生命期望指数的分析,结果表明,LC10和LC30处理的虚伪新小绥螨中有近40%个体的存活时间较对照有显著的延长,且LC10和LC30处理后虚伪新小绥螨的种群期望指数均显著高于对照。综上所述,阿维菌素对虚伪新小绥螨的生殖能力存在一定的负面影响,但对于虚伪新小绥螨的个体发育影响与对照相比影响不大。该结论为利用阿维菌素开发耐药性(抗药性)的虚伪新小绥螨提供了理论依据。     

Relationship Between Production of the Phytotoxin Prehelminthosporol and Virulence in Isolates of the Plant Pathogenic Fungus Bipolaris sorokiniana

A gas chromatographic method was developed to quantify the phytotoxin prehelminthosporol, which is a sesquiterpene metabolite of the plant pathogen Bipolaris sorokiniana. The toxin was extracted from mycelium or culture filtrates, pre-cleaned using solid phase extraction, and analyzed by gas chromatography as a trimethylsilyl-derivative. The detection limit of the method was 5ngl^–1 (signal to noise ratio 4:1) which corresponds to ca. 15ng prehelminthosporol per mg dry weight of mycelium or 15ng prehelminthosporol per ml culture filtrate. The total amount of prehelminthosporol (mycelium plus culture filtrate) increased with cultivation time when examined in six isolates of B. sorokiniana after 6, 9, 12 and 15 days of incubation. The screening experiment of 17 isolates for prehelminthosporol production after 8 days of incubation revealed significant differences in the toxin production between the isolates. The isolates with low toxin production had lower virulence towards barley roots compared to those with higher production of the toxin. However, the virulence did not increase with prehelminthosporol level among the high producing isolates. Prehelminthosporol was also analyzed in a number of related Bipolaris and Drechslera species. In addition to B. sorokiniana, three out of six Bipolaris species (B. setariae, B. zeicola, B. victoriae) produced prehelminthosporol, which indicates that ability to produce prehelminthosporol is conserved among closely-related Bipolaris species.     

Monitoring of the winter populations of cereal aphids near Wageningen,the Netherlands,in 1982/1983

Cereal aphids on a wheat crop were sampled through the winter of 1982/1983 using both fixed and random quadrats.Sitobion avenae overwintered successfully anholocyclically although there was a substantial decline in the population of this species. No evidence for successful anholocyclic overwintering in other aphid species was found, althoughRhopalosiphum padi was seen to colonise the crop in early winter and was found until the end of December.Eggs ofR. padi onPrunus padus were observed through the winter. A steady decline in their numbers occurred. The overall survival rate of the 5385 eggs was c.30%.Eggs ofMetopolophium dirhodum onRosa spp. were also monitored. They also showed a steady decline in numbers through the winter. The overall survival rate of the 1360 eggs was c.34%.Egg hatch in bothR. padi andM. dirhodum was closely synchronised with bud burst of their host plant. For the latter species this resulted in egg hatch starting in January.Samenvatting In de winter van 1982/1983 werden de graanluizen in een tarwegewas regelmatig geteld in willekeurig en in van tevoren gekozen monstereenheden. Hoewel er een aanmerkelijke afname van de populatie vanSitobion avenae werd waargenomen, overwinterde deze soort toch anholocyclish. Er werden geen aanwijzingen gevonden dat de andere bladluissoorten anholocyclish overwinterden hoewel kolonies vanRhopalosiphum padi tot eind december werden waargenomen.De gehele winter werden eieren vanR. padi opPrunus padi aangetroffen, de aantallen ervan namen geleidelijk af; van de 5385 getelde eieren overleefde ongeveer 30%. Ook de aantallen eieren vanMetopolophium dirhodum opRosa spp. werden reglematig vastgesteld; ook hier werd een geleidelijke afname geconstateerd. Van de oorspronkelijk getelde 1360 eieren overleefde ongeveer 34%.Het uitkomen van de eieren vanR. padi enM. dirhodum viel nauw samen met het uitlopen van de knoppen van hun waardplant. VoorM. dirhodum betekende dit dat de eerste eieren al begin januari uitkwamen.     

沉默转录因子OsERF7提高水稻对褐飞虱和白背飞虱的抗性

为了解植物中特有的转录因子乙烯响应因子(ethylene responsive factor,ERF)在植物诱导抗虫反应中的作用,通过克隆1个水稻ERF转录因子基因OsERF7,并结合分子生物学、反向遗传学及生物测定,探究其在水稻防御褐飞虱Nilaparvata lugens和白背飞虱Sogatella furcifera为害过程中的作用。结果显示,机械损伤处理与褐飞虱产卵雌成虫为害均能在中后期诱导OsERF7的表达。沉默OsERF7能显著降低水稻上褐飞虱及白背飞虱卵的孵化率,并延长褐飞虱卵的发育历期;与野生型水稻相比,褐飞虱和白背飞虱在沉默突变体品系R1和R30上的卵孵化率分别只有野生型水稻上的62.5%～68.3%和68.0%～76.0%,褐飞虱卵的发育历期则延长0.37～0.45 d。沉默OsERF7不影响褐飞虱产卵雌成虫为害诱导的水稻防御相关信号分子—茉莉酸(JA)、水杨酸(SA)、乙烯(ET)和过氧化氢(H_2O_2)的含量。表明转录因子OsERF7作用于防御相关信号途径的下游,并且负调控水稻对褐飞虱和白背飞虱的抗性。     

Genetic Analysis of the Role of Trichothecene and Fumonisin Mycotoxins in the Virulence of Fusarium

The phytotoxicity of the Fusarium trichothecene and fumonisin mycotoxins has led to speculation that both toxins are involved in plant pathogenesis. This subject has been addressed by examining virulence of trichothecene and fumonisin-nonproducing mutants of Fusarium in field tests. Mutants were generated by transformation-mediated disruption of genes encoding enzymes that catalyze early steps in the biosynthesis of each toxin. Two economically important species of Fusarium were selected for these studies: the trichothecene-producing species Fusarium graminearum, which causes wheat head blight and maize ear rot, and the fumonisin-producing species F. verticillioides, which causes maize ear rot. Trichothecene-non-producing mutants of F. graminearum caused less disease than the wild-type strain from which they were derived on both wheat and maize, although differences in virulence on maize were not observed under hot and dry environmental conditions. Genetic analyses of the mutants demonstrated that the reduced virulence on wheat was caused by the loss of trichothecene production rather than by a non-target mutation induced by the gene disruption procedure. Although the analyses of virulence of fumonisin-non-producing mutants of F. verticillioides are not complete, to date, the mutants have been as virulent on maize ears as their wild-type progenitor strains. The finding that trichothecene production contributes to the virulence of F. graminearum suggests that it may be possible to generate plants that are resistant to this fungus by increasing their resistance to trichothecenes. As a result, several researchers are trying to identify trichothecene resistance genes and transfer them to crop species.     

Occurrence of pepper yellow vein in the Netherlands

Samenvatting Het verschijnsel van geelnervigheid bij paprika (Capsicum annuum) kon door verenting en met de schimmelOlpidium brassicae worden overgebracht. Hierdoor bleek de ziekte identiek te zijn met een eerder in Engeland gemelde ziekte. Door inoculatie met zoösporen of rustsporen vanO. brassicae werden ook symptomen verkregen inC. baccatum, C. chacoense enC. frutescens. S. villosum bleek een waardplant te zijn voor het geelnervigheidsagens, waarbij zwakke nerfchlorosen werden waargenomen.Seconded to the Glasshouse Crops Research Station, P.O. Box 8, 2670 AA Naaldwijk, the Netherlands.     

Effects of the saprophytic leaf mycoflora on growth and productivity of winter wheat

The effects of the saprophytic mycoflora and its interference with cereal aphids on growth and yield of winter and spring wheat was studied in field experiments in 1980, 1981 and 1982.Yields varied between 5000 and 8000 kg dry matter of kernels per ha. The effect of the saprophytic mycoflora on yield was determined in different treatments: A) no control measures against cereal aphids and saprophytic and necrotrophic fungi, B) no control of cereal aphids, control of saprophytic and necrotrophic fungi, C) control of cereal aphids and control of saprophytic and necrotrophic fungi, D) control of cereal aphids and stimulation of saprophytic mycoflora and E) control of cereal aphids, no control of saprophytic and necrotrophic fungi nor stimulation of saprophytic mycoflora.Considerable differences in top densities of saprophytic mycoflora (10 times as large in A and D as in B and C) were determined. The consequences of these differences for the growth and productivity of wheat were minor. A negative effect of saprophytic mycoflora on the yield could not be detected in 1981 and 1982, whereas a small positive significant effect was found in 1980. This stimulation may have been due to competition between necrotrophic fungal pathogens and saprophytic mycoflora. As a result of favourable weather conditions necrotrophic fungal pathogens were very numerous in 1980 and could form an important yield reducing factor. Yield levels may effect the importance of the necrotrophic and saprophytic mycoflora as yield reducing factors. Additionally, in the presence of aphid honeydew captafol was found to be relatively ineffective against saprophytic fungi.     

Parasitoid community of the loreyi leaf wormMythimna (Acantholeucania) loreyi: Novel host-parasitoid associations and their efficiency in the eastern mediterranean region of Turkey

The loreyi leaf worm,Mythimna (Acantholeucania) loreyi Duponchel (Lepidoptera, Noctuidae), is a pest of gramineous crops and causes significant economic damage to maize. In field surveys on maize to determine the parasitoid community and its impact on the pest in the eastern Mediterranean region of Turkey, nine parasitoid species were found associated with immature stages ofM. loreyi: The hymenopteran (Braconidae and Ichneumonidae) parasitoidsCotesia (=Apanteles) ruficrus (Haliday),Chelonus oculator Panzer,Meteorus ictericus Nees,Hyposoter didymator (Thunberg),Sinophorus sp.; and the dipteran (Tachinidae) parasitoidsPseudogonia rufifrons Wiedeman,Exorista rossica Mesnil,Gonia picea (Robineau-Desvoidy) andLinnaemya vulpina (Fallen) — the last three recorded for the first time as parasitoids ofM. loreyi in Turkey.C. ruficrus was the dominant parasitoid species, being recovered from 38.5% of the larvae collected and was also the most prevalent species, existing in 91.0% of the fields in whichM. loreyi was found. Total parasitism levels achieved by braconid species was 41.4%, by ichneumonid parasitoids 4.8%, and by tachinid parasitoids 1.9%. In a separate field experiment, seasonal population fluctuations and natural efficiency ofC. ruficrus onM. loreyi were found to be 35.1% and 42.4%, respectively. Population levels ofC. ruficrus were closely related to fluctuations in the population ofM. loreyi, with parasitism ranging between 0 and 77.3% during the study. http://www.phytoparasitica.org posting Aug. 28, 2005.     

Systemic toxicity of spinosad to the greenhouse whiteflyTrialeurodes vaporariorum and to the cotton leaf wormSpodoptera littoralis

When spinosad was administered at the stem base of tomato plants grown in rockwool, the main substrate used in greenhouses in northern Europe, it was taken up by the roots and transported to the leaves. Laboratory toxicity experiments showed that systemically applied spinosad, at doses as low as 2 mg active ingredient per plant, gave excellent control of nymphs of the greenhouse whiteflyTrialeurodes vaporariorum, but was less toxic to adults. The toxicity of spinosad on Homoptera has not been documented yet and a dose-response relationship was established. The persistence of toxicity was at least 22 days for whitefly nymphs. A dose-response relationship of systemically applied spinosad was also determined on third-instar larvae of the cotton leaf wormSpodoptera littoralis; a dose of 5 mg per plant consistently killed all larvae. The persistence of systemically applied spinosad reached up to 45 days after treatment. Systemically applied spinosad was harmless to the parasitic waspEncarsia formosa. http://www.phytoparasitica.org posting Nov. 29, 2005.     

Aetiology and causal agents of mango sudden decline disease in the Sultanate of Oman

Mango sudden decline is a recently introduced, economically serious disease in Oman. Affected mango trees have wilting symptoms that usually begin on one side and later spread to involve the entire tree. Trees exude amber-coloured gum from the bark of their trunks or branches and vascular tissues are discoloured. Having entered Oman in the recent past, survey data is presented that shows the disease to have spread throughout the northern part of the country. Evidence is presented that the vascular wilt pathogen Ceratocystis fimbriata causes mango sudden decline disease in Oman, possibly in concert with Lasiodiplodia theobromae and the recently described Ceratocystis omanensis. Isolates of these fungi from affected trees, cause infection and can be recovered from inoculated seedlings. Bark beetles (Hypocryphalus mangiferae) are shown to carry C. fimbriata and L. theobromae and are presumably responsible for transmitting both pathogens to healthy mango trees. Acting as a wounding agent and vector, the bark beetle is likely to have assisted the rapid spread of the disease across Oman.