B型烟粉虱和温室白粉虱在温度逆境下的生存特性比较

为了明确B型烟粉虱和温室白粉虱在温度逆境下的生存特性对其种群发展的影响,通过进行高温和低温暴露试验,研究了B型烟粉虱和温室白粉虱卵、伪蛹、成虫在37℃,39℃,41℃,43℃,45℃下暴露1～2 h后的存活率,以及这两种粉虱卵、2～3龄若虫、伪蛹和成虫在2℃下暴露1～12 d后的存活率。结果表明：两种粉虱的卵、伪蛹和成虫在37℃～45℃下暴露1～2 h,其存活率均随着温度的上升而降低;但在相同处理条件下B型烟粉虱3种供试虫态的存活率要高于温室白粉虱。B型烟粉虱在2℃下暴露2～12 d,各供试虫态的存活率迅速下降,卵、2～3龄若虫、伪蛹在2℃下暴露12 d后均不能存活,成虫在2℃下暴露4 d后也全部死亡;而温室白粉虱卵、伪蛹在2℃下暴露12 d后其存活率还能超过45%,成虫在2℃下暴露7 d后仍有80.9%能够存活。结果说明,B型烟粉虱和温室白粉虱对温度逆境的适应性存在差异,B型烟粉虱对高温的适应性要高于温室白粉虱;温室白粉虱对高温敏感,但对低温的适应性要显著高于B型烟粉虱。据此推测,两种粉虱对温度逆境适应性的差异是导致其种群发生存在差异的一个重要原因。     

烟粉虱及温室白粉虱为害后对后续粉虱种群的影响

【目的】分析烟粉虱Bemisia tabaci(Gennadius)或温室白粉虱Trialeurodes vaporariorum(Westwood)为害番茄后对后续温室白粉虱和烟粉虱生长、发育、成虫寿命和繁殖等产生的促进或抑制作用,可为明确寄主植物番茄介导的温室白粉虱-烟粉虱的种间互作,开展粉虱的科学防控提供科学依据。【方法】通过在寄主植物番茄叶片上先将B型烟粉虱或温室白粉虱按不同的顺序、时间间隔分开接种,再系统观察后续接上的两种粉虱生长、发育、繁殖等种群参数的变化。【结果】(1)先期接上烟粉虱对后续温室白粉虱的发育、寿命、产卵量有明显的促进作用;这种作用需烟粉虱的持续诱导,若去掉烟粉虱,其对温室白粉虱的促进作用即消失;先期接上温室白粉虱可缩短后续烟粉虱伪蛹期,但温室白粉虱的持续存在不利于烟粉虱的产卵,且明显降低烟粉虱的内禀增长率和净增殖率。(2)先后在番茄上同时接上温室白粉虱可降低后续烟粉虱的单雌产卵量和雌、雄虫的成虫寿命;先后同时接种烟粉虱却显著地增加了温室白粉虱的单雌产卵量;烟粉虱的提前存在降低了后续烟粉虱单雌产卵量。(3)但两种粉虱之间作用存在着一定的时间滞后性。烟粉虱对温室白粉虱的发育、寿命、产卵量产生的促进作用大约在其卵期后的一段时间才能显现出来;温室白粉虱对烟粉虱伪蛹期的缩短作用也需提前诱导;而温室白粉虱对温室白粉虱的促进作用相当滞后,直到成虫期才显现出来。【结论】B型烟粉虱和温室白粉虱之间可通过寄主番茄产生相互影响,前期烟粉虱为害可显著促进后续温室白粉虱卵和若虫的发育,而前期温室白粉虱为害对烟粉虱的发育不利。     

烟草品种和温度对B型烟粉虱和温室白粉虱生物学参数的影响

在室内20℃、26℃和30℃三个设定温度条件下,研究了CF-965、NC-89和NC-82三个烟草品种对B型烟粉虱和温室白粉虱生长发育和繁殖的影响.结果表明:26℃时两种粉虱在CF-965、NC-89和NC-82三个烟草品种上的发育历期没有明显差异,但温室白粉虱卵期和若虫期的发育历期较烟粉虱依次分别延长了1.32d、2.81d和 2.04d.在CF-965上,B型烟粉虱卵期和若虫期的总存活率和平均单雌产卵量分别为54.19%和55.17粒,温室白粉虱仅分别为31.99%和39.17粒;在NC-89上,B型烟粉虱卵期和若虫期的总存活率和平均单雌产卵量分别为23.47%和37.50粒,温室白粉虱仅分别为15.75%和17.25粒;两种粉虱在NC-82上卵期和若虫期的总存活率和平均单雌产卵量差异不大,表明B型烟粉虱对CF-965和NC-89的适应能力较温室白粉虱强.两种粉虱在20℃时的发育历期最长,32℃时最短,26℃时居中.20°C时烟粉虱卵期和若虫期的存活率20.96%为最低,26℃和32℃时分别达54.19% 和53.29%;而温室白粉虱在32℃条件下存活率11.66%为最低,20℃和 26℃时分别达31 34% 和31.99%.温室白粉虱在20℃时产卵量大于烟粉虱, 在26℃时的产卵量小于烟粉虱,30℃时则不能产卵,但烟粉虱成虫30℃时的产卵量仍可达21.06粒.由此说明烟粉虱在较高温度条件下的适应能力显著强于温室白粉虱.山东烟区烟草生长中期的田间平均温度多在22～30℃,适合B型烟粉虱的发生,应引起高度重视.     

一种改进的粉虱成虫生物测定方法

生物测定是检测害虫抗药性的一项重要技术。利用100mL插口圆底聚丙烯离心管对现在应用较多的粉虱成虫生物测定方法——琼脂保湿浸叶法进行了改进。改进后的方法不影响粉虱成虫的持续取食,具有操作简单、结果重复性好及无需对成虫麻醉等优点。同时发现茄子叶片对于B型烟粉虱Bemisia tabaci(Gennadius)B-biotype和温室白粉虱Trialeurodes vaporariorum(Westwood)成虫均是一种非常适合的生测材料。利用该方法分3次独立测定了烯啶虫胺对B型烟粉虱和温室白粉虱混合日龄成虫的毒力,结果具有很好的重复性。     

甘蓝与黄瓜寄主上B型烟粉虱和温室白粉虱蜜露糖分、氨基酸和挥发物组分的比较分析

粉虱蜜露是粉虱寄生性天敌搜索寄主的主要利它素源。应用离子色谱分别对甘蓝与黄瓜上B型烟粉虱(Bemisia tabaci B-biotype)蜜露以及黄瓜上温室白粉虱Trialeurodes vaporariorum蜜露的接触性利它素糖和氨基酸组分和含量进行了比较研究。结果表明：2种粉虱在不同寄主植物上的蜜露均富含糖和氨基酸,其中糖含量占绝对优势,甘蓝上B型烟粉虱蜜露、黄瓜上B型烟粉虱蜜露和黄瓜上温室白粉虱蜜露中的糖含量分别是相应氨基酸含量的42.5、2.6和5.4倍,其中糖类物质中又以寡糖含量占绝对优势,分别占89.3%、81.7%和88.2%。不同寄主植物和粉虱种类显著影响蜜露中糖和氨基酸的组成和含量。其中,甘蓝上B型烟粉虱蜜露中的寡糖以二糖占优势,占97.3%;二糖中又以蔗糖异构糖和松二糖占优势,分别占52.7%和35.4%。黄瓜上B型烟粉虱蜜露和温室白粉虱蜜露寡糖中以三糖和四糖占优势,分别占73.1%和85.4%;优势糖水苏（四）糖和松三糖分别占40.3%和 26.2%及49.9%和27.0%。甘蓝上B型烟粉虱蜜露中氨基酸以丙氨酸占优势,含量为66.5%;而黄瓜上B型烟粉虱及温室白粉虱蜜露中氨基酸以甘氨酸含量最高,分别占氨基酸总量的38.2%和51.7%。应用GC-MS对甘蓝上B型烟粉虱蜜露和黄瓜上温室白粉虱蜜露挥发物组分的鉴定结果显示,两种粉虱蜜露中共同含有的主要挥发物为邻苯二甲酸二（2-乙基）己酯。     

B型烟粉虱和温室白粉虱热激蛋白90基因（hsp90）的全长cDNA克隆与系统发育分析

B型烟粉虱Bemisia tabaci (Gennadius) biotype B和温室白粉虱Trialeurodes vaporariorum均为全球普遍发生的重要害虫。本研究以其他昆虫热激蛋白90基因（hsp90）保守区域设计兼并引物扩增两种粉虱hsp90中间片段, 然后利用RACE技术获得全长cDNA。温室白粉虱hsp90全长cDNA的开放性阅读框2 166 bp, 编码722个氨基酸; 烟粉虱hsp90全长cDNA的开放性阅读框2 160 bp, 编码720个氨基酸。两种粉虱HSP90的完整氨基酸序列相似性高达92.94％, 并均具有定义HSP90家族签名序列的5个氨基酸保守区域和末尾基序“MEEVD”。通过real-time PCR技术, 探测到两个基因在mRNA水平上皆能高温诱导表达。采用昆虫纲所有完整HSP90氨基酸序列进行Kimura双参数遗传距离分析并构建NJ进化树, 结果显示hsp90在昆虫纲低级阶元水平和高级阶元水平系统进化上能得到一个较理想结果。本研究结果为B型烟粉虱和温室白粉虱抗逆适应性研究提供基础, 并进一步验证保守的功能基因hsp90可以作为研究生物系统发育的手段之一     

烟粉虱天敌日本刀角瓢虫的捕食行为

研究了日本刀角瓢虫雌成虫和幼虫捕食粉虱时的各种行为时间分配.结果表明,日本刀角瓢虫成虫的捕食行为可分为爬行、取食、清洁、静息、整翅和排泄6个部分.饥饿后的日本刀角瓢虫幼虫捕食烟粉虱卵时,幼虫各龄期间的取食和爬行时间无显著差异,对烟粉虱卵的处置时间随瓢虫幼虫虫龄的增大而缩短.日本刀角瓢虫雌成虫捕食烟粉虱卵时,饥饿后的雌成虫用于取食的时间显著长于非饥饿的雌成虫,而用于清洁、静息和爬行的时间显著短于非饥饿的雌成虫;饥饿后的瓢虫雌成虫对卵的处置时间显著长于非饥饿的雌成虫.饥饿后的日本刀角瓢虫雌成虫捕食烟粉虱若虫时,瓢虫雌成虫的取食时间随烟粉虱若虫虫龄的增大而增加,清洁和静息时间随烟粉虱若虫虫龄的增大而缩短,对若虫的处置时间随烟粉虱若虫虫龄的增大而增加.     

寄主植物对B型烟粉虱(Bemisia tabaci)和温室粉虱(Trialeurodes vaporariorum)个体发育和种群繁殖的影响

烟粉虱Bemisia tabaci（Gennadius）和温室粉虱Trialeurodes vaporariorum（Westwood）在我国北方常混合发生,为了解两种粉虱所造成的危害和自身种群的增长变化,制定科学的综合防治措施,在（27±1）℃条件下研究了两种粉虱在棉花Gossypium hirsutum L.（泗棉3号）、黄瓜Cucumis sativas L.（北京202）、茄子Solanum melongena L.（北京七叶茄）和番茄Lycopersicum esculentum Mill.（佳粉十号）上各虫态大小、存活率、发育历期、成虫寿命、平均产卵量等生物学参数。在同一种寄主植物上,温室粉虱的1,2龄若虫的体长和体宽均显著大于烟粉虱,3龄以后两种粉虱的体型则变异较大。两种粉虱从卵到成虫羽化,在棉花上的发育历期无显著差异,在黄瓜、茄子和番茄上,温室粉虱的发育历期（19.7、19.4、20.8d）显著长于烟粉虱（17.3、17.6、18.3d）。在黄瓜和番茄上,烟粉虱的平均寿命（31.2、32.1）显著长于温室粉虱的平均寿命（26、24.9d）;在棉花、黄瓜和番茄上,烟粉虱的单雌产卵量（122.2、220.2、266．5粒）显著高于温室粉虱（97．1、186．6、197．1粒）。烟粉虱在棉花、黄瓜、茄子和番茄上的总存活率分别为67.9％、77.8％、67.8％和59．0％,温室粉虱依次为62．2％、67．2％、64．4％和66．1％。综合比较4种寄主植物,烟粉虱比温室粉虱具有个体发育时间短、种群繁殖速度快、生殖竞争能力强等特点。     

漆酶-1基因在烟粉虱MEAM1隐种和温室粉虱中的表达模式比较

【目的】漆酶-1(LAC1)在粉虱-植物互作中发挥重要作用,本研究旨在探讨烟粉虱Bemisia tabaci MEAM1隐种和温室粉虱Trialeurodes vaporariorum两种存在竞争关系的粉虱中LAC1基因表达模式是否存在差异。【方法】测定烟粉虱MEAM1隐种和温室粉虱唾液漆酶-1活力;对温室粉虱LAC1基因进行了克隆和测序;通过荧光定量PCR测定和比较了LAC1在两种粉虱不同发育阶段和成虫不同组织中的表达谱以及取食外施水杨酸(0. 5 mmol/L)的番茄植株后两种粉虱不同发育阶段和成虫不同组织中LAC1的表达水平,同时检测了成虫存活率和产卵量。【结果】酶活力测定结果表明两种粉虱的唾液中漆酶-1活力差异不显著。温室粉虱PCR扩增后得到大小639 bp的LAC1基因中间片段。发育表达谱结果表明,LAC1基因在两种粉虱各个发育阶段均有表达,在烟粉虱MEAM1隐种成虫期表达量逐渐升高,而在温室粉虱各发育时期的表达量无显著差异;烟粉虱MEAM1隐种成虫期LAC1的表达量高于温室粉虱。组织表达结果表明,LAC1在两种粉虱成虫的头胸部、中肠和腹部残骸中均有表达,但在中肠中丰度最高。取食外施水杨酸番茄植株的烟粉虱MEAM1隐种,随取食时间的延长成虫存活率下降,与对照(取食喷施清水的植株)相比差异显著。羽化后14 d时,取食外施水杨酸植株的烟粉虱MEAM1隐种存活率仅为对照的一半,而取食外施水杨酸植株的温室粉虱的存活率与对照相比差异不显著。无论是取食外施水杨酸的植株还是取食对照植株,烟粉虱MEAM1隐种体内LAC1表达量和产卵量均高于温室粉虱。【结论】LAC1在两种粉虱体内表达模式存在差异,这可能在两种粉虱的竞争适应中具有一定作用。     

浙江B型与一非B型(China-ZHJ-1)烟粉虱形态学和生物学特性的比较研究

本文对新入侵我国的B型与浙江一非B型（China-ZHJ-1种群）烟粉虱之间的生殖亲和性进行了测定,并对两个生物型在形态特征、发育历期、诱导西葫芦银叶反应及寄主植物适应性几方面进行了比较研究。结果表明,当将B型与非B型ZHJ-1种群进行杂交组合时,两生物型之间虽然有求偶行为发生,但从不发生交配,后代全部为孤雌生殖产下的雄虫;而B型、非B型各自内部羽化后0～72 h的平均交配次数分别为4.4次和1.0次, 所产后代的雌雄性比分别为2.8∶1、1.0∶1,前者性比显著高于后者。两生物型之间伪蛹形态存在明显差异,非B型ZHJ-1种群的前、后蜡缘饰宽度分别为B型的2.5～2.7倍、1.8～2.1倍。在棉花上,除B型1龄若虫历期较非B型的略长外,两生物型之间其他各虫态的发育历期均无显著差异;从2龄若虫起,非B型各虫态的体长明显长于B型,并且同一生物型内,4龄雌性若虫个体明显大于同龄雄性若虫。B型在多种寄主植物上的存活力比非B型的显著要强。B型与非B型ZHJ-1种群生物学特性的比较,为对我国烟粉虱这两个生物型进行深入的比较研究、探讨B型烟粉虱的入侵生物学提供了基础。     

Factors that affect the selection of tomato leaflets by two whiteflies,Trialeurodes vaporariorum and Bemisia tabaci (Homoptera: Aleyrodidae)

In Japan, although greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and sweet potato whitefly, Bemisia tabaci (Gennadius), co-occur on tomato plants under greenhouse conditions, the two whiteflies are distributed differently with regard to leaf position. To elucidate the factors that determine the leaf position of these whiteflies, we investigated traits for leaflets collected from three positions on tomato plants. Furthermore, we examined leaflet selection by and fertility of the two whiteflies under choice and non-choice conditions. In addition, the effect on whitefly behavior of volatile compounds released from leaflets was evaluated by use of a Y-tube olfactometer test. Nitrogen and carbon content were highest for upper leaflets. In choice tests, more T. vaporariorum and B. tabaci adults selected upper and middle leaflets, respectively. Similarly, they oviposited more eggs on upper and middle leaflets. In non-choice tests, T. vaporariorum oviposited more eggs on upper leaflets, but B. tabaci oviposited equally on each leaflet. In Y-tube olfactometer tests, more T. vaporariorum adults moved to upper leaflets whereas more B. tabaci adults moved to middle leaflets. These results suggest that different leaflet selection by adults of these two whiteflies is likely to be associated with the different volatile compounds emitted by tomato leaflets at each position.     

Beauveria bassiana ARP14 a potential entomopathogenic fungus against Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)

The sweet potato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), and the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), are important pests of protected crops grown in warm climates. We compared efficacy of a new strain of the entomopathogenic fungus Beauveria bassiana (ARP14) isolated from Riptortus pedestris (Hemiptera: Alydidae) with a commercial strain (GHA) against different life stages of both B. tabaci and T. vaporariorum. Eggs, nymphs, and adults were exposed to 1 × 10⁸ conidia/mL of each strain using the leaf-dipping method. The mycosis rate of B. tabaci eggs (as a proportion) was relatively low (0.13 for B. bassiana ARP14 and 0.10 for B. bassiana GHA), while, for T. vaporariorum eggs, mycosis rate was 0.44 for B. bassiana GHA and 0.27 for B. bassiana ARP14. However, mycosis rate of 1st instars of both whiteflies was much higher than for eggs, for both strains (ARP14 and GHA). The developmental period of B. tabaci eggs exposed to ARP14 was significantly shorter than for either eggs treated with GHA or the control. For 2nd and 4th instar nymphs and adults of both whiteflies there were no differences in mycosis rates between the two B. bassiana strains. These results suggest that, B. bassiana ARP14 could be commercialized as a native biological control agent for control of B. tabaci and T. vaporariorum.     

Effects of temperature on the growth and reproduction characteristics of Bemisia tabaci B‐biotype and Trialeurodes vaporariorum

The development period, survival rate, longevity and fecundity of two whiteflies, Bemisia tabaci B‐biotype and Trialeurodes vaporariorum (Homoptera: Aleyrodidae) were compared under different temperature laboratory conditions (15°C, 18°C, 21°C and 24°C). Egg development of B. tabaci B‐biotype was significantly longer compared with that of T. vaporariorum at 15°C, 18°C and 24°C. Significantly longer pseudo‐pupae development and lower survival rate were found in B. tabaci B‐biotype at 15°C compared with those at 18°C, 21°C and 24°C. Significantly higher fecundity was found in B. tabaci B‐biotype at 24°C compared with that at 15°C, 18°C and 21°C. However, the fecundity of T. vaporariorum was significantly lower at 24°C relative to that at 15°C, 18°C and 21°C. Significantly shorter 1st instar larval development was found in T. vaporariorum compared with that of B. tabaci at 15°C and 18°C. Significantly longer 2nd instar larval development was found in B. tabaci and T. vaporariorum at 15°C compared with that at 18°C, 21°C and 24°C. However, significantly shorter 3rd instar larval development was found in T. vaporariorum compared with that of B. tabaci at 15°C, 18°C and 24°C. The adaptive divergence of tolerance to relatively low temperature may be an important factor that results in the interspecific differentiation between the seasonal dynamics of these two whiteflies in China.     

Host preferences and biotic potential of <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> and <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Hemiptera: Aleyrodidae) in tomato and pepper

Whiteflies Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are important pests in pepper (Capsicum annuum L.) and tomato (Solanum lycopersicum L.) crops in many countries. Contrary to what is observed for all other countries, in Uruguay, B. tabaci is mainly found on pepper and rarely on tomato, while T. vaporariorum is exclusively found on tomato. This study tested the oviposition preferences and biotic potential of these two whiteflies reared on both host plants. The developmental time, survival rates, longevity, fecundity and main population parameters were characterized. Both whitefly species showed different preference patterns regarding their host plants. T. vaporariorum preferred tomato instead of pepper to oviposit. Their developmental time is longer on pepper. B. tabaci preferred pepper, but the difference from tomato was not very strong. Pepper affects the biotic expression of T. vaporariorum negatively, while B. tabaci is able to develop equally on both host plants. These results show that the distribution differences of both whiteflies observed on both host plants could have a biological basis.     

可用于黑刺粉虱快速鉴定的SCAR分子标记技术

针对粉虱类害虫难以准确快速地进行形态鉴别的问题, 以局部发生的黑刺粉虱Aleurocanthus spiniferus (Quaintance)为对象, 采用特征序列扩增区域 (SCAR) 标记法, 研究其快速分子检测技术。利用SCAR标记技术获得了长度为987 bp的黑刺粉虱特异性片段 (GenBank登录号为FJ613323), 根据此片段的碱基序列设计黑刺粉虱特异性引物1对(AS-F518/AS-R938), 其扩增片段为421 bp。种特异性检验结果显示, 该对引物只对黑刺粉虱的基因组具有扩增能力, 对同域发生的桔绿粉虱 Dialeurodes citri (Ashmead)以及其他种类的粉虱如烟粉虱Bemisia tabaci (Gennadius) B型、Q型、ZHJ-1型和ZHJ-2型, 温室粉虱Trialeurodes vaporariorum (Westwood)以及螺旋粉虱Aleurodicus disperses (Russell)等的基因组不具有扩增效果。该引物不仅对成虫具有良好的扩增效能, 对卵、2龄若虫和拟蛹等亦具有同样的扩增能力, 其最低检出限为1/1 920头成虫。该技术体系的建立在茶树和柑桔苗木调运的害虫检疫和监测/检测中具有重要意义。     

The status ofBemisia tabaci (Hom.: Aleyrodidae),Trialeurodes vaporariorum (Hom.: Aleyrodidae) and their natural enemies in Crete

The non «B» biotype ofBemisia tabaci (Gennadius) is recorded for the first time in Crete in 1992, in the north east and south east of the island.Trialeurodes vaporariorum (Westwood) is the predominant whitefly on plants in the north and west of the island. Three surveys of Crete were made in 1992 and 1993 for natural enemies ofB. tabaci andT. vaporariorum and resulted in the collection of 4 species ofEncarsia, (plus a number of species that are unidentifiable at this time), anEretmocerus sp. (unidentifiable at this time) and a fungal pathogen,Paecilomyces farinosus (Dickson Ex Fries) Brown &; Smith.Encarsia adrianae was identified fromT. vaporariorum; which constitutes its most westerly distribution point and a new host record respectively.B. tabaci andT. vaporariorum were found on horticultural crops, ornamentals and weeds. Populations of both whitefly species were severely depleted on field hosts throughout the island during the winter of 1992/93. Climatic constraints, competition withT. vaporariorum in otherwise suitable niches, effective natural enemies and an observed low level of polyphagy may explain the present limited distribution of the non «B» biotype ofB. tabaci in Crete.     

Influences of tetracycline on the reproduction of the B biotype of Bemisia tabaci (Homoptera: Aleyrodidae)

Wolbachia are extensively harbored by Bemisia tabaci (Gennadius) populations, which could induce reproductive alteration in the whitefly. Previous studies have indicated that Wolbachia in B. tabaci could be effectively eliminated by antibiotics. In the present study, the antibiotic tetracycline was used to remove Wolbachia from the B-biotype of B. tabaci, and its influences on the reproduction and development of the whitefly were investigated by biological crossing experiments. The results indicated that antibiotic treatment could induce almost complete unidirectional cytoplasmic incompatibility in B. tabaci populations. Specifically, the offspring sex ratio from the antibiotic-treated female × untreated male crossings was significantly male-biased. Moreover, the antibiotic cure also induced a developmental delay in the offspring of the whiteflies. However, molecular detection revealed that Wolbachia was not completely eliminated from the host whiteflies by tetracycline. Our data suggested that the reduction but not elimination of Wolbachia by antibiotic treatment could definitely alter the reproductive consequences and developmental process of the whitefly B. tabaci. This is the first report of unidirectional cytoplasmic incompatibility caused by Wolbachia in B. tabaci.     

Efficacy of multiple biocontrol agents against the sweet potato whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) on tomato

Abstract: Biological control provides an environmentally harmonious and potentially stable management tactic to combat noxious pests such as Bemisia tabaci, notorious for its resistance to synthetic pesticides. Bioassays conducted under control chamber conditions integrating applications of the parasitoid Encarsia formosa, reared for 20 years on Trialeurodes vaporariorum, and the fungus Verticillium lecanii on the third‐fourth instar nymphs of B. tabaci on tomato, showed a comparable effect between the parasitoid‐fungus combined treatment and the fungus treatment alone (70.7% vs. 70.4%). Analysis of our results indicates antagonism between the two biocontrol agents related to the parasitoids’ ability to discriminate between infected and healthy B. tabaci nymphs. The parasitoid treatment alone produced 36.3% mortality, with no mortality in the distilled water controls. The behavioural performance of the parasitoid could have either genetic or environmental causes. Bioassays studying the feeding habit of the imported mirid predator Macrolophus caliginosus (adults) and the indigenous mirid Camptotylus reuteri (nymphs and adults) on eggs, or early second instar nymphs of B. tabaci, and choice preference tests indicated a significant difference in feeding between M. caliginosus and C. reuteri. There was no significant difference in percentage feeding of M. caliginosus on eggs (2.2%) or second instar nymphs (8.0%). There was a significant difference in feeding of M. caliginosus adults (18.6%) when offered eggs and second instars in the same arena compared with eggs or second instars offered separately. These results could be attributed to the biological behaviour of the predator having a type III functional response. Studies with the local C. reuteri species showed no significant difference in adult and nymphal consumption on second instars of B. tabaci compared with nymphs on eggs. However, C. reuteri adults fed less on eggs compared with nymphs. This local predatory species appears to be more efficient than M. caliginosus in feeding on particular stages of B. tabaci without depending on prey density. This is further supported by the low consumption of both adults and nymphs in the choice test (4% and 2.3%, respectively) compared with M. caliginosus adults (18.6%).