Interspecific interactions between Bemisia tabaci biotype B and Trialeurodes vaporariorum (Hemiptera: Aleyrodidae)

Bemisia tabaci (Gennadius) biotype B and Trialeurodes vaporariorum (Westwood) are invasive whitefly species that often co-occur on greenhouse-grown vegetables in northern China. Although B. tabaci biotype B has been present in China for a relatively short period of time, it has become dominant over T. vaporariorum. We studied the interspecific competitive interactions between the two species in single or mixed cultures at 24 ± 1 °C, 40 ± 5% RH, and L14:D10 h photoperiod. Female longevity on tomato was not significantly different between species, but B. tabaci reproduced 4.3 to 4.9 fold more progeny. The ratio of female to male progeny in both instances was greater for B. tabaci. When cultured on tomato, cotton, and tobacco, B. tabaci developed 0.8, 3.3, and 4.7 d earlier in single culture, and 1.8, 3.9, and 4.3 d earlier in mixed culture. B. tabaci displaced T. vaporariorum in four, five and six generations when the initial ratios of B. tabaci to T. vaporariorum were 15:15, 20:10, or 10:20 on tomato. Populations of B. tabaci were 2.3 fold higher than that of T. vaporariorum on tomato plants for seven consecutive generations in single culture. B. tabaci performed better in development, survival, fecundity, and female ratio. We conclude that B. tabaci could displace T. vaporariorum in as short as four generations in a controlled greenhouse environment when they start at equal proportions. Warmer greenhouse conditions and an increase in total greenhouse area could be contributing factors in the recent dominance of B. tabaci.     

烟粉虱和温室粉虱在甘蓝上的刺探取食行为比较

利用刺吸电波图技术研究B型、ZHJ_1型烟粉虱Bemisia tabaci(Gennadius)和温室粉虱Trialeurodes vaporariorum(Westwood)在甘蓝上的取食行为,将3种粉虱的电波图进行比较,其中,B型和ZHJ_1型烟粉虱记录到np,C,pd,E1,E2,F和G波7种波形,温室粉虱只记录到刺探波形,少有取食波形。B型的20个记录中只有1个没有持续吸食波形;ZHJ_1型的25个记录中有10个记录没有持续吸食波形;温室粉虱没有持续吸食记录。甘蓝叶片韧皮部的结构或汁液的化学成分与温室粉虱的抗性密切相关。     

黑龙江地区烟粉虱和温室白粉虱发生动态

本文报道了我国高纬度地区(黑龙江哈尔滨)烟粉虱和温室白粉虱的全年发生过程。连续2年调查结果显示,粉虱在哈尔滨地区只能在温室中越冬,于来年5月大棚的第一茬蔬菜上首先发生,至7月第二茬大棚作物时才在大田有少量(低于300头/百叶)出现,在7月末的部分保护地作物上,粉虱种群密度可达到6000头/百叶;而大棚蔬菜中则以番茄和黄瓜上发生最为严重,少量大棚因此绝收;入秋后又从大田消失。结果显示,我国高纬度省份的保护地(温室和大棚)粉虱为害仍然严重,迫切需要从切断源头和迁移扩散路线进行有效防治。     

Monitoring adult Eretmocerus mundus, Encarsia lutea and Bemisia tabaci with yellow sticky traps in cotton Gossypium hirsutum

Abstract:  The efficiency of yellow sticky traps for estimating adult population dynamics of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) and its parasitoids Eretmocerus mundus Mercet, Encarsia lutea (Masi) (Hym., Aphelinidae) was examined in cotton in choice and no-choice studies in Çukurova, Turkey in 2004 and 2005. In the no-choice study, traps were suspended individually on the third, fifth or eighth main stem node branches from the tops of cotton plants. For the choice study, three traps were suspended on the same individual node branches on different plants. Trap captures were counted weekly. Mean (±SE) numbers of B. tabaci captured on traps were higher in no-choice (max.: 697.8 ± 55.6) compared with choice (max.: 533.3 ± 47.4) studies each year. Population fluctuation patterns of E. mundus and E. lutea adults were similar to those of adult B. tabaci on traps with low weekly mean numbers occurring initially and increasing to peak levels in mid-August, then decreasing in later weeks of the studies. The relationship between weekly mean numbers of B. tabaci and E. lutea was greater than the relationship between B. tabaci and E. mundus . Mean numbers of E. mundus and E. lutea on traps were higher at the third main stem nodes than traps suspended on the fifth or eighth node. Mean numbers of E. lutea pupae were usually higher than E. mundus from the first sampling date throughout the end of the growing season on leaves. The relationship between parasitoid pupae and adults captured in traps is discussed.     

B型烟粉虱不同寄主种群伪蛹形态的可塑性比较

烟粉虱Bemisia tabaci(Gennadius)是一种包含多个生物型的复合种,其中B型烟粉虱是一个入侵能力较强的生物型。对在不同寄主植物上B型烟粉虱入侵种群伪蛹形态系统量化研究结果表明:B型烟粉虱伪蛹蛹壳规则比例、蛹壳背部大刚毛数量、蛹壳整体的长度和宽度、前缘蜡饰的宽度、后缘蜡饰的宽度、皿形孔盖瓣的长度和宽度以及舌状突的长度等许多性状在不同寄主植物上具有不同程度的形态可塑性,而且这种可塑性与寄主植物叶背特征具有密切的相关性。最后,探讨B型烟粉虱伪蛹形态可塑性在该害虫成功入侵过程中的作用以及研究意义。     

B型与浙江非B型烟粉虱药剂敏感性的比较

比较了新入侵我国的B型烟粉虱Bemisiatabaci(Gennadius)与非B型烟粉虱ZHJ-1种群对5%吡虫啉乳油和5%吡丙醚乳油2种杀虫剂的敏感性。ZHJ-1种群卵、若虫和成虫对这2种药剂的敏感性均比B型的明显或显著要高。吡丙醚具有高杀卵活性,在有效成分为0.25mg/L时,2个烟粉虱种群卵的死亡率高于90%。药剂敏感性的差异可能是B型竞争取代本地非B型烟粉虱的一个重要原因。     

Inheritance of pyriproxyfen resistance in the whitefly, Bemisia tabaci (Q biotype)

The inheritance of resistance to pyriproxyfen, an insect growth regulator (a juvenoid, with ovicidal and larvicidal activities), was studied in the whitefly Bemisia tabaci (Gennadius). Two parental strains, both belonging to Q biotype, were assayed with pyriproxyfen; a susceptible strain (ALM-1) originating from Spain and a pyriproxyfen-resistant one (Pyri-R) from Israel. The resistance ratio between the two parental strains was approximately 7,000-fold. Concentration-mortality lines for F(1) heterozygous females from reciprocal crosses (SS female symbol X R male symbol and RR female symbol X S male symbol ) were derived by statistical modelling and proved intermediate to those of the parents. The pooled degree of dominance from both reciprocal crosses was +0.26, indicating that resistance was incompletely or partially dominant. Mortality curves for F(2) males produced by virgin F(1) heterozygous females displayed a broad plateau at 50% mortality, indicating that resistance to pyriproxyfen in B. tabaci is conferred primarily by a mutant allele at a single locus. The role of arrhenotoky in influencing the mode of inheritance of resistance, and its selection in field populations, is discussed.     

The effect of varying Bemisia argentifolii and Eretmocerus mundus ratios on parasitism

We investigated the effects of different host: parasitoid ratios on the efficacy of the parasitoid Eretmocerus mundus attacking the silverleaf whitefly, Bemisia argentifolii. When host density was held constant (100 second instars) and parasitoid density was decreased from 15 to 1 females, the percentage of total host mortality was significantly lower at low parasitoid densities. The number of host nymphs killed, and the number of female parasitoid progeny per female, increased 3.6 and 20.4 times, respectively. The emergence rate, sex ratio, longevity, and body lengths of progeny were significantly larger at the lowest parasitoid density while developmental time was significantly shorter. When the number of hosts was increased from 5 to 250 and parasitoid density was held constant (5 females), the percentage of nymphal mortality decreased 1.6 times. The percentage of desiccated nymphs was significantly highest (65.7%) at the lowest host density, while percentage parasitism (34.3%) was significantly lowest at the lowest host density. The data could be described using a Type I functional response curve. We propose a generalized index of efficacy (GIE) to summarize and compare the total effects of parasitoid--host ratios. This index showed that the most efficient ratio was one parasitoid female per ten second instar host nymphs.     

The parasitoids of the aleyrodid Bemisia tabaci in Israel: development, host preference and discrimination of the aphelinid wasp Eretmocerus mundus

Developmental history and behavior of Eretmocerus mundus Mercet, a parasitoid of Bemisia tabaci was studied at 25°C. The eggs may be laid under all four nymphal instars but not under the pupa. Yet the second and third instars are preferred. The egg hatches only under the fourth instar or the pupa. Developmental medians at 25°C are: Instar I-2.5, II-4, II-4, prepupa-2 and pupa 8 days. When ovipositing, the female stands at an angle of 90° to the host, with wings raised and inserts the ovipositor under the whitefly nymph. The egg is laid close to the insertion point of the whitefly's proboscis into the leaf. After oviposition, the female apparently marks the host while drumming on it with her hind legs. She distinguishes already parasitized hosts from unparasitized ones and refrains from laying under the former. Discrimination is accomplished after antennal drumming only.

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Les parasitoïdes de Bemisia tabaci (aleyrodidae) en Israel: développement, ponte et sélection des hôtes ches Eretmocerus mundus (aphelinidae)

Résumé Le développment et le comportement de E. mundus, parasitoïde de B. tabaci, ont été étudiés à 25°C. Les oeufs sont pondus sous les quatre stades larvaires (les deuxième et troizième sont préférés) mais pas sous les nymphes. Les oeufs n'éclosent que sous les larves du quatrième stade ou les nymphes. Les temps de développement médiaux sont à 25°, les suivants: stade I: 2,5j; stade II: 4j; stade III: 4j et nymphe 8j. Pendant la ponte, la femelle est à 90° sur son hôte, les ailes dressées, et insère sa tarière sous la larve d'aleurode. L'oeuf est déposé près du point d'insertion de la trompe dans la feuille. Après l'émission, la femelle marque apparemment son hôte pendant qu'elle tambourine avec ses pattes postérieures. Elle distingue les hôtes parasités ou non, et limite sa ponte dans les premiers. La sélection est effectuée seulement après tambourinage antennaire.

     

New records of entomopathogenic fungi infecting Bemisia tabaci and Trialeurodes vaporariorum, pests of horticultural crops, in Argentina

The whiteflies Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are major crop pests throughout the world. Although extensive research about biological control of whitefly by parasitoids and predators has been conducted, also entomopathogenic fungi can be considered as potential biological control agents. Surveys for entomopathogenic fungi were carried out in organic and conventional horticultural crops in greenhouses and open fields in Buenos Aires and Corrientes provinces, Argentina. These surveys resulted in the recovery and isolation of the following fungi from whiteflies: Lecanicillium lecanii (Zimmerm.) Zare & W. Gams, L. muscarium (Petch) Zare & W. Gams, L. longisporum (Petch) Zare & W. Gams, Isaria fumosorosea Wize and I. javanica (Frieder. & Bally) Samson & Hywel-Jones. Pathogenicity tests were conducted against T. vaporariorum nymphs using a conidial suspension (1 × 10⁷ conidia/ml) of the fungi. A mortality rate between 26.6% and 76.6% was obtained at 7 days post-infection. These are the first records of natural infections in the southernmost region of the South American continent of L. lecanii, L. muscarium, L. longisporum and Isaria javanica (Ascomycota: Hypocreales) on T. vaporariorum and also the first report of I. fumosorosea on B. tabaci.     

微卫星位点在Q型烟粉虱入侵种群中的多态性分析

近年来烟粉虱Bemisia tabaci(Gennadius)Q型入侵我国并在部分地区取代B型成为了烟粉虱优势生物型。外来物种的入侵过程及农药使用等因素可影响种群的遗传多样性水平及其遗传结构。本研究分析了4个微卫星位点在Q型烟粉虱入侵种群的多态信息含量(PIC),并在此基础上进行了遗传多样性分析。结果表明这些微卫星位点在Q型烟粉虱入侵种群中具有中度或高度多态性,说明微卫星位点能有效分析Q型入侵种群的遗传多态性。本研究为利用微卫星标记研究Q型入侵种群的遗传结构奠定了基础。     

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。     

Adult Bemisia tabaci biotype B can induce silverleafing in squash

Bemisia tabaci biotype B is one of three genetic groups able to induce silverleafing in squash. Several earlier studies had observed that this physiological change was induced only through the feeding of juvenile whiteflies. This study uses adult males only to show that after 11 days the adult males were able to begin to induce silverleafing. Further, the response was density-dependent with 120 adults inducing the first signs of silverleafing in 11 days, 90 adults in 13 days and 60 adults in 15 days.     

Predatory effect of Coccinella septempunctata on Thrips tabaci and Trialeurodes vaporariorum

Abstract:  The predatory effect of adult ladybird Coccinella septempunctata L. on adults of thrips, Thrips tabaci Lindeman, and whiteflies, Trialeurodes vaporariorum (Westwood), was examined in controlled environment chambers, on tomato leaves, in transparent small plastic cages at proportions of 1/(10 + 10), 1/(20 + 20), 1/(30 + 30) and 1/(40 + 40) predator/number of thrips and whiteflies. We conclude that C. septempunctata could be used with success for the biological control of thrips and whiteflies in greenhouse crops, with almost the same effectiveness as for aphids, at predator/prey proportions near 1 : 30. Additionally, it was found a prey preference for T. tabaci in comparison with T. vaporariorum . According to the model used, effective predation is correlated with predator/prey ratio rather than to prey preference.     

Variation between laboratory populations in the performance of the parasitoid Encarsia formosa on two host species, Bemisia tabaci and Trialeurodes vaporariorum

We tested the hypothesis that populations of the parthenogenetic parasitic wasp Encarsia formosa Gahan (Hymenoptera: Aphelinidae) differed in their ability to use two different host species, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae). Of the three wasp populations tested, two populations had been reared for many generations on B. tabaci and one population had been reared for many years on T. vaporariorum. Performance was measured by the number of whitefly nymphs that were successfully parasitized by individual wasps, and performance on either host was measured in separate experiments. There was variation between wasp populations in their performance on the host B. tabaci, with one wasp population reared for many years on this host performing considerably better than the other two populations. There were no significant differences between populations in their use of the preferred host, T. vaporariorum. The experiments were conducted in such a way that we could distinguish heritable differences between populations from environmentally-induced conditioning differences due to the immediate host from which an individual wasp enclosed. In either experiment there were no significant effects of conditioning, although there was a trend within each population for wasps conditioned on T. vaporariorum to have higher performance than those conditioned on B. tabaci. Thirdly, we conducted a selection experiment, initiated with wasps from a single population historically reared on T. vaporariorum, to measure the effect of laboratory rearing on different hosts for 17 generations. We did not see any difference in the performance of wasps on B. tabaci after this period of rearing on either of the two hosts. In summary, populations of E. formosa do differ in their relative performance on B. tabaci. The one population that was tested further did not show any response to selection by rearing, but the ability to respond to selection on performance may not be equal for all populations. The possibility that wasp populations have differential performance on particular hosts may affect the use of this species as a biological control agent.     

Ultrastructure of the endosymbionts of the whitefly,Bemisia tabaci andTrialeurodes vaporariorum

Summary The ultrastructure of the mycetocytes and mycetome micro-organisms of the sweetpotato whitefly,Bemisia tabaci Genn. andTrialeurodes vaporariorum West are described. InB. tabaci, two morphologically distinct types of micro-organisms were observed in mycetocytes. The predominant type lacked a distinct cell wall, was pleomorphic in shape with a surrounding vacuole. The second type was a coccoid organism, with inner and outer cell membranes. The coccoid organism was often found in groups of varying number within vacuoles, and in many cases appeared to be undergoing degradation. InT. vaporariorum mycetocytes, pleomorphic and coccoid organisms were found, although the coccoid micro-organism inT. vaporariorum, had a thicker cell wall than the coccoid micro-organism inB. tabaci.Abbreviations C coccoid micro-organism - P pleomorphic micro-organism     

Identification of the molting hormone of the sweet potato (Bemisia tabaci) and greenhouse (Trialeurodes vaporariorum) whitefly

In order to identify the whitefly molting hormone, whole body extracts of mature 4th instar and newly formed pharate adult Bemisia tabaci (Biotype B) and Trialeurodes vaporariorum were prepared and subjected to reverse phase high performance liquid chromatography (RPHPLC). Ecdysteroid content of fractions was determined by enzymeimmunoassay (EIA). The only detectable ecdysteroids that were present in significant amounts in whitefly extracts were ecdysone and 20-hydroxyecdysone. The concentrations of 20-hydroxyecdysone in B. tabaci and T. vaporariorum extracts, respectively, were 40 and 15 times greater than the concentrations of ecdysone. The identity of the two ecdysteroids was confirmed by normal phase high performance liquid chromatography (NPHPLC). When ecdysteroid content of RPHPLC fractions was assayed by radioimmunoassay (RIA), small amounts of polar ecdysteroids were also detected indicating that these ecdysteroids have a very low affinity for the antiserum used in the EIA. Ecdysteroid at 10.4 mM administered by feeding stimulated 2nd instar whitefly nymphs to molt. Based on our results, it appears that 20-hydroxyecdysone is the whitefly molting hormone.     

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.     

寄主转换对B型烟粉虱生长发育和繁殖的影响

在实验室恒温条件下,对B型烟粉虱Bemisiatabaci(Gennadius)寄主转换后的生长发育和繁殖进行初步研究。结果表明:B型烟粉虱从番茄转移到国抗22棉花上后,第1代转寄主烟粉虱的发育历期比第2代长19.2%,存活率低16.4%,第2代和第3代之间没有明显差异。受体寄主对B型烟粉虱发育速率的恢复有一定的影响。