Biological aspects of Bemisia tabaci (Genn.) B biotype (Hemiptera: Aleyrodidae) on six bean genotypes

The silverleaf whitefly is one of the most harmful pests that attack bean crops, mainly for extracting large quantities of phloem sap and transmitting the bean golden mosaic virus. Resistant germoplasm plants can be an important method for controlling this pest. The biological aspects of Bemisia tabaci B biotype on bean (Phaseolus vulgaris) genotypes were evaluated. The tests were conducted under laboratory conditions, with the following genotypes: Arc 1, Arc 3s, Arc 5s, G13028, G11056 and Porrillo 70. The bean plants in a stage IV-1 were infested during one day with silverleaf whiteflies. Afterwards the eggs and nymphs were observed until adult emergence. Longevity and fecundity of emerged insects were also evaluated. The longest development time occurred for nymphs fed on Arc 3s genotype (26.5 days), following by G11056 (25.9 days) and G13028 (25.3 days). The development period was 5.5 days longer in Arc 3s when compared with Porrillo 70. Also, the wild genotypes Arc 3s and G11056 showed higher mortality rates (94.7% and 83.1%, respectively), which may suggest antibiosis and/or feeding nonpreference resistance type. For this reason, although longevity and fecundity were not influenced when the whitefly fed on resistant genotypes (Arc 3s, G11056, G13028 and Arc 5s), those genotypes can be used for bean breeding program towards B. tabaci B biotype.     

Performance of Bemisia tabaci (Genn.) Biotype B (Hemiptera: Aleyrodidae) on Weeds

Bemisia tabaci (Genn.) biotype B (Hemiptera: Aleyrodidae) is regarded as a pest with a large number of hosts, including crops and weeds. The performance of this whitefly on seven weeds was evaluated in order to identify the most suitable host. The following weeds that are very common in intense agricultural areas in the state of São Paulo, Brazil, were selected for this study: spurge (Euphorbia heterophylla), beggarticks (Bidens pilosa), red tasselflower (Emilia sonchifolia), small-flower galinsoga (Galinsoga parviflora), pigweed (Amaranthus viridis), black nightshade (Solanum americanum), and morning glory (Ipomoea sp.). In free-choice tests, adult preference and oviposition were greatest on spurge. In contrast, morning glory was the least attractive and least oviposited plant. In assays carried out for egg–adult development, egg viability was greater than 87% over all weeds, whereas nymph viability ranged from 74 to 97%. The developmental period from egg to adult ranged from 26.7 to 49.1 days among the hosts under study. The lowest nymph density rate was observed for beggarticks and morning glory. Cluster analysis resulted in a single group formed by spurge, indicating its superiority as a host for B. tabaci biotype B. Even though the parameters evaluated indicate that spurge is the most suitable host among the weeds, all the others allow the reproduction of B. tabaci biotype B. For this reason, they should be observed during cropping and the intercrop period in areas infested by this whitefly.     

Influence of trichomes on attractiveness and ovipositional preference of Bemisia tabaci (Genn.) B biotype (Hemiptera: Aleyrodidae) on tomato genotypes

Brazil is one of the world's largest tomato producer, but considerable part of the production is lost due to the attack of Bemisia tabaci (Genn.) B biotype. Resistant germoplasm plants can be an important method for B. tabaci control in integrated pest management approaches. The attractiveness and ovipositional preference of B. tabaci for 17 tomato genotypes were evaluated in a free-choice test. Trials were set up in a randomized block design with ten replicates. Each replicate (one tomato plant per pot) was placed in a cage (80 x 50 x 50 cm) and infested with 1,000 adults during four days. Linear correlation tests were applied between the number of insects and eggs and number of trichomes in each tomato genotype. LA716, LA444-1 and PI134418 genotypes were the least attractive, while the 'Santa Clara' was the most attractive; PI134417 trapped the largest number of adults. LA716 genotype (4.1 eggs/leaflet and 2.1 cm2/eggs per leaflet) was the least preferred for whitefly oviposition; NAV1062, 'Fanny', LA1335, 'Santa Clara' and IAC294 were the most preferred genotypes. The glandular trichomes density was negatively correlated with whitefly's attractiveness and oviposition per leaflet and per leaf, and positively with the number of trapped insects. The non-glandular trichomes density was negatively correlated with the number of trapped insects and positively with whitefly's oviposition per cm2/leaflet andper cm2/leaf. LA716 had high antixenosis level (ovipositional nonpreference) toward B. tabaci B biotype related with type IV glandular trichome.     

Resistance of soybean genotypes to Bemisia tabaci (Genn.) Biotype B (Hemiptera: Aleyrodidae)

The silverleaf whitefly Bemisia tabaci (Genn.) biotype B has become a serious problem for soybean cultivation because it can significantly reduce soybean productivity. The use of soybean cultivars resistant to whitefly attack is an important strategy in an integrated pest management (IPM) program. This study evaluated the preference for oviposition and colonization by B. tabaci biotype B on different soybean genotypes. In the free-choice test, the genotypes studied were 'IAC 17' and 'IAC 19' as the standards for resistance and 'IAC Holambra Stwart' as the standard for susceptibility, as well as BABR01-0492, BABR01-0173, BABR01-1259, BABR01-1576, BABR99-4021HC, BABR99-4021HP, 'Barreiras', 'Conquista', 'Corisco', 'BRS Gralha', PI274454, PI227687, and PI171451. In the no-choice test, the four best genotypes selected in the free-choice test, in addition to the susceptible and resistant standards were evaluated. Our data indicated 'Barreiras' as the most resistant genotype against B. tabaci biotype B. 'BRS Gralha', which was the least attractive to whitefly adults in the free-choice test, did not show resistance to insect attack when they were confined in cages in the no-choice test. Despite the high number of eggs observed, BABR01-1576 and BABR99-4021HC showed a reduced number of nymphs, indicating antibiosis. The genotypes with a high level of resistance can be used as a tool against B. tabaci in IPM or as a source of resistance in plant-breeding programs.     

Silicon influence on resistance induction against Bemisia tabaci biotype B (Genn.) (Hemiptera: Aleyrodidae) and on vegetative development in two soybean cultivars

The potential of populations of Bemisia tabaci (Genn.) to become resistant to insecticides has stimulated research into alternative tactics of integrated pest management such as the induction of host-plant resistance. Recent data have shown that silicon can increase the degree of resistance of host plants to insect pests. Therefore the aim of our work was to study the effects of silicon application on the vegetative development of soybean plants and on the induction of resistance to the silverleaf whitefly, B. tabaci biotype B. We performed choice and no-choice tests of oviposition preference on two soybean cultivars, IAC-19 (moderately resistant to B. tabaci biotype B) and MONSOY-8001 (susceptible), with and without application of silicon. Silicon did not affect silverleaf whitefly oviposition preferences, but caused significant mortality in nymphs. Thus, silicon increased the degree of resistance to silverleaf whitefly. Silicon decreased the production of phenolic compounds, but did not affect lignin production. However, when applied to cultivar IAC-19, it increased the production of non-protein organic nitrogen. Silicon had no effect on the vegetative development of soybean plants, but it increased the degree of resistance to the silverleaf whitefly. We conclude that silicon applications combined with cultivar IAC-19 can significantly decrease silverleaf whitefly populations, having a positive impact both on the soybean plant and on the environment.     

Records of Natural Enemies of Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) Biotype B in Brazil

Collections of natural enemies of Bemisia tabaci biotype B (Genn.) (Hemiptera: Aleyrodidae) were made in Lavras, state of Minas Gerais, Brazil. In the greenhouse, 6,495 predators and 16,628 parasitoids belonging to three families were collected. In the field, 267 predators and 344 parasitoids belonging to five families were found. For the first time in Brazil, five species of predators associated with this whitefly were reported. Because of the diversity of natural enemies of B. tabaci biotype B recorded, this study points out the importance of these data for studies on integrated pest management.     

Machine vision algorithm for whiteflies (Bemisia tabaci Genn.) scouting under greenhouse environment

One of the main problems in greenhouse crop production is the presence of pests. Detection and classification of insects are priorities in integrated pest management (IPM). This document describes a machine vision system able to detect whiteflies (Bemisia tabaci Genn.) in a greenhouse by sensing their presence using hunting traps. The extracted features corresponding to the eccentricity and area of the whiteflies projections allow to establish differences among pests and other insects on both the trap surfaces and dust generated artefacts. Because of whiteflies geometrical characteristics, it was possible to design an efficient (related to manual counting) machine vision algorithm to scout and count units of this pest within a greenhouse environment. These algorithm results show high correlation indexes for both, sticky screens (R² = 0.97) and plant leaf situations (R² = 1.0). The machine vision algorithm reduces the scouting time and the associated human error for IPM‐related activities.     

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.     

Rickettsia influences thermotolerance in the whitefly Bemisia tabaci B biotype

Abstract The whitefly Bemisia tabaci harbors Portiera aleyrodidarum, an obligatory symbiotic bacterium, as well as several secondary symbionts, including Rickettsia, Hamiltonella, Wolbachia, Arsenophonus, Cardinium and Fritschea, the function of which is unknown. In Israel, Rickettsia is found in both the B and Q of B. tabaci biotypes, and while all other secondary symbionts are located in the bacteriomes, Rickettsia can occupy most of the body cavity of the insect. We tested whether Rickettsia influences the biology of B. tabaci and found that exposing a Rickettsia‐containing population to increasing temperatures significantly increases its tolerance to heat shock that reached 40°C, compared to a Rickettsia‐free population. This increase in tolerance to heat shock was not associated with specific induction of heat‐shock protein gene expression; however, it was associated with reduction in Rickettsia numbers as was assessed by quantitative real‐time polymerase chain reaction and fluorescence in situ hybridization analyses. To assess the causes for thermotolerance when Rickettsia is reduced, we tested whether its presence is associated with the induction of genes required for thermotolerance. We found that under normal 25°C rearing temperature, genes associated with response to stress such as cytoskeleton genes are induced in the Rickettsia‐containing population. Thus, the presence of Rickettsia in B. tabaci under normal conditions induces the expression of genes required for thermotolerance that under high temperatures indirectly lead to this tolerance.     

Field evaluation of resistance to pyriproxyfen in Bemisia tabaci (B biotype)

We determined effects of aerial sprays of the insect growth regulator pyriproxyfen on sweetpotato whitefly, Bemisia tabaci (Gennadius) (B biotype), in Arizona cotton (Gossypium spp.) fields. We measured survival for males and females from a susceptible strain and a laboratory-selected resistant strain, as well as for hybrid female progeny from crosses between the strains. Insects were exposed directly to pyriproxyfen sprays in the field or indirectly in the laboratory by rearing them on sprayed leaves collected from the field. In all tests, survival was higher for the resistant strain than the susceptible strain, but did not differ between sexes in each strain. Survival to the adult stage did not differ between eggs and nymphs directly exposed to sprays. For susceptible and hybrid individuals, survival was lower on leaves collected the day of spraying than on leaves collected 2 wk after spraying. In contrast, survival of resistant individuals did not differ based on the timing of exposure. Dominance of resistance to pyriproxyfen depended on the type of exposure. Resistance was partially or completely dominant in direct exposure bioassays and on leaves collected 2 wk after spraying (h > 0.6). Resistance was partially recessive on leaves collected the day of spraying (mean h = 0.34). Rapid evolution of resistance to pyriproxyfen could occur if individuals in field populations with traits similar to those of the laboratory-selected strain examined here were treated intensively with this insecticide.     

Biology and non-preference for oviposition by Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae) on cotton cultivars

The purposes of this work were to evaluate some biological aspects of Bemisia tabaci (Gennadius) biotype B at egg and nymphal stages and to evaluate the non-preference for oviposition and its correlation with the number and type of trichomes on the cotton cultivars BRS Ipê, BRS 186-Precoce 3, BRS Acala, BRS Verde, BRS-200 Marrom, BRS Cedro, BRS Ita 90-2 and BRS Aroeira. The experiments were conducted in climatic chambers at 28 +/- 2 degrees C, 70% RH and photophase of 14h, and in greenhouse. Egg fertility was not affected by the cotton cultivars but survival in egg-adult period was influenced by the host plant. There was no influence of cultivars neither on the duration of egg stage, nymphs at 2nd, 3rd and 4th instars nor on the duration from egg to adult, but nymphs reared on the cultivar BRS Ipê had their 1st instar extended. Low number of eggs was detected on the cultivars BRS Aroeira, BRS Verde and BRS Ita 90-2 in both experiments with and without oviposition choice, indicating a possible mechanism of resistance, but no correlation could be established between trichome densisty and oviposition non-preference.     

烟粉虱B型和Q型群体遗传结构的RAPD分析

近20年来,烟粉虱B型传入世界各地并暴发成灾,成为一种重要的农业入侵害虫; 烟粉虱Q型则是近几年引起人们高度重视的一种新的入侵生物型,目前已传入许多国家并造成一定危害。本文利用RAPD分子标记对烟粉虱B型和Q型不同地理种群的遗传结构进行了分析。结果表明：（1）引物H16对烟粉虱B型不同种群扩增的特异带,能有效区分烟粉虱B型和Q型、浙江非B/Q型种群;（2）烟粉虱Q型种群各项遗传多样性指数均比烟粉虱B型的要高;（3）我国烟粉虱Q型来自伊比利亚半岛的可能性比来自中东地区的可能性要大。另外,聚类分析结果提示,RAPD分子标记能有效地区分烟粉虱不同生物型,但可能不适用于生物型之间亲缘关系分析。     

Studies on the olfaction and colour sensitivity of Bemisia tabaci (Genn.) (Homoptera, Aleyrodidae)

The whitefly, b. tabaci, is attracted by two groups of wavelengths of transmitted light, the blue/ultra-violet, and the yellow parts of the spectrum. A mixture of these components in a reflecting surface however is not attractive. A possible explanation of this is that ultraviolet radiation induces migratory behaviour, whereas yellow radiation induces vegetative behaviour. It has further been found that B. tabaci has no easily detectable olfactory reactions. In this, and in its reactions to coloured surfaces, it appears to differ from the whitefly Aleyrodes brassicae, which may explain the different host range of the two species.

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Zusammenfassung Die Mottenschildlaus, b. tabaci, wird nachweislich von zwei Wellenlängenbereichen des Spektrums angezogen: vom Blau/Ultraviolett-und vom Gelb-Anteil. Jedoch wirkt ein Gemisch dieser Komponenten auf einei reflektierenden Oberfläche nicht attraktiv. Eine mögliche Erklärung dafür ist, daß die Ultraviolett-Strahlung Ausbreitungsverhalten, die Gelb-Strahlung jedoch vegetative Antriebe hervorruft. Es wurde weiterhin festgestellt, daß B. tabaci keine leicht entdeckbaren olfaktorischen Reaktionen aufweist. Darin sowie in ihrem Verhalten zu farbigen Oberflächen scheint sie sich von der Mottenschildlaus Aleyrodes brassicae zu unterscheiden, und diese Tatsachen stehen wahrscheinlich in Beziehung zu dem verschiedenen Wirtspflanzenspektrum der beiden Arten.

     

Comparative study on biological parameters of Bemisia tabaci (Genn.) collected on four host plants from Varamin-Iran

During 2003 biological parameters of sweetpotato whitefly, B. tabaci (Genn.) (Horn. Aleyrodidae) as a major pest of field crops, vegetables and ornamentals were studied. In this study, the infested leaves of cucumber (Cucumis sativus L.) zucchini (Cucurbita pepo L.) eggplant (Solanum melongena L.) and cotton (Gossypium hirsutum L.) with whitefly nymphs and pupae were collected from Varamin-Iran, and were transferred to the laboratory. The newly emerged males and females of each population were released separately into a large cage set on cotton plants. Experiments were carried out in a growth chamber on cotton, (Varamin 76 variety) at 24+/-2 degrees C, 55+/-3% RH and 16:8 h (L: D) photoperiod. The adults of every collected population after emergency were reared in the large cages (40 x 50 x 70) containing pots of cotton plant. The preimaginal developmental time and reproductive parameters of 40 mated females were calculated for each population. The results revealed that the intrinsic rates of increase (r(m)), on cucumber, zucchini, eggplant and cotton were 0.093, 0.068, 0.085 and 0.078 respectively, gross fertility rate, were 67.92, 59.08, 76.13 and 63.14 respectively and mean generation time (T(c)) were 27.4, 27.74, 27.73 and 27.52 days respectively. Other demographic parameters such as intrinsic birth rate (b), intrinsic death rate (d), finite rate of increase (lambda), doubling time (DT), net fecundity rate, net fertility rate , gross fecundity rate, mean age gross fecundity and fertility, mean age net fecundity and fertility, mean age hatch, number of eggs/female/day and daily reproductive rate were also calculated. The results revealed that there were not significant differences between parameters of demography in different populations and the host plant has no significant influence on biological parameters.     

Characterization and distribution of esterase electromorphs in the whitefly,Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae)

Esterase profiles were examined for over 40 populations of the whitefly,Bemisia tabaci, obtained from native and cultivated plant hosts worldwide. Twelve unique electromorphs were identified from distinct populations concentrated largely in Central America, Africa, and India. One electromorph, type B, has recently been proposed as a separate species,Bemisia argentifolii, and has recently spread throughout much of the world. When considered with evidence from mating studies and the ability to induce phytotoxic disorders (squash silverleaf disorder), our data suggest that the single taxonBemisia tabaci may actually represent a species complex.     

国内烟粉虱B生物型的分布及其控制措施研究

收集了国内 15个省 2 6个不同地区的烟粉虱种群 ,根据有关报道合成了一个随即引物H16 ,对不同地区的烟粉虱DNA进行了RAPD -PCR扩增 ,根据扩增结果分析了不同烟粉虱种群的生物型。结果表明 ,在以上不同省市和地区中 ,北京、山东等 11个省 19个地区都有烟粉虱B型的分布。以烟粉虱B型为防治对象 ,比较了使用高效氯氰菊酯、高效大功臣 2种化学农药 ,和应用桨角蚜小蜂、粉虱座壳孢 2种寄生性天敌 ,对黄瓜上烟粉虱种群的控制效果 ,结果表明在一个世代内 ,喷施高效大功臣 (10 0 0× ,1次 ) ,喷施粉虱座壳孢 (5× 10 6 个孢子 /ml,2次 ) ,和释放桨角蚜小蜂 (3头雌蜂 /株 ,2次 ) ,对烟粉虱种群的控制作用分别达到 78.2 1%、95 .74 %和 5 7.5 8% ,三者都可以对烟粉虱起到较好的防治效果。     

施用噻虫嗪可降低B型烟粉虱群体的遗传多样性

用4个具有多态性的微卫星位点（BEM15、BEM25、BEM31和BT-b53）分析了施用化学农药噻虫嗪 （thiamethoxam）对B型烟粉虱Bemisia tabaci（Gennadius）群体遗传结构的影响。结果表明：噻虫嗪汰选18代的B型烟粉虱处理种群（抗性种群）抗药性上升到对照种群（敏感种群）的19.08倍,同时其微卫星位点不同等位基因频率分布发生了变化,等位基因数（N_a）平均值由2.750降到2.250,杂合度（h）平均值由0.459降到0.299（降低了34.8%）,多态信息含量（PIC）平均值由0.393降到0.250,有效等位基因数（N_e）平均值由2.051降到1.488;抗性种群与敏感种群的标准遗传距离为0.15。结果提示,化学农药的施用可能是B型烟粉虱群体遗传结构的重要影响因素之一。     

B型烟粉虱对不同蔬菜品种趋性的评价

B型烟粉虱是目前我国蔬菜作物上的主要害虫之一。为探索有效的B型烟粉虱非化学防治方法 ,作者于 2 0 0 1年 8月至 9月进行了该粉虱对 2 1个蔬菜品种趋性的田间评价。结果表明 ,B型烟粉虱最嗜好西瓜 ,对结球茴香最不敏感。在可选择的条件下 ,B型烟粉虱成虫对作物的趋性依次为西瓜 >黄瓜 ,十字花科类 ,番茄 >甜 (辣 )椒 >结球茴香     

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.     

Defense against Pieris rapae in cabbage plants induced by Bemisia tabaci biotype B

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and Pieris rapae L. (Lepidoptera: Pieridae) are serious pests of vegetables, that can occur simultaneously on a single cabbage plant [Brassica oleracea var. capitata L. (Brassicaceae)]. We determined whether pre‐feeding or infestation by B. tabaci on cabbage could induce physiological and biochemical responses of the plant against P. rapae. Developmental time, length, and weight of immature P. rapae, and defense‐related plant compounds (SOD, superoxide dismutase; POD, peroxidase; CAT, catalase; APX, ascorbate peroxidase) were measured. Development of P. rapae larvae was 21% slower on B. tabaci‐pre‐infested plants than on plants without B. tabaci infestation. When feeding on B. tabaci‐pre‐infested plants, 22% of P. rapae larvae pupated as compared with 83% on B. tabaci‐free plants. Weights of P. rapae from first to fourth instars that fed on B. tabaci‐pre‐infested plants were also reduced, whereas those of fifth instars and pupae were not. Similarly, body length of P. rapae from first to fourth instars was affected by B. tabaci pre‐infestation, whereas that of the fifth instars was not. Peroxidase and APX activities of the B. tabaci‐pre‐infested plants increased more than SOD and CAT. Peroxidase and SOD activities of B. tabaci and P. rapae co‐infested plants increased as compared with those of P. rapae‐infested plants; however, CAT and APX activities were not different between B. tabaci‐ and P. rapae‐infested plants. These results showed that B. tabaci infestation had a negative effect on P. rapae when they occurred simultaneously on the same host plant. The implications of the induced plant changes on the herbivore are discussed.