Phytoseiid predators as potential biological control agents for Bemisia tabaci

Mites of the family Phytoseiidae are known to be predators of whiteflies in several agroecosystems, especially of Bemisia tabaci Gennadius, a pest with high resistance to chemical insecticides that occurs in greenhouses in temperate regions. We collected predatory mites that were found to co-occur with whiteflies in the Middle East for control of B. tabaci: Typhlodromus athiasae (Porath and Swirski), Neoseiulus barkeri Hughes, Typhlodromips swirskii (Athias-Henriot), Euseius scutalis (Athias-Henriot), Phytoseius finitimus Ribaga. As a first step in the evaluation of these species as biological control agents, we measured their life-history traits when feeding on whiteflies. The intrinsic rates of increase (r _m) of the predatory mite species ranged between 0.131 and 0.215 per day and E. scutalis had the highest r _m estimated. Comparisons with the r _m of B. tabaci indicate that some of the species should be capable of suppressing local populations of whitefly. The ability of predators to use alternative food was also tested, since it facilitates the setup of mass cultures and it can promote their persistence in the crop, even if the prey is scarce. All predatory mite species tested were able to survive and reproduce on a diet of broad bean pollen.     

Evaluation of the pathogenicity of Aschersonia aleyrodis on Bemisia tabaci in the laboratory and greenhouse

The entomopathogenic fungus Aschersonia aleyrodis (Webber) is a promising fungal species against whiteflies. In this work, the pathogenicity of A. aleyrodis isolate Aa005 against MEAM1 Bemisia tabaci (Gennadius) was evaluated under laboratory and greenhouse conditions. The bioassay results indicated that the percentage of larval mortalities was concentration and age dependent. A. aleyrodis showed high pathogenicity against second and third instars and pupae with LC₅₀ values of 7.93?×?10⁶, 1.08?×?10⁷, and 1.56?×?10^7?conidia?mL^?1, respectively. The median lethal time (LT₅₀) was lower (4.60 days) for second instars and was the highest (6.17 days) for pupae when inoculated with a concentration of 1?×?10^7?conidia?mL^?1. Weekly sampling of immatures showed that the per cent mortality caused by A. aleyrodis at a conidial concentration of 1?×?10^7?conidia?mL^?1 was 71.21% in small nymphs, 69.31% in large nymphs and 53.36% in pupae. The dispersion index (DI) and Lloyd’s Index of Patchiness (LIP) values indicated that the infected immatures had a tendency to aggregate. The study demonstrated that A. aleyrodis isolate A005 is an effective biocontrol agent for B. tabaci control under laboratory and greenhouse conditions.     

Intraguild predation of Serangium parcesetosum (Coleoptera: Coccinellidae), on whitefly Bemisia tabaci (Homoptera: Aleyrodidae) parasitized by Eretmocerus mundus (Hymenoptera: Aphelinidae)

We studied intraguild predation of Serangium parcesetosum on Eretmocerus mundus, both natural enemies of Bemisia tabaci, on eggplant under laboratory conditions. Fourth instar and adult predators attacked parasitized and unparasitized hosts equally if immature parasitoids were larvae, but avoided predating on parasitized hosts containing pupae.     

烟盲蝽对不同虫态烟粉虱的捕食作用及捕食偏好性

杂食性昆虫烟盲蝽Nesidiocoris tenuis是烟粉虱Bemisia tabaci的重要天敌之一。为探索烟盲蝽对不同虫态烟粉虱的捕食作用及捕食偏好性,在室内进行了非选择性和选择性试验。结果表明,在非选择性试验中,烟盲蝽雌成虫、雄成虫以及5龄若虫可以捕食烟粉虱成虫和各龄若虫,但极少捕食卵。其中,烟盲蝽雌成虫、雄成虫及5龄若虫对烟粉虱1龄若虫的捕食量最大,分别为134.2头、101.3头和88.1头,其次是2~3龄若虫,捕食量分别为94.1头、64.2头和53.4头。而在选择性试验中烟盲蝽雄虫更偏好捕食烟粉虱的2~3龄若虫,其次是1龄若虫、4龄若虫和成虫。该结果对了解烟盲蝽控制烟粉虱的作用以及如何对烟盲蝽和其他天敌组合应用提供了参考信息。     

Population suppression of Bemisia tabaci (Hemiptera: Aleyrodidae) using yellow sticky traps and Eretmocerus nr. rajasthanicus (Hymenoptera: Aphelinidae) on tomato plants in greenhouses

We conducted three experiments for management of Bemisia tabaci (Gennadius) biotype ‘B’ on tomatoes under greenhouse conditions: (i) vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3‐m row; (ii) releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m² in the high whitefly density greenhouses (> 10 adults/plant), or twice at 15 adults/m² at a 5‐day interval in the low whitefly density greenhouses (< 10 adults/plant); and (iii) using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m² in high whitefly density greenhouses or twice at 15/m² at a 5‐day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m² in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m² in low whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs of B. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m² in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m² at a 5‐day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.     

Evaluation of Serangium n. sp. (Col., Coccinellidae), a predator of Bemisia tabaci (Hom., Aleyrodidae) on cassava

Abstract  The potential of a new, previously unidentified Serangium species (Col., Coccinellidae) to control the high Bemisia tabaci (Gennadius) (Hom., Aleyrodidae) populations on cassava was evaluated. Field and laboratory studies were carried out to determine the abundance and feeding capacity of this Serangium species feeding on B. tabaci on cassava. Serangium nymphs and adults were most abundant in cassava fields late in the season, rising sharply from 5 months after planting (MAP) to a peak at 7–8 MAP. Pre-imaginal development averaged 21.2 days and was longest in eggs and shortest in the L₁ instar. Mean total prey consumption of immature Serangium increased with the stage of development with the lowest consumption in the L₁ instar and highest in the L₄ instar. Mean daily consumption was lowest on the first day after hatching in the L₁ instar and rose to a peak on the 13th day after hatching in the L₄ instar. Each Serangium larva consumed a mean of over 1000 nymphs during its entire development. These results have demonstrated the potential of this Serangium species to control B. tabaci populations on cassava.     

利用植绥螨防治烟粉虱的研究进展

对目前利用植绥螨防治烟粉虱Bemisia tabaci(Gennadius)的研究现状进行综述。主要介绍植绥螨作为生防作用物的应用历史、替代食物在利用植绥螨进行生物防治中的作用,并对代表种Typhlodromips(Amblyseius)swirskiiAthias-Henriot等作为烟粉虱生防作用物的最新研究进展、产业化现状、应用前景及可能存在的问题进行了分析,以期为这些植绥螨的引进和利用提供参考。     

Macrolophus caliginosus in the biological control of Bemisia tabaci on greenhouse melons

This work presents the results of an investigation that aimed to evaluate the effectiveness of releases of the omnivorous predator Macrolophus caliginosus Wagner (Heteroptera, Miridae) in the control of Bemisia tabaci Gennadius (Homoptera, Aleyrodidae) on greenhouse melon. Two greenhouse trials were performed, one in spring and one in summer. Adults of M. caliginosus were released at two release rates (two and six per plant) in an initial infestation of 10 adult whitefly per plant. The high release rate did control the whitefly populations. Results of the lower release ratio did not work in the second trial, presumably due to excessive pruning of the crop that may have affected predator establishment. No damaged fruits were recorded. Laboratory trials were also done to examine the effects of plant and variable prey availability on predator fertility and survivorship. Results showed that low-prey availability significantly reduced survivorship and fertility of M. caliginosus, and explained why predator establishment was the same for both predator release rates.     

Distribution patterns of the Q and B biotypes of Bemisia tabaci in the Mediterranean Basin based on microsatellite variation

At least five of the biotypes described in the Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) complex are known to be present in the Mediterranean Basin area. Only two of them, however, are economically relevant, that is, biotypes B and Q. Biological and genetic differences between the two biotypes have been well studied, but less is known about their patterns of genetic variation and population structure. To address these issues, a study was undertaken based on variation at six microsatellite loci among a subset of nine B. tabaci populations (five belonging to the Q and four to the B biotype). The data obtained show that (i) these loci showed considerable polymorphism in the Q and B biotypes populations although the presence of null alleles can obscure the picture; (ii) the Iberian‐Q, Canarian‐Q, and Egyptian‐B populations exhibit heterozygosity excess as a result of bottleneck events; (iii) the low genetic differentiation between the Israeli, Iberian Peninsula, and Italian populations suggest that these populations share a common gene pool; (iv) the genetic distances between the Canarian‐Q population and the geographically close population from Morocco indicates spatial isolation and a limited gene flow; and finally (v) the microsatellite data for the B populations indicate that the whiteflies from Egypt and Israel have a close phylogenetic relationship, but the source of these biotype B invasions into the Mediterranean area remains unknown.     

Development of a biological control-based Integrated Pest Management method for Bemisia tabaci for protected sweet pepper crops

The tobacco whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is a key pest in commercial sweet pepper crops in southeast Spain. Its biological control is currently based on augmentative introductions of the parasitic wasp Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae), which need to be occasionally supplemented with pesticide applications. These pesticides can be harmful for the biological control agents. Therefore, it is important to improve the current strategy by reducing dependency on pesticides. Two potential solutions are conceivable: addition of another effective biocontrol agent or application of pesticide prior to the release of biocontrol agents. The mirid bug Nesidiocoris tenuis Reuter (Heteroptera: Miridae) and the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) are promising candidates as additional biocontrol agents. The aim of the present study was to test these possible solutions in two subsequent trials, i.e., a 'selection' and an 'improvement' experiment. In the selection experiment, four treatments were compared: E. mundus , N. tenuis  +  E. mundus , A. swirskii  +  E. mundus , and A. swirskii  +  N. tenuis  +  E. mundus . Amblyseius swirskii appeared able to significantly increase effectiveness against the pest, in contrast to N. tenuis, which did not contribute to whitefly control. The best strategy was the combination of E. mundus and A. swirskii . In the improvement experiment, three treatments were compared: E. mundus , A. swirskii  +  E. mundus , and A. swirskii  +  E. mundus +  pesticides. Amblyseius swirskii again proved capable of significantly reducing whitefly populations, and the implementation of pesticides before the release of the biocontrol agents was shown to increase the effectiveness against the pest even more.     

烟粉虱在温室内甘薯寄主上生物学特性的研究

对烟粉虱Bemisia tabaci(Gennadius)在温室内甘薯寄主上主要生物学特性的研究表明：烟粉氮成虫喜光、喜湿,晴朗高温时活动性强,但扩散飞行能力弱;多在白天交尾,多在中午产卵,具有强的惫鬃性．若虫一生脱皮3次,若虫(除一龄初期)固定生活。卵的孵化及成虫的羽化也多发生在中午。雌雄性比为1．628：1,成虫平均寿命14．25天,雌成虫平均寿命比雄成虫长6．9天,每雌平均产卵158．5粒。以两性生殖为主,也可孤雌生殖,两性生殖的产卵量及卵孵化率均高于孤雌生殖。     

Performance on different host plants of an alien and an indigenous Bemisia tabaci from China

The capacity of the Middle East‐Asia Minor 1 putative species of the whitefly Bemisia tabaci (Gennadius) species complex, commonly referred to as the ‘B biotype’, to invade has often been linked to its presumed wider host range than the indigenous competitors. To determine whether this alien putative species and the indigenous Asia II 1 whitefly putative species, commonly referred to as the ‘ZHJ2 biotype’, differ in their ability to use different host plants, we compared their development, survival and reproduction on eight crop species/cultivars that are commonly cultivated in Zhejiang, China. Of the eight host plants tested, B performed substantially better than ZHJ2 on squash, tomato and tobacco, B and ZHJ2 preformed equally well on cotton and sweet potato, while ZHJ2 performed better than B on kidney bean and pepper. These results indicate that while B generally has a wider host range than many indigenous B. tabaci, an indigenous B. tabaci can perform as well as or better on some host plants. These results combined with the cropping patterns in Zhejiang suggested that the differential capacity to use various host plants between whitefly species is important in mediating the process of invasion by an alien whitefly species.     

胡瓜钝绥螨对日光大棚茄子上烟粉虱的控制作用

为了评价胡瓜钝绥螨在我国日光大棚中对茄子上烟粉虱虱的控制作用。笔者研究了在24～34℃下胡瓜钝绥螨以烟粉为猎物时的发育历期,并在我国山东省寿光市的蔬菜基地上开展了利用胡瓜钝绥螨控制日光大棚茄子上烟粉虱的研究与应用。结果表明:胡瓜钝绥螨能够取食烟粉虱的卵、成虫、若虫及伪蛹;利用胡瓜钝绥螨能有效地控制烟粉虱成虫、卵、若虫种群数量的增长。根据胡瓜钝绥螨和烟粉虱的生物学特性,结合大棚茄子栽培过程中的环境条件,笔者提出了在日光大棚中应用胡瓜钝绥螨控制茄子上烟粉虱的策略:(1)在茄子的整个生长季节(250d)中需释放胡瓜钝绥螨4～6次,苗期每次每株释放5～10头,结果期每次每株释放20～40头;(2)释放胡瓜钝绥螨的生防区比常规化防区减少农药使用18次;(3)安装防虫网、适时释放胡瓜钝绥螨是生防成功之关键,生防区配合使用黄板效果更好。     

New insights into the mitochondrial phylogeny of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) in the Mediterranean Basin

The whitefly Bemisia tabaci is vector of plant infecting viruses and it is considered as one of the most important agricultural pests around the Mediterranean basin. At present, five biotypes of B. tabaci have been reported in the Mediterranean Basin: B, Q, S, T and M. To establish the phylogeographic relationship of these Mediterranean biotypes with others, 54 samples collected in Europe and Africa were analysed by sequencing the mitochondrial cytochrome oxidase I gene (mtCOI). The phylogeny showed that Spanish samples corresponding to the biotype S were related to the haplotype Uganda 2 of the African clade, associated with recent epidemic upsurges of cassava mosaic virus (CMD) in that country. This phylogeographic relationship gave support to a distinct subgroup revealed within the African clade. Bemisia tabaci collected from Euphorbia plants in Italy (biotype T) formed one of the three distinct subgroups existing within the Southeast/Far East Asian clade, while samples from Turkey (biotype M) clustered together with reference mitochondrial sequences from whiteflies from Pakistan and Thailand. Recent reports indicate that Bemisia populations corresponding to the biotypes S and T are distributed in areas larger than those initially delimited. Other results indicated that samples collected in Sudan grouped within the Mediterranean–North Africa clade together with reference sequences of the biotype Q corresponding to insects collected in Spain and Morocco. Mitochondrial haplotypes of B. tabaci samples collected on sweet potato in Ghana clustered with reference sequences of samples from Cameroon corresponding to one of the five Sub-Saharan subgroups already described in the African clade. These data extends the phylogenetic information of the B. tabaci species complex and present new questions to be investigated.     

我国烟粉虱主要捕食和寄生性天敌控制能力研究进展

烟粉虱Bemisia tabaci Gennadius是一种广泛分布于世界各地的多食性害虫,对我国多个省市区的农作物和观赏植物造成了严重的危害。化学杀虫剂的大量使用在杀伤天敌的同时使烟粉虱产生了不同程度的抗性,防治越来越困难;相较于化学防治,在不同地区筛选有效的天敌对烟粉虱进行生物防治是对烟粉虱进行有效控制的重要方法。我国报道的捕食性天敌共计26科109种,寄生性天敌共计2科59种。烟粉虱防治过程中由于单一的防治效果不理想,联合多个天敌资源的利用是增加对烟粉虱的生物防治效果的重要手段。本文通过对我国烟粉虱捕食性和寄生性天敌种类系统全面的整理,同时对烟粉虱优势种天敌中的单种或者多种组合利用后对烟粉虱的的控害潜能进行综述,以期为烟粉虱天敌昆虫种类的筛选和实现高效的生物防治提供科学依据。     

Evaluation of a banker plant system for biological control of Bemisia tabaci (Hemiptera: Aleyrodidae) on tomato,using two aphelinid parasitoids under field-cage conditions

ABSTRACT

This study evaluated the potential of two aphelinid parasitoids, Encarsia sophia (Girault & Dodd) and Eretmocerus hayati (Zolnerowich & Rose) to control the sweetpotato whitefly Bemisia tabaci, (Gennadius) using a banker plant system over two consecutive years. The parasitism rates of both parasitoids on a tomato (Solanum lycopersicum L.) crop were determined using melon, Cucumis melo L. (Cucurbitaceae) and castor bean, Ricinus communis L. (Euphorbiaceae), as banker plants, respectively. The emergence rates of Er. hayati and En. sophia parasitoids from parasitised whiteflies on both banker plants exceeded 90% and 85%, respectively, which is 17–20 percentage points higher than that on the pupal card under field cage conditions. Parasitism (%) on banker plants was significantly higher for both parasitoids in the third week after release as compared to adult releases in the first year, reaching 15.2?±?1.3 and 24.0?±?1.4% for En. sophia and Er. hayati, respectively. However, no significant difference in parasitism (%) was observed between banker plant and pupal card release treatments in the second year. The combined release of the two parasitoids during the second year clearly showed a continuous increase in parasitism, which was higher than parasitism in the single parasitoid-release treatments by the 4th week after release. Whitefly populations were significantly lower in all parasitoid-release treatments than in the no-release control by 4–6 weeks into the study period in the second year, while no other significant differences were observed between treatments in either year. This study found that both banker plants efficiently supported populations of both parasitoids and improved their emergence compared to the pupal card.     

Bemisia tabaci (Homoptera: Aleyrodidae) instar effects on rate of parasitism by Eretmocerus mundus and Encarsia pergandiella (Hymenoptera: Aphelinidae)

Studies were conducted to compare preference among Bemisia tabaci Gennadius, biotype B instars for parasitization by Eretmocerus mundus Mercet and Encarsia pergandiella Howard when provided one instar only, two different instars, and four different instars simultaneously. In the single‐instar no choice treatment, Er. mundus was more successful in parasitizing the younger host instars, while En. pergandiella parasitized a greater proportion of the older instars. Similar results were observed when parasitoids were provided a choice of two instars in six different pair combinations. When all four instars were provided simultaneously, the numbers of first, second, and third instars parasitized by Er. mundus were not significantly different from each other (range 10.3–16.4%), but all were significantly higher than parasitism of fourth instar nymphs (2.1%). The highest percentage parasitization by En. pergandiella was in third instar (17.2%), and the lowest in first instar (2.8%).     

Effect of host plant species of cotton whitefly Bemisia tabaci Middle East‐Asia Minor 1 (Hemiptera: Aleyrodidae) on the development,survival and reproduction of its predaceous ladybeetle Serangium japonicum (Coleoptera: Coccinellidae)

1. The ladybeetle Serangium japonicum has great potential to control the invasive pest Bemisia tabaci Gennadius Middle East‐Asia Minor 1 (MEAM1) in China. However, whether and how the host plant species of B. tabaci MEAM1 affect S. japonicum remains largely unexplored.
2. The present study investigated the influence of five host plant species of B. tabaci MEAM1, namely tobacco, cucumber, cotton, tomato and eggplant, on the pre‐imaginal development, survival of immature stages, adult weight, adult acquired rate and fecundity of S. japonicum under laboratory conditions.
3. The results obtained indicate that the developmental time from first instar to adult eclosion in S. japonicum was shortest when fed on B. tabaci MEAM1 reared on cotton and longest on cucumber. The survival rate of immature stages and the adult acquired rate were highest for cotton and tomato and lowest for tobacco. The fresh weight of adults and the number of eggs laid by S. japonicum were highest for cucumber and lowest for tobacco. The egg hatch rate was lowest for tobacco and highest for tomato.
4. These findings support suggest that host plant species should be factored into integrated pest management to maximize control efficiency when utilizing S. japonicum to control B. tabaci MEAM1.