Invasion and Displacement of Experimental Populations of a Conventional Parasitoid by a Heteronomous Hyperparasitoid

Aphelinid parasitoids have an outstanding record of success in programmes of classical biocontrol against whiteflies and scale insects. Heteronomous hyperparasitoids are aphelinids in which the sexes develop on or in different hosts. The female always develops as a primary endoparasitoid of Homoptera. The male develops as a secondary parasitoid hyperparasitoid of his own or another species of homopteran endoparasitoid. Caged experiments were performed with the cabbage whitefly, Aleyrodes proletella, to examine the invasion of a population of a conventional parasitoid, Encarsia inaron both sexes primary endoparasitoids by a heteronomous hyperparasitoid, E. tricolor. In all cages the heteronomous hyperparasitoid successfully invaded an established population of the conventional parasitoid and the conventional species population declined to very low levels within 8 weeks of the introduction of the heteronomous hyperparasitoid. The patterns of invasion were different in each cage. In two cages, high levels of male production by E. tricolor were observed, indicating that hyperparasitism of the conventional species was probably an important factor in causing the decline in the E. inaron population. In a reciprocal experiment in which E. inaron was introduced to an established population of E. tricolor the conventional species failed to invade or persist. A survey of published references to complexes of parasitoids containing a heteronomous hyperparasitoid and one or more conventional species indicated that, in the majority of cases, the heteronomous hyperparasitoid was the most important species in the complex. There are clear implications for the use of these parasitoids in programmes of classical biocontrol. This is because high competitive ability against other parasitoids is not necessarily a good indicator of the ability of a species to maintain high levels of pest control, especially when hyperparasitic behaviour is involved.     

The critical field photoperiod inducing ovarian diapause in the cabbage whitefly, Aleyrodes proletella (Homoptera: Aleyrodidae)

ABSTRACT. The ovarian and fat body development of cabbage whitefly, Aleyrodes proletella L., has been determined from field samples taken during the transition from a summer to an overwintering population. Between mid and late September 1983, the state of ovarian development decreases as the proportion of diapausing females increases. This is accompanied by maximum fat body development. Diapausing females emerge from late August onwards, and the critical photoperiod, based upon known larval sensitivity and including civil twilight as part of the photophase, is LD 15.5:8.5h. This is in agreement with laboratory studies. The majority of overwintering females are mated. Very few males survive the autumn.     

中国新记录种——忍冬粉虱Aleyrodes lonicerae Walker(半翅目:粉虱科)

在北京房山区上方山的白屈菜Chelidonium majus L.叶背上发现了一种粉虱。这是一种中国新记录种:忍冬粉虱Aleyrodes lonicerae Walker 1852。本文描述了其各期的形态特征及种类鉴别特征,并列出世界已知的11科23种寄主植物,记录了2种寄生蜂:恩蚜小蜂Encarsia sp.和桨角蚜小蜂Eretmocerus sp.nr.emiratus,并提供了粉虱及寄生蜂的生态图。     

Cabbage whiteflies colonise Brassica vegetables primarily from distant,upwind source habitats

The occurrence of species in rapidly changing environments, such as agricultural landscapes, is affected by their ability to recolonise habitats. Knowledge of the landscape scale affecting colonisation is essential for large‐scale pest management. Colonisation by insects can be affected on multiple landscape scales, as different morphs of a species may have specific dispersal abilities. The cabbage whitefly, Aleyrodes proletella (L.) (Hemiptera: Aleyrodidae), a major pest of Brassica vegetables, is known to colonise Brassica vegetables primarily from fields of oilseed rape, Brassica napus L. (Brassicaceae). We used field mapping and remote sensing to characterise the relevant scales for colonisation of Brussels sprouts by cabbage whiteflies. Surprisingly, oilseed rape fields in wide landscapes (2–8 km around study sites) explained colonisation better than oilseed rape areas in local landscapes (200–1 000 m around study sites). The explained variance increased when additional weight was given to upwind source habitats, indicating wind transport of whitefly colonisers. Low importance of local compared to wide landscape source habitats can be explained by the flight behaviour of whitefly morphs. Migratory morphs show phototactic attraction but are attracted by hosts only during the later phases of flight. Therefore, they ignore host plants close to their origin and disperse several kilometres. Trivial flight morphs rarely move more than a few hundred metres. In conclusion, as most whitefly colonisers reached Brassica vegetables from source habitats at a distance of 2–8 km, predictions on pest pressure and landscape‐scale whitefly management should consider these distances. In contrast, oilseed rape fields in the local landscape, which usually worry farmers, had little effect.     

甘蓝粉虱入侵中国大陆

甘蓝粉虱是一种危险性入侵害虫,中国大陆于2012年7月在北京市朝阳区首次发现,寄主植物为抱茎苦买菜;翌年8月份又在新疆乌鲁木齐和吐鲁番发现,寄主植物为开花生菜和抱茎苦买菜。文章描述了甘蓝粉虱的危害方式、寄主植物、分布范围、识别特征、天敌种类以及传播扩散方式,并分析了在我国大陆的发展趋势和需要密切关注的区域。     

基于种特异性COI标记的新入侵种甘蓝粉虱快速鉴定技术

【目的】针对粉虱类害虫种类多、体型微小、形态相似、难以准确快速识别的问题,以新入侵我国大陆的甘蓝粉虱 Aleyrodes proletella (L.)为靶标,以田间常见的其他10种/隐种粉虱为参照,采用基于线粒体DNA细胞色素C氧化酶亚基I (mitochondrial DNA cytochrome c oxidase subunit I, mtDNA COI) 基因的种特异性 (species-specific COI, SS-COI) PCR方法,研究其快速分子检测技术。【方法】利用mtDNA COI基因通用型引物LCO-1490/HCO-2198获得甘蓝粉虱及其他常见粉虱的COI序列,根据测序结果设计种特异性SS-COI引物1对（APZYJF/APZYJR）,其扩增片段大小为384 bp,同时对该对引物的种特异性及灵敏性进行检测。【结果】种特异性检验结果显示,该对引物仅对甘蓝粉虱的mtDNA COI基因具有扩增效果,对我国常见的其他种类的粉虱包括温室粉虱 Trialeurodes vaporariorum (Westwood)、柑橘粉虱 Dialeurodes citri (Ashmead)、螺旋粉虱 Aleurodicus disperses (Russell)、双钩巢粉虱 Paraleyrodes pseudonaranjae Martin、非洲伯粉虱 Bemisia afer (Priesner et Hosny)以及烟粉虱B. tabaci (Gennadius)5个隐种（MED, Asia I, Asia II 1, Asia II 3和China 1）等不具有交叉反应扩增能力。灵敏性检验结果显示,该对引物不仅对不同性别的成虫具有良好的扩增效能,对2-4龄若虫甚至单粒卵或单头初孵若虫亦具有同样的扩增能力,其最低检测阈值为14.00±0.37 pg/μL（相当于1/25 600头雌性成虫）。【结论】该技术体系完全可用于甘蓝粉虱的快速准确识别及检测监测,对有效阻截其进一步扩张蔓延意义重大。     

Hyperparasitism behaviour of the autoparasitoid <Emphasis Type="Italic">Encarsia tricolor</Emphasis> on two secondary host species

Hyperparasitism by virgin female Encarsia tricolor was studied by direct observation of its behaviour when contacting two secondary host species (Encarsia formosa and E. tricolor) at different host stages (first and second larval stage, third larval stage, and pupal stage). The searching and hyperparasitism behavioural sequence of E. tricolor was independent of the host stage of the whitefly (Aleyrodes proletella), and was similar to several related primary parasitoid species. In experiments with equal numbers of secondary hosts, encounter frequencies were equal for both secondary host species in all developmental stages observed. However, rates of hyperparastism were different according to host stage and host species. Hosts in the late larval stages were most preferred for hyperparasitization and the heterospecific E. formosa was more preferred as a secondary host than the conspecific, E. tricolor, in particular from the prepupal stage onwards. The window of vulnerability, i.e., the duration of the period in which a secondary host is susceptible to hyperparasitism, was largely determined by the occurrence and rate of melanization after the onset of pupation. The duration of a successful hyperparasitization event was longer than one that failed. Superparasitism occurred only once in all cases. The potential effect of autoparasitoids on biological control programs and the consequences for selection and release of an effective, yet ecologically safe agent are discussed. Handling editor: Torsten Meiners.     

Suitability of Aphis fabae, Myzus persicae (Homoptera: Aphididae) and Aleyrodes proletella (Homoptera: Aleyrodidae) as prey for Coccinella undecimpunctata (Coleoptera: Coccinellidae)

The suitability of Aphis fabae Scopoli, Myzus persicae Sulzer and Aleyrodes proletella L. as food sources for Coccinella undecimpunctata L. was evaluated by studying the impact of prey consumption on the predator’s population growth parameters and feeding parameters. Unlike A. proletella, A. fabae and M. persicae supported the development and reproduction of C. undecimpunctata. A. fabae and M. persicae were considered to be essential prey, whereas A. proletella was considered to be an alternative prey. Aphid species showed different degrees of suitability: M. persicae significantly decreased the pre-oviposition period and increased adult longevity, fecundity and fertility compared with A. fabae. Moreover, A. fabae represents a suitable diet for larval development, but is not a suitable food source for adult reproduction. The predator’s population growth parameters, R₀, r_m and λ were increased with M. persicae, whereas T decreased. We found that the 4th instar larvae were the most voracious, particularly when fed on M. persicae; nevertheless, with this prey daily weight gain and feeding efficiency of 4th instar larvae were similar to that of individuals fed with A. fabae.     

Does pirimicarb affect the voracity of the euriphagous predator, Coccinella undecimpunctata L. (Coleoptera: Coccinellidae)?

Pirimicarb is considered a selective and effective insecticide for the control of aphids and whiteflies. Coccinella undecimpunctata L. is a euriphagous predator autochthonous to the Azores, which feeds preferentially on aphids. The voracity of 4th instars and adults (males and females) of C. undecimpunctata using Aphis fabae Scopoli or Aleyrodes proletella L. as preys was evaluated in laboratory, as well as the impact of pirimicarb on the feeding performance using A. fabae as prey. In the absence of chemical treatment and when the prey was A. proletella, satiation lower limits were estimated on a density of 200 individuals in a 24-h period, for 4th instars, adult females and males of C. undecimpunctata. With A. fabae, satiation was attained when 200, 150 and 100 aphids were provided to 4th instars, adult females and males, respectively. C. undecimpunctata exhibited a type II functional response for both prey species. Fourth instars displayed a lower handling time than the adults; handling times of the adults where higher when A. fabae was the prey and attack rates were sex-dependent, that is, attack rate of females was higher on A. fabae while of males was higher on A. proletella. Voracity of C. undecimpunctata was not significantly affected by pirimicarb; therefore, the use of this insecticide can constitute a complementary component for the integrated management of A. fabae.     

The control of ovarian development during adult diapause in the cabbage whitefly, Aleyrodes proletella

ABSTRACT. Field collections of overwintering cabbage whitefly, Aleyrodes proletella L. (Homoptera: Aleyrodidae) taken during the autumn and winter of 1982/83 and 1983/84 have shown that ovarian development proceeds at a low, but near uniform rate throughout diapause. Extensive fat body is recorded during the autumn and early winter of both periods, but this gradually diminishes during February and March. There does not appear to be a true refractory phase during the dormancy. A period of chilling primes the females for accelerated ovarian development in favourable conditions. When field collected females were transferred to light: dark 16:8 h (15°C) or L:D 12:12 h (15°C) in the laboratory, the subsequent rates of ovarian development were not significantly different, suggesting that temperature is the major regulator of the activation phase, although there was some evidence to suggest that an increase in photoperiod also has a role.