Intraguild predation involving Harmonia axyridis: a review of current knowledge and future perspectives

As an effective generalist predator of aphids and other hemipteran pests H. axyridis has been a successful biological control agent. However, the very functional traits that have contributed to its success in this regard also implicate it as an intraguild predator that poses a significant risk not only to the diversity of other natural enemies of Hemiptera (and their associated ecosystem services), but to biodiversity more widely. In this paper we will specifically review the existing data on intraguild predation involving H. axyridis, and consider the strength and symmetry of such interactions both within its native guild and within exotic guilds where it has established as an invasive alien. We will use these studies to interpret the observed population declines in predator diversity in the field, predict species at risk in regions not yet invaded and consider implications for resulting ecosystem services. We will also indicate gaps in our knowledge that require further study in order to identify opportunities for mitigation.     

Ladybird population dynamics in potato: comparison of native species with an invasive species, Harmonia axyridis

Following the detection of the harlequin ladybird, Harmonia axyridis, in 2003 in potato crops in Belgium, a study was carried out between 2004 and 2006 on the phenology of this species compared to native species in potato. The results confirmed the success of H. axyridis, with high population levels in 2004 and 2005. In 2006, aphid populations were very low and no H. axyridis larvae were sampled in potato, but the indigenous species Coccinella septempunctata and Propylea quatuordecimpunctata were detected. A species by species comparison of the date of first larvae detection, the larvae population peak, and the difference between this peak and the aphid population peak was performed. Results showed a clear correlation between C. septempunctata and P. quatuordecimpunctata and potato aphids, with a delay of 3.5 and 6.5 days between the aphid and ladybird population peaks for the two native species. H. axyridis arrived 7–8 days after the two indigenous species and the larval peak population occurred 15.8 days after the aphid population peak. This meant that H. axyridis had to complete its larval development with very low aphid populations or even with no aphids at all. The reason for its late arrival and the possible food resources used by H. axyridis larvae are discussed.     

The mortality and fat content of Adalia bipunctata during hibernation

Coccinellids were sampled at intervals from natural hibernation sites, to determine mortality in relation to fat content. The fat content was reduced by 65%, while fresh weight remained constant. A 36% mortality occurred in early spring, which was independent of the fat content and attributable to fungal pathogens.

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Résumé Des échantillons de coccinelles ont été récoltés à plusieurs reprises au cours de l'hiver, dans leurs lieux naturels d'hibernation, pour déterminer la mortalité en fonction de l'épuisement des réserves en graisse.Le poids frais reste constant pendant l'hibernation, tandis que la teneur en graisse baisse de 65% par un taux moyen de 0,01 mg par jour. On constate que la teneur en graisse dépend du poids sec et de la taille de la coccinelle. Une mortalité de 36% se produit au début du printemps, indépendemment de la teneur en graisse, par suite de l'action de champignons pathogènes.

     

Overwintering, phenology and fecundity of Harmonia axyridis in comparison with native coccinellid species in Italy

Classical biological control is generallyunderstood as an environmentally safe practiceof insect pest management. However, questionshave been raised about possible negativeeffects for native species. As part of a riskassessment study a semi-field trial was carriedout in northern Italy in order to compare theoverwintering of the native species Propylea quatuordecimpunctata (L.) and Adalia bipunctata (L.) (Coleoptera:Coccinellidae) with the exotic Harmoniaaxyridis (Pallas) (Coleoptera: Coccinellidae).All the experiments were carried out from April1998 to April 2001. Harmonia axyridis wasable to overwinter successfully in northernItaly. Fecundity, oviposition rate, longevityand rate of increase of overwintering femaleswere calculated and the phenology of the threespecies was studied. Harmonia axyridisoverwintering mortality (31.9%) was lower incomparison with mortality of native species(68.9% for P. quatuordecimpunctata and61.3% for A. bipunctata). As aconsequence, post-overwintering rate ofincrease of the exotic species was higher.Longevity of overwintered females was similaramong the species. Mean fecundity of H. axyridis (783.8 eggs per female) was slightlyhigher than A. bipunctata (720.2 eggs perfemale), and much higher than P. quatuordecimpunctata (193.7 eggs per female). H. axyridis and A. bipunctatacompleted four generations and P. quatuordecimpunctata three generations in a year. The results show that H. axyridisappears to posses a high potential for establishment in Italy.     

Interactions between the fungal pathogen Beauveria bassiana and three species of coccinellid: Harmonia axyridis, Coccinella septempunctata and Adalia bipunctata

Harmonia axyridis is a predatory coccinellid, native to central and eastern Asia. It has been available in many countries for use as a biological control agent of pest aphids and scale insects. In many of these countries, including the USA, H. axyridis has established. It is now considered an invasive alien species for a number of reasons, including its impact on functional biodiversity. Beauveria bassiana is known to be a natural mortality agent of overwintering coccinellids and is a potential candidate for the biological control of H. axyridis. In this paper we compare the susceptibility of three species of coccinellid, H. axyridis (cultures derived from Japan and UK), Coccinella septempunctata and Adalia bipunctata to infection by B. bassiana (commercial strain GHA) after exposure at three doses (10⁵, 10⁷, 10⁹ conidia ml⁻¹). The two subpopulations of H. axyridis (Japan and UK) were more resistant to B. bassiana infection than either A. bipunctata or C. septempunctata. This is exemplified by the median lethal doses at 10 days post-inoculation (LD₅₀) of 10^6.2, 10^6.0, 10^8.3, 10^9.6 conidia ml⁻¹ for A. bipunctata, C. septempunctata, H. axyridis (Japan) and H. axyridis (UK), respectively. Only doses of 10⁹ conidia ml⁻¹ resulted in mortality of H. axyridis, in contrast, 80% of C. septempunctata and 70% of A. bipunctata exposed to 10⁷ conidia ml⁻¹ of B. bassiana succumbed to infection. The fecundity (cumulative mean egg production over 10 days) of A. bipunctata and H. axyridis (UK) was also assessed. The fecundity of C. septempunctata could not be assessed because this species requires diapause prior to the onset of reproduction and these studies were on beetles that had recently eclosed (2–8 weeks). Harmonia axyridis (Japan) produced no eggs in most treatments including the control and so was excluded from analysis. High dose (10⁹ conidia ml⁻¹) inoculation reduced the fecundity of A. bipunctata to zero but egg production was similar for individuals inoculated with doses of 10⁵, 10⁷ conidia ml⁻¹ and control individuals. In contrast, all doses of B. basssiana reduced H. axyridis (UK) egg production dramatically. We discuss these results in relation to the potential for control of H. axyridis using B. bassiana.     

Expansion of the geographical distribution of an exotic ladybird beetle, Adalia bipunctata (Coleoptera: Coccinellidae), and its interspecific relationships with native ladybird beetles in Japan

The first record of the exotic ladybird beetle, Adalia bipunctata (Coleoptera; Coccinellidae), in Japan was in 1993 at Osaka Nanko Central Park. Since that time, studies on the life history and geographical distribution of A. bipunctata have been ongoing, and its establishment in the Osaka Nanko area has been confirmed. A. bipunctata is a predacious ladybird beetle and a member of a guild that overlaps in habitat and prey with that of native ladybird beetles such as Harmonia axyridis and Menochilas sexmaculatus. We investigated the distribution of A. bipunctata and its interspecific relationships with native predacious ladybird beetles. In some areas, A. bipunctata was dominant in interspecific relationships with native ladybird beetles. For the first 10 years after A. bipunctata was discovered, it occurred only in the Osaka Nanko area, but the present geographical distribution indicates that it has expanded its range. Though the population density of this species was highest at the area recorded first, and tended to decrease in inverse proportion to the distance from Osaka Nanko Central Park, a satellite occurrence was observed in a remote area. The numbers of aphid and tree species (leaf shelter for aestivation and over-wintering) utilized by A. bipunctata have recently increased. Such increases will cause the rate of distribution of A. bipunctata to accelerate. Interspecific competition between H. axyridis and A. bipunctata, which occurs earlier than H. axyridis, may be avoided by desynchronization of the occurrence seasons, and another common predacious ladybird beetle, Coccinella septempunctata, may escape interspecific competition by habitat segregation.     

Chemical protection of Calvia quatuordecimguttata eggs against intraguild predation by the invasive ladybird Harmonia axyridis

Intraspecific and interspecific predation of eggs is a well documented phenomenon amongst aphidophagous coccinellids. The invasive species Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is known to be a top intraguild predator and reported to attack the eggs of many coccinellid species both in a laboratory setting and in the wild. A previous laboratory study highlighted that while many species’ eggs were highly palatable to H. axyridis, the eggs of Calvia quatuordecimguttata (Linnaeus) (Coleoptera: Coccinellidae) appeared to be extremely well protected from attack. Here we present the results of behavioural experiments testing the hypothesis that substances on the egg surface are responsible for this protection, and report preliminary results of GC-MS analysis of these compounds. When the coatings of C. quatuordecimguttata eggs were removed using hexane, they became significantly more susceptible to predation by neonate H. axyridis larvae. However, their overall palatability was not affected, in that complete consumption was never or rarely observed. This suggests that the surface compounds are a true indicator of unpalatability in this species. The effect of hexane-washing on already palatable conspecific eggs was also analysed but had no significant effect on the susceptibility of eggs to cannibalism. We conclude that the eggs of at least one European species are effectively protected by surface deterrents from intraguild predation by H. axyridis. This effect might be due to both the diversity and abundance of hydrocarbons present within the egg coating, the presence of alkenes and/or the presence of patches of a red substance on the eggs’ surface, which is thought to belong to the acid group. In conjunction with data on the susceptibility of other immature stages of C. quatuordecimguttata, this finding may indicate a decreased risk of the species falling victim to invasive H. axyridis, despite their coincident habitat ranges.     

Intraguild predation of immature stages of British and Japanese coccinellids by the invasive ladybird Harmonia axyridis

Declines in native aphidophages in North America have been linked to intraguild predation (IGP) by the invasive coccinellid Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). It is feared that many British species will face a similar fate following the recent establishment of H. axyridis in the UK. Meanwhile, H. axyridis exists in apparent ecological equilibrium with other members of its guild in Japan. The impact of H. axyridis on British coccinellids is uncertain but intraguild predatory interactions do occur, particularly amongst immature stages. This study investigates IGP between immature stages of H. axyridis and various British and Japanese coccinellids. The only asymmetric IG predator of H. axyridis at first instar was Anatis ocellata (Linnaeus). Harmonia axyridis engaged in symmetric IGP with Coccinella septempunctata Linnaeus, Calvia quatuordecimguttata (Linnaeus), Harmonia quadripunctata (Pontoppidan) and Eocaria muiri Timberlake, but was the asymmetric IG predator of all other species studied. The level of IGP was high between fourth instar larvae, and frequently biased towards H. axyridis, except in the case of A. ocellata, which again was the only IG predator of H. axyridis. In interactions between fourth instar larvae and pre-pupae, IGP was unidirectional towards H. axyridis for all species except A. ocellata, which acted as both IG predator and IG prey. Pupae were better protected against IGP than pre-pupae but most species were still susceptible to attack by H. axyridis, although IGP was symmetric with A. ocellata, and H. quadripunctata pupae were never attacked. The differences in susceptibility of the various species and developmental stages to IGP by H. axyridis are discussed in relation to physical defence structures. We find no evidence that Japanese species have superior defences to British ones and suggest that behavioural strategies may enable co-existence in the native range. We discuss the relevance of IGP by H. axyridis to the species it is likely to encounter in Britain.     

The inheritance of a wingless character in the 2spot ladybird (Adalia bipunctata)

A viable wingless 2spot ladybirdAdalia bipunctata (L.) was found in the wild. Breeding through four generations revealed that the wingless trait was controlled by a recessive allele which displays variable levels of expression. The wingless ladybird is discussed in relation to its potential as a biocontrol agent. One ladybird also occurred in this stock which is suggestive of a supergene controlling the colour polymorphism in this species.     

Intraguild responses of aphid predators on apple to the invasion of an exotic species, Harmonia axyridis

The effects of the invasion ofan exotic predator, Harmonia axyridis(Pallas) (Coleoptera: Coccinellidae), wereinvestigated using three experiments on theecology of aphid predators on apple. Oneexperiment, 1992, was collected prior to theH. axyridis invasion, and two others,1996 to 1997 and 1999 to 2000, were collectedafter the invasion. Except for one year, 1999,H. axyridis was the dominant coccinellid,replacing the formerly dominant Coccinellaseptempunctata L. (Coleoptera: Coccinellidae),another exotic species. The dominance of H. axyridis was greater among larvae thanamong adults. There was no apparent effect ofthe H. axyridis invasion on abundance ofthe predator, Aphidoletes aphidimyza(Rondani) (Diptera: Cecidomyiidae) and apossible positive effect on the abundance ofchrysopids (Neuroptera: Chrysopidae). Principal component analysis indicated thatalthough individual species were affected, theoverall effect of H. axyridis invasion onthe predator guild as a whole was negligible. The data indicate that the interaction betweenthe two exotic species, H. axyridis andC. septempunctata, may be allowing nativecoccinellids to become more abundant on applethan when C. septempunctata was thedominant coccinellid.     

Mechanisms of prey finding in the aphidophagous ladybird beetle,Harmonia axyridis [Coleoptera: Coccinellidae]

The mechanism of prey finding in adultHarmonia axyridis was investigated by presenting beetles with small gauze or polyethylene bags containing either aphidinfested leaves or healthy leaves alone together with empty control bags. Beetles were attracted to bags by olfactory and visual cues suggesting the presence of aphids, including the odor of aphid-infested leaves, the odor of aphids, the odor of healthy leaves, and the sight of leaves. Particularly effective in prolonging beetles's stay on bags visited was the odor of aphid-infested leaves. It is suggested that adults ofH. axyridis use olfactory and visual cues to detect prey before actual contact occurs. Use of such cues seems more advantageous than random searching, as has been reported in many previous studies of coccinellid foraging.

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Résumé Le mécanisme de découverte de la proie chez l'adulte d'Harmonia axyridis est étudié en donnant aux Coccinelles de petits sacs en gaze ou en polyéthylène contenant soit des feuilles infestées de pucerons, soit des feuilles saines seules, avec des sacs vides comme témoins. Les coccinelles sont attirées vers les sacs par des indicateurs olfactifs ou visuels suggérant la présence de pucerons, incluant l'odeur des feuilles infestées de pucerons, l'odeur des pucerons, l'odeur des feuilles saines et la vue des feuilles. L'odeur des feuilles infestées de pucerons est particulièrement efficace en prolongeant le séjour des Coccinelles sur le sac visité. Il est suggéré que les adultes d'H. axyridis utilisent des indicateurs olfactifs et visuels pour détecter leur proie avant que s'établisse le véritable contact. L'emploi de tels indicateurs semble plus avantageux que la recherche au hasard, comme cela a été indiqué dans de nombreuses études antérieures sur la quête alimentaire des Coccinelles.

     

Effects of competition,cannibalism and intra‐guild predation on larval development of the European coccinellid Adalia bipunctata and the invasive species Harmonia axyridis

Abstract 1. Resource competition and intra‐guild predation (IGP) are important determinants of the structure of aphidophagous guilds. The likelihood and outcome of IGP is influenced by the density of extra‐guild prey and the characteristics of the species involved. 2. The nature of intra‐guild interactions between alien and indigenous coccinellids often determines the success of coccinellid invasions, as exemplified by Adalia bipunctata in Japan and Harmonia axyridis in North America and Europe. 3. Harmonia axyridis has negatively impinged on indigenous species in its introduced range, and its recent arrival in Britain poses a threat for members of native aphidophagous guilds. IGP and inter‐specific competition between H. axyridis and British coccinellids are predicted to occur. However, the results of such interactions have been little studied. 4. Here we investigate the effects of different diets, designed to mimic possible conditions in the wild, on the survival, development, and adult size of H. axyridis and A. bipunctata. Results demonstrate a skew in the consequences of IGP between the two species: the supplementation of a limited aphid diet with non‐conspecific eggs leads to a significant advantage for H. axyridis in respect of all parameters assessed, but gives no benefit to A. bipunctata. 5. We conclude that IGP of A. bipunctata by H. axyridis will contribute to the spread and increase of H. axyridis in Britain. 6. We further conclude that the skewed nature of IGP between A. bipunctata and H. axyridis at least in part explains the limited spread of A. bipunctata in Japan.     

Phenotypic variation in invasive and biocontrol populations of the harlequin ladybird, Harmonia axyridis

Despite numerous releases for biological control purposes during more than 20 years in Europe, Harmonia axyridis failed to become established until the beginning of the 21st century. Its status as invasive alien species is now widely recognised. Theory suggests that invasive populations should evolve toward greater phenotypic plasticity because they encounter differing environments during the invasion process. On the contrary, populations used for biological control have been maintained under artificial rearing conditions for many generations; they are hence expected to become specialised on a narrow range of environments and show lower phenotypic plasticity. Here we compared phenotypic traits and the extent of adaptive phenotypic plasticity in two invasive populations and two populations commercialized for biological control by (i) measuring six phenotypic traits related to fitness (eggs hatching rate, larval survival rate, development time, sex ratio, fecundity over 6 weeks and survival time of starving adults) at three temperatures (18, 24 and 30°C), (ii) recording the survival rate and quiescence aggregation behaviour when exposed to low temperatures (5, 10 and 15°C), and (iii) studying the cannibalistic behaviour of populations in the absence of food. Invasive and biocontrol populations displayed significantly different responses to temperature variation for a composite fitness index computed from the traits measured at 18, 24 and 30°C, but not for any of those traits considered independently. The plasticity measured on the same fitness index was higher in the two invasive populations, but this difference was not statistically significant. On the other hand, invasive populations displayed significantly higher survival and higher phenotypic plasticity when entering into quiescence at low temperatures. In addition, one invasive population displayed a singular cannibalistic behaviour. Our results hence only partly support the expectation of increased adaptive phenotypic plasticity of European invasive populations of H. axyridis, and stress the importance of the choice of the environmental parameters to be manipulated for assessing phenotypic plasticity variation among populations.     

Interaction between Podisus maculiventris and Harmonia axyridis two predators used in augmentative biological control in greenhouse crops

Intraguild predation (IGP) betweenthe pentatomid Podisus maculiventris(Say) and the coccinellid Harmoniaaxyridis (Pallas) in the absence or presenceof the extraguild prey Spodopteralittoralis (Boisduval) and Myzuspersicae (Sulzer) was studied in thelaboratory. Interactions were asymmetric infavor of the pentatomid. Podisusmaculiventris readily fed upon eggs and larvaeof H. axyridis, but adult beetles wererarely attacked. Success of attacks by P.maculiventris was stage dependent, fourthinstars and adults being more successful inkilling ladybeetle larvae than second instars.Attacks by H. axyridis on the pentatomidwere rare and none of them were successful. Theeffect of introducing extraguild prey on thelevel of IGP was tested both in petri dishesand on caged sweet pepper plants. Whensufficient numbers of S. littoralislarvae were present to satiate the pentatomid,predation on H. axyridis larvae decreasedsignificantly, indicating that the coccinellidis a less preferred or less vulnerable prey.When the aphid M. persicae was presentedas extraguild prey, levels of IGP were notaltered. Nymphs of P. maculiventrissuccessfully completed development whenexclusively fed on larvae of H. axyridis,but developmental time was longer than onlepidopteran prey. No pentatomid nymphs reachedadulthood on aphids alone. IGP by P.maculiventris on H. axyridis may be ofsome importance in greenhouse crops, where bothpredators are being used increasingly inaugmentative biological control programs.Nonetheless, it is expected that in practicelarger larvae and adults of H. axyridiswill escape most attacks by the pentatomid.     

The role of natural enemy guilds in Aphis glycines suppression

Generalist natural enemy guilds are increasingly recognized as important sources of mortality for invasive agricultural pests. However, the net contribution of different species to pest suppression is conditioned by their biology and interspecific interactions. The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is widely attacked by generalist predators, but the relative impacts of different natural enemy guilds remains poorly understood. Moreover, low levels of A. glycines parasitism suggest that resident parasitoids may be limited through intraguild predation. During 2004 and 2005, we conducted field experiments to test the impact of different guilds of natural enemies on A. glycines. We contrasted aphid abundance on field cages with ambient levels of small predators (primarily Orius insidiosus) and parasitoids (primarily Braconidae), sham cages and open controls exposed to large predators (primarily coccinellids), and cages excluding all natural enemies. We observed strong aphid suppression (86- to 36-fold reduction) in treatments exposed to coccinellids, but only minor reduction due to small predators and parasitoids, with aphids reaching rapidly economic injury levels when coccinellids were excluded. Three species of resident parasitoids were found attacking A. glycines at very low levels (<1% parasitism), with no evidence that intraguild predation by coccinellids attenuated parasitoid impacts. At the plant level, coccinellid impacts resulted in a trophic cascade that restored soybean biomass and yield, whereas small natural enemies provided only minor protection against yield loss. Our results indicate that within the assemblage of A. glycines natural enemies in Michigan, coccinellids are critical to maintain aphids below economic injury levels.     

Harmonia axyridis in Great Britain: analysis of the spread and distribution of a non-native coccinellid

Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is native to Asia, and was widely introduced as a biocontrol agent of aphids and coccids in Europe and North America. In Europe H. axyridis is considered to be an invasive alien species. Although not known to have been deliberately introduced to Great Britain, it was first recorded there in 2004, in south-east England. Harmonia axyridis arrived in Great Britain by various means, primarily from mainland Europe, but also from Canada. Extensive national and local media coverage, and a dedicated website (), facilitated public involvement in recording H. axyridis in Great Britain; in excess of 4,000 verified records of the species were received between 2004 and 2006. Through detailed mapping, the objective of our study was to quantify and analyse the spread of H. axyridis in its early stages of invasion in Great Britain. Our data shows that between 2004 and 2006, the species spread north through Great Britain at the rate of 58 km year^-1 and west at the rate of 144.5 km year^-1. In England H. axyridis spread north to Yorkshire and west to Cornwall by the end of 2006, and also reached Wales. Recorded occurrence (of one or more H. axyridis individuals at larval, pupal and/or adult stage) in 10 km squares in Great Britain was: 2004—51; 2005—149; 2006—447. Records of juvenile H. axyridis extend through most of the recorded British range of the species, and we present evidence of bi-voltinism in the population in 2006.     

Suitability of exotic and native lady beetle eggs (Coleoptera: Coccinellidae) for development of lady beetle larvae

Predation upon lady beetle (Coleoptera: Coccinellidae) eggs in the field is most often instances of egg cannibalism by larvae or adults while the majority of the remaining predation events upon coccinellid eggs is done by other species of Coccinellidae. Thus the recent introduction and establishment of Harmonia axyridis in the US could negatively affect native species of Coccinellidae via egg predation. However, little is known regarding the suitability of interspecific coccinellid eggs as a food source for larval development. In this study, it was found that native first or third instar Coleomegilla maculata and Olla v-nigrum larvae were incapable of surviving to the adult stage when provided solely exotic H. axyridis eggs. In stark contrast, H. axyridis larvae survived equally well when cannibalizing eggs or eating eggs of either native species. When C. maculata and O. v-nigrum were grouped as ‘native’ and compared with the exotic H. axyridis, more native eggs were attacked than exotic eggs and a higher percentage of eggs was attacked by H. axyridis larvae. Native and exotic larvae attacked a similar percentage of native eggs but native larvae attacked significantly fewer exotic eggs than did exotic larvae. These data suggest that H. axyridis may prey upon the eggs of these native species, when encountered in the field, compared with the likelihood of the native species preying upon H. axyridis eggs. Therefore, eggs of the native species C. maculata and O. v-nigrum will continue to be subjected to cannibalism and also to possible predation by other native species and the exotic H. axyridis.     

Effects of augmentative releases of the coccinellid, Adalia bipunctata, and of insecticide treatments in autumn on the spring population of aphids of the genus Dysaphis in apple orchards

The impact of augmentative releases of indigenous predators and insecticide applications to control the autumn aphid forms of the genus Dysaphis (Homoptera: Aphididae), major pest insects on apple trees, was assessed in one-year field experiments in Switzerland. Eggs and larvae of the two-spot ladybird beetle Adalia bipunctata (L.) (Coleoptera: Coccinellidae) were released on 4-year old apple trees in various numbers at five different dates in autumn 1998 when sexuales of the aphids were present. Additionally, Pyrethrum HP was sprayed at the same five dates to compare the effectiveness of these augmentative releases to a commonly applied insecticide. Augmentative releases of larvae before mid-October significantly prevented the deposition of overwintering eggs by aphids of the genus Dysaphis and consequently reduced the number of hatched fundatrices in spring, 1999. There was a significant negative functional response among the number of released coccinellid larvae in autumn 1998 and the number of observed fundatrices on apple trees in spring 1999. Applications of Pyrethrum HP before mid-October were more effective than augmentative releases of larvae of A. bipunctata. The release of coccinellid eggs had no impact on the number of fundatrices of the genus Dysaphis in the next spring because they did not hatch due to bad weather conditions. The weather conditions in autumn seemed to have an impact on the autumn migration of the winged aphids back to their primary host. The prevention of egg deposition of aphids in autumn is a promising control strategy and deserves further exploration for practical use.     

Harmonia axyridis in Europe: spread and distribution of a non-native coccinellid

Native to Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is considered an invasive alien ladybird in Europe and North America, where it was widely introduced as a biological control agent of aphids and coccids. In Europe, H. axyridis was sold by various biological control companies from 1995 in France, Belgium and the Netherlands, and was also intentionally released in at least nine other countries. It has spread very rapidly, particularly since 2002, and is now regarded as established in thirteen European countries. The established range extends from Denmark in the north to southern France in the south, and from Czech Republic in the east to Great Britain in the west. In this paper we map the spread and distribution of H. axyridis in Europe, and examine the situation on a country-by-country basis. We report first records of the species in five countries; Spain, Sweden, Denmark, Czech Republic and Italy; and first evidence of H. axyridis establishment in the latter three countries. Despite releases of H. axyridis in Portugal, Spain and Greece, there is little evidence of establishment in southern Europe. It is predicted that the spread and increase within Europe will continue and that H. axyridis will become one of the most widely distributed coccinellids in the continent.     

Influence of diet and photoperiod on development and reproduction of European populations of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)

The current study examines the effect of photoperiod (16:08 or 12:12 h L:D) and diet (eggs of Ephestia kuehniella Zeller (Lepidoptera: Phycitidae) or the pea aphid Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae)) on the development and reproduction of the multicoloured Asian lady beetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). A long-term laboratory population of H. axyridis (since 1998) and a melanic and non-melanic population originating from field collected individuals of H. axyridis in Belgium were used in this study. Long day conditions (16 h photoperiod) shortened development of the field populations with 2–3 days when compared with short day conditions (12 h photoperiod). Oviposition in the field populations was delayed by 1–3 months when reared at a 12 h photoperiod. Dissections indicated that the females were in reproductive diapause. As compared with live pea aphids, a diet consisting of E. kuehniella eggs yielded heavier adult body weights (up to 12%) and increased the number of egg laying days (by 45–169%) for both field populations at a 16 h photoperiod and lengthened adult life span (by 45–92%) under both light regimens. The morph types differed in their response to the foods offered in terms of developmental rate, pre-oviposition period and number of oviposition days. The laboratory and field strains responded differentially to regimens of food and photoperiod. The study indicated a greater nutritional plasticity of the non-melanic morphs which may offer them a competitive advantage that may in part explain the predominance of non-melanic morphs in newly colonized areas.