Biology of Lilioceris spp. (Coleoptera: Chrysomelidae) and their parasitoids in Europe

The biology and parasitoid complex of the lily leaf beetle (LLB), Lilioceris lilii Scopoli, and two congeneric species were investigated in Europe, as part of a biological control program against the LLB in North America. Eggs, larvae, and adults of L. lilii were collected in several countries in Europe, on both cultivated and wild Lilium spp., and reared in the laboratory and under natural conditions. Parasitoids were obtained and their biologies were studied. Similar investigations were made in Switzerland on two closely related species Lilioceris tibialis (Villa) found on wild Lilium spp., and Lilioceris merdigera (L.) on several other Liliaceae. The three species are strictly univoltine. Adults overwinter and lay eggs on leaves in early spring. The three beetle species have four instars, which were characterized by their head capsule width. Pupation occurs in a cocoon in the soil. Adults emerge in late summer and start feeding before reaching overwintering sites. Egg and larval parasitoids were obtained. Eggs of L. lilii and L. merdigera were parasitized by the mymarid Anaphes sp., a multivoltine species that needs alternate hosts for overwintering. Larvae were heavily attacked by several parasitoids, among which the most abundant were three ichneumonids, Lemophagus pulcher (Szepligeti), L. errabundus (Gravenhorst), and Diaparsis jucunda (Holmgren), and the eulophid Tetrastichus setifer Thomson. All four parasitoid species were found in the three beetles and in most European regions, but strong variations were observed in their relative abundance among hosts and geographic regions. Three of the four main larval parasitoids are strictly univoltine, whereas L. pulcher has a partial second generation. Lemophagus spp. are frequently parasitized by the ichneumonid hyperparasitoid Mesochorus lilioceriphilus Schwenke. Further details of the biology of the parasitoids are described, and their potential as biological control agents is discussed.     

Survey of brown soft scale Coccus hesperidum L. parasitoids in southern California citrus

The parasitoid complex of brown soft scale, Coccus hesperidum L., a multivoltine soft scale, was determined in southern California citrus over the period February 2004–March 2006. The survey was conducted by placing brown soft scale-infested yucca leaves in the canopy of citrus trees and subsequently rearing individually isolated parasitized scales in the laboratory. A total of 14 species parasitized brown soft scale in the field, the most abundant ones belonging to the genus Metaphycus Mercet (75%). The most abundant parasitoid species was Metaphycus angustifrons Compere (38% parasitism), and this is a new record of establishment for this species in California. Coccophagus species accounted for only 11% parasitism. There were important spatio-temporal differences across the parasitoid complex survey locations. We also found that the five most abundant encyrtid parasitoid species showed preferences for scales of different sizes. Our results have implications for biological control of citricola scale, Coccus pseudomagnoliarum (Kuwana), an important pest of citrus in the San Joaquin Valley of central California. Notably, this species is nearly absent in southern California. Brown soft scale is considered to be an alternate host for parasitoids of citricola scale, a univoltine soft scale, at times when the latter species is unavailable for parasitism.     

Nondevelopment ofCotesia kariyai(Hymenoptera: Braconidae) in Entomopoxvirus-Infected Larvae ofPseudaletia separata(Lepidoptera: Noctuidae)

Interaction between an entomopoxvirus (PsEPV) and a gregarious braconid endoparasitoid,Cotesia kariyai,inPseudaletia separatalarvae showed that infection of larvae with PsEPV was deleterious to the development and survival ofC. kariyai.The survival and development ofC. kariyaiin PsEPV-infectedP. separatalarvae depended on the length of time between parasitization and viral infection. No parasitoid larvae emerged from PsEPV-infected hosts when host larvae were exposed simultaneously to parasitization and PsEPV inoculation whereas more than 80% of the hosts produced parasitoids when PsEPV was administered 5 days postparasitization.C. kariyailarvae in PsEPV-infected hosts showed a retarded development, shrank, and died about 8 days after viral exposure. Virion-free plasma from PsEPV-infectedP. separatalarvae was toxic to the parasitoid larvae even up to a dilution level of 32 when it was injected intrahemocoelically into the host larvae. Development of parasitoids in hosts that were simultaneously parasitized and injected with the virion-free plasm never progressed beyond the egg stage. The parasitizedP. separatalarvae injected with the virion-free plasma did not pupate and died within 30 days after injection.     

Influence of Clavicipitaceous Endophyte Infection in Ryegrass on Development of the ParasitoidMicroctonus hyperodaeLoan (Hymenoptera: Braconidae) inListronotus bonariensis(Kuschel) (Coleoptera: Curculionidae)

Laboratory experiments were conducted to examine the effect of ryegrass infection by the endophytic fungusAcremonium loliiLatch, Christensen and Samuels onMicroctonus hyperodaeLoan, a parasitoid ofListronotus bonariensis(Kuschel). Progression of parasitoids through the larval instar stages was shown to depend on adequate nutrition of the weevil host. Compared to confinement on endophyte-free ryegrass, parasitized weevils held on nonpreferred diets comprising leaf segments from endophyte-infected ryegrass and switchgrass contained parasitoid larvae with retarded development. Similarly, development of parasitoid larvae was retarded in hosts feeding on artificial diet containing diterpenes and alkaloids ofA. loliiorigin. Several diterpenes incorporated into the diet reduced survival of the parasitoid larvae. Attack rate of parasitoids was reduced when the quality of potential host weevils was compromised by confinement on nonpreferredA. lolii-infected ryegrass or without food for 14 days.     

Geographical variation in encapsulation ability ofDrosophila melanogaster larvae and evidence for parasitoid-specific components

Summary The ability ofDrosophila melanogaster larvae in Europe to encapsulate the eggs of their most important parasitoids,Asobara tabida andLeptopilina boulardi, shows a large amount of geographical variation. Interestingly, encapsulation ability againstA. tabida is not correlated with encapsulation ability againstL. boulardi. This indicates that the encapsulation system ofD. melanogaster larvae has parasitoid-specific components. The variation in encapsulation ability can only partly be explained by the incidence of parasitism on the larvae. This means that factors other than the two parasitoid species must be selection pressures on the encapsulation ability ofD. melanogaster larvae.     

The Bionomics ofCoptera Haywardi(Ogloblin) (Hymenoptera: Diapriidae) and Other Pupal Parasitoids of Tephritid Fruit Flies (Diptera)

The endoparasitoidCoptera haywardi(Ogloblin) (Diapriidae) was discovered in Mexico attacking the pupae of the Mexican fruit fly,Anastrepha ludens(Loew). Typically, parasitoids of Diptera Cychlorrhapha pupae develop as ectoparasitoids and are generalists that attack hosts in a number of families. Aspects of the bionomics ofC. haywardiwere compared to those of two chalcidoid ectoparasitoids,Dirhinus himalayanusWestwood andSpalangia geminaBoucek.C. haywardideveloped in three genera of Tephritidae, but not in species of other families. The two species of chalcidoids developed in all the calypterate and acalypterate hosts to which they were exposed. In an olfactometerC. haywardipreferredAnastrepha suspensa(Loew) pupae, while the chalcidoids preferred the pupae ofMusca domestica L.This preference inS. geminawas diminished in insects that had been reared onA. suspensa. C. haywardioviposited in theA. suspensapupae that had been previously parasitized by the braconidDiachasmimorpha longicaudata(Ashmead). However, it completed development only in unparasitized pupae. Mortality of the primary parasitoid due toD. himalayanuswas approximately two-thirds the mortality inflicted on the host fly.S. geminadid not discriminate between parasitized and unparasitized pupae ofA. suspensaand developed in both.C. haywardiappears to have a more restricted host range relative to chalcidoid pupal parasitoids and this may be due to its endoparasitic development.     

A survey of black scale,Saissetia oleae [Hom.: Coccidae] parasitoids [Hym.: Chalcidoidea] in southern California

A survey of black scaleSaissetia oleae (Olivier) parasitoids present in southern California was conducted between September 1987 and September 1989. From 308 collections of black scale-infested citrus, olive, and oleander twigs from 19 sites in southern California, 1,610 specimens were collected. Nine primary and six secondary parasitoid species were identified. Four primary species were abundant in southern California:Metaphycus bartletti Annecke & Mynhardt,M. helvolus (Compere),Scutellista caerulea (Fonscolombe) (=S. cyanea Motschulsky), andDiversinervus elegans Silvestri. The most common secondary parasitoids wereMarietta mexicana (Howard),Cheiloneurus noxius Compere, andTetrastichus minutus (Howard). In the coastal region of southern California,M. bartletti was the most abundant parasitoid, followed in order byD. elegans, S. Caerulea, andM. helvolus. In the intermediate and interior regions,M. helvolus was most abundant.D. elegans was second most abundant in the intermediate region, but was rare in the interior region.M. bartletti was second in abundance in the interior region and third in the intermediate region.      

Suitability of lepidopteran stemborers for parasitization by novel-association endoparasitoids

Extensive study of insect immune systems has yielded abetter understanding of the mechanisms used by insects to defendagainst invaders. This knowledge can be used to predict hownatural enemies utilize potential hosts, which will aid in theplanning of biological control programs. Our experimental systemconsists of novel host-parasitoid associations, with two NewWorld pyralid stalk borers, Diatraea saccharalis and D.grandiosella; one Old World crambid borer, Ostrinia nubilalis;and three Old World microgastrine braconid parasitoids, Cotesiachilonis, C. sesamiae, and C. flavipes. Experiments on hostsuitability indicate that parasitoids that are taxonomically,behaviorally and ecologically very similar may differ in theirability to utilize a host of the same species. Likewise,utilization of related hosts can produce different outcomes for agiven parasitoid species. D. saccharalis is a suitable host forall three parasitoid species, whereas D. grandiosella oftenencapsulates C. sesamiae and C. flavipes. O. nubilalis is anunsuitable host for all three species. Different species ofparasitoids may use different factors at different times afterparasitization to counter the host's immune response. This studysuggests that the physiological host range of these parasitoids willbe narrow, thus limiting effects on non-target species. However,the lack of consistent patterns also shows that explicit testingwill be needed to determine host ranges.     

Competitive interaction between two ichneumonid parasitoids of Spodoptera litura

The outcome of competition between Campoletis chlorideae Uchida and Eriborus argenteopilosus (Cameron) (Hymenoptera: Ichneumonidae), two indigenous larval parasitoids of the noctuid pest, Spodoptera litura (Fabricius), was investigated in the laboratory by way of two experiments. In the individual exposure experiment, the host larvae were exposed to the parasitoids either alone or one after the other at different time intervals and were considered to be parasitised when the parasitoid was observed to sting the host larva. When they stung the host larva singly, the parasitism rates by C. chlorideae and E. argenteopilosus was either similar to or higher than the parasitism recorded by each parasitoid in the different combination/interaction treatments. C. chlorideae cocoons were formed from majority of the host larvae, which were stung by both parasitoid species, one after the other, in most oviposition orders and delays between ovipositions. E. argenteopilosus appeared to be the dominant parasitoid only in those treatments where it was the first one to parasitise and the delay in C. chlorideae parasitism was more than 18 h. and it never dominated the interactions, when it was the second one to parasitise. This implied that C. chlorideae had an almost consistent advantage over E. argenteopilosus. In the mass exposure experiment, the two parasitoid species (either alone or together) were allowed to forage and parasitise the host larvae in cages. When the two parasitoid species were allowed to forage in the same host patch simultaneously, the performance of C. chlorideae when it was alone was statistically similar to its performance in the presence of E. argenteopilosus. However, E. argenteopilosus performed better when it could forage alone. The results of both experiments revealed that C. chlorideae was the more competitive of the two species.     

The impact of a stem-boring insect on the tissues, physiology and reproduction of Russian thistle

A stem-boring moth, Coleophora parthenica was introduced into California from Pakistan, in 1973, in a biological control attempt against the weed, Russian thistle (Salsola australis). A population of Russian thistle plants growing near Coalinga, California, which were infested and damaged by varying numbers of C. parthenica larvae, was studied to better understand the moth's impact.The xylem sap pressures were measured during the period of seed set. No significant correlations were obtained between the measured levels of water stress and the amounts of C. parthenica infestations and damage in these plants, except late in the season, but these are not considered to be important. Translocation of carbon-14 was studied during seed set. The levels of translocation and C. parthenica infestations and damage in the plants were not correlated. Measured levels of various reproductive indices did not correlate significantly with the levels of larval infestation and damage. Histological and x-ray examinations of the damaged stems showed that once C. parthenica larvae enter the stems of Russian thistle they feed only in the pith and do not damage the critical xylem and phloem. This explains why the plant's translocation, water balance, and reproduction were unaffected by C. parthenica. Coleophora parthenica appears to have very limited value as a biological control agent of Russian thistle, except perhaps as part of a complex of natural enemies attacking the plant.

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Résumé Coleophera parthenica Meyrick (Lep., Coleophoridae), mineuse de tiges, a été introduite en 1973 du Pakistan en Californie, pour lutter contre Salsola australis. Pour mieux appréhender l'effet de C. parthenica, une population de S. australis attaquée par la mineuse a été suivie près de Coalinga (Californie).La pression de sève du xylème a été mesurée pendant la période de production des graines. Aucune corrélation n'est apparue entre les niveaux de stress hydrique et les taux d'infestation et les dégâts de C. parthenica, sauf en fin de saison; mais ils n'ont pas été alors estimés importants.Le transfert de C¹⁴ a été étudié pendant la période de production de graines; aucune corrélation n'est apparue avec les infestations et les dégâts de C. parthenica. Les différents indices de la reproduction n'étaient pas significativement liés aux niveaux d'infestation et de dégâts larvaires.Les examens histologiques et par rayons X des tiges attaquées ont montré qu'après la pénétration des chenilles de C. parthenica dans les tiges de S. australis, celles-ci ne s'alimentent que dans la moelle sans atteindre gravement le xylème et le phloème.Ceci explique pourquoi, les transferts dans la plante, la circulation de l'eau et la reproduction, ne sont pas modifiés par C. parthenica; cet insecte semble n'offrir que très peu d'intérêt pour la lutte biologique contre S. australis, sauf peut-être comme élément du complexe des ennemis naturels de cette plante.

     

Larvicidal activity of lectins onLucilia cuprina: mechanism of action

Foraging behaviour and host-instar preference of young and old females of the solitary aphid parasitoid,Lysiphlebus cardui Marshall (Hymenoptera: Aphidiidae), were studied in the laboratory. The analysis of interactions between parasitoids and different stages ofAphis fabae cirsiiacanthoidis Scop. (Homoptera: Aphididae) revealed that encounter rates between aphids and parasitoid females and defence reactions of the aphids influenced the degree to which a particular aphid age class is parasitized. Encounter rates between hosts and parasitoid females depended on the foraging pattern of the parasitoid, which varied with age. In mixed aphid colonies patch residence time increased with parasitoid age. Furthermore, younger parasitoids (≦1 day old) laid more eggs into second and third instars, while older parasitoids (≧4 days old) did not show distinct host instar preferences. It is suggested that the oviposition behaviour ofL. cardui is influenced by the physiological state, i.e. the age of the wasp.     

Impact of the egg parasitoid Uscana lariophaga and the larval-pupal parasitoid Dinarmus basalis on Callosobruchus maculatus populations and cowpea losses

In West Africa, Uscana lariophaga Steffan (Hymenoptera: Trichogrammatidae) and Dinarmus basalis (Rondani) (Hymenoptera: Pteromalidae) parasitize the eggs and larvae, respectively, of Callosobruchus maculatus Fab. (Coleoptera: Bruchidae), an important pest of stored cowpea. The impact of the parasitoids on pest populations was evaluated in clay pots similar to the ones used in traditional storage in Niger. At the beginning of the storage period, cowpeas were infested with one density of C. maculatus and with either one or both of the parasitoid species. If the parasitoids we inoculated as single species in stores, both D. basalis and U. lariophaga significantly suppressed the bruchid population, but the former did so more effectively than the latter. A combination of D. basalis and U. lariophaga resulted in the same suppression of bruchid populations as when D. basalis was the only parasitoid. Fifteen weeks after storage, the parasitoids reduced the number of grains damaged significantly by 38–56%. The effect of inoculating single or multiple parasitoid species on C. maculatus populations in an augmentation strategy is discussed.     

Foraging behaviour of the whitefly parasitoidEncarsia formosa on tomato leaflets

IndividualEncarsia formosa parasitoids were observed continuously until the parasitoids flew away, either on clean tomato leaflets, on leaflets with honeydew, or on leaflets with unparasitized and parasitized whitefly larvae. Encounters with unparasitized and parasitized whitefly larvae, and contact with honeydew arrested the parasitoids on the leaflet. The walking speed increased linearly from 0.179 to 0.529 mm/s between 15 and 25–30°C. The walking activity showed another relationship with temperature: it was below 10% at 15 and 18°C, and increased to about 75% at 20, 25 and 30°C. It was not affected by host encounters or by 1 to 4 ovipositions. The total handling time of hosts was between 1.8–21.8% of the total time on the leaflet. Self-superparasitism was not observed. Conspecific-superparasitism did occur in 14% of the encounters with hosts containing a parasitoid egg, but was not observed anymore when the parasitoid egg had hatched. Experienced parasitoids superparasitized as often as naive females. The foraging behaviour ofE. formosa from landing on a leaf until departure has now been quantified and is discussed.     

Hymenopterous parasitoids of bark beetles [Scolytidae] in Israel: Relationships between host and parasitoid size,and sex ratio

Information on parasitoids of bark beetles infesting conifers and broadleaves is presented to show the relations between host and parasitoid size, and parasitoid sex ratios. Sticky traps were employed to determine the sex ratios of parasitoid species operating on beetle-infested material. A wide range in body length was found for most species. Females ofCerocephala eccoptogasteri Masi,Cheiropachus quadrum Febr.,Eurytoma morio Boheman,Heydenia pretiosa Forster,Metacolus unifasciatus Forster,Rhaphitelus maculatus Walker andRoptrocerus xylophagorum (Ratz.) were usually significantly longer than their males, whereas the males of all fourDendrosoter spp. were significantly longer than the females. Body lengths of the males and females were almost identical inEntedon ergias Walker andEcphylus caudatus Rusch. The sex ratio varied markedly within most species; the mean ratio for 5 of them differed significantly from 1∶1. The sex ratio ofM. unifasciatus andE. morio was significantly related to host size. The sex-ratio of parasitoids trapped on sticky traps varied with time in relation to the phenology of the host beetle. Females were more numerous during the larvae development while males were more abundant between the pupal stage and emergence of the host. Male courtship behaviour ofDendrosoter caenopachoids Rusch.,D. protuberans (Nees),M. unifasciatus andR. xylophagorum is described. The effect of host size, the diversity in sex ratios, and possible interaction between parasitoid size and sex-ratio are discussed. Contribution from the Agricultural Research Organization, Bet Dagan, Israel. N° 1328-E, 1984 series.     

Mass rearing and augmentative releases of the native parasitoid Chouioia cunea for biological control of the introduced fall webworm Hyphantria cunea in China

The fall webworm, Hyphantria cunea Drury, is an economically important introduced pest in China. A native pupal endoparasitoid, Chouioia cunea Yang (Hymenoptera: Eulophidae, Tetrastichinae) causes considerable mortality of H. cunea pupae in some areas of China. Alternative hosts of C. cunea were tested to find potential substitute hosts for mass rearing the parasitoid. Antheraea pernyi Guerin-Meneville (Lepidoptera: Saturniidae) was chosen as a surrogate host as a single pupa produced an average of 6552 wasps and a maximum of 11,256 per pupa. A mass-rearing technique and successful release program of this parasitoid is described. Parasitism by C. cunea in the areas where it was released averaged 67.74% and was usually over 80%. Other native parasitoids, such as Coccygomimus disparis (Viereck), C. parnasae (Viereck) (Hymenoptera: Ichneumonidae) and Exorita japonica Townes (Diptera: Tachnidae), caused the total average parasitism to exceed 90% on average, reaching a maximum of 96.28% in the release areas. These successful releases indicate that an introduced pest species can also be controlled by the mass-rearing and release of native parasitoids in the country of introduction.     

Bioecology ofLydella thompsoni Herting, [Dip. Tachinidae] within the Rhone Delta in Southern France

Lydella thompsoni Hertin,Tachinidae, is an endoparasitoid frequently associated in southern France with larvae ofOstrinia nubilalis, Pyralidae, Sesamia nonagrioides, Noctuidae, Archanara geminipuncta andA. dissoluta, Noctuidae. The tachinid was reared successfully at 21°C in the laboratory by providing the adult flies with a high humidity, a light intensity of 8,000–10,000 lux for mating and a mixture of casein proteolysate and honey as food. Under such conditions, the flies lived for about 30 days and about half of them mated successfully. Hosts were infested by dissecting mature tachinid females and placing 1–2 of the extracted planidia onto each moth larva. Half of the planidia successfully entered their larval hosts. The biology of the tachinid larvae was studied on the 2 main hosts,O. nubilalis andS. nonagrioides. At 21°C, 25°C and 28°C, larval development took less time onO. nubilalis than onS. nonagrioides. At 25°C, female larvae onO. nubilalis required 9.0±0.5 days and onS. nonagrioides 10.5±0.3 days, male larvae onO. nubilalis required 8.3±0.5 days and onS. nonagrioides 10.6±0.3 days. Pupal duration was also influenced by the larval host. In winter, 2nd instar larvae ofL. thompsoni enter a resting or quiescent condition. This condition is terminated sooner (December–January) in larvae developing onS. nonagrioides than in those developing onO. nubilalis (February–March). The life cycle of the tachinid in the field was studied by trapping flies in water dishes and by collecting parasitized host larvae from various plants. Flies were caught from April to October, mainly in September. Larvae of the spring generation of the parasitoid developed on larvae of species ofArchanara that fed on the reed,Phragmites communis. From 1976 to 1982, parasitism averaged about 16%. Parasitism by summer generation onS. nonagrioides was highest (4–5%) in June. Parasitism ofO. nubilalis did not change by more than 2 fold in either of the 2 summers studied (10–17 % in 1981, 6–10 % in 1982). By September the numbers of host larvae had increased to 10–20 times the number available earlier in the season. Larval populations ofL. thompsoni similarly increased from 3–400 larvae per ha in June to 4–5,000 per ha in September. The stability of the relationship between this parasitoid and its hosts in southeastern France is discussed and compared to relationship described elsewhere.     

Host-plant mediated effects of transgenic maize on the insect parasitoid Campoletis sonorensis (Hymenoptera: Ichneumonidae)

Determining the impact of genetically modified (GM) crops on beneficial organisms is an important aspect of the environmental risk assessment of GM crops. In the present study, the impact of Bt maize expressing Cry1Ab on the development and behaviour of the parasitoid Campoletis sonorensis was compared to individuals reared on hosts fed conventionally bred plants partially resistant to the European corn borer (Ostrinia nubilalis Hübner) and on susceptible maize hybrids. Adult parasitoids reared on Bt maize-fed Spodoptera frugiperda larvae were significantly smaller (15–30%) than those reared in hosts fed either of the conventional maize hybrids. The magnitude of this effect was dependent on the size of the host at oviposition and its subsequent growth rate. The development time of C. sonorensis was not affected by the maize treatment. In choice tests, female parasitoids displayed no preference for hosts fed a specific maize hybrid. No Cry1Ab was detected within adult parasitoids.     

Variation in diapause and sex ratio in the parasitoidAsobara tabida

Asobara tabida Nees (Hymenoptera: Braconidae) is a widespread parasitoid, attacking larvae ofDrosophila (Diptera: Drosophilidae) species in fermenting substrates. In this species, geographic variation is found in the percentage of parasitoids entering diapause and in the sex ratio of emerging parasitoids. Percentage diapause appears to be influenced by host species (more parasitoids enter diapause inD. melanogaster Meigen than inD. subobscura Collin) and temperature. It is not correlated with any of the abiotic factors investigated, but is correlated with survival probability inD. melanogaster larvae and with the time of year in which the experiment was conducted (even though none of the parasitoids experienced natural day light). Sex ratio was only found to correlate with percentage diapause, suggesting that males enter diapause more frequently than females. It is concluded thatA. tabida uses diapause to survive both unfavourable abiotic and biotic circumstances.     

Transgenic GNA Expressing Potato Plants Augment the Beneficial Biocontrol of Lacanobia Oleracea (Lepidoptera: Noctuidae) by the parasitoid Eulophus Pennicornis (Hymenoptera; Eulophidae)

The effect of expressing the gene encoding snowdrop lectin (Galanthus nivalis agglutinin, GNA) in transgenic potato plants, on parasitism of the phytophagous insect pest Lacanobia oleracea by the gregarious ectoparasitoid Eulophus pennicornis, was investigated in glasshouse trials. Expression of GNA (approx. 1.0% total soluble protein) by transgenic plants significantly reduced the level of pest damage, thus confirming previous studies. Furthermore, the presence of the parasitoid significantly reduced the levels of damage incurred either by the transgenic or control plants when compared to those plants grown in the absence of the parasitoid. For the GNA expressing plants the presence of the parasitoid resulted in further reductions (ca. 21%) in the level of damage caused by the pest species. The ability of the wasp to parasitise and subsequently develop on the pest larvae was not altered by the presence of GNA in the diet of the host. E. pennicornis progeny that developed on L. oleracea reared on GNA expressing plants showed no significant alteration in fecundity when compared with wasps that had developed on hosts fed on control potato plants, although mean size and longevity of female parasitoids was significantly reduced. The number of F ₂ progeny produced by parasitoids derived from hosts fed on GNA-expressing plants was not significantly different to those produced by parasitoids from hosts fed control plants. Results from the present study demonstrate that the use of transgenic plants expressing insecticidal proteins can be compatible with the deployment of beneficial insects and that the two factors may interact in a positive manner.     

Parasitism by Pteromalus cerealellae (Hymenoptera: Pteromalidae) on the Cowpea weevil, Callosbruchus maculatus (Coleoptera: Bruchidae): Host density, temperature effects, and host finding ability

Studies on interactions between a larval parasitoid, Pteromalus cerealellae (Boucek) and one of its hosts, Callosobruchus maculatus (F.) were carried out in the laboratory. The number of host larvae parasitized by P. cerealellae increased with host larvae at low densities and tended to a plateau at a density of 25 larvae per female parasitoid. Each parasitoid was able to parasitize more hosts and produced more offspring at 20 and 25 °C than at 30 °C. The number of non-infested seeds mixed with seeds infested with the last instar of C. maculatus did not preclude P. cerealellae from identifying infested seeds and attacking larvae inside them. When infested seeds were tightly packed, several host larvae escaped parasitism. P. cerealellae may be a useful biological control agent in newly harvested cowpea with low C. maculatus infestation, and lowering the temperature of the storage system may enhance the effectiveness of this parasitoid.