Side-effects of organic and synthetic pesticides on cold-stored diapausing prepupae of <Emphasis Type="Italic">Trichogramma cordubensis</Emphasis>

The side-effects of three insecticides (deltamethrin, lambda-cyhalothrin and Bacillus thuringiensis Berliner) and one fungicide (basic copper sulphate) were tested on cold-stored diapausing prepupae of Trichogramma cordubensis Vargas and Cabello (Hymenoptera: Trichogrammatidae). Pesticides were directly sprayed on parasitized host eggs (being the diapausing parasitoids in the prepupal stage) after cold storage (3°C) for three different periods (60, 120 and 180 days). Regardless of the period of cold storage, both pyrethroids reduced the emergence rates of T. cordubensis (both <25%) compared to the control (emergence varied from 83% to 89%). The most toxic pyrethroid was lambda-cyhalothrin; Trichogramma cordubensis adult emergence varied from 7% to 15%. Lambda-cyhalothrin also negatively affected the longevity and fecundity of parasitoids cold stored for 60 days. Bacillus thuringiensis Berliner subsp. kurstaki and basic copper sulphate had little or no adverse effect on emergence rates (generally >80%), longevity nor fecundity of T. cordubensis, indicating that these pesticides could be successfully integrated into pest management programs using wasps that were cold stored under diapause. Such integration would be valuable to pest management programs by reducing the costs of T. cordubensis mass rearing and by allowing producers to stockpile parasitoids for release in the growing season. However, since the emergence rate, longevity and fecundity of T. cordubensis generally decreased with increasing duration in cold storage, wasps to be used in integrated pest management programs should only be stored at 3°C for 60 days maximum. Handling Editor: Sam Cook.     

Short-distance dispersal behavior and establishment of the parasitoid Gonatocerus ashmeadi (Hymenoptera: Mymaridae) in Tahiti: Implications for its use as a biological control agent against Homalodisca vitripennis (Hemiptera: Cicadellidae)

The egg parasitoid Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae), was introduced into French Polynesia as a biological control agent to control the invasive plant feeding pest Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). The short-distance dispersal of G. ashmeadi was monitored as part of the biological control program. G. ashmeadi showed exponential dispersal capacity with 47 m/day being a minimum estimate of its natural rate of spread at high host densities (>150 nymphs per minute of sweep net sampling) in urbanized areas at sea level, which were characterized by a high diversity of exotic ornamental plants. This rate of spread contrasted starkly with almost nonexistent establishment and dispersal where host densities were very low (<2 nymphs per minute of sweep net sampling) at high elevation (800 m) with relatively undisturbed native vegetation. Survey results across different altitudes revealed an effect of vegetative diversity and host density on the measurable mobility and establishment of G. ashmeadi. In contrast, no significant influence of wind direction was found on G. ashmeadi dispersal rate or direction. Survey results for G. ashmeadi from French Polynesia suggest that the best release establishment strategies for classical biological control of H. vitripennis are: (1) many small releases where host density is high, or (2) larger and fewer releases where host densities are low.     

Maternal and progeny quality of Habrobracon hebetor Say (Hymenoptera: Braconidae) after cold storage

The ectoparasitoid Habrobracon hebetor Say (Hymenoptera: Braconidae) is an important biological control agent for lepidopterous pests of stored products. We investigated the effects of low temperature storage on the quality of adult parasitoids and their progeny. Newly emerged females were stored for 10, 20, 30, 40, 50, and 70 days at 5 ± 1 °C. Several reproductive and developmental parameters were then assessed to determine the quality of the adult parasitoids and their progeny. After more than 30 days of storage, there was a decrease in parental parasitism, but low temperature storage of parents had no effect on parasitism of the F1 generation. Parental longevity and fecundity decreased after more than 20 days of storage, but there was no effect of storage duration on the fecundity and longevity of the F1 generation until a storage duration of 50 days. Development time varied with storage duration but differences were within 2 days. Storage duration had no effect on the sex ratio of F1 and F2 generations. Our data show that H. hebetor can be cold stored for up to 20 days without adversely affecting the performance of the parasitoid. Therefore, short-term storage of H.hebetor adults could be used for maintaining and accumulating large numbers of parasitoids in mass rearing programs.     

Determination of Homalodisca coagulata (Hemiptera: Cicadellidae) egg ages suitable for oviposition by Gonatocerus ashmeadi, Gonatocerus triguttatus, and Gonatocerus fasciatus (Hymenoptera: Mymaridae)

Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) eggs 1–10 days of age were exposed to Gonatocerus ashmeadi Girault, Gonatocerus triguttatus Girault, and Gonatocerus fasciatus Girault (all Hymenoptera: Mymaridae) in no choice laboratory trials to investigate egg age utilization and to determine which egg ages are vulnerable to attack by these three parasitoids. The H. coagulata egg ages that were most suitable for oviposition by G. ashmeadi, G. triguttatus, and G. fasciatus were eggs 3, 4, and 2 days of age, respectively. Egg ages least suitable for parasitoid development were 6–10 days for G. ashmeadi (resulting in <50% parasitism), 1–2 and 7–10 days for G. triguttatus (resulting in <25% parasitism), and 3–10 days for G. fasciatus (resulting in <11% parasitism). Pooling parasitism data across all egg ages showed that parasitism by G. ashmeadi was 12.9 and 28.5% higher compared with G. triguttatus and G. fasciatus, respectively, and G. triguttatus resulted in 15.6% higher percentage parasitism compared with G. fasciatus. Egg age had a significant effect on the percentage of female G. ashmeadi offspring produced, but this was not significant for G. triguttatus, and low G. fasciatus parasitism prevented statistical analyses for comparisons. Results from tests where females were offered a choice for oviposition between eggs 1, 3, and 5 days of age demonstrated that G. ashmeadi and G. triguttatus showed no significant oviposition preference, while percentage parasitism by G. fasciatus was 29.4 and 7.4% higher when females were presented eggs 1 and 3 days of age, respectively, compared with eggs 5 days of age. Choice tests indicated that an overlap in egg age suitability for oviposition exists between G. ashmeadi, G. triguttatus, and G. fasciatus, and that interspecific competition for eggs 1, 2, and 3 days of age may occur in the field environment.     

Oviposition and reproductive performance of a generalist parasitoid (Trichogramma pretiosum) exposed to host species that differ in their physical characteristics

The response of generalist egg parasitoids to alternative natural hosts that are present simultaneously is not well known. We investigated the behavior of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) in relation to two field hosts Helicoverpa armigera Hübner and Spodoptera litura Fabricius, in choice and no choice tests. We quantified the effects of natal host species and post-emergence adult age on the oviposition preference of the parasitoids. H. armigera eggs were consistently preferred over S. litura eggs, regardless of the natal host and adult age. When only S. litura eggs were available as hosts, they were parasitized at statistically similar rates to H. armigera eggs (average of 17 ± 2.7 vs. 13 ± 3.0, H. armigera to S. litura). The adult lifespan and lifetime fecundity of T. pretiosum were variable but were affected by natal host species and/or host species to which they were exposed. Mean lifespan and fecundity of parasitoids that had developed in H. armigera eggs and were exposed to H. armigera eggs for oviposition were 13.9 ± 1.8 days and 98.7 ± 11.0 adult offspring. By contrast, those that developed in S. litura eggs and were exposed to S. litura eggs for oviposition lived for 7 ± 0.9 days and produced 53.8 ± 8.0 adult offspring. The ovigeny index (OI) was significantly lower in the parasitoids exposed to H. armigera eggs than in those exposed to S. litura eggs, regardless of the natal host, indicating that H. armigera eggs sustain the adult parasitoids better than S. litura eggs. These results are used to predict parasitoid behavior in the field when both hosts are available.     

Use of life table statistics and degree-day values to predict the invasion success of Gonatocerus ashmeadi (Hymenoptera: Mymaridae), an egg parasitoid of Homalodisca coagulata (Hemiptera: Cicadellidae), in California

Life table statistics and degree-day requirements for Gonatocerus ashmeadi Girault, a parasitoid of the glassy-winged sharpshooter Homalodisca coagulata (Say), were used to estimate the number of expected parasitoid generations in California (USA). Between two to 51 and one to 37 generations per year were estimated across different climatic regions in California, using life table and degree-day models, respectively. Temperature-based values for net reproductive rate, R_o, were estimated in California using a laboratory-derived equation and ranged from zero to approximately 48 and analyses indicate that a minimum of eight generations are required each year to sustain a population increase of G. ashmeadi. Long-term weather data from 381 weather stations across California were used with an Inverse-Distance Weighting algorithm to map temperature-based estimations for the entire state of California. This Geographic Information Systems model was used to determine number of G. ashmeadi generations based on day-degree accumulation, T_c, and R_o. GIS mapping indicated that Californian counties in the north, central west coast, central west and Sierra Nevada regions may be climatic conditions unfavorable for supporting the permanent establishment of invading populations of G. ashmeadi should H. coagulata successfully establish year-round populations in these areas. Southern counties in California that experience warmer year round temperatures and support year round populations of H. coagulata, appear to be conducive to the establishment of permanent populations of G. ashmeadi. The mechanisms facilitating G. ashmeadi invasion and the implications of these temperature-based estimates for biological control of H. coagulata are discussed.     

Reproductive and developmental biology of Gonatocerus ashmeadi (Hymenoptera: Mymaridae), an egg parasitoid of Homalodisca coagulata (Hemiptera: Cicadellidae)

The reproductive and developmental biology of Gonatocerus ashmeadi Girault, a parasitoid of the glassy-winged sharpshooter Homalodisca coagulata (Say), was determined at five constant temperatures in the laboratory: 15; 20; 25; 30; 33 °C. At 30 °C, G. ashmeadi maintained the highest successful parasitism rates with 46.1% of parasitoid larvae surviving to adulthood. Lifetime fecundity was greatest at 25 °C and fell sharply as temperature either increased or decreased around 25 °C. Temperature had no effect on sex ratio of parasitoid offspring. Mean adult longevity was inversely related to temperature with a maximum of 20 days at 15 °C to a minimum of eight days at 33 °C. Developmental rates increased nonlinearly with increasing temperatures. Developmental rate data were fitted with the modified Logan model for oviposition to adult development times across each of the five experimental temperatures to determine optimal and upper lethal temperature thresholds. The lower developmental threshold estimated by the Logan model and linear regression were 1.10 and 7.16 °C, respectively. Linear regression of developmental rate for temperatures 15–30 °C indicated that 222 degree-days were required above a minimum threshold of 7.16 °C to complete development. A temperature of 37.6 °C was determined to be the upper development threshold with optimal development occurring at 30.5 °C. Demographic parameters were calculated and pseudo-replicates for intrinsic rate of increase (r_m), net reproductive rates (R_o), generation time (T_c), population doubling time (T_d), and finite rate of increase (λ) were generated using the bootstrap method. Mean bootstrap estimates of demographic parameters were compared across temperatures using ANOVA and nonlinear regression.     

Suitability of the maize weevil and angoumois grain moth as hosts for the parasitoidsAnisopteromalus calandrae andPteromalus cerealellae

Two parasitoids,Pteromalus cerealellae (Ashmead) andAnisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), were compared for their ability to parasitize two important internally-developing insect pests of stored maize (Zea mays L.). Parasitism byP. cerealellae was greater on Angoumois grain moth,Sitotroga cerealella (Olivier), than on maize weevil,Sitophilus zeamais Motschulsky, in no-choice experiments.Anisopteromalus calandrae parasitized more maize weevils than didP. cerealellae. The former parasitoid parasitized only a few Angoumois grain moths successfully in maize, but parasitized many in wheat if the hosts were younger than 3 weeks old. Thus, both host age and type of grain affect suitability for parasitism. The effects of parental host (species on which the female developed) and experimental host (species exposed to parasitism) on parasitism rate ofP. cerealellae were tested in a host-switching experiment. Parasitism by parasitoids reared on maize weevils was 23% lower than that of parasitoids reared on Angoumois grain moth. This effect was independent of which host the filial generation of parasitoids was tested on. However, the experimental host species had a much greater effect on parasitoid fecundity than the parental host species. Female progeny had smaller body sizes when emerging from maize weevil than from Angoumois grain moth, which may explain the parental host effect on fecundity. There was also a slight intergenerational effect of host species on parasitoid body size.     

Superparasitism in mass reared Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), a parasitoid of fruit flies (Diptera: Tephritidae)

Superparasitism frequency and its effects on the quality of mass-reared Diachasmimorpha longicaudata (Ashmead) parasitoids were investigated under laboratory conditions. Percentage of adult emergence, sex ratio, survival, fecundity and flight ability of adult parasitoids that emerged from Anastrepha ludens (Loew) pupae with different levels of superparasitism were determined. A high prevalence of superparasitism was observed. The number of scars per pupa, produced by insertion of the parasitoid ovipositor, ranged from 1 to 30, with an average (±SD) of 8.3 ± 6.2. Adult parasitoid emergence decreased as the level of superparasitism increased. However, the fraction of females rose with increasing superparasitism and the flight ability was lower in adults emerging from pupae with only one scar, compared with adults emerging from superparasitized hosts. Female longevity and fecundity were not affected by superparasitism. Our results support the hypothesis that superparasitism in D. longicaudata might be adaptive, since adults emerging from hosts with moderate levels of superparasitism showed the highest percentage of emergence and there were no significant differences in the other quality control parameters tested. Our findings are relevant to the mass rearing process, where the ratio of hosts to parasitoids can be optimized as well as the distribution of eggs deposited in host larvae. This contributes to efficient mass rearing methods for augmentative biological control programs.     

Comparative Development and Performance of Artificially Reared versus Host-RearedDiapetimorpha introita(Cresson) (Hymenoptera: Ichneumonidae) Wasps

Diapetimorpha introita(Cresson) (Hymenoptera: Ichneumonidae), a native ectoparasitoid ofSpodopteraspp. pupae, was reared in the laboratory on an artificial diet devoid of any insect host components. Diet-reared wasps demonstrated a propensity to search for and parasitize natural hosts in a field cage trial. Longevity of the diet-reared wasps was comparable with the longevity of wasps reared on host pupae. Survival rate ofD. introitawas 61.3% when reared on diet and 76.3% when reared on host pupae. Wasps reared on the artificial diet had longer developmental times, reduced fecundity, and reduced adult weights compared to wasps reared on host pupae. These studies suggest that future research efforts should focus on increasing fecundity and weight of diet-reared wasps and decreasing the mortality and developmental time of wasps reared on the artificial diet. The ability to rearD. introitaon an inexpensive, artificial diet significantly enhances the potential of mass rearing this parasitoid for inundative releases againstSpodopteraspp.     

Lifetime Reproductive Success in the Solitary Endoparasitoid, Venturia canescens

Parasitoid wasps have long been considered excellent organisms in studies examining the evolution of reproductive and life-history strategies. In examining the lifetime reproductive success of parasitoids in the laboratory, most investigations have provided the insects with excess hosts and food, where they exist in a relatively constraint-free environment. Importantly, these conditions may not accurately reflect the true heterogeneity of natural systems, where suitable hosts and food sources are likely to be limiting. This study examines the influence of differences in host and food availability on reproductive and life-history parameters in an asexual strain of the solitary endoparasitoid, Venturia canescens (Hymenoptera: Ichneumonidae). Lifetime reproductive success in V. canescens was measured in response to temporal variations in host and food (honey solution) access. Cohorts of parasitoids were provided with 200 fifth-instar larvae of the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae), and food for variable periods daily after eclosion. V. canescens is synovigenic, and host-deprived wasps continued to mature eggs over the first few days after eclosion until the egg storage capacity was reached in the oviducts. When these wasps were subsequently provided with hosts, oogenesis resumed and continued until later in adult life. Constantly fed wasps lived longer and produced more progeny than wasps from cohorts which were alternately fed and starved or were starved from eclosion. Moreover, wasps with constant host and food access produced most progeny early in life and usually experienced prolonged periods of postreproductive survival. In contrast, the reproductive period of wasps with limited host access was more evenly distributed throughout the adult life. Consequently, the cumulative progeny production by V. canescens with constant food access was fairly uniform irrespective of host availability. Longevity and fecundity in V. canescens were positively correlated with adult size. However, variable host access had little effect on the longevity of wasps which were constantly supplied with honey. Over the first 2 days of adult life, variation in food access also had no effect on progeny production by V. canescens. We argue that manipulating temporal host and food access to parasitoids in the laboratory more closely approximates natural conditions, where these resources are likely to be spatially separated. Moreover, our findings suggest that many highly synovigenic parasitoids like V. canescens, which produce microtype (=hydropic) eggs, have a considerably higher reproductive potential than ovary dissections have revealed. Our findings are discussed in relation to life-history evolution in the parasitic Hymenoptera.     

Evaluating the impact of a biological control parasitoid on invasive Vespula wasps in a natural forest ecosystem

The overall impact of the parasitoid Sphecophaga vesparum vesparum on invasive Vespula wasps in New Zealand native beech forest was evaluated by assessing the levels of parasitism achieved and the parasitoid’s effect at nest level and population level. The maximum proportion of nests parasitised was 17%, but there was no significant increase with time (r² = 0.139; p = 0.115). However, there was an exponential reduction in the number of parasitoids produced per parasitised nest from a peak of 570 (SE = 143) parasitoids per nest in 1990, declining to only 15 (SE = 6) parasitoids per nest in 2004. Even when parasitoid density was high, the parasitoid had no detectable impact on the number of small cells or the total host nest size, but it halved the number of large (reproductive) cells produced. This may have resulted in fewer queens produced per parasitised nest. Wasp nest density was highly variable from year to year, but there was no evidence that the wasp population density at the parasitised site (Pelorus Bridge) had declined relative to the five sites where the parasitoid had not established. We conclude that the parasitoid is unlikely to have had any significant effect on wasp populations hitherto, nor is it likely to impact host populations in the future. We recommend other biological control programs adopt pre-release assessment of per capita impact as a way of identifying agents that are more likely to be successful and hence minimising economic and potential ecological costs of biocontrol.     

Variation in selected life-history parameters of the parasitoid wasp,Aphidius ervi: Influence of host developmental stage

We determined the age-specific fecundity and survival of the solitary parasstoid wasp,Aphidius ervi Haliday (Hymenoptera: Aphidiidae), under constant laboratory conditions. Wasps were reared in each of the four nymphal instars of apterous pea aphids,Acyrthosiphon pisum (Harris) (Homoptera: Aphididae): L₁ (age 24h), L₂ (48 h), L₃ (72 h), and L₄ (120 h). Age-specific survival (l_x) and fecundity (m_x) differed between parasitoids developing in different aphid instars. The wasps’ life-time reproductive success, as indexed by the intrinsic rate of population increase (r_m), varied non-linearly with adult biomass and host size at parasitization. A close agreement between larval growth rates in different host instars and adult reproductive performance suggests that, inA. ervi, fitness correlates may be significantly influenced by larval ontogeny and trade-offs in resource allocation.     

Genome shuffling amplifies the carbon source spectrum and improves arachidonic acid production in Diasporangium sp.

The aim of this study was to develop a new fungal strain that simultaneously amplifies the carbon source spectrum and increases arachidonic acid (AA) productivity using genome shuffling between Diasporangium sp. and inactive Aspergillus niger. Through three rounds of genome shuffling, one of the stable daughter strains (F₁) acquired the ability to produce arachidonic acid and utilize various carbon sources. Compared to the parental Diasporangium sp., which could only use four out of eight carbon sources tested, F₁ could utilize all eight carbon sources. During fermentation with CMC-Na as the carbon source, F₁ was able to obtain 30.16% of lipid effectively whereas the parental Diasporangium sp. was not able to grow at all. When glucose was used as the carbon source, the CMCase activity of F₁ was 879.36 U, 298.23% higher than that of the parental Diasporangium sp. Under optimized fermentation conditions in a 5-L fermentation container, the AA yield of F₁ reached 0.81 g/l, 94.78% higher than that of the parental generation. These results indicate that inter-kingdom genome shuffling can be used successfully in eukaryotic microorganisms and that it can effectively improve the production of desired metabolites within a short period of time. The findings of this study may be useful for extending the application of genome shuffling in eukaryotic microbial breeding.     

Cold stored ectoparasitoid of Cydia fruit moths released under different temperature regimes

Cold storage of parasitoids to be used in biological control programs is desirable but risky for the performance of the stored parental generation as well as for its offspring. We studied the performance of cold stored and unstored parasitoids after release at different temperature regimes in the laboratory at the level of two subsequent generations in Hyssopus pallidus (Askew) (Hymenoptera: Eulophidae). This gregarious ectoparasitoid is a candidate biocontrol agent of Cydia pomonella L. (Lepidoptera: Tortricidae) and Cydia molesta (Busck) (Lepidoptera: Tortricidae) larvae, two fruit pests of high economic significance in apple cultivation. Cold storage for 14 days at 4°C imposed to the pupal stage of the parasitoid did not reduce the parasitism capacity of the parental generation, nor did it alter the female biased sex ratio of the progeny. Remarkably, this short-term storage of the parental generation exhibited a significant and consistently positive effect on offspring weight throughout all ambient temperature regimes, resulting in an increased offspring weight. Furthermore, offspring number was only reduced after release at low ambient temperatures, but not at 25°C and 30°C. Irrespective of whether the parasitoids originated from the stored or unstored group, highest parasitism rate was achieved at temperatures above 20°C. In conclusion, this candidate biocontrol agent can be cold stored for short periods without any measurable quality loss after release at most except at low ambient temperatures. Our findings suggest that H. pallidus is a thermophilous parasitoid that will perform best when applied at warm ambient temperatures in fruit orchards.     

Lethal and sublethal effects of spinosad-based GF-120 bait on the tephritid parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

Experiments were performed to determine the likely compatibility of spinosad-based GF-120 applications and mass-releases of the braconid parasitoid Diachasmimorpha longicaudata (Ashmead) for control of tephritid fruit flies. Severe effects on D. longicaudata survival and reproduction in the laboratory contrasted with mild effects in semi-field studies. Topical application and contact with dried residues on plastic surfaces in the laboratory generally resulted in high mortality of wasps and significantly reduced survival times compared to controls. Survival times of both sexes were more severely affected when exposure to dried residues on mango leaves compared to wasps that were offered GF-120 mixed with honey. Brief (24 h) exposure to GF-120 in honey or dried residues on mango leaves did not affect total progeny production by wasps, whereas continuous exposure over a 10 d period resulted in reductions in female survival, progeny production and net fecundity (∑L_xM_x) compared to honey-fed controls. During the rainy season, wasp survival times in field cages with young mango trees that had been sprayed with GF-120 or treated with GF-120 mixed with honey were only reduced by 1 or 2 days, respectively, compared to average 10.1 d survival of honey-fed controls. During the dry season, wasp mortality was not significantly affected by exposure to GF-120 residues on mango leaves that had been subjected to natural weathering in the field, compared to controls. Our results suggest that applications of GF-120 are unlikely to adversely influence the effectiveness of mass-releases of D. longicaudata. This prediction requires validation from comparative field studies on parasitoid populations in treated and untreated areas.     

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.     

Venom is beneficial but not essential for development and survival of Nasonia

1. Parasitoid wasps sting and inject venom into arthropod hosts, which alters host metabolism and development while keeping the host alive for several days, presumably to induce benefits for the parasitoid young. 2. This study investigates the consequences of host envenomation on development and fitness of wasp larvae in the ectoparasitoid Nasonia vitripennis, by comparing wasps reared on live unstung, previously stung, and cold‐killed hosts. Developmental arrest and suppression of host response to larvae are major venom effects that occur in both stung and cold‐killed hosts, but not in unstung hosts, whereas cold‐killed hosts lack venom effects that require a living host. Thus, cold‐killed hosts mimic some of the effects of venom, but not others. 3. Eggs placed on live unstung hosts have significantly higher mortality during development; however, successfully developing wasps from these hosts have similar lifetime fecundity to that of wasps from cold‐killed or stung hosts. Therefore, although venom is beneficial, it is not required for wasp survival. 4. While wasps developing on both cold‐killed and stung hosts have similar fitness levels, rearing multiple generations on cold‐killed hosts results in significant fitness reductions of wasps. 5. It is concluded that the largest benefits of venom are induction of host developmental arrest and suppression of host response to larva (e.g. immune responses), although more subtle benefits may accrue across generations or under stressful conditions.     

Influence of larval rearing temperature on the quality of cold‐stored Oomyzus sokolowskii Kurdjumov (Hymenoptera: Eulophidae)

Oomyzus sokolowskii, an important parasitoid of Plutella xylostella, has great potential for use in biological control. Storage at suboptimal temperature is valuable for increasing the shelf‐life of insect parasitoids. In this study, O. sokolowskii larvae were reared at 30/25, 25/25 and 25/20°C light/dark (65 ± 5% RH, 16 : 8 h L : D) until pupation. The pupae were then cold‐stored at 4 ± 1°C (60 ± 5% RH, full darkness). The pupae were removed out from the storage at 10, 20, 30 and 40 days after storage (DAS) and maintained at 25 ± 2°C until adults emerged or pupae died. Quality of the emerging adults and their F₁ offspring were assessed. Incidence of parasitism by O. sokolowskii was higher at 30/25°C than at 25/20°C. Cold storage of O. sokolowskii pupae greatly affected the fitness of the parasitoid: adult emergence rates were lower in the 40 DAS treatment than in other treatments; when O. sokolowskii larvae developed at 25/25°C, female proportions of the emerged adults were lower in the 40 DAS treatment than in the 0 and 10 DAS treatments. Larval rearing temperature mildly affected the adult emergence rate, post‐storage developmental time and female proportion with a few exceptions. Number of parasitoids emerged per host pupa, and incidence of parasitism by the females were neither affected by larval rearing temperature nor cold storage duration. Trans‐generational effects on F₁ offspring were evident in adult emergence rate, egg‐adult developmental time and female proportion which were negatively affected by long duration of storage (40 days), but not by larval rearing temperature with a few exceptions. In conclusion, O. sokolowskii pupae could be stored at 4°C for up to 30 days without significant fitness loss.     

Aspects of life-table studies and functional response of Lysiphlebia mirzai

The fecundity, reproductive rate, and survival of Lysiphlebia mirzai parasitising third instar nymphs of the cereal aphid Rhopalosiphum maidis were measured at six different host densities under constant laboratory conditions. The survival rate (l_x) of the female parasitoids was unaffected by host density, with an average adult life-span of 5–6 days at all densities. The age-specific fecundity rate (m_x) was host density-dependent. The value of m_x decreased rapidly from the first day of parasitisation. The number of hosts available determined the maximum possible number of mummies. At 200 hosts available per day, the average fecundity was 184.6 mummies/female; the maximum number of mummies yielded by any female was 200. The relationship between host density and the number of aphids parasitised per female was linear at 50 aphids/cage/day, but at higher host densities (100 aphids/cage/day) a significant curvilinear regression was observed. The intrinsic rate of natural increase (r_m) increased with increasing host density. Maximum value of r_m (0.262) was obtained at a host density of 200. The response of r_m to changes in host density and parasitoid sex ratio is shown. A typical type II functional response was observed for L. mirzai. The curve was described by a logistic curve, N_p=200/[1+exp(5.65–1.60 ln N_o)]. The search rate of the parasitoid was inverse host density-dependent. No significant variation in the sex ratio of F₁ offspring was observed at different initial host densities. Sex ratio values exceeded 0.5 at all host densities. The results evaluated the reproductive potential of L. mirzai as a promising biological control agent.