Reproductive performance of Nesolynx thymus (Hymenoptera: Eulophidae), in relation to age of Musca domestica (Diptera: Muscidae)

An investigation was undertaken to record the influence of host age on the reproductive performance of Nesolynx thymus (Hymenoptera:Eulophidae). This is an indigenous, gregarious, ecto-pupal parasitoid of certain dipteran insects, including the tachinid fly, Exorista bombycis (Louis) which is a well-known endo-larval parasitoid of the silkworm, Bombyx mori. Each gravid N. thymus female was allowed to parasitise 1–4-day-old puparia of Musca domestica L. for 2 days at a parasitoid–host ratio of 1:20. The parasitised host puparia were observed for progeny recovery, sex ratio, female longevity and fitness (adult size). In addition, reproductive performance of the parasitoid progeny was assessed by allowing its females to parasitise for 2 days, 3-day-old puparia of E. bombycis at a parasitoid–host ratio of 1:4. There was a significant negative correlation between host age and parasitisation rate, parasitoid developmental duration, sex ratio and female longevity while the correlation was positive between host age and parasitoid recovery per host puparium. Similarly, negative correlation was observed between host age and morphometric parameters (body length, head width and wing span of male and female and length and width of female abdomen) of the progeny adults. Host age did not have any impact on the reproductive performance of progeny adults when allowed to parasitise puparia of E. bombycis.     

Limited protection of the parasitoid Pachycrepoideus vindemiae from Drosophila suzukii host‐directed spinosad suppression

Laboratory trials were conducted to determine whether the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), puparium can provide an effective physical barrier to protect immature stages of the pupal parasitoid Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) from spinosad treatments. Spinosad insecticides are currently an important suppression strategy for D. suzukii in organically managed fruit orchards although they are well known to cause mortality in hymenopteran parasitoids. High adult P. vindemiae female mortality (83%) occurred within 24 h of exposure to D. suzukii pupae treated with 10 mg a.i. l^?1 spinosad and female parasitoids did not avoid the pupae treated with similar low levels of spinosad in choice tests that included untreated pupae. Pachycrepoideus vindemiae develops as an idiobiont ectoparasitoid on host fly pupa within the sclerotized host puparium. Significant P. vindemiae survival and emergence was recorded when parasitized D. suzukii puparia were exposed to field treatment levels of spinosad; however, the parasitoid survival was dependent on the time of the spinosad treatment of the host post‐parasitization. Significant parasitoid survival occurred when the host puparia were treated at 2 weeks when the parasitoid was in the pupal stage but did not occur when the host puparia were treated at 1 week post‐parasitization, when the parasitoids were still in a larval stage. The parasitoid adults consumed or otherwise came in contact with residual degrading spinosad when they exited the treated host, and consequently high and low adult parasitoid mortality occurred when the adults emerged from puparia treated at 2 and 1 week(s), respectively. Our study indicates that generally the integration of P. vindemiae parasitism into a sustainable D. suzukii management program is not compatible with spinosad treatments, although P. vindemiae in the pupal stage inside sclerotized host puparia appear to be minimally impacted by spinosad treatments, provided that the spinosad degrades before parasitoid emergence.     

Effects of relative humidity on cocoon formation and survival in the braconid wasp Cotesia glomerata

Abstract The effects of relative humidity (RH) on cocoon formation and survival in the braconid parasitoid wasp Cotesia glomerata (L.) (Hymenoptera: Braconidae) are investigated under various humidity conditions (50, 75, 90, 95 and 100% RH) at 20 °C and under an LD 16 : 8 h photoperiod. The mortality rate at the time of egression from hosts under 100% RH is significantly higher than for other RHs. Cocoon clusters formed at 100% RH spread significantly more than those formed at 50, 75, or 90% RH. Developmental periods differ significantly among RHs under which wasps developed. The mean period from the egression from hosts to adult emergence is 8.7 days when developed at 50–95% RHs, and 8.0 days at 100% RH. The emergence rates of C. glomerata that are maintained under the same humidity conditions after egression from hosts are not significantly different among RHs. However, emergence rates from cocoons that are transferred from 100% RH to 50 and 75% RH are < 70%, although the rates are > 90% in most cases. Some wasps do not emerge from cocoons: more than 60% die after adult eclosion at all RHs; the relative frequency of adult deaths is approximately 90% at 50% RH. Relative humidity influences the cluster and cocoon status strongly: both good clusters and cocoons are formed at low RHs. Emergence rates from cocoons of different ranks are significantly different: the rates of low‐rank cocoons are low at low RHs. The survival of C. glomerata is affected strongly by RH through cocoon formation.     

Pupal and larval-pupal parasitoids (Hymenoptera) obtained fromAnastrepha Spp. andCeratitis capitata (Dipt.: tephritidae) pupae collected in four localities of Tucuman province,Argentina

Pupal and larval-pupal parasitoids were obtained from 5 % of the 1,413 tephritid puparia collected in four localities of the Tucumán province, Argentina, from April, 1991 to April, 1993.Ceratitis capitata (Wiedemann) was attacked byPachycrepoideus vindemmiae (Rondani) (Pteromalidae), a pupal parasitoid, andAganaspis pelleranoi (Brèthes) (Eucoilidae), a larval parasitoid.Anastrepha spp. were attacked byDoryctobracon areolatus (Szépligeti) (Braconidae), a larval parasitoid, and also byA. pelleranoi. Information about parasitism, percentage of emergence of tephritid species and pupal viability in different localities is provided.     

European field collections and Canadian releases ofCeranthia samarensis (Dipt.: Tachinidae), a parasitoid of the gypsy moth

A programme to collect, import and release into Canada the gypsy moth parasitoid,Ceranthia samarensis (Diptera: Tachinidae) is described. The parasitoid's potential for biological control in Canada is also discussed. The parasitoid was collected in Europe by exposing experimental gypsy moth larvae in areas where local gypsy moth populations were at low densities. Following field exposure, the host larvae were returned to the laboratory and parasitoids reared from them. This technique has shown thatC. samarensis is the suffers 7–16% hyperparasitism. From 83–90% of theC. samarensis typically enter diapause as pharate adults within the puparia. Laboratory tests of post-exposure host rearing conditions indicate that constant temperatures disrupt the normal parasitoid diapause and that this effect can not be offset by use of either static long or short photoperiods or natural daylengths. Shipping and cold-storage procedures for puparia are described. Post-storage time to emergence of adultC. samarensis decreased with longer cold storage periods and with higher post-storage incubation temperatures. Emergence requires 112 degree-days above a threshold of 8°C after a period of at least 8 months cold storage. Releases of adultC. samarensis into field cages at four locations in southern Ontario are documented. While dissection of host larvae from the field cages has failed so far to demonstrate evidence of parasitism, we remain hopeful that some establishment of the parasitoid has occurred.      

Improvement of quality control methods for augmentative releases of the fruit fly parasitoids,Diachasmimorpha longicaudata and Psyttalia fletcheri (Hymenoptera: Braconidae)

Criteria were established to improve quality control methods for augmentative releases of the opiine parasitoids, Diachasmimorpha longicaudata (Ashmead) and Psyttalia fletcheri (Silvestri). These included correlating puparial weight with adult emergence and sex ratio at the Honolulu rearing facility, and determining the effect of air shipments and field releases on parasitoid emergence and subsequent mortality. There was a positive relationship between the weight of 7–10‐day‐old host puparia and percentage of emergence for both D. longicaudata and P. fletcheri. Standardization of shipping methods included placement of ice blocks in the top levels of the ice chests, prompt shipment and pick‐up of samples, and cooling of puparia before shipment to minimize metabolic heat generated in the samples, and to delay emergence of samples. Before standardization, emergence losses of up to 58% were observed for D. longicaudata and 18% for P. fletcheri. When shipping methods were standardized, emergence was no longer reduced. In addition, low emergence rates were associated with reduced flight propensity of D. longicaudata (R_s = ‐ 0.45 at Kilauea and ‐ 0.54 at Kealia). At the two release sites, 88–95% of adult D. longicaudata that did not escape the release containers were males.     

Effects of cold storage on life-history traits of Aphidius matricariae

Aphidius matricariae Haliday (Hymenoptera: Braconidae) is a polyphagous solitary endoparasitoid, attacking more than 40 species of aphids. This parasitoid is an important commercial product of many companies that produce biological control agents. Storage at low temperature increases the shelf life of many biocontrol agents, allowing companies to provide a steady and sufficient supply of insects for biocontrol programs. In the current study, the effects of cold storage of 1-day-old host mummies with A. matricariae for various time periods (5, 10, 15, 20, and 30 days) at 5 °C on the parasitoid’s key life-history traits were investigated. Parameters assessed after storage included adult emergence rate, offspring sex ratio, adult longevity, oviposition period, fecundity, and life-table parameters (R₀, r, λ, T, and DT). Our results showed that the mummies of A. matricariae could be stored at 5 °C for 5 days without loss of quality and for 10–15 days with minimal reduction in quality (e.g., some reduction in adult longevity and R₀). If parasitoids were stored for >15 days, quality was more strongly affected. In conclusion, A. matricariae pupae could be stored at 5 °C for up to 15 days without significant negative post-storage effects on fitness of the parasitoid. These results could be used to improve the planning of mass rearing and mass release of A. matricariae in augmentative biological control programs.     

Effects of temperature and other environmental factors on the post‐diapause development of walnut husk fly Rhagoletis completa (Diptera: Tephritidae)

To more effectively manage walnut husk fly Rhagoletis completa (Diptera: Tephritidae), in California walnut orchards, it is important to understand the factors that affect the timing of adult emergence. In the present study, we examine the effects of incubation temperature, pre‐chill and chill durations, latitude, cultivar and size on the post‐diapause development of R. completa puparia. The lower developmental threshold, upper developmental threshold and optimal temperature for puparial development are estimated to be 4, 34 and 26.6 °C, respectively. The thermal requirement for adult emergence after 120 days of chilling is estimated to be 2024 degree days. Percentage adult emergence declines at both higher and lower incubation temperatures. Chill duration at 5 °C for diapausing puparia has a nonlinear negative effect on the thermal requirement but no effect on percentage emergence. Insufficient chilling leads to poor synchronization of adult emergence. Greater pre‐chill duration at room temperature increases the thermal requirement and slightly decreased percentage emergence. Latitude has a negative effect on the thermal requirement. Puparia from northern California black walnut (Juglans hindsii) have a slightly greater thermal requirement than puparia from cultivated walnut (Julgans regia). There is no significant difference in puparial fresh weight or mean thermal requirement between males and females, although the positive correlation between thermal requirement and puparial fresh weight is stronger for females than males. The effects of temperature and other environmental factors on the post‐diapause development of R. completa are discussed in relation to observations from other Rhagoletis species.     

Suboptimal oviposition of tephritid flies supports parasitoid wasps

1. Female insects lay eggs on low‐quality plants, resulting in progeny with no or low reproductive potential; this is referred to as ‘suboptimal oviposition’ in this study. 2. Here, it is reported that suboptimal oviposition of a tephritid fly species (Tephritis femoralis) supports the populations of parasitoid wasp species in a Tibetan alpine meadow. 3. Suboptimal oviposition was confirmed because the adult flies emerging from Asteraceae species Anaphalis flavescens flowerheads did not survive cold winters. 4. DNA barcoding of puparia indicated that tephritid larvae developing from suboptimal oviposition hosted populations of at least five parasitoid wasp species. Consequently, suboptimal oviposition has significant effects on parasitoid population dynamics and species diversity.     

Seasonal parasitism and biological characteristics of Habrobracon hebetor (Hymenoptera: Braconidae) – a potential larval ectoparasitoid of Helicoverpa armigera (Lepidoptera: Noctuidae) in a chickpea ecosystem

Seasonal parasitism of Habrobracon hebetor (Say) on Helicoverpa armigera (Hübner) in chickpea was studied for three consecutive years. Parasitism by H. hebetor on larvae of H. armigera reached 12.3%. The parasitoid maintained reproductive activity on H. armigera from February to April coinciding with pod formation and maturation stages of the crop. In laboratory assays, we investigated the suitability of larval instars of H. armigera to the parasitoid H. hebetor. This parasitoid attacked third to sixth instars, though fourth and fifth instar larvae were found most suitable with 100% parasitism and development to adults. Parasitoid developmental time was longest in fifth instar (9.1 days) compared to other instars (8.1–8.9 days). Fifth instar larvae resulted in highest numbers of cocoons and adult emergence. In addition, suitability of seven lepidopteran species to H. hebetor was investigated. Corcyra cephalonica, Galleria mellonella and H. armigera were the most suitable hosts with 100% parasitism and development to adults. It was followed by Maruca vitrata and Autographa nigrisigna with 60–76.7% and 40–70% parasitism and parasitoid developmental success, respectively. Though there was 23.3% parasitism, there was no parasitoid development in Spodoptera litura. No parasitism was recorded in Spilarctia obliqua. Development of H. hebetor was most rapid in C. cephalonica (8.7 days), and longest in G. mellonella (9.3 days). Parasitoids that developed on these hosts resulted in highest numbers of cocoons and adult emergence. The parasitoid could be exploited for the biological control of H. armigera in a chickpea ecosystem.     

Does host age affect progeny production and progeny fitness in Trichopria sp.?

The gregarious endoparasitoid Trichopria sp. (Hymenoptera: Diapriidae) is currently under evaluation for its potential to suppress the levels of parasitism in larvae of the silkworm Bombyx mori (Lepidoptera: Bombycidae) caused by the tachinid fly Exorista bombycis (Louis) (Diptera: Tachinidae) in the rearing houses of sericulture farmers in southern India. Parasitism by E. bombycis currently results in cocoon yield reductions of 10–20 %. Prior to the mass production and release of Trichopria sp., there is a need to understand the factors that affect progeny production and fitness. Within this framework, we have attempted to determine whether host age has an impact on the numbers of Trichopria sp. progeny produced and on the subsequent fitness of the adults of the wasp. Two day-old adult females of the parasitoid were allowed to parasitize day (D) 1, 3, 5, 7, and 9 puparia of E. bombycis at a ratio of 1:4 (wasp:host). After eclosion of the parasitoid adults, data on the rate of parasitism, developmental period, brood allocation, progeny production, sex ratio, female progeny longevity and adult size were recorded. The reproductive performance of the adult progeny was also recorded by allowing them to parasitize three day-old E. bombycis puparia. Host age was seen to have an effect on several of the parameters recorded, such that while the most progeny were produced by the youngest (D1) hosts, larger wasps emerged from older E. bombycis puparia. It was, however, apparent that all but the oldest hosts (D9) examined were able to support adequate parasitoid development. Further, only relatively minor impacts on progeny fitness were observed between wasps deriving from hosts of different ages. However, the results strongly indicate that optimal production and parasitoid performance will be obtained by using young hosts of less than three days old.     

In vitro rearing ofExorista larvarum on tissue culture-based diets

Exorista (=Tachina) larvarum (L.) (Diptera, Tachinidae), a polyphagous parasitoid that attacksLymantria dispar L. andHyphantria cunea (Drury), was rearedin vitro from egg to adult on four tissue culture media-based diets (TMM-FH, SCHNEIDER'S, EX-CELL 400, and SF-900). The kind of tissue culture media in the diets did not influence the adult yield (34 to 55%) and puparium weight (26–27 mg). Adult yield and the puparium weight ofE. larvarum developed on TNM-FH and SCHNEIDER'S-based diets containing different amounts ofGalleria mellonella pupal extract (PE) (0, 1.25, 2.5 and 5%), were lower on diets without PE. In diets without PE development times from oviposition to adult emergence, were shorter on TNM-FH (19 days) than on SCHNEIDER'S-based diet (25–26 days). The adults that developed on artificial diets were able to parasitize the factitious hostG. mellonella and produce viable progeny. The results demonstrate thatE. larvarum is the most promising parasitoid ever studied forin vitro mass production.     

Bionomics of Opius bellus (Hymenoptera: Braconidae), an endoparasitoid of Anastrepha fraterculus (Diptera: Tephritidae) in fruit-growing areas of Northwestern Argentina

Opius bellus is a neotropical larval-prepupal parasitoid known to attack the pestiferous fruit fly, Anastrepha fraterculus. Due to interest in the use of native parasitoids in forthcoming fruit fly biocontrol programmes in Argentina, O. bellus was colonised for the first time using laboratory-reared A. fraterculus larvae. A series of experiments were conducted to (1) best achieve an efficient parasitoid rearing by determining optimal larval host age, host:parasitoid ratio and host exposure time and (2) assess their potential as biological control agents by determining reproductive parameters. The most productive exposure regimen was: 7–9 d-old (early and middle third-instars) A. fraterculus larvae for 4 h at a 4:1 host:parasitoid ratio; this array of factors was sufficient to achieve the highest average adult emergence (48%) and an offspring sex ratio at equitable proportion. Increasing both host:parasitoid ratio further than 4:1 and the host exposure time beyond 4 h did not significantly enhance parasitoid female offspring yield. Females produced eggs for 29.5 ± 1.4 days. At 32 days of age, 50% of the females were still alive. The majority of the progeny were produced by females between 20 and 24 d-old. At 26°C, gross fecundity rate, net reproductive rate, intrinsic rate of increase and mean generation time were 20.7 ± 4.2 offspring/female, 9.6 ± 2.5 females/newborn females, 0.06 ± 0.01 females/female/day and 8.4 ± 0.2 days, respectively. The long lifespan and reproductive parameters suggest that this parasitoid species has suitable attributes for mass-rearing.     

Nosema Disease of the Parasitoid Muscidifurax raptor (Hymenoptera: Pteromalidae): Prevalence, Patterns of Transmission, Management, and Impact

The microsporidium Nosema muscidifuracis was found in 1.1 and 10.7% of wild Muscidifurax raptor collected on New York dairy farms in 1991 and 1992. Higher (84%) levels of infection were observed on farms where infected M. raptor from a commercial insectary were released. Adult M. raptor became infected (100%) after feeding on spore suspensions of N. muscidifuracis, whereas house fly (Musca domestica L.) adults and larvae did not. Adult M. raptor became infected (16-25%) after feeding on infected parasitoid immatures within host puparia. Transmission rates of N. muscidifuracis increased with increasing parasitoid crowding levels because of cannibalism by healthy parasitoid immatures on infected immatures in superparasitized hosts. Maternal transmission was 100% efficient but there was no paternal or venereal transmission. Disease was reduced 35-93% by immersing infected parasitoid eggs within fly puparia in a 47°C water bath for 30-60 min. Eliminating disease from an established laboratory colony of M. raptor resulted in a 10-fold increase in parasitoid fecundity.     

Bioecological characteristics of Bassus tumidulus (Nees) (Hym., Braconidae), a parasitoid of the poplar twig borer, Gypsonoma aceriana (Dup.) (Lep., Tortricidae) in Bulgaria

Main aspects of biology and ecology of Bassus tumidulus (Nees), a parasitoid of Gypsonoma aceriana (Dup.), were studied during the period 1989–2000. Poplar tender shoots with G. aceriana larvae were collected at four localities in Bulgaria (Sofia, Svoge, Vardim and Pazardzhik) and examined in laboratory conditions. B. tumidulus was recovered in the Sofia and Svoge localities. It is a solitary internal parasitoid that attacks young larvae of G. aceriana (first–second instars) and kills host pre‐pupae. It develops two generations and overwinters as a larva in the host. Adult emergence of both overwintering and summer generation of B. tumidulus coincides with adult emergence of the host. In 1997, the first generation emergence of B. tumidulus was in relatively good synchrony with the first larval population of G. aceriana. However, the second generation B. tumidulus was not very well synchronized with the life cycle of G. aceriana because adult parasitoids appeared mostly in the beginning of the host larval population. The average mortality of G. aceriana, caused by this parasitoid in 1997 in Sofia, was 15.7 and 23.3% for the overwintering and summer generation, respectively. The highest level of parasitism by B. tumidulus, observed in individual study, was 61.5%, occurring during the summer generation in 1997.     

Impacts of two conventional insecticides on different stages of Encarsia inaron Walker parasitizing the whitefly,Trialeurodes vaporariorum Westwood under greenhouse condition

In this research, for the first time, compatibility of imidacloprid and pyriproxyfen was assayed with both pupa and adult stages of Encarsia inaron Walker parasitizing Trialeurodes vaporariorum Westwood. First, the insecticides were sprayed on bean plants containing the parasitoid pupae, thenceforth, survival of the adult parasitoid was evaluated 24 h post-exposure to fresh, 1-, 4-, 7-, 14-, and 21-day-old residues of them on bean leaflets in Petri dishes. Both insecticides significantly reduce E. inaron adult emergence. Mortality of the parasitoid pupa in treatment with imidacloprid (69.7%) was significantly higher than mortality with pyriproxyfen (28.6%). Pyriproxyfen was non-toxic to the adult parasitoid when residues were dried in fresh and aged through the experiment, while in the same condition, imidacloprid significantly killed the adult parasitoids up to 7 days after application. Results have been discussed on the potential compatibility of the insecticides with E. inaron in an integrated pest management (IPM) approach.     

Effect of different cold storage periods on parasitization performance of Trichogramma cacoeciae (Hymenoptera,Trichogrammatidae) on eggs of Ephestia kuehniella (Lepidoptera,Pyralidae)

The parasitism rates by Trichogramma cacoeciae Marchal (Hymenoptera, Trichogrammatidae) using Ephestia kuehniella Zell. (Lepidoptera, Pyralidae) eggs held at 0, 4 and 8°C and for up to 31 days was measured. Parasitism was lowest on eggs held at 8°C and highest on eggs held at 0°C. The highest parasitism, 97.8%, was measured for parasitoids attacking eggs held for 3 days and stored at 0°C. Parasitism of eggs stored at all three temperatures decreased with increasing duration of storage. The number of T. cacoeciae successfully developing and emerging as adults after storage in E. kuehniella eggs held at 0, 4 and 8°C was measured. Parasitoid emergence was >83% from E. kuehniella eggs stored at 8°C for 3 weeks. Storage at 0°C caused a significant decline in parasitoid emergence after 2 weeks (P<0.05). Storage at 0°C for more than 4 weeks reduced fecundity by 50%. T. cacoeciae parasitized the highest number of E. kuehniella eggs 1 day after adult emergence. The oviposition period lasted 6–7 days, although the parasitoids lived up to 13–14 days. Impact of storage time and temperature on parasitism rates by T. cacoeciae stored while in E. kuehniella eggs was measured. As storage time and temperature increased, subsequent parasitism rates of resulting adult T. cacoeciae decreased. Eggs of E. kuehniella can be stored at 0°C for up to 31 days. Trichogramma cacoeciae developing in eggs of E. kuehniella can be stored at 4°C for up to 5 weeks prior to release.     

Influence of parasitism and soil compaction on pupation of the green bottle fly,Lucilia sericata

The influence of parasitoids and soil compaction on pupation behavior of blow flies was examined in a host–parasitoid system involving Lucilia sericata (Meigen) (Diptera: Calliphoridae) and Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae). Larvae of L. sericata were introduced to containers with soil of different compaction levels, with or without parasitoids. Although females of N. vitripennis did not significantly affect the pupation depth of L. sericata, they increased the rate of pupal development by 15.0–23.7 h at 28.4 ± 1.2 °C, and increased the clumping of puparia. Pupation depth of L. sericata was negatively related to soil compaction; mean depth of pupation was 4.4 cm in uncompacted soil and 0.5 cm in high‐compaction soil. In high‐compaction soil, pupal development increased by 10.5–18.8 h at 25.2 ± 0.3 °C, and puparia were clumped. These results provide a framework for locating puparia in forensic investigations and releasing appropriate parasitoids for biological control of blow flies.     

Natural mortality of immature stages of Bactrocera oleae (Diptera: Tephritidae) in traditional olive groves from north-eastern Portugal

From 2006 to 2008, we studied the natural mortality of olive fly, Bactrocera oleae (Rossi), eggs and larvae as collected in fruit on the tree, in two to five ‘traditional’ olive groves of Trás-os-Montes (north-eastern Portugal), per year. We also studied the fate of 2044 puparia that were buried in the soil from November to May for two seasons, by using exclusion cages to estimate predation. Mortality of eggs inside the fruit was estimated as between 5.4±2.4 and 16.6±6.1%, and as 10.7±2.1 and 100.0% for young larvae. Similarly, the estimated mortality of mature larvae was between 0 and 66.7±33.3%. The highest mortality levels for young larvae could reach 100% during August, and 47.4% during the first fortnight of December, coincident with high temperatures in summer or low temperatures at the end of autumn and early winter. Mortality (winter disappearance) of puparia was estimated at up to 98.5% of the population. Predation of eggs was low, at 0.6±0.3 to 6.3±4.0% in 2006, 0 to 4.1±1.1% in 2007, and 0 to 3.6±3.6% in 2008. Parasitism was insignificant during the study, and only one parasitoid was identified, the eulophid Pnigalio agraules (Walker). We also surveyed entomopathogenic fungi associated with the insect in 12 olive groves, and evaluated three of the latter against larvae, puparia, and adult B. oleae in the laboratory. Of the 15 fungal species identified from immature stages, three were considered to be entomopathogenic (i.e. Cordyceps bassiana, Penicillium corylophilum and Mucor hiemalis). We observed up to 20.0±3.2% and 94.0±2.5% mortality of larvae and puparia, respectively when treated with P. corylophilum and up to 32.5±11.1% of adults when treated with M. hiemalis.     

Biological assessment of Tetrastichus brontispae,a pupal parasitoid of coconut leaf beetle Brontispa longissima

To control coconut leaf beetle, Brontispa longissima (Gestro), the pupal parasitoid Tetrastichus brontispae Ferrière was imported from Taiwan and its biology was studied in quarantine in Hainan, China. The parasitoid development includes an egg, three larval instars and three pupal stages. Its developmental time from egg to adult was 19.5±0.5 days under conditions of 24±2°C and 75±5% relative humidity (RH). Temperature had no effect on the sex ratio of offspring, but significantly affected the parasitism rate and reproduction. The parasitism rates were 98.07, 97.97 and 95.03% at 28, 24 and 20°C, respectively, whereas the parasitism rate was 52.18% at 18°C and 69.48% at 30°C, respectively. Furthermore, the parasitoids reared at 18 and 30°C produced fewer offspring than those at 20, 24 and 28°C, respectively. With the increase in temperature, developmental time decreased linearly from 46.19 days at 18°C to 17.10 days at 28°C. RH significantly influenced development, parasitism rate and the reproduction of T. brontispa. With the decrease of RH, developmental time increased from 22.94 days at 20% RH to 18.84 days at 95% RH. In contrast, parasitism rate and the number of offspring per female increased with the increase of RH. Though emergence rates between 50 and 95% RH were much higher than those between 20 and 35% RH, the sex ratios between 20 and 95% RH were not different. Photoperiod had no effect on parasitism, the number of offspring per female, emergence and the sex ratio of T. brontispae, but developmental time was significantly different for different photoperiods. Sucrose, honey and glucose significantly enhanced adult longevity, parasitism and the number of offspring per female of T. brontispae, but had no effect on the sex ratio and survival. Females of T. brontispae only parasitized fourth to fifth larval instars and 1–5-day-old pupae, but there was a significant difference in the number of offspring per female, development time, emergence and the sex ratio of offspring in different instars. These results showed that 1-day-old pupae, a temperature of 24–28°C and 65–95% RH were optimal for T. brontispae. These findings should be helpful in developing a production system to rear and release T. brontispae in large enough quantities to effectively control coconut leaf beetle.