Effects of host stages and temperature on population parameters of Oomyzus sokolowskii, a larval-pupal parasitoid of Plutella xylostella

Oomyzus sokolowskii is alarval-pupal parasitoid of diamondback moth, Plutella xylostella. In a host stage preference test, the parasitoid parasitised all larval and pupal stages, but exhibited a strong preference for larvaeover prepupae or pupae, and did not show a preference among the larval instars. At 25°C, the developmental time, number and sex ratio of offspring per host pupa, and successful parasitism did not differ significantly among parasitoids reared from host larvae of different instars, indicating similar host suitability between larvae of different instars. Mean developmental times from egg to adult at 20, 22.5, 25, 30, 32.5, and 35°C were 26.5,21.0, 16.0, 12.7, 11.9 and 13.4 days, respectively. The favourable temperature range for development, survival, and reproduction of the parasitoid was 20--30°C. However, wasps that developed and emerged at a favourable temperature could parasitise effectively at 32--35°C for 24 hours. Life-fertility table studies at 20, 25, and 30°C showed that each female wasp on average parasitised 3.1, 13.2, 6.8 larvae of diamondback moth and produced 20.5, 92.1, 50.4 offspring, respectively, during her lifetime. The highest intrinsic rate of natural increase (r _m) of 0.263 female/day was reached at 30°C as a result of the short mean generation time at this temperature compared to that at 20 and 25°C, suggesting that the parasitoid had the highest potential for population growth at relatively high temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Parasitism on medfly by Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) in different guava cultivars

The parasitism efficiency of the Braconidae wasp, Diachasmimorpha longicaudata (Ashmead), was checked on four guava cultivars (Paluma, Sassaoca, Pedro Sato and Kumagai) infested with larvae of medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Five blocks of eight fruits, each with two fruits of each cultivar, were put inside C. capitata adult cages, during 2h for oviposition, and a week later, when the larvae inside guavas were developed, the fruits were exposed to parasitoids for 24h. The mean fruit weight, larvae mortality, number of pupae, percentage of medfly and parasitoid emergence were evaluated. There was not statistical difference among cultivars to weight, larvae mortality, number of pupae e emergence of medfly. The percentage of parasitism was higher in Pedro Sato cultivar (19.8%) compared with Kumagai cultivar (2.9%), but it was statistically similar to the other cultivars.     

Abiotic factors affecting Diachasmimorpha longicaudata (Hymenoptera: Braconidae) activity as a natural enemy of Ceratitis capitata (Diptera: Tephritidae) under semi‐natural conditions in the Mediterranean region

The larval–pupal endoparasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) is currently the most commonly employed biological control agent against Tephritid fruit flies in the Americas. However, this parasitoid remains largely ignored and is not used in many regions, including the Mediterranean Basin. In this study, the potential of D. longicaudata as a biocontrol agent against the Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera: Tephritidae) was addressed in an area of eastern Spain (the Valencian community). The parasitic activity of parasitoids and the effects of climatic conditions were evaluated throughout a 1‐year period in field‐cage experiments in which parasitoids were confined with apples artificially infested with medfly larvae. The following parameters were calculated and related statistically to several environmental conditions: the parasitism rate, the induced mortality and progeny sex ratio. The results show that D. longicaudata is able to parasitize medfly larvae throughout the year under semi‐natural conditions. Important fluctuations in the parasitism rate (from almost zero to 42%) and the induced mortality (from 6% to 80%) were partially influenced by climatic conditions. The parasitism rate increased with mean temperature and decreased with mean relative humidity, while the induced mortality decreased with minimum relative humidity. The optimal climatic conditions for the activity of the parasitoid were a mean temperature of 16–24°C combined with a relative humidity of 45%–60%. Overall, these results suggest that reduction in the medfly population due to D. longicaudata activity is feasible and provide information about the optimal time period for parasitoid release in the field. In conclusion, D. longicaudata has a significant potential to control C. capitata in the Mediterranean region.     

Parasitism of Aganaspis daci against Ceratitis capitata under Mediterranean climate conditions

The effect of environmental factors is essential to the success of parasitoids as biological control agents, as it determines their foraging activity, development, and survival. The larval‐pupal parasitoid wasp Aganaspis daci (Weld) (Hymenoptera: Figitidae) is known to have a very low fertility (i.e., offspring production) in the field in certain Mediterranean areas, probably due to its inability to efficiently oviposit under such climatic conditions. In this study, the percentage of parasitism and induced mortality (mortality of host pupae attributed to parasitoids, from which adults do not emerge) caused by this wasp to the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), was assessed under field conditions across 1 year, using medfly‐infested apples and parasitoid‐confined release in a lemon orchard of southeastern Spain. As A. daci is known to have very few emergences in the field, fertility was assessed in the laboratory from parasitized pupae recovered from the field. We found average parasitism rates of 27% and high induced mortality rates of 66% under field conditions. Consequently, medfly population reduction (total mortality of C. capitata caused by A. daci, i.e., induced mortality + % parasitism) was, on average, 87%. Parasitism and induced mortality varied throughout the year, depending on the average temperature and relative humidity. The interaction of these factors resulted in the highest parasitism rates at low mean temperature and humidity values; likewise, the highest percentages of induced mortality were obtained with a combination of high mean temperature and low mean humidity values. In conclusion, A. daci may exert a strong impact on medfly populations, being a good candidate for inundative field releases for the management of C. capitata in the Mediterranean Basin.     

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.     

Hymenopteran parasitoids of diamondback moth (Lepidoptera: Ypeunomutidae) in northern Thailand

Larvae of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Ypeunomutidae), cause severe economic damage to cabbage, Brassica oleracea L. variety capitata (Brassicaceae) and related vegetables in Thailand. Overuse of broad-spectrum insecticides for diamondback moth control is a serious problem and has obscured the contributions of indigenous parasitoids. Our objectives were to identify indigenous diamondback moth parasitoids in northern Thailand and to assess their potential for natural control. Six parasitoid species were reared from diamondback moth larvae and pupae collected in 1990 and in 2003-2004. These included the larval parasitoid Cotesia plutellae Kurdjumov (Braconidae), a larval-pupal parasitoid Macromalon orientale Kerrich (Ichneumonidae), and pupal parasitoids Diadromus collaris Gravenhorst (Ichneumonidae) and Brachymeria excarinata Gahan (Chalcididae). Single specimens of Isotima sp. Forster (Ichneumonidae) and Brachymeria lasus Walker (Chalcididae) also were reared from diamondback moth hosts. C. plutellae was the dominant larval parasitoid and was often reared from host larvae collected from fields sprayed regularly with insecticides; parasitism ranged from 14 to 78%. Average parasitism by M. orientale was only 0.5-6%. Parasitism of host pupae by D. collaris ranged from 9 to 31%, whereas B. excarinata pupal parasitism ranged from 9 to 25%. An integrated pest management (IPM) protocol using simple presence-absence sampling for lepidopterous larvae and the exclusive use of Bacillus thuringiensis (Bt) or neem resulted in the highest yields of undamaged cabbage compared with a control or weekly sprays of cypermethrin (local farmer practice). IPM programs focused on conservation of local diamondback moth parasitoids and on greater implementation of biological control will help alleviate growing public concerns regarding the effects of pesticides on vegetable growers and consumers.     

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.     

Efficiency of the newly recorded pupal parasitoid Pediobius furvus (Gahan) for controlling Sesamia cretica (Led.) pupae in Egypt

Abstract

Pediobius furvus (Gahan) (Eulophidae: Hymenoptera) was recorded as a new pupal parasitoid (gregarious endo-parasitoid) of Sesamia cretica pupae (Led.) in El-Noubaria region (El-Beheira Governorate), Egypt. This study was conducted in maize and sorghum fields in El-Beheira and Giza Governorates in Egypt during 1994 and 1995. The percentage parasitism was 8.4 and 15.4% in August and September, respectively. The number of parasitoids emerging from one pupa ranged from 28 to 222. It has been concluded that this new species is a gregarious endo-parasitoid that pupates inside its host. Pediobius furvus has a high reproductive ability, which may afford mass production and enable mass release of the parasitoid to control S. cretica in maize fields.     

Evaluation of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) as a mortality factor of Ceratitis capitata (Diptera: Tephritidae) infesting Citrus species under laboratory and field-cage conditions

Ceratitis capitata (or medfly) is one of the major pests currently affecting fruit crops in northwestern Argentinian Citrus-producing areas. Medfly populations are sustained in large exotic fruits, such as Citrus paradisi, Citrus aurantium and Citrus sinensis, which are known to hinder the activity of almost all native parasitoid species. Therefore, a feasible approach to controlling medfly involves the use of exotic parasitoids such as Diachasmimorpha longicaudata. In this study, the prediction that parasitoid females would be proficient at finding medfly larvae infesting the Citrus species mentioned earlier was tested. Particularly, the variation in fruit species preference by parasitoid females, the efficacy of the parasitoid to kill medfly and the effect of host density on parasitoid performance were determined. Parasitoids were allowed to forage for 8 h on grapefruits and oranges artificially infested with medfly larvae under controlled (laboratory) and uncontrolled (field cage) environmental conditions. Fruit choice and no-choice tests were performed. Results were assessed by comparing the number of female visits to and ovipositor insertions into the fruit, and parasitoid emergence, parasitism and additional host mortality percentages. Parasitoid preference for visiting larger fruits (sour orange and grapefruit) may be related to the increased fruit surface area. Ovipositional activity on fruit was influenced by the variation of the larval host density per unit of fruit surface. The higher parasitism rates recorded from sweet orange would be mainly a result of both increased host density and fruit physical features. Nevertheless, D. longicaudata showed the capacity to parasitise hosts in all Citrus species tested.     

Evidence from a gelechiid leaf-tier on mesquite (Mimosaceae: Prosopis) that semi-concealed Lepidopteran biological control agents may not be at risk from parasitism in Australian rangelands

Parasitism can limit the effectiveness of weed biological control agents. In this study, we surveyed larval and pupal parasitoids of the leaf-tying moth, Evippe sp. #1 (Gelechiidae), a biological control agent released widely in rangeland Australia against mesquite (Mimosaceae: Prosopis spp.). This moth was expected to be vulnerable to parasitism, as it has a semi-concealed feeding habit, is a member of a well-represented family, and is a herbivore on a well-represented family of trees and shrubs. We conducted surveys in four regions across Australia to determine whether parasitoids were responsible for differential performance of the moth in rangeland Australia, and what the consequences might be for the release of further semi-concealed Lepidoptera. The parasitoid fauna was found to be diverse, but the composition was similar across the four regions surveyed. It included primary and hyperparasitoids of both larvae and pupae. Parasitism rates were generally low, rarely above a few percentage points in any one survey, and therefore, unlikely to threaten moth populations. There was also no relationship between parasitism rates and leaf-tie abundance. These results suggest that any new semi-concealed lepidopteran biological control agents in rangeland Australia might also be parasitised by a diverse fauna. However, a better understanding of what determines parasitism rates is required to predict whether it would be sufficient to threaten biological control.     

Parasitoids of the African wild silkmoth,Gonometa postica (Lepidoptera: Lasiocampidae) in the Mwingi forests,Kenya

Gonometa postica Walker produces silk of high quality, but it is affected by parasitoids attack. A study on the parasitism of G. postica larvae and pupae on host and non‐host plants were undertaken for the first and second generations, corresponding to the long (March–May) and short (October–December) rainy seasons in 2006 at six field sites, three each in the Imba and Mumoni forests of Mwingi, eastern Kenya. All freshly spun cocoons of G. postica were sampled at each site from a total of 100 trees of host plants and other non‐host plants where they have migrated before pupation. The cocoons were kept individually in fine net‐sealed plastic vials to determine percentage parasitism. Two dipterans and four hymenopteran larval–pupal parasitoids were identified from the two forests. The most common parasitoids were Palexorista sp. (Diptera: Tachinidae) and Goryphus sp. (Hymenoptera: Ichneumonidae) with parasitism ranging from 1.8 to 32.7% and 2.2 to 7.5%, respectively. Parasitism varied significantly according to host or non‐host plants, seasons and sites. This study indicates that, of the six parasitoid species recovered, only two had a significant impact in reducing the quality of the cocoons.     

Low Temperature Storage of <Emphasis Type="Italic">Telenomus remus</Emphasis> (Nixon) (Hymenoptera: Platygastridae) and its Factitious Host <Emphasis Type="Italic">Corcyra cephalonica</Emphasis> (Stainton) (Lepidoptera: Pyralidae)

We conducted three bioassays to evaluate the effect of low-temperature storage of eggs (host) and pupae and adults (parasitoid) on the biology and parasitism capacity of the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). Viable stored Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) eggs were parasitized to the same degree or even higher than fresh eggs when stored until 14 days at 5°C or until 21 days at 10°C. In contrast, the percentage of parasitized sterilized eggs was equal to the control only when stored for 7 and 14 days. Survival of T. remus pupae declined with storage time at both studied temperatures (5 and 10°C). However, after 7 days of storage, survival of pupae was still 86.3 and 64.9% at 10 and 5°C, respectively. The number of adult male survivors remained similar until the fourth storage day at both 5 and 10°C. In contrast, female survival did not differ until day 8 at 10°C or day 6 at 5°C. Parasitism capacity of stored adults was not altered by storage compared with the control. Therefore, we conclude that the maximal storage time at 10°C is 21 days for viable C. cephalonica eggs and 7 days for T. remus pupae, while parasitoid adults should not be stored for more than 4 days at either 5 or 10°C.     

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.     

Effects of cold storage on Thripobius javae (=T. semiluteus) (Hymenoptera: Eulophidae)

Thripobius javae (Girault) was introduced in 1995 from Israel into Italy to control the greenhouse thrips, Heliothrips haemorrhoidalis (Bouché). Following introduction, successive augmentative releases of this parasitoid gave unsatisfactory and contradictory results, mainly due to the difficulty in synchronising its availability in sufficient number at the time of release. Efficient storage of this biological control agent could improve its current production and use. The effects of different sets of storage techniques at a single temperature and with a combination of different temperatures and instars on several fitness traits (residual developmental time to adult emergence after the end of storage, pupal mortality, longevity with and without hosts and progeny of emerged adults) were evaluated in order to determine the best conditions for storing the parasitoid.

For the pupal stage, increasing storage up to 14 days, at 10°C, gave only a moderate reduction (33%) of a modified composite quality index of its fitness. In contrast, when adults were stored for more than 10 days, at 15°C, residual longevity and progeny were reduced significantly. A combination of two temperatures (10 and 15°C) for pupal storage and a combination of pupal (10°C) and adult (15°C) storage had detrimental effects on parasitoid fitness. Temperatures of storage lower than 15 and 10°C had detrimental effects on adults and pupae, respectively.     

Parasitoids of the arctiid mothPareuchaetes pseudoinsulata (Lep.: Arctiidae), an introduced biocontrol agent against the weedChromolaena odorata (asteraceae), in asia and Africa

The leaf-feeding arctiid mothPareuchaetes pseudoinsulata has been released widely in tropical countries for the control of the weedChromolaena odorata. P. pseudoinsulata is now widespread and locally abundant in Ghana, Indonesia, India, Sri Lanka, Malaysia, Micronesia and the Philippines. In the West Indies where it is native,P. pseudoinsulata is host to 2 species of egg parasitoids, 4 species of tachinid larval parasitoids, 1 larval-pupal parasitoid, and 1 pupal parasitoid, as well as a virulent nuclear-polyhedrosis virus.P. pseudoinsulata is not significantly parasitised where it is established in south-east Asia, Oceania or Africa. No egg parasitoids have been reported, and only 3 larval or larval-pupal parasitoids. Only one of these, the larval-pupal tachinidExorista xanthaspis, is regularly encountered, and rarely exceeds 10% parasitism in the field. These results confirm the pattern that herbivorous insects from families with exposed larvae are unlikely to be heavily parasitised in a new geographic range.     

The Distributions of Parasitoids (Hymenoptera) of Anastrepha Fruit Flies (Diptera: Tephritidae) along an Altitudinal Gradient in Veracruz, Mexico

In the state of Veracruz, Mexico, fruits from 38 sites at various altitudes were collected monthly over a period of 2 years, and the tephritid fruit flies of the genus Anastrepha and associated parasitoids that emerged from these fruits were identified and counted. Of the 26 species of fruits that contained Anastrepha larvae, 18 species also contained a total of 10 species of Anastrepha parasitoids. These consisted of 4 native and 1 exotic species of opiine braconid larval–pupal parasitoids, 2 native species of eucoilid larval–pupal parasitoids, 1 exotic species of eulophid larval–pupal parasitoid, 1 exotic species of pteromalid pupal parasitoid, and 1 native species of diapriid pupal parasitoid. Overall parasitism (including flies from fruit species that bore no parasitoids) was 6% and was greatest, 16%, at 600–800 m in altitude. The relative contributions of individual parasitoid species to overall parasitism were frequently influenced by both the altitude (and correlated changes in temperature and precipitation) and the species of plant in which the Anastrepha larvae were found. This was particularly the case among the more abundant and widespread Braconidae. To distinguish the role of altitude from that of the distributions of the host plants, these braconids were examined in 4 individual species of fruit that grew over a broad range of altitudes. In guava (Psidium guajava L.) and “jobo” (Spondias mombin L.) the parasitoid Doryctobracon areolatus (Szepligeti) was relatively more common at low altitudes. Its congener, Doryctobracon crawfordi (Viereck), was relatively more abundant at high altitudes in sour orange (Citrus aurantium L.). Utetes anastrephae (Viereck) became relatively more common at higher altitudes in S. mombin, whereas Diachasmimorpha longicaudata (Ashmead) tended to become relatively rare at the highest altitudes in C. aurantium, but increased at high altitudes in P. guajava compared to other braconids. Different altitudinal patterns of abundance in different fruits suggests the importance of both biotic and abiotic factors in parasitoid distributions. We discuss the effect of an expanding agricultural frontier on parasitoid abundance and relate our findings to the design of a fruit fly biological control program that tailors mass releases to parasitoid climate preferences.     

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.     

Effect of cold storage of pupae parasitoid wasp,Habrobracon hebetor (Say) (Hymenoptera: Braconidae), on its efficiency

Cold storage is an appropriate way to extend the life of natural enemies such as insect parasitoids. Identification of risk factors for use in biological control and replacing it instead of chemical control is important, and therefore wasp species of genus Bracon have been used for controlling various pests in the past and present. The aim of this study was to determine the optimum temperature and time of storage of parasitoids pupae, Habrobracon hebetor (Say) in cold conditions. After in vitro rearing of the insect, the pupae of H. hebetor at the temperatures of 12, 9 and 4?°C for a period of six weeks in five replicates were stored. After these times, the effect of storage on the percentage of emerged adults and the longevity of male and female adults was evaluated on a weekly basis. The results of the survey conducted at 12?°C showed that the percentage of adults emerged from the first week has dropped by almost half. H. hebetor pupae could be stored for a week at 9?°C. At 4?°C, a significant reduction was caused in the efficacy of the stored pupae and is not recommended.     

Discrimination by Coptera haywardi (Hymenoptera: Diapriidae) of hosts previously attacked by conspecifics or by the larval parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

Coptera haywardi (Oglobin) is an endoparasitoid of fruit fly pupae that could find itself in competition with other parasitoids, both con- and heterospecific, already resident inside hosts. In choice bioassays, ovipositing C. haywardi females strongly discriminated against conspecifically parasitised Anastrepha ludens (Loew) pupal hosts. They also avoided pupae previously attacked by Diachasmimorpha longicaudata (Ashmead), a larval–prepupal koinobiont endoparasitoid, and the degree of larval-parasitoid superparasitism had no effect on this avoidance. There was no difference in the number of ovipositor insertions when hosts previously parasitised by a conspecific and D. longicaudata were exposed simultaneously. As females aged the degree of host discrimination declined. An ability to discriminate against pupae previously attacked as larvae suggests low levels of both conspecific and heterospecific competition in the field.     

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.