Parasitoid Production Research Articles

Cost-effectiveness evaluation of mass-rearing Cadra cautella (Lepidoptera: Pyralidae) based on harvest theory for sustainable alternative prey production.

Cadra cautella (Walker) (Lepidoptera: Pyralidae) is a pest in barn, and its eggs are often utilized as an alternative prey or as hosts for mass production of insect predators and parasitoids. To aid in developing a mass-rearing system for C. castella, the suitability of using an artificial diet based on brown rice flour and whole brown rice was compared using the age-stage, 2-sex life table. Compared with those reared on brown rice, the insects reared on an artificial diet had a shorter preadult period (32.08 vs 37.38 d), higher fecundity (468.14 vs 356.20 eggs/female), greater intrinsic rate of increase (0.1509 vs 0.1145 d-1), and higher net reproductive rate (199.28 vs 103.52 offspring). Small populations were required to rear the moth on an artificial diet to achieve the same daily production of C. cautella. Still, the food expense was only 60.2% of that of C. cautella reared on brown rice. Approximately 99.44% of the eggs in each rearing procedure could be supplied as alternative prey for predators, with the remainder served to maintain the colonies for subsequent batches. Only eggs laid within 6 d would be utilized to ensure the high quality of alternative prey for the mass production of predacious bugs. Additionally, a multifunctional device was designed for moth rearing and egg collection, reducing labor input and minimizing health risks for workers coping with inhaled scales. To encourage the production of natural enemies, a cost-effective diet for maintaining a sustainable colony, and a system for daily egg-harvesting of alternative prey were proposed.

Evaluation of key factors for mass rearing the egg parasitoid Telenomus remus Nixon (Hymenoptera: Scelionidae)

BackgroundTelenomus remus is an egg parasitoid used as a biocontrol agent to control the invasive pest Spodoptera frugiperda. The use of high-quality factitious hosts is needed for efficient mass rearing of high-fitness parasitoids for biological control releases. To improve the efficiency and quality of parasitoid production for mass rearing, we evaluated host perference, supplemental nutrition, ultraviolet (UV) irradiation, parasitoid density, and exposure duration. Quality control for the mass rearing of Te. remus has not been conducted previously. This study determined the conditions and quality control factors necessary for the effective mass rearing of Te. remus.MethodsThe preferred host of Te. remus was determined and the effects of supplemental nutrition on Te. remus adults, as well as those of ultraviolet (UV) irradiation on host eggs were evaluated. The subsequent impact on the quality of Te. remus were also assessed. The optimal parasitoid-to-host eggs ratio and exposure duration were studied.ResultsTelenomus remus preferred S. frugiperda eggs as the host. Nutrition supplementation prolonged female longevity and increased fecundity of Te. remus. UV irradiation caused S. frugiperda eggs to shrivel, having a negative effect on Te. remus reproduction. When the ratio of Te. remus to S. frugiperda eggs ranged from 1:4 to 1:10 and the exposure duration was 48 h, a lower wizened egg rate, higher emergence rate, and greater female proportion was obtained.ConclusionsThe use of S. frugiperda eggs as the host for mass rearing of Te. remus was indicated, and it was found Spodoptera litura eggs could sever as an alternative host. Nutrition supplementation and non-UV-irradiated S. frugiperda eggs should be provided. The suitable ratio of Te. remus to S. frugiperda eggs ranges from 1: 4 to 1:10, and the exposure duration should be 48 h, as determined by the ratio of parasitoid to host eggs.

Factitious hosts for Goniozus omanensis (Hymenoptera: Bethylidae), a parasitoid of the lesser date moth Batrachedra amydraula Meyrick (Lepidoptera: Batrachedridae)

ABSTRACT The bethylid wasp Goniozus omanensis has been identified as a key natural enemy of Batrachedra amydraula Meyrick (Lepidoptera: Batrachedridae), an important pest of date palm. Efficient rearing of natural enemies can be an important part of biological pest control programmes but cultures of G. omanensis are challenging to maintain on B. amydraula. We evaluate two readily available species of Pyralid moths, Corcyra cephalonica and Galleria mellonella, as potential factitious hosts. We find that G. omanensis can develop on the larvae of either species, but the probability of failure is circa 75% overall. Both trialled host species were approximately equally suitable, but failures were typically during the early stages of brood production when presented with C. cephalonica and during the later stages when presented with G. mellonella. This suggests that C. cephalonica larvae may be more difficult to suppress and that G. mellonella larvae may be of lower nutritional value. The average production of adult parasitoids per host provided was approximately 1 and, given the observed female biased sex ratio, the average number of females was around 0.8. We suggest potential routes to improving the efficiency of rearing G. omanensis on these factitious hosts.

Impacts of Climate Change on the Number of Days per Generation of the Egg-Parasitoid Telenomus Remus Nixon, 1937 (Hymenoptera: Scelionidae) in Egypt

In this research, we forecasted both the degree-day units and annual generations of the egg parasitoid Telenomus remus Nixon, which parasitizes fall armyworm (Spodoptera frugiperda). The aim was to comprehend its potential spread across diverse agro-climatic zones, considering both current conditions and potential future climates. This was achieved by examining the correlation between degree-day units and population fluctuations. Climate change data from the HadCM3 model was utilized, focusing on A1 scenarios recommended by the Intergovernmental Panel on Climate Change (IPCC). We aimed to evaluate how temperature projections are anticipated to impact the annual generations in three Egyptian governorates. The investigation revealed that T. remus populations in Aswan, an Upper Egyptian governorate, exhibited a higher number of generations compared to other regions, namely El Sharkia and Beni Suef governorates, in the current climate. The completion of generations by T. remus in El Sharkia, Beni Suef, and Aswan took 13.42, 12.6, and 10.08 days, respectively. The results highlighted that the average generation period in 2021 was the longest, reaching 13.42 ± 6.17 days in El Sharkia governorate. Predictions suggest that T. remus is anticipated to undergo 23 generations between 2040 and 2060, indicating a two-generation increase from 2021. Conversely, in the Beni Suef governorate, where T. remus completed generations in 10.86 ± 5.72 days, the generation period was the longest in 2021. Projections indicate that T. remus is expected to have 24 generations in 2040 and 28 generations in 2060, compared to 22 generations in 2021. Additionally, Aswan’s T. remus is forecasted to experience 32 generations in 2040 and 35 generations in 2060, up from 29 generations in the 2021 climate. The duration of the first generation took 13, 11, and 12 days in the years 2021, 2040, and 2060, respectively. A comprehensive understanding of thermal requirements and biological factors is crucial for accurately predicting generation duration, serving as a valuable reference for the mass production and preservation of parasitoids.

Rice moth, <i>Corcyra cephalonica</i> (Lepidoptera, Pyralidae) – A boon for biocontrol as a factitious host for mass production of parasitoids and predators

The eggs, larvae and pupae of the rice moth, Corcyra cephalonica (Lepidoptera, Pyralidae), have been found to serve as factitious/ alternative hosts for mass-production of at least 78 species of natural enemies – 60 parasitoids, 18 predators – belonging to 35 genera in 18 families under 8 orders that include Hymenoptera, Diptera, Arachnida and Nematoda for parasitoids while Coleoptera, Hemiptera, Hymenoptera and Neuroptera for predators. A list of these natural enemies is provided. Thus, though C. cephalonica is a serious pest of stored grains under natural conditions, it is a boon in laboratories as a factitious host for economic mass production of a variety of parasitoids and predators like Trichogramma, Chrysoperla, etc., which are extensively utilized in augmentative biological control.

Evaluation of comparative parasitic efficiency and biology of hymenopteran egg parasitoids, Trichogramma chilonis and T. japonicum on Corcyra cephalonica and Helicoverpa armigera

Aim: To evaluate the comparative parasitic efficiency and biology of Trichogrammatid wasps on noble laboratory host Corcyra cephalonica as well as on Helicoverpa armigera, the cosmopolitan, polyphagous and precarious insect pest of many cultivated crops. Methodology: The biology of Trichogramma chilonis and T. japonicum, their sex ratio, and parasitic efficiency were studied. Host insects were reared on artificial diet to obtain their eggs for initiating the experiment. Egg-card pieces were prepared with the irradiated eggs of respective host insects. Egg-cards were introduced into the tubes containing freshly emerged adult parasitoids. Parasitized egg-cards (Trichocards) were kept separately in plastic tube to study the biological attributes and percent parasitization of the parasitoids. Egg cards of different host eggs taking eggs of different age groups were prepared to study the effect of age of host eggs on the biological efficiency of the parasitoids. Results: Irrespective of Trichogramma species, the duration (d) of eggs to adult period was more when reared on the eggs of H. armigera than on the eggs of C. cephalonica. Maximum life stage duration of T. chilonis and T. japonicum from egg to adult was 8.2 days and 10.2 days, respectively, when reared on H. armigera eggs. There was maximum parasitization (84.8%) of fresh eggs of C. cephalonica by T. chilonis as compared to the egg parasitization of 73.4% by T. japonicum. Likewise, extreme parasitization of fresh eggs of H. armigera was recorded as 62.4% when parasitized by T. chilonisas against 59.7% parasitization by T. japonicum. Interpretation: According to the study, H. armigera eggs have the finest biological and parasitic features in terms of the highest adult longevity, sex ratio, mean progeny female-1, and mean adult egg-1, making them the best for mass production of the egg parasitoids, T. chilonis. Key words: Corcyra cephalonica, Host eggs, Helicoverpa armigera, Parasitization, Trichogramma

First attempt to develop a rearing method for the native green lacewing Chrysoperla lucasina in Tunisia

Green lacewing (Chrysoperla lucasina) is well known for its polyphagous predator larvae which are commonly used in pest’s biological control worldwide. In Tunisia, this auxiliary occurs in the nature in association with several pests but it has never been mass reared and released in biological control programs. Hence, the chrysopid species C. lucasina was chosen for an attempt of rearing in order to strengthen its natural populations. The study was carried out in the insectarium of the company ControlMed specialized in Trichogramma parasitoid production. All equipment used for green lacewing larvae and adult rearing was newly designed for this study. Two diets were given to larvae and adults to assess their biological performances. The first diet was based on pollen for adults and eggs of Ephestia kuehniella for larvae. The second diet consisting of a pasty mixture of honey, yeast and eggs of E. kuehniella, was supplied to adults and larvae. The laboratory rearing conditions were kept constant with 26 ± 2°C, 65 ± 5% RH and a photoperiod of 16L: 8D. The diets based on pollen and E. kuehniella eggs gave the best biological parameters for both adults and larvae. This study which allowed to design a simple technique to rear green lacewing based on affordable material, is a first step for developing a mass rearing of chrysopids in Tunisia. However, further improvements are required for adult and larvae diets to increase reproductive and developmental performance, as well as an economic feasibility study.

Influence of host larval weight of Anastrepha ludens on production parameters and quality attributes in the mass rearing of the parasitoid Diachasmimorpha longicaudata

AbstractLarvae of Anastrepha ludens (Loew) (Diptera: Tephritidae) are non‐native hosts of the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). These hosts appear to be a very good resource for the development of D. longicaudata in a wide range of larval weights. Therefore, the present study aimed to evaluate whether the larval weight of A. ludens influences the emergence and mass‐rearing parameters of D. longicaudata, including the parasitoid's adult attributes and host selection capacity. Three mean larval weights of 29, 25, and 21 mg were considered as high, medium, and low categories for the analysis. The tests included the effect of management of host larvae in the mass rearing of the parasitoids. In addition, evaluations of flight ability, survival, fecundity, and size were carried out in the adults that emerged from the larvae of the various weight categories. There was a direct relationship between host larval weight and parasitoid pupal weight, but there was no relationship with the emergence of adult parasitoids. However, a high percentage of females emerged from heavier larvae. Similarly, although adults that developed in the heaviest larval category were larger, adult quality parameters were not affected. In the evaluations of host selection, the parasitoids oviposited randomly in the larvae from the various weight categories; there was only selection if larvae of different weights were mixed. In addition, superparasitism did not differ between larval weight categories. In the evaluation of competition for hosts in cages under field conditions, larger female parasitoids that developed in the heaviest host larvae landed more frequently on infested fruit, but oviposition was similar between females of different sizes. In conclusion, the larval weight of A. ludens influenced the size of the host puparia and of adults of D. longicaudata, but the emergence and attributes of the developed adults were similar. Therefore, it can be concluded that the low larval weights of A. ludens evaluated in this study are within the range for proper development of D. longicaudata in mass rearing. This allows several options to produce hosts at a lower cost without negatively affecting the quality of parasitoid production.

Optimizing Mass Rearing of the Egg Parasitoid, Telenomus podisi, for Control of the Brown Stink Bug, Euschistus heros

The parasitoid Telenomus podisi Ashmead, 1893 is used in biological control programs in Brazil against eggs of Euschistus heros (Fabricius, 1798), a key pest of soybean, Glycine max (L.) Merr. To optimize the mass production of parasitoids, artificial diets and storage of host eggs at low temperatures have been developed; however, direct comparisons of the effects of these conditions have not occurred. We assessed a double factorial arrangement composed of six treatments (fresh or cryopreserved E. heros eggs from adults fed on natural or two artificial diets). We evaluated the biological characteristics and parasitism capacity of T. podisi produced from these treatments across seven temperatures. The thermal range between 21 and 30 °C resulted in satisfactory daily parasitism in all treatments tested, with an inverse relationship between temperature and female survival. The best parasitoid biological parameters were found between 21 and 27 °C, where all tested diets supported T. podisi development, with the best results from artificial diets. Fresh eggs and those frozen in liquid nitrogen and stored at -196 °C until use supported parasitoid development. These results suggest that the best method to mass rear T. podisi is to use artificial diets to rear E. heros and store eggs until needed, and then rear parasitoids at 24 °C.

Biotic and abiotic factors that affect parasitism in Trichogramma pintoi (Hymenoptera: Trichogrammatidae) as a biocontrol agent against Heortia vitessoides (Lepidoptera: Pyralidae).

The parasitoid wasp, Trichogramma pintoi, is a promising candidate for inundative release against Heortia vitessoides. Parasitoid females can regulate the sex of their offspring in response to environmental and biological factors. In pest control programs utilizing these parasitoids, male overproduction is not conducive to success. To optimize the production of T. pintoi as an egg parasitoid of H. vitessoides, factors affecting the rates of parasitism and eclosion and the percentage of females among T. pintoi offspring, such as temperature, photoperiod, host age, host density, maternal age, maternal density, and food, were investigated. The proportion of T. pintoi female offspring was significantly affected by temperature, photoperiod, host density, maternal age, and maternal density. The female offspring percentage decreased in response to host density (160 eggs), maternal age (≥ 4 days old), maternal density (≥ 4 females), photoperiods (24:0 and 18:6 L:D), and extremely low temperature (15 °C). However, host age and female diet did not affect the proportion of female offspring. According to the present work, female parasitoid production can be maximized under laboratory conditions of 25 °C, 75% relative humidity, and a photoperiod of 0:24 h (L:D) via exposure of forty 1-day-old H. vitessoides eggs for 24 h or eighty 1-day-old H. vitessoides eggs to a newly emerged, mated female fed a 10% sucrose solution until the female dies. These findings will guide mass production efforts for this parasitoid.

Effects of Host and Parasitoid Ages on Parasitism Efficiency of Dirhinus giffardii (Silvestri)1 against Zeugodacus cucurbitae2

Pesticides threaten the environment and increase amounts of resistance by pests. Ecologically friendly biological control of pests is being considered in scientific and political spheres. Fruit flies cause huge economic losses to more than 81 fruit and vegetable species. They are major pests in tropical and subtropical areas. This study used pupae of melon fly, Zeugodacus cucurbitae (Coquillett), as a host and Dirhinus giffardii (Silvestri) as the parasitoid, the biological control agent. During host-parasitoid interaction at different conditions of exposure, the rate of parasitism of a host by D. giffardii differed significantly in time. Least parasitism was of 1-day-old pupae (13.41 ± 1.10) exposed for 6 hours. Greatest percentage of parasitism was to 3-day-old pupae (43.5 ± 1.12) exposed for 24 hours. Few pupae younger than 3 days old were parasitized. Parasitoid emergence rate from pupae increased from 6 hours (21.49 ± 1.46), to 12 hours (28.30 ± 2.00), and 24 hours (33.93 ± 0.66). Percentage of emergence of 3-day-old pupae was 28.40 ± 0.59 at 6 hours, 29.51 ± 0.45 at 12 hours, and 34.11 ± 0.224 at 24 hours. To maximize in vivo production of parasitoids, 5-day-old female D. giffardii should be provided pupae ≤3 days old. Results contribute to further understanding host-parasitoid interaction important for sustainable and integrated pest management practices throughout the world.

Banker Plant Bonuses? The Benefits and Risks of Including Brassicas in Field Margins to Promote Conservation Biocontrol of Specialist Pests in Oilseed Rape.

European agri-environment schemes include the use of flower-rich field margins to promote on-farm biodiversity, but species mixtures rarely include Brassicaceae. As pests of oilseed rape (OSR; Brassica napus) and their parasitoids are mostly brassica specialists, including brassica 'banker plants' in the mixtures would help support these important biocontrol agents and improve pest control throughout the crop rotation. We assessed the potential of six brassicaceous plants (replicated plots grown in the field) to enhance populations of parasitoids of OSR pests whilst minimising proliferation of their pest hosts. Fodder radish (Raphanus sativus) facilitated high production of parasitoids of the pollen beetle pest (Brassicogethes aeneus) but may proliferate Ceutorhynchus weevil pests due to low parasitism. Turnip rape (B. rapa) and the B. rapa hybrid 'Tyfon' showed potential to perform a trap cropping function for pests, but their early flowering phenology resulted in B. aeneus larvae escaping parasitisation, potentially assisting proliferation of this pest. Forage rape B. napus exhibited similarly high B. aeneus parasitoid production characteristics to R. sativus but did not potentiate problems with other pests, indicating that it would be a favourable banker plant option. Careful selection of plants in field margin mixtures is therefore needed to maximise their benefits and ideally the whole crop pest-beneficial complex needs to be studied, as focus on a single major pest risks unintended consequences with other pest problems.

Effect of Larval Diets on House Fly (Diptera: Muscidae) Production and Host Suitability for a Pupal House Fly Parasitoid (Spalangia gemina) (Hymenoptera: Pteromalidae).

A larval medium for house fly (Musca domestica L.) suitable for house fly parasitoid production was developed from locally available and inexpensive food ingredients. Biological parameters and life table parameters were estimated for house flies treated with five different diets. It was found that percentage survival of 1st-3rd instar larvae of house fly, percentage of pupation, percentage of hatching adults, growth index, and life table parameters (net reproductive rate [R0] the cohort generation time [T], intrinsic rate of increase [r], and finite rate of increase [λ]) were significantly highest on larvae produced on diet 5 (composed of rice barn and chicken feed). Diet composition and performance of house fly larvae in larval medium are discussed, based on the results. The results of Spalangia gemina Bouček (Hymenoptera, Pteromalidae) parasitization on house fly pupae revealed that the number of total parasitized pupa and number of parasitoids hatched from pupa reared with diet 5 (rice bran and chicken feed) were greater than with diet 1 (rice bran, powdered milk, dry yeast, fish meal, soybean meal, and chicken feed). Additionally, S. gemina offspring from diet 5 treatment had a higher proportion of females. Our results indicated that pupal size resulting from larval diet was an important factor for parasitization.

Evaluation of three cold storage methods of Bagrada hilaris (Hemiptera: Pentatomidae) and the effects of host deprivation for an optimized rearing of the biocontrol candidate Gryon gonikopalense (Hymenoptera: Scelionidae)

The cold storage of host eggs has been utilized in the production of egg parasitoids used in biological control programs. However, similar stockpiling methods can lead to various responses depending on the parasitoid species considered. Hence, standardization of storage methods is difficult. The egg parasitoid Gryon gonikopalense Sharma, is currently being evaluated as a biocontrol agent of Bagrada hilaris (Burmeister), an invasive pest on Brassicaceae crops in the Americas. In this study, we investigated cold storage methods and the effect of host deprivation on G. gonikopalense in order to optimize its rearing process. Laboratory tests were conducted with bagrada bug eggs stored under three temperature treatments (-20 °C, 5 °C, 13 °C) and six durations (one week to three months). In addition, we assessed the effect of host deprivation on parasitoid fecundity and progeny development. Bagrada bug eggs stored at 5 °C up to one month allowed three and nine times more parasitism than eggs stored at 13 and -20 °C respectively. Progeny emergence rate was also the best with eggs stored at 5 °C (94.1%) while eggs stored at 13 and -20 °C led to 77.7 and 89.2 % of emergence respectively. However, the different storage treatments led to similar longevities and body lengths for male and female progeny. In addition, G. gonikopalense did parasitize bagrada eggs after 60 days of host deprivation, but fecundity was reduced by 84%. The results can be used to optimize bagrada bug egg production for use in laboratory and / or field experiments and improve G. gonikopalense rearing and production.

BIOLOGI Ooencyrtus malayensis Ferr. PARASITOID TELUR Dasynus piperis China, PADA INANG ALTERNATIF Nezara viridula L.

<p><strong>Biology of egg parasitoid ('Ooencyrtus malayensis Ferr.) ofpepper bug on alternate egg host (Nezara viridula L)</strong></p><p>Pepper bug (Dasynus piperis China) is an important pest of pepper. The pest widely spread in most pepper plantations of Indonesia. The level of the pest attack varied depended on crop cultivation treatment. Ooencyrtus malayensis is one of natural enemies which is able to control the population of pepper bug in plantation. The objective of this research was to study some aspects of the egg parasitoid biology by using eggs of Nezara viridula as the alternate host. This research was designed in a completely randomized block with four replicates. Dasynus piperis was collected from Bangka island and reared in Laboratory of the Research Institute for Spice and Medicinal Crops (RISMC ). Nezara viridula was fed with cowpea bean. This reascarch was conducted from July 1998 to February 1999. Experiment was divided into seven steps such as oviposition. pre adult period, production of parasitoid per host egg. egg preference, infestation period effect of cold storage (4°C) and parasitoid population. Research results showed that there were 85.5 parasitoid produced during its life time. Pre adult period lasted from 12 to 16 days, alternate host produced 3 parasitoids. The parasitoid pefeed the host of 0-2 days old. The eggs could be stored for 25 days in a efrigenerator (4°C). The longer the infestation and the larger number of parsitoid infested the larger numbers of parasitoid produced.</p>

The impact of fruit fly gut bacteria on the rearing of the parasitic wasp Diachasmimorpha longicaudata

AbstractArea‐wide integrated pest management strategies against tephritid fruit flies include the release of fruit fly parasitic wasps in the target area. Mass rearing of parasitic wasps is essential for the efficient application of biological control strategies. Enhancement of fruit fly host fitness through manipulation of their gut‐associated symbionts might also enhance the fitness of the produced parasitic wasps and improve the parasitoid rearing system. In the current study, we added three gut bacterial isolates originating from Ceratitis capitata (Wiedemann) and four originating from Bactrocera oleae (Rossi) (both Diptera: Tephritidae) to the larval diet of C. capitata and used the bacteria‐fed larvae as hosts for the development of the parasitic wasp Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). We evaluated the effect of the bacteria on wasp life‐history traits and assessed their potential use for the improvement of D. longicaudata rearing. Enterobacter sp. AA26 increased fecundity and parasitism rate and accelerated parasitoid emergence. Providencia sp. AA31 led to faster emergence of both male and female parasitoids, whereas Providencia sp. 22 increased the production of female progeny. Bacillus sp. 139 increased parasitoid fecundity, parasitism rate, and production of female progeny. Serratia sp. 49 accelerated parasitoid emergence for both males and females and increased production of female progeny. Klebsiella oxytoca delayed parasitoid emergence and Enterobacter sp. 23 decreased parasitoid fecundity and parasitism rate. Our findings demonstrate a wide range of effects of fruit fly gut symbionts on parasitoid production and reveal a great potential of bacteria use towards enhancement of parasitic wasp rearing.

Irradiation of early immature Anastrepha ludens stages for the rearing of Doryctobracon areolatus (Hymenoptera: Braconidae), a fruit fly parasitoid.

Doryctobracon areolatus is a native parasitoid of the Neotropical region that presents the highest percentages of natural parasitism of fruit flies of the genus Anastrepha. In the Moscafrut Program SADER-SENASICA, located in Metapa de Domínguez, Chiapas, Mexico, a laboratory colony of this species is maintained on Anastrepha ludens, the Mexican fruit fly, with the aim to scale the production of the parasitoid up to massive levels. In order to eliminate unwanted emergence of adult flies during the rearing process, this study evaluated the effect of irradiation (at doses of 20, 30, 40, and 50 Gy) applied to eggs, and first and second instar larvae of A. ludens; all irradiated stages were subsequently exposed as second instar larvae to adult females of D. areolatus. Irradiation did not affect the eclosion of A. ludens eggs but, at doses of 40 and 50 Gy, it did cause delayed larval development and pupation, as well as lower larval weight. Adult fly emergence was suppressed at all doses, except in eggs irradiated at 20 Gy. Doses of 20 and 30 Gy applied to the eggs and larvae did not affect the emergence, survival, fecundity or flight ability of the emerged parasitoids, but the second instar larvae were easily handled during the rearing process. Our results suggest that D. areolatus can be successfully produced in second instar larvae of A. ludens irradiated at 30 Gy.

The cost of parasitism: High larval developmental mortality following attacks by a parasitoid fig wasp on a fig pollinating wasp

Parasitoids contribute to controlling phytophagous insect populations. Their action on a host is often measured by numbers of emerging adult parasitoids. However, parasitoid oviposition attempts may lead to host mortality and sometimes both host and parasitoid die during larval development. Therefore, establishing the effect of parasitoids on host populations requires estimating total effect of parasitoids.The communities of wasps developing in figs (the closed inflorescences of Ficus) have become a model system to investigate micro-hymenopteran interaction networks. A galled ovule produces either a single galling wasp or a single parasitoid providing a simple way to measure costs. However, some galled flowers produce no wasps. We show that about one quarter of galled flowers fail to produce pollinator offspring in the absence of parasitoids. In the presence of parasitoids, the number of empty galls is increased. For each emerging parasitoid, 1.9 pollinator larvae were killed. Hence, host mortality induced by parasitoids is much larger than actual parasitoid production, a feature documented in some other host-parasitoid interactions and that may be pervasive in nature.

Effects of exposure time and ratio of irradiated larvae from three medfly strains on progeny yield in Diachasmimorpha longicaudata (Hymenoptera: Braconidae) mass rearing

ABSTRACTAn augmentative biological control strategy against Ceratitis capitata (= medfly) in fruit-producing irrigated-valleys of San Juan, central-western Argentina, has been recently implemented by the San Juan Fruit Fly Control and Eradication Program. The Asian-native parasitoid Diachasmimorpha longicaudata is currently reared at the San Juan Medfly and Parasitoids Mass Rearing Facility for this purpose. In this regard, the objective of this study was to evaluate adult emergence and offspring sex ratio to improve parasitoid production. Three medfly strains at different host larvae densities and exposure times to female parasitoids were assessed. Prevalence of superparasitism was also considered. Three parasitoid population lines were used in the trials: one reared on medfly larvae of the Vienna-8 temperature-sensitive lethal (tsl) genetic sexing strain without inversion, and the other two on larvae of biparental medfly strains native to San Juan (central-western Argentina) and Tucumán (northwestern Argentina). Gamma-irradiated 6 d-old larvae (early third-instars) of each medfly strain were exposed to parasitoids for 30, 60, 90, and 120 min at 3:1, 6:1, and 9:1 host/parasitoid ratios. The Vienna-8 C. capitata strain was as efficient in producing parasitoids as both biparental native strains. Medfly larvae exposed to 10 female parasitoids for a relatively long time (1.30 hrs) at a high ratio (6–9:1) of host to parasitoid were enough to achieve the highest mean adult emergence (50–60%) and a female-biased offspring sex ratio. Superparasitism positively influenced female parasitoid production. These findings may be used to develop a more cost-effective mass rearing method for D. longicaudata.

Using Gamma Irradiated Galleria mellonella L. and Plodia interpunctella (Hübner) Larvae to Optimize Mass Rearing of Parasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae)

We evaluated possible improvements to the mass rearing of the larval parasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae) on irradiated host wax moth Galleria mellonella L. and Indian meal moth Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) larvae. The use of irradiated G. mellonella and P. interpunctella larvae at the dose of 150 Gy proved useful for enhancing the parasitism and adult emergence of H. hebetor due to the absence of negative repercussions on parasitoid development. Overall, parasitism was increased as the host larvae was irradiated with higher doses, while significantly higher parasitism was recorded at 150 and 300 Gy compared to lower doses. The female parasitoids preferred the irradiated larvae and significantly higher numbers of larvae were parasitized compared with non-irradiated larvae. The results also showed that irradiated larvae of G. mellonella served better as hosts for H. hebetor as compared with irradiated larvae of P. interpunctella. The implementation of these findings would be helpful for improving the mass production of parasitoids and the effectiveness of releases of biocontrol agents for the control of stored product pests.