Parasitoid Emergence Research Articles

Temporal Distribution of Eois Immatures (Lepidoptera, Geometridae) in a Tropical Forest

Studies of populations on a temporal scale are essential to accessing the real diversity of an area since species may not be distributed equally over time. The temporal distribution of species can be related to climatic conditions, such as temperature and precipitation, which play an important role in biological systems, influencing biotic interactions. Insects may optimise their life-cycles to benefit from suitable environmental conditions, including food availability and escape from predators and parasitoids. The goal of this study is to describe the temporal distribution of Eois Hübner abundance associated with species of Piper and to investigate the role of climate and parasitoid wasps on monthly distributions of immature abundance. The study was carried out in an area of Atlantic Forest in Serra do Japi Biological Reserve (SJ), Jundiaí - SP, Brazil. For 13 months, from June 2015 to July 2016, Eois immatures were sought monthly under all leaves of 24 individuals from ten Piper species and reared until the emergence of adults or parasitoids. A total of 778 immature Eois specimens were sampled, and all abundance peaks were concentrated between March to June. No correlation was found between monthly Eois distribution with precipitation and temperature. Otherwise, the results showed a time-delayed correlation between the rate of parasitism and the abundance of Eois immatures, with the highest rate of parasitism occurring after peak abundance of immatures.

Kudzu Bug (Megacopta cribraria) and Associated Egg Parasitoids Emergence Rates in Alabama are Predicted by Weather Indices.

The kudzu bug, Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae), is a major economic pest of soybean in the southeastern United States. With climate warming, this pest is expected to move northward and cause additional crop damage. Parasitoid biocontrol is a potential method of integrated pest management for kudzu bug. Two species of egg parasitoid wasps have been observed emerging from kudzu bug egg masses in the southeastern United States: Paratelenomus saccharalis (Dodd) (Hymenoptera: Platygastridae) and Ooencyrtus nezarae (Ishii) (Hymenoptera: Encyrtidae). This paper used egg mass emergence data collected between 2018 and 2020 in Alabama soybean fields and compared the data to weather indices. Indices included the number of days with minimum temperatures below zero, accumulated rainfall (mm m-2), as well as species specific metrics of accumulated growing degree days, accumulated daily minimum temperature (°C), and accumulated daily maximum temperature (°C). Emergence of the generalist parasitoid, O. nezarae, was highly correlated with kudzu bug nymph abundance, accumulated degree day, accumulated daily temperatures, and precipitation. Ooencyrtus nezarae emergence was predicted in a stepwise regression equation by aggregated degree day and date of collection, which indicates that seasonality may be a predictor of its presence. In contrast, collections of the specialist parasitoid, P. saccharalis, were near-zero throughout the collection period, suggesting that this species may no longer be a usable biocontrol agent in the southeastern United States as a result of external limiting factors.

No adverse effects of symbiotic control on the parasitism of Halyomorpha halys by egg parasitoids

The brown marmorated stink bug Halyomorpha halys is a polyphagous insect, which has a devastating impact on agricultural production in many countries. The alteration of symbiont vertical transmission, by removing symbionts from stink bug eggs (symbiotic control), has been recently introduced in control programmes against this insect. A major advantage of this strategy is the compatibility with natural enemies, since it allows an insecticide-free approach that is not harmful to other agroecosystem components. However, the effect of anti-symbiont products on parasitism by egg parasitoids is still unexplored. Here, we investigated the impact on parasitism by native (Anastatus bifasciatus, Ooencyrtus telenomicida and Trissolcus kozlovi) and exotic (Trissolcus japonicus and Trissolcus mitsukurii) parasitoids that attack H. halys eggs, after treatment with the micronutrient biocomplex Dentamet®, used for symbiotic control. The native wasp species were tested in no-choice bioassays, showing that treatment of the egg masses did not affect emergence percentages, but the non-reproductive effects were often reduced by the biocomplex. The exotic species T. japonicus and T. mitsukurii were used in no-choice and paired choice bioassays, showing an opposite influence of Dentamet® on emergence percentage and preference in the two species. No-choice tests indicated the highest successful parasitoid emergence on biocomplex-treated egg masses for T. japonicus, while no preference in the paired comparison with eggs treated with water or untreated. In contrast, T. mitsukurii displayed the lowest parasitism after Dentamet® treatment in no-choice tests, and preferred egg masses without Dentamet® in paired choice tests. We did not record any natural symbiont acquisition by the parasitoids emerged from H. halys egg masses, indicating that the wasp fitness is very unlikely to be altered by dysbiotic effects resulting from treatments. Therefore, our results support a further implementation of symbiotic control in different crops in combination with biological control, as sustainable options for H. halys integrated pest management.

SELECTIVITY OF REGISTERED AGROCHEMICALS FOR SOYBEANS AIMING IMMATURE PHASES OF Trichogramma pretiosum

The aim of this study was to evaluate the effects of agrochemicals registered for soybean on parasitoid Trichogramma pretiosum in immature stages. Bioassays were conducted in the laboratory by exposing eggs parasited, using the methods proposed by the International Organization for Biological and Integrated Control of Noxious Animals and Plants (IOBC). The experimental design was completely randomized with eight replicates per treatment. The parameter for the classify agrochemical were based on the reduction of emergence of parasitoids (RE) evidenced by the number of parasitized eggs per female in the control. Based on the results obtained, all agrochemicals were innocuous to T. pretiosum in their immature stages.

Landscape composition affects parasitoid body size in species-specific manner: A case study in Asian rice systems

The top-down effect of natural enemies on pests is a crucial ecosystem service supporting integrated pest management. However, the variation in morphological traits of parasitoids in different landscape contexts and the differences in parasitoid emergence rate caused by this variation are still poorly known. We measured the inter-tegular distance (ITD) and body mass of three parasitoids– Cotesia chilonis (Munakata), Eriborus sinicus (Holmgren), and Microgaster russata Haliday – on overwintering larvae of Chilo suppressalis (Walker), the rice stem borer (RSB), collected from 20 rice paddies along a landscape heterogeneity gradient. Our objectives were to assess how landscape composition and landscape diversity affect functional traits (ITD and body mass) of species-specific parasitoid, and individual body size for its impact on biological control. From a total of 5002 sampled individuals of the three parasitoids, regression analysis revealed that (1) the presence of water bodies within the landscape respectively positive affected the ITD of E. sinicus and M. russata at 2000 m scales, landscape factors had yet no discernible effects on either the body size (ITD or body mass) of C. chilonis, (2) habitats with high landscape diversity had a negative effect on body size (ITD and body mass) of the solitary parasitoids E. sinicus at 200 m scales, and (3) a significantly negative correlation was found between the parasitoid emergence rate and ITD of E. sinicus. Our findings suggest that parasitoids’ body sizes may respond differently among species to landscape features. Solitary parasitoids in our study were more sensitive to variation in habitat resource-availability than was the gregarious parasitoid. We conclude that landscape habitat changes can affect the body size and parasitism of parasitoids, modifying their biocontrol services against pests.

Interactions between the Entomopathogenic Fungus Metarhizium anisopliae ICIPE 20 and the Endoparasitoid Dolichogenidea gelechiidivoris, and Implications for Combined Biocontrol of Tuta absoluta.

Simple SummaryThe theory of beneficial species association in a cropping system can sustain ecosystem services and reduce pest pression under economic injury levels. For the control of the invasive pest, Tuta absoluta we assessed the susceptibility of Dolichogenidea gelechiidivoris to Metarhizium anisopliae ICIPE 20 through adult parasitoid and parasitised larval infection; furthermore, we evaluated the preference and performance of sprayed and non-sprayed host plants. We concluded an additive effect for Tuta absoluta control by the two biocontrol technologies even though the entomopathogenic fungus reduces the fitness of the parasitoid, such as adult longevity and its performance, and parasitised larval emergence.The Integrated Pest Management (IPM) approach have been widely promoted and used for the management of native and invasive pests, while the use of various components of the IPM can have a synergetic, additive, or antagonistic effect on each other; this study evaluated the susceptibility of Dolichogenidea gelechiidivoris (Marsh) (Hymenoptera: Braconidae), to the Metarhizium anisopliae (Metschnikoff) ICIPE 20 through direct and indirect infection approaches. The effect of fungus on parasitoid longevity, survival of parasitized-larvae, preference of the parasitoid to fungal treated and untreated larvae, and percent parasitism of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under different infection scenarios were assessed. The direct application of dry conidia to the parasitoid prior to exposure to the host, reduced D. gelechiidivoris longevity, though the infected female wasps still yielded high parasitism (over 70%). Infecting the parasitized larvae at different ages led to a respective reduction of parasitoid emergence by 35% and 23% for infection at 1 and 5 days post-parasitisation. Exposure of healthy-D. gelechiidivoris adults to a plant-sprayed with fungus did not affect their longevity, and no discriminatory host selection was observed. The highest mortality (~80%) of T. absoluta was achieved when D. gelechiidivoris and M. anisopliae ICIPE 20 were used in combination, indicating an additive impact on the target pest; however, field validation can shed more light on this outcome.

Differential immune responses in new and old fruit fly-parasitoid associations: Implications for their management.

The oriental fruit fly, Bactrocera dorsalis (Hendel), and marula fruit fly, Ceratitis cosyra (Walker), are major fruit-infesting tephritids across sub-Saharan Africa. Biological control of these pests using parasitic wasps has been widely adopted but with varying levels of success. Most studies investigating host-parasitoid models have focused on functional and evolutionary aspects leaving a knowledge gap about the physiological mechanisms underpinning the efficacy of parasitoids as biocontrol agents of tephritids. To better understand these physiological mechanisms, we investigated changes in the cellular immune responses of C. cosyra and B. dorsalis when exposed to the parasitic wasps, Diachasmimorpha longicaudata (Ashmaed) and Psyttalia cosyrae (Wilkinson). We found that B. dorsalis was more resistant to parasitisation, had a higher hemocyte count, and encapsulated more parasitoid eggs compared to C. cosyra, achieving up to 100% encapsulation when exposed to P. cosyrae. Exposing B. dorsalis to either parasitoid species induced the formation of a rare cell type, the giant multinucleated hemocyte, which was not observed in C. cosyra. Furthermore, compared to P. cosyrae-parasitized larvae, those of both host species parasitized by D. longicaudata had lower encapsulation rates, hemocyte counts and spreading abilities and yielded a higher number of parasitoid progeny with the highest parasitoid emergence (72.13%) recorded in C. cosyra. These results demonstrate that cellular immune responses are central to host-parasitoid interaction in tephritid fruit flies and further suggest that D. longicaudata presents greater potential as a biocontrol agent of B. dorsalis and C. cosyra in horticultural cropping systems.

Hymenopteran Parasitoids of Leucotaraxis argenticollis (Diptera: Chamaemyiidae) and Leucotaraxis piniperda: Implications for Biological Control of Hemlock Woolly Adelgid (Hemiptera: Adelgidae).

The hemlock woolly adelgid (Adelges tsugae (Annand)) is a serious invasive pest of hemlock trees in eastern North America. Multiple biological control agents have been the focus of research aimed at pest management and conserving hemlock communities. Three promising A. tsugae specialist predators are the beetle Laricobius nigrinus (Fender) (Coleoptera: Derodontidae) and flies in the genus Leucotaraxis (Diptera: Chamaemyiidae), Leucotaraxis argenticollis (Zetterstedt), and Leucotaraxis piniperda (Malloch). However, these flies are vulnerable to parasitism by wasps in the genera Pachyneuron (Walker) (Hymenoptera: Pteromalidae) and Melanips (Walker) (Hymenoptera: Figitidae). This study explores parasitoid wasp interactions with these Leucotaraxis species in their native western North American range and potential impacts on the biological control program in the East. Leucotaraxis, La. nigrinus, and parasitoid emergences were observed from adelgid-infested foliage collected from Washington State and British Columbia in 2018, 2019, and 2020. Undescribed species of Pachyneuron and Melanips emerged from puparia as solitary parasitoids. Parasitoid emergence was positively correlated with Leucotaraxis emergence. Percent parasitism increased between February and July, with the months of June and July experiencing higher parasitoid emergence than Leucotaraxis. Differences in emergence patterns suggest that Pachyneuron may be more closely associated with Le. argenticollis as a host, and that Melanips may be associated with Le. piniperda. High parasitism in Leucotaraxis had no effect on La. nigrinus larval abundance, whereas the combined emergence of parasitoids and Leucotaraxis was positively correlated with La. nigrinus. This suggests that there is limited competition among these predators.

Biological control in a changing climate: plant-mediated impact of elevated CO2 concentration on Lobesia botrana eggs and egg parasitism by Trichogramma cacoeciae

Climate change can affect biological pest control by altering trophic interactions. Elevated carbon dioxide (CO2) concentrations can reduce host plant quality and, in turn, alter herbivore and natural enemy preference and performance. Using the Geisenheim VineyardFACE (free-air carbon dioxide enrichment) facility, we studied plant- and herbivore-mediated bottom-up effects of elevated CO2 concentration on the European grapevine moth, Lobesia botrana, and the parasitoid Trichogramma cacoeciae. Grapevine inflorescences of two cultivars cultivated at ambient or elevated CO2 (aCO2 and eCO2: 400 and 480 ppm) in the VineyardFACE were incorporated into L. botrana artificial diet. Eggs laid by the respective adults were parasitized by T. cacoeciae. Egg size and emergence rate of L. botrana as well as parasitism rate, parasitoid emergence rate and egg size preference of T. cacoeciae were evaluated. We observed an indirect grapevine cultivar-dependent bottom-up effect of CO2 on both herbivore and egg parasitoid. Compared to aCO2, eCO2 resulted in larger host eggs and higher parasitism rates regarding Riesling-feeding but not regarding Cabernet Sauvignon-feeding L. botrana larvae. Parasitoid emergence rate was higher when L. botrana had fed on Riesling compared to Cabernet Sauvignon-diet. Egg size preference depended on the host’s diet: T. cacoeciae preferred larger L. botrana eggs when the larvae had fed on grapevine-containing diet but not when they fed on standard artificial diet. Our results highlight the importance of the host’s diet for the parasitoid’s preference and performance. They furthermore suggest that the future efficiency of L. botrana-biocontrol by T. cacoeciae will not decrease under elevated CO2 concentrations.

The Spatial and Temporal Variations in the Superparasitism ofDiachasmimorpha longicaudataPopulation Lines on Different Hosts After Field Release.

Evaluating the behavior of the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) in the field allows improving strategies for its release. Thus, the aim of this study was to evaluate spatial and temporal variations in the superparasitism of two populations of D. longicaudata on two fruit fly hosts after releasing them in a guava (Psidium guajava L.; cultivar 'Paluma') orchard. The two parasitoid populations used were CS and AS, which were reared on Ceratitis capitata (Wiedemann) and Anastrepha fraterculus (Wiedemann), respectively. Four releases were carried out without host choice. Host larvae were offered to the parasitoids in sentinel traps attached at varying heights on the plant, and in plants located at eight different directions and seven distances (7.0, 21.0, 35.0, 49.0, 59.4, 63.0, and 69.3m) from the center of the parasitoid release point. The traps remained in the orchard for 24, 48, and 168h after release. After removing the traps, they were taken to the laboratory for scar counting. The percentages of parasitism, superparasitism, mortality, and emergence of parasitoids were determined. Data were analyzed using the generalized linear mixed-effect model (GLMM). The AS females were more active, as they exerted higher parasitism and superparasitism at the first distance and 48h after release, leaving a higher number of oviposition scars on the host A. fraterculus. Additionally, higher host mortality was observed in A. fraterculus at the closest points and the first 48h. The highest percentage of parasitoid emergence was observed in C. capitata parasitized by AS females.

Increasing radiation doses in Anastrepha obliqua (Diptera: Tephritidae) larvae improve parasitoid mass-rearing attributes.

Doses of 40, 80, 120, and 160 Gy were applied to 5-, 6-, 7-, and 8-day-old Anastrepha obliqua larvae, which were exposed to the Neotropical-native braconids Doryctobracon crawfordi and Utetes anastrephae and the Asian braconid Diachasmimorpha longicaudata. These tests were performed to know the effect of the increase in host radiation on the emergence of the aforementioned parasitoids and the related consequences of oviposition on the host. The study was based on the fact that higher radiation doses may cause a decrease in the host immune activity. There was a direct relationship between the increase in radiation dose and the parasitoid emergence. Both, the weight and the mortality of the host larvae were not affected by radiation. Although the larval weight of the larvae was lower and the mortality was higher in the younger larvae. Both, the number of scars and immature stages per host puparium originated from the younger larvae were lower than those from older larvae. Only U. anastrephae superparasitized more at lower radiation. Superparasitism by D. longicaudata was more frequent at 160 Gy. Qualitative measurements of melanin in the larvae parasitized showed that the levels were lower with increasing radiation. As radiation doses increased, the antagonistic response of the A. obliqua larva was reduced. Host larvae aged 5- and 6-day-old irradiated at 120-160 Gy significantly improve parasitoid emergence. This evidence is relevant for the mass production of the three tested parasitoid species.

Toxicity of chemical pesticides commonly used in maize to Trichogramma ostriniae (Hymenoptera: Trichogrammatidae), an egg parasitoid of Asian corn borer

Chemical pesticides are largely applied worldwide for the control of agricultural pests, and often cause lethal and sublethal side effects on natural enemies. To determine the compatibility of chemical pesticides, commonly used by maize growers, with Trichogramma ostriniae, the toxicities of four herbicides (pendimethalin, topramezone, glyphosate, and atrazine), three insecticides (imidacloprid, emamectin benzoate, and ethiofencarb), and three fungicides (propiconazole, benzoyl cyclazole, and difenoconazole) were tested under laboratory conditions, measuring residual toxicity to T. ostriniae adults, their lethal effects on the parasitoid’s eggs inside the host egg, and on the reproduction of the parasitoid’s female offspring. Three tested pesticides including ethiofencarb, glyphosate, and benzoyl cyclazole were slightly harmful to T. ostriniae adults, whereas the other seven pesticides were moderately harmful. The pesticide residues of ethiofencarb, and emamectin benzoate, showed slightly persistence of toxicity to T. ostriniae adults, in contrast to the remaining pesticides. Glyphosate, emamectin benzoate, imidacloprid, ethiofencarb, and propiconazole were classified as harmless, causing < 30% reduction in emergence rate of wasps from host eggs, while atrazine, pendimethalin, topramezone, benzoyl cyclazole, and difenoconazole were classified as slightly harmful, causing 31–52% reduction in parasitoid emergence rates. Furthermore, the number of eggs subsequently laid by T. ostriniae females that had emerged from parasitized host eggs treated with atrazine was significantly reduced compared to which of untreated parasitized host eggs. No negative effects were observed with atrazine treatment on the emergence rates of F1 wasps, their wing deformity rates and sex ratios. The data presented here indicate that the safety interval between pesticide applications and releases of T. ostriniae wasps is 2–3 weeks, which provide valuable information in designing a sound maize integrated pest management program that combines chemical pesticide applications with augmentative releases of T. ostriniae wasps.

Assessing the optimal frequency of early parasitoid releases in an apple orchard to control Dysaphis plantaginea: a proof-of-concept study

ABSTRACT Alternatives to pesticides to control the rosy apple aphid, Dysaphis plantaginea, are being developed. Natural enemies usually arrive too late after the first aphid infestation to provide effective control. This study tested the effects of mass release of two parasitoid species, Aphidius matricariae and Ephedrus cerasicola, on the numbers of aphid colonies and aphids per tree. In a trial undertaken in two years in an organic apple orchard, parasitoids were released three times early in the season to match the presence of aphid fundatrix (sensitive stages), on a weekly or bi-weekly frequency. The degree-days necessary for parasitoid emergence in the field after release were calculated. A sufficient level of aphid control by parasitoids was reached during the first month of the survey (March), but for both release treatments the control mostly failed during the second part of the monitoring session (April to late May) compared with the control treatment with neem oil. The relative effects of release frequencies were different between the two years, probably because of interannual differences in aphid population dynamics and initial infestation in orchards. The field survey suggested that parasitoid releases, at either frequency, were promising candidates for biological control of the rosy aphid, although the method still needs further calibration. This case study laid the first empirical basis to help develop future control methods of aphids by parasitoid releases in apple orchards. Releases should be done one to two weeks before first aphid detection to account for long development times of parasitoids at relatively low temperatures.

The Effects of an Arbuscular Mycorrhizal Fungus and Rhizobium Symbioses on Soybean Aphid Mostly Fail to Propagate to the Third Trophic Level.

The cascading effects of microbe–plant symbioses on the second trophic level, such as phytophagous insects, have been most studied. However, few studies have examined the higher third trophic level, i.e., their natural enemies. We investigated the effects of the symbiotic associations between an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis (Glomerales: Glomeraceae), a nitrogen-fixing bacterium, Bradyrhizobium japonicum (Rhizobiales: Bradyrhizobiaceae), and soybean, Glycine max (L.) Merr. (Fabaceae) on two natural enemies of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), the ladybird beetle Coleomegilla maculata (De Geer) (Coleoptera: Coccinellidae), and the parasitoid Aphelinus certus Yasnosh (Hymenoptera: Aphelinidae). We measured the growth and survival in the predator and parasitoid reared on aphids feeding on soybean inoculated seedlings. The rhizobium symbiosis alone was affected with a decreased rate of parasitoid emergence, presumably due to decreased host quality. However, number of mummies, sex-ratio, development time, and parasitoid size were all unaffected by inoculation. AM fungus alone or co-inoculated with the rhizobium was unaffected with any of the parameters of the parasitoid. For the predator, none of the measured parameters was affected with any inoculant. Here, it appears that whatever benefits the microbe–plant symbioses confer on the second trophic level are little transferred up to the third.

Effects of different Philosamia ricini (Lepidoptera: Saturniidae) cold storage periods on Ooencyrtus pityocampae and Ooencyrtus kuvanae (Hymenoptera: Encyrtidae) rearing.

Ooencyrtus pityocampae and Ooencyrtus kuvanae are egg parasitoids that are considered potential candidates for the control of different pest species through inundative release. The aim of this study was to assess the effects of different cold-storage periods of Philosamia ricini eggs (host) on the rearing parameters of O. pityocampae and O. kuvanae. Host eggs were stored at 3 °C, and a factorial experiment involving two parasitoid species, nine host storage periods (1, 5, 10, 15, 30, 45, 60, 75 and 90 days) and a control, and two host ages (1 and 2 days) was conducted, with 10 replications including 40-P. ricini eggs each. Adult emergence, development time, longevity, and fecundity were investigated. The parasitoid adult emergence percentage significantly varied with storage duration. These values were lower in O. kuvanae than in O. pityocampae. The development time of O. kuvanae progeny increased in both host age groups except in the 1-day storage period subgroup. However, the development times of the progeny of O. pityocampae reared on one-day-old eggs stored for 5, 10, 60, and 75 days were increased, and the development times of the progeny of O. pityocampae reared on 2-day-old eggs stored for 45 and 90 days were increased. The longevity of the F1 progeny of O. kuvanae was negatively affected by storage time. There was no difference in the longevity of the F1 progeny of O. pityocampae compared to that of the control. Additionally, the fecundities of the F1 progeny of O. pityocampae and O. kuvanae were 54.7 and 47.0 offspring/female, respectively. These results provide useful information for guiding the development of mass rearing methodologies for both parasitoid species.

Biological quality of Anisopteromalus calandrae (Hymenoptera: Pteromalidae) reared with cold-stored larvae of Lasioderma serricorne (Coleoptera: Anobiidae)

An effective storage method for larvae of the tobacco beetle Lasioderma serricorne (F.) (Coleoptera: Anobiidae) would be useful for rearing and studying its larval parasitoid Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), which is an idiobiont ectoparasitoid. In this study, we observed the survival of L. serricorne larvae that were refrigerated under different conditions (stored at 7 °C, 10 °C, and 13 °C for 30, 45, 60, and 75 days) and the number of emerging A. calandrae under these conditions, aiming to determine the optimal temperature for L. serricorne larvae storage. Our results showed that 10 °C was the optimum temperature for storing L. serricorne larvae, with no significant differences recorded in the number of parasitoids that emerged from L. serricorne larvae that had been refrigerated for 75 days compared with the control. After refrigeration at 7 °C for 45 days, L. serricorne larvae were almost dead, with no parasitoid emergence, suggesting that dead host larvae were not used for rearing A. calandrae. Interestingly, when stored for more than 45 days at 13 °C, L. serricorne larvae developed abnormally and died, and the number of parasitoids that emerged was also significantly reduced. Subsequently, we tested the adaptive parameters of A. calandrae reared with L. serricorne larvae after cold storage at 10 °C for different periods, including development time, sex ratio, longevity, adult body length, and fecundity. These parameters were not significantly different from those of the control with the exception of fecundity, which indicated that progeny production on refrigerated hosts gradually declined with storage duration. In summary, A. calandrae could successfully parasitize and utilize L. serricorne larvae as hosts for long-term refrigeration at 10 °C for up to 45 days without considerable undesirable effects on offspring suitability. These results may have practical implications regarding the development of efficient mass-rearing systems for A. calandrae.

Anastrepha striata1 Parasitic Wasps in Guava Crops at Fragmented Landscapes of Nayarit, Mexico

Biological control using native parasitoids is a sustainable alternative to control tephritid flies. We tested whether landscape attributes surrounding guava trees might affect incidence of fruit flies and their parasitoids. From July to September 2019, we collected guava fruit at six locations at Nayarit, México. Pupae obtained from the fruit collected were reared in a laboratory until emergence of adult flies and parasitoids. We combined in situ georeferenced information with 2019 SPOT-7 satellite images to characterize the landscape in circular 500-m buffers. Spearman-rank tests were used to analyze correlation between abundance of Anastrepha striata and parasitoids with the proportion of each soil coverage. Mann-Whitney U and Kruskal-Wallis tests were used to evaluate the influence of management intensity with abundance of the fruit fly and parasitoids. We collected 15.7 kg of guava fruit from six localities. Anastrepha striata was at all localities sampled. Infestation of fruit was 9.4%, ranging from 0.5 to 35.2 larvae per kilogram. The four parasitic wasp species attacking A. striata were Doryctobracon areolatus, Trichopria drosophilae, Aceratoneuromyia indica, and Leptopilina boulardi and are new records of interactions in the State of Nayarit. The wasps attacked 7.5% of the fruit fly pupae.

Ratio dependence effects of the parasitoid Dolichogenidea gelechiidivoris on its associated host Tuta absoluta

ABSTRACT The invasion of Africa by the South American leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has caused a severe threat to the production of tomato, Solanum lycopersicum L. (Solanaceae) crops. The excessive use of pesticides for controlling this pest has increased, together with the associated environmental and human health risks. The parasitoid, Dolichogenedia gelechiidivoris Marsh. (Hymenoptera: Braconidae), has been imported into Africa for classical biological control of T. absoluta. To facilitate the mass production of the parasitoid and to predict the success under field conditions, its performance under laboratory conditions was investigated at five densities of T. absoluta larvae, viz. 20, 50, 100, 150, and 200 offered to either a single or group of mated parasitoid females. The findings revealed that D. gelechiidivoris exhibited a type II functional response. Host and parasitoid densities affected superparasitism, which was generally low, less than 5%. Parasitoid offspring emergence ranged from 8 to 39 wasps for a single foraging female, and 6-59 wasps, for a group of foraging females. The host larval densities did not affect the male: female ratio. This study showed that D. gelechiidivoris acts in a density-dependent manner. Therefore, for optimisation of the mass production of the parasitoid, the maximum number of hosts should be offered to a female. The results suggest that D. gelechiidivoris could be effective for classical biological control of T. absoluta, albeit field evaluation is required to validate this finding.

Role of Egg Parasitoids in Controlling the Pine Processionary Moth in the Cedar Forests of Chréa National Park (Algeria)

The sustainable protection of cedar stands in Chréa National Park can only be accomplished through the stability of the ecosystem. Outbreaks of Thaumetopoea pityocampa are a major threat and are largely attributed to the high population fecundity, changes in the diversity of natural enemies and global interactions within the ecosystem. Egg parasitoids (Hymenoptera) are essential in the biological control of T. pityocampa. To assess the impact of the parasitoids on the populations of the pine processionary moth, egg masses from cedar plantations were collected, reared in a laboratory and checked regularly for the emergence of the egg parasitoids: Trichogramma embryophagum, Baryscapus servadeii and Ooencyrtus pityocampa. Observations showed an inter-annual variation in the abundance of the three parasitoids as a result of the variation in the population density of the processionary moth, and on the underlying effect of temperature. Parasitoids had variable parasitism rates, with yearly averages ranging from 3.86% to 51.14%, dependent on the spatiotemporal distribution of the host populations. The aggregate effect of multiple parasitoid species could optimize control of T. pityocampa in cedar stands.

Comparison of the Parasitization of Chelonus inanitus L. (Hymenoptera: Braconidae) in Two Spodoptera Pests and Evaluation of the Procedure for Its Production.

Simple SummarySuccessful integrated pest management of horticultural crops requires the evaluation of natural enemies used in biological control. To improve the mass rearing of Chelonus inanitus (L.) in the factitious host Ephestia kuehniella Zeller, we investigated the influence of host age and number of females parasitizing simultaneously on quality parameters evaluated in the commercial production of biological control agents, such as overall rearing success, duration of life cycle and body size. Under semi-field conditions, we investigated how the competition among females impacted the parasitism success on important pests Spodoptera exigua (Hübner) and S. littoralis (Boisduval). For the parasitoid mass rearing optimization, mature eggs seem to be more convenient because they increased the female percentage in the offspring and shortened the parasitoid life cycle. Furthermore, a high number of females parasitizing simultaneously reduced the emergence of non-parasitized hosts. Under more realistic conditions, the parasitoid effectively controlled both pests, but S. exigua may be a more convenient host because the parasitoid offspring was much larger. With this research, we provide a foundation that aims to better manage these cosmopolitan, highly polyphagous pests that exhibit long-distance migratory potential, alongside the potential use of this natural enemy.Chelonus inanitus (L.) is an egg-larval parasitoid of noctuids Spodoptera exigua (Hübner) and S. littoralis (Boisduval), whose mass rearing or real potential has not been targeted yet. To improve the rearing in the factitious host Ephestia kuehniella Zeller, we investigated the influence of host age and number of females parasitizing simultaneously on the overall rearing success, the influence of host age on the life cycle, and the influence of host species on the parasitoid body size. The proportion of emerging C. inanitus was higher from young host eggs, but more females emerged from mature eggs. Under high parasitoid competition, we observed a reduction in non-parasitized hosts without reducing parasitoid emergence. The parasitoid life cycle was longer in females, but the mismatch between sexes was smaller in mature eggs. The parasitoid size was smaller in the factitious host than in the natural hosts. Under semi-field conditions, we investigated the competition among parasitoid females on the overall parasitism success. The reproductive parasitism was more successful in S. exigua than in S. littoralis, and the maximum emergence was reached with three and four females, respectively. The control of S. littoralis may be attributed to the high developmental mortality, a non-reproductive parasitism that is often underestimated.