A Minor Role of Host Fruit on the Parasitic Performance of Aganaspis daci (Hymenoptera: Figitidae) on Medfly Larvae

Host fruit is known to strongly affect the performance of both fruit pests and their potential natural enemies. This is particularly important in the control of tephritid fruit flies, whose larvae develop inside the fruit and thus create a set of foraging problems for parasitoids. In the present study, we assessed the response of female Aganaspis daci (Weld) (Hymenoptera: Figitidae), one of the most promising parasitoids for tephritid biocontrol in the Mediterranean Basin, to different potential host fruit species. We measured the olfactory response to medfly-infested and uninfested fruits, and several biological parameters of A. daci when different infested fruits were offered under both laboratory and greenhouse conditions. Our results showed that this parasitoid was significantly more attracted to apples and uninfested fruit. Moreover, parasitic activity was similar among the tested fruits under both conditions, showing very high values in the laboratory and a much poorer performance when conditions were variable. This suggests that A. daci may be a good candidate to be included in mass releases against the medfly regardless of the affected crop, but only when climate conditions are not expected to hinder its normal activity

Life History Parameters of Diachasmimorpha longicaudata on Ceratitis capitata Under Laboratory Conditions: Implications for Mass Rearing and Biological Control

The Mediterranean fruit fly, Ceratitis capitata, is considered one of the most destructive pests worldwide. The braconid Diachasmimorpha longicaudata is the most widely used parasitoid in biological control programs of tephritids. It has been mass-reared and used in augmentative releases against major fruit fly species in tropical and subtropical countries, and recently in the Mediterranean Basin. After its introduction into Spain and then Tunisia, reproductive and demographic parameters have been studied on C. capitata under laboratory conditions. These parameters were compared to those published elsewhere. The role of artificial diet for rearing the host is discussed. Our findings showed the good fitness of the parasitoids produced on C. capitata in laboratory with a generation time of 28.1 days, a reproductive rate of 39.2, an intrinsic rate of increase of 0.125, a doubling time of 5.2 days and the finite rate of increase (per day) was 1. Involvements on the biological control of the Mediterranean fruit fly in Tunisia are discussed

Diachasmimorpha longicaudata as Biological Control agent of the Mediterranean fruit fly, Ceratitis capitata: biotic and abiotic factors affecting its implementation in citrus crops of the Mediterranean basin

Ceratitis capitata Wiedemann (Diptera: Tephritidae) is a cosmopolitan pest, originary from West-Africa, that has invaded almost all the temperate and tropical countries by the unwanted aid of the men. During its adaptation to these new environments, C. capitata has widened its host plant portfolio, being nowadays a key pest for more than 400 plant species of economic importance. Due to this importance, many importing countries had established quarantine measures and borders against fruit world-wide trade, which had directly impacted on the plant protection policies of producer countries. Spain and Tunisia are located in the Mediterranean basin; the first known world-wide dispersal point of C. capitata. In these two countries, C. capitata is considered a key pest mainly for citrus species and other soft-fruits. From a historical point of view, Plant Protection policies in Spain were switched from a nearly ecological management (with great losses) to mainly chemical-based treatments with the spread of organosphosphate compounds early on XX century. With the development of European Union, national Plant Protection plans were modified, introducing the Integrated Pest Management programs (IPM), on which environment and human-friendly methods should be selected instead of the most damaging chemical treatments. Following these steps, Tunisia is integrating the use of biorrational methods while keeping the use of chemicals as low as possible. To this end, in the present thesis dissertation, I would focus on the use of natural enemies as the best and sustainable control method, coming back to the Biological Control programs that were successful in the past against other pests in both countries. More precisely, this dissertation is presenting the results on the implementation of Classical Biological Control against C. capitata in citrus, by the importation, evaluation and release of the parasitoid species Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) in both countries. This parasitoid species, native from East Asia, is currently used against other tephritid pest species, key species for other countries and commodities. In the First Chapter I will present a literature review on the Plant protection policies against this key pest, and what is know about the performance and success of this parasitoid species. At the Second Chaper, I will present the results of the implementation of laboratory rearings of both insects to achieve all the remaining objectives, along with the determination of life parameters of the specie that will determine its success as natural enemy. In this second chapter I will also present the determination of biotic (host densities and availability) and abiotic (temperature, RH, rainfall) factors affecting the performance of D. longicaudata over C. capitata. During the Third Chapter, I will demonstrate that D. longicaudata is able to exhert control of C. capitata under natural Mediterranean climatic conditions when either challenging the parasitoid with hosts directly from the laboratory rearing or in a more natural condition, within the fruits, a forestep required to determine its inclusion in the national Plant Protection Policies. Results show that D. longicaudata exhert up to 30% of medfly population reduction by means of induced mortality along the provisioning of new parasitoid offspring that would propagate and establish in the country. Along these results I showed that D. longicaudata was able to control medfly infestation foci at a rate that depend on climatic conditions and on the number of released females. At the Fourth Chapter, I will reveal the results of D. longicaudata dispersion abilities along its capability to exhert control of C. capitata populations while applied joinly with SIT, by means of open-field test trials, with a new developed sentinel fruits methodology. In this chapter, I consider also the abiotic factors that could determine its naturalization in other Mediterranean countries with similar climatic conditions. The results of this chapter highlight the need of such dispersal studies at the corresponding local climatic conditions to establish the release procedures. At the Fifth Chapter, I will expose the results of importation and naturalization of D. longicaudata in Tunisia, with the required studies on the presence of native enemies and the identification of a new parasitoid Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae)., the establishment of laboratory rearings for the release trials, and the side-effects of the available control measures that will face D. longicaudata in Tunisian citrus orchards which will determine the procedure in tempo and form for the releases. At the end of this dissertation, I will present the main conclusions achieved that can be summarized in: (i) D. longicaudata is a viable natural enemy that can be successfully released in Mediterranean countries against C. capitata; (ii) Its biotic potential under the mild climatic conditions identified will help in the naturalization of this species, and in the establishment of release protocols, but also, (iii) its climatic requirements highlight the need of switching from Classical Biological Control to Inoculative Biological control, that means that both countries require mass-rearing facilities to provide these insects, along the involvement of growers in the application of IPM measures including the augmentoriums to facilitate the naturalization of the introduced species along the preservation of the native ones.Programa de Doctorat en Cièncie

Effect of cold storage on the performance of Trichogramma bourarachae (Pintureau and Babault) (Hymenoptera: Trichogrammatidae)

6 p.-3 fig.-2 tb.In Tunisia, the use of the egg parasitoid trichogrammatid wasps to cope with several economic pests is gaining increasing attention. Trichogramma bourarachae (Pintureau & Babault) is among the Trichogramma wasps naturally present in Tunisia and regarded as a potential natural enemy to be used in biological control programs of many lepidopteran pests that cause economic losses. The propensity of T. bourarachae to cold storage with and without diapause induction was studied. The effect of this technique on its emergence rate and parasitic activity was investigated. The study showed that wasps of T. bourarachae treated at the induction temperature of 15 °C for 5 days can be stored at 4 ± 1 °C for more than 30 days without significant loss of their performances. By using this prestorage temperature, T. bourarachae could keep its emergence capacity (77.5%) up to 60 days of cold storage at 4 ± 1 °C. However, its parasitic activity decreased significantly (37.16%) after 45 days of cold storage. These results are promising for its mass production, transport, and release in the framework of national campaigns to control several agricultural pests of economic importance.Peer reviewe

Using Age-Stage Two-Sex Life Tables to Assess the Suitability of Three Solanaceous Host Plants for the Invasive Cotton Mealybug <i>Phenacoccus solenopsis</i> Tinsley

Phenacoccus solenopsis Tinsley (Hemiptera: Coccomorpha: Pseudococcidae), the cotton mealybug, is an invasive polyphagous species that has been extending its geographic range, posing a conspicuous threat to many Mediterranean crops of economic importance. These include three species of Solanaceae, namely Solanum lycopersicum L. (tomato), Solanum tuberosum L. (potato) and Solanum melongena L. (eggplant) all of which are economically important worldwide. In this study, we used age-stage two-sex life tables to investigate the suitability of these three plant species as hosts for P. solenopsis and to calculate pest fitness, life history parameters and population projection parameters. All tested host plants that were suitable for the pest and eggplant host plant induced a higher fecundity (276.50 ± 10.78 eggs/female), net reproductive rate (R0) (243.32 ± 15.83 offspring/female) and finite rate of increase (λ) (1.18 ± 0.0043 day−1) and more extended adult longevity (males: 6.50 ± 0.34 days and females: 24.15 ± 0.50 days). Population growth predictions over a period of 90 days of infestation, commencing with an initial population of 10 eggs showed that adult population size was 674,551 on tomato, 826,717 on potato and 355,139 on eggplant. Our data on plant host preference of P. solenopsis will aid the development of appropriate management strategies and achieve successful control of this invasive pest in key Mediterranean crop systems

The black fig fly Silba adipata (Diptera: Lonchaeidae) as an emerging pest in Tunisia: preliminary data on geographic distribution, bioecology and damage

International audienc

Emergence of the apricot seed wasp Eurytoma samsonowi Vassiliev (Hymenoptera: Eurytomidae) as an economic pest of apricots in Tunisia

International audienceMany eurytomid (Eurytomidae) wasps are plant parasites, and some of them are economic agricultural pests. In 2015, a new eurytomid wasp species was detected attacking apricots in the governorate of Gafsa located in the southern west region of Tunisia. Morphological and molecular identifications allowed to identify the pest as the apricot seed wasp Eurytoma samsonowi Vassiliev, a new record in Tunisia and Africa. Besides, field surveys were performed from 2017 to 2021 in order to assess the distribution of E. samsonowi in the main Tunisian apricot production areas, to characterize its symptoms of attack and to assess its damage on different apricot cultivars. The pest has limited distribution in Tunisia as it was found only in the governorates of Gafsa, Sidi Bouzid and Tozeur. Larvae of this pest feed on apricot nucellar tissues. Infested fruits either prematurely fall on the ground or turn black, become 'mummified', and remain attached to the tree. The highest infestation rates were recorded on Bayoudhi cultivar ranging from 64 to 76% depending on the year. Infestation rates registered on Bedri and Amor Leuch cultivars ranged from 24% to 51% and 27 to 53%, respectively. Therefore, this insect should be considered as an economic pest of apricots in Tunisia. Possible management measures and future outlooks are discussed