STUDIO DEL VELENO DEL PARASSITOIDE DI AFIDI APHIDIUS ERVI

Superparasitism (repeated oviposition in same host) indicates either a fitness benefit for the parasitoid or an inability of ovipositing females to discriminate parasitised versus unparasitised hosts Superparasitism in Diaeretiella rapae the solitary endoparasitoid of cabbage aphid Brevicoryne brassicae was studied in the laboratory When given a choice of parasitised and unparasitised aphids 70 of females made their attack on unparasitised hosts first even though alreadyparasitised aphids were less defensive to parasitoid attack and ovipositing females had shorter hosthandling time The female superparasitised hosts during repeated attack and the large hosts were superparasitised more often than the small ones Although superparasitised hosts carried two to five parasitoid larvae only one larva developed into an adult The body size of parasitoid larvae as measured 4 days after oviposition was affected by the total number of larvae in the host Superparasitism strategies of D rapae are discussed in the context of reproductive fitness

Many aphid species cause the reduction of crop yield and monetary loss through feeding and pathogen vectoring. Current pest management strategies for aphids require a range of control methods. However, increased resistance to these methods in certain populations of aphids could impact successful control of these pests. This thesis focuses specifically on the Potato aphid, Macrosiphum euphorbiae, and its innate resistance to the parasitic wasp, Aphidius ervi, a common natural enemy of multiple aphid species. I first discuss population dynamics of M. euphorbiae within the UK and its existence as a handful of strictly asexual genotypes. The distribution is skewed towards genotypes potentially linked to increased host range, while the genotype with low susceptibility to A. ervi (genotype 1) has lower frequency in comparison. A cost associated with A. ervi parasitism-resistance in potato aphids has yet to be demonstrated, while also exhibiting no detrimental effects on fitness in a response to A. ervi challenge as well as potentially having increased tolerance to sub-zero temperatures. To further study innate parasitoid resistance, I generated a draft genome of the genotype 1 Potato aphid (and its obligate symbiont Buchnera aphidicola) using a mixture of long-read sequencing and chromosome scaffolding techniques. Comparative genomics between this aphid genotype with other genotypes of Potato aphid and other aphid species provides a list of immune functioning genes that could play a role in immunity, either through sequence variation or copy number aberrations. However, it is difficult to highlight any specific pathway as the cause of parasitism-resistance to A. ervi. Metabolome comparison between Potato aphid genotypes 1 and 2 highlights variance between genotypes and in response to parasitoid challenge, and suggests the mounting of an immune response through the increased conversion of trehalose to glucose, previously observed in cellular immunity. The data generated over the course of this project will provide useful information for integrated pest management of Potato aphids, as well as providing more resources for further comparative genomics studies within Aphididae.

Parasitoid wasps have evolved a variety of strategies to regulate the physiology of their hosts in order to regulate the host's immunity and physiology for the interest of the development of its offspring. The venom of parasitic Hymenoptera, one of the major actors in the host regulation, has the potencial for developing novel environmentally safe insect control strategies and it is a blend of biologically, pharmacologically and physiologically complex mixture of peptides, amines, proteinaceous and nonproteinaceaous compounds). The neurotoxicity of the components present in the venom of Bracon species stimulated considerable research interests in this area, with the aim of isolating new agrochemical leads. However, the characterization of venom produced by Bracon species is restricted to B. hebetor, B. brevicornis and B. gelechie. In B. hebetor, paralytic activity is mediated by three partially characterized proteins that presynaptically block glutaminergic transmission , and other unknow factors seem to affect host endocrine balance and metabolic activity. In this work the interaction between ectoparasitoids and their hosts has been analyzed in the B. nigricans - Spodoptera littoralis model. The parasitism does not induce a rapid suppression of the host, even though the unaltered viability of hemocytes is associated with a suppression of their cellular division and/or production by haematopoietic organs. However, clear signs of a more subtle host regulation are evident, such as the reduction of CO2 emission and the significant increase of hemolymph proteins and carbohydrates. The resulting enhancement of host nutritional suitability is associated with the success of progeny development and structural changes of the fat body cells, which interact with hemocytes and show signs of cell degeneration. The combined approaches of transcriptomic analysis on venom glands and proteomic study on crude venom resulted in the identification of several proteins, including a putative phospholipase A2 of 17 kDa. This protein is probably the main toxin involved in the paralytic activity of B. nigricans venom. Additionally, a chromatographic fraction containing a protein band of about 17 kDa induces, when injected, a temporary paralysis in S. littoralis larvae. The identification of this protein and the production of recombinant phospholipase A2 will provide explanations on the functional role played by this bioactive component in the host regulation process. Finally, as required by the PhD program, I have spent a period abroad where I studied the effects of silver nanoparticles against the red clover root borer, Hylastinus obscurus (Marsham) (Coleoptera: Curculionidae). Bioassays with silver nanoparticles showed that nanoparticles act as a feeding deterrent.

The behavior of Aphidius sp. and B. brassicae populations on cabbage cultivars Kobayashi, Roxo, Chato de Quintal, Coracao de Boi and Matsukase were studied in natural field conditions. Monthly samples were collected from August to December 1995. Leaf discs measuring 6.1cm2 were taken from sites showing higher aphid concentration from each most infected leaf. The percentage of parasitized insects was determined by the number of mummified aphids among the total on each leaf disc. Although Roxo and Kobayashi cultivars showed the highest aphid infestation, they were the least parasitized by Aphidius sp. , with 23.3% and 25% parasitism, respectively. Coracao de Boi and Chato de Quintal cultivars were the least infested by the aphid, but showed the highest parasitoid populations, as 51.7% and 67.5% respectively. The lower aphid and parasitoid populations were observed on Matsukase cultivar. Chato de Quintal, Coracao de Boi and Matsukase cultivars presented a high aphid and parasitoid populations in August, which decrease in September and December and rose in October and November. On Kobayashi and Roxo cultivars both populations increased until November and decreased in December. Generally, higher B. brassicae and Aphidius sp. populations were found during August, October and November. The average parasitism in all cultivars was 36%. The highest parasitism level was 55.8, observed in August. KEY-WORDS: Aphidius ; Brevicoryne brassicae ; comportamento; parasitism; behavior.

Continuous monitoring of aphid population on cauliflower seed crop from December to April revealed an increase in infested plants (23 to 48%). aphid population (8 to 131/plant) and parasitization (I to 3.8%) during January to mid-March, followed by a decline in aphid infestation and further increase in parasitization (to 7.4%) till April 6, despite prominence of coccinellid activity (0.8-9.5 beetles/plant). There was concomitant occurrence of Brevicoryne brassicae (Linnaeus) and Myzus persica (Sulzer), the former being predominant (65.3%) and their parasitization varied from 0.7-8.3 (av. 3.6 and 8-8.2 per cent (av. 4.4). respectively. Intra-plant distribution indicated that aphid infestation was maximum on inner whorl of leaves. followed by middle and outcr whorls. but number of mummified aphids did not vary significantly in respect of position of leaves. During mid-March to early-April also, H. brassicae outnumbered M. persicae on terminal bolts and thcil' parasitizlltion was 27.4 and 14.5 per cent. From the mummies of aphids collected from the cabbage fields during Decemher. and May-June, the arasitoid Diaeretiella rapae (M'Intosh) (Aphidiidae) and thc hypeqlanlsitoid Pachyneuron aphids (Bouche) (Pteromalidae) emerged. but the emergence was poor (5.6 and 6.3% respectively), The mummics from which the parasitoid emerged were bigger with oval and uniform emergence holes around cornicles than the mummies from which hyperparasitoid emerged, The emergence holes or the lattel was irregular, smaller and often towards anterior side of the body,

The effect of parasitism by Aphidius ervi Haliday (Hymenoptera Aphidiidae) on development survival and reproduction of pea aphid Acyrthosiphon pisum (Harris) (Hemiptera Aphididae) of different ages was studied in the laboratory Aphids parasitised when 1 and 2 days old (1st and 2nd instar) died at the 4th instar However those parasitised when 3 to 6 days old (3rd and 4th instar) could reach the adult stage following parasitism and those that were parasitised after 4 days old (late 3rd instar) were still able to produce progeny In comparison with the unparasitised aphids the parasitised aphids had a significantly shorter reproductive period and produced significantly fewer progeny and thus had significantly lower intrinsic rates of increase net reproductive rates shorter generation time and longer doubling time The potential impact of the parasitoid on host population growth is discussed

Parasitism and mating activities of Diaeretiella rapae were studied in a shadehouse under ambient environmental conditions during September (early spring) and November (late spring) Before collecting the data the parasitoid and its aphid host colonies were left to develop undisturbed on cabbage seedlings for 3 months in about 25 m2 area The plants were highly infested with aphids (average 27225 aphids/plant) and parasitism by D rapae varied between 25 and 36 during the study period There was no significant change in parasitism rate during the 10week study period (P069) Adult parasitoids emerged from aphid mummies at a rate of more than 90 with a higher number of females than males The mean female/male parasitoid sex ratio was greater in the second 5week (late spring) than the early 5week period (early spring) (P

Aphidius ervi Haliday is an important parasitoid of several aphid species and information is needed for the development of massrearing techniques and better understanding of biological control ecology The emergence sexual maturation and oviposition of A ervi on pea aphid Acyrthosiphon pisum (Harris) was studied in the laboratory at 201deg;C and 6070 RH with 168 h lightdark About 95 of parasitoids emerged during the photophase Females needed a significantly longer time than males to complete their life cycle Newly emerged males were able to perform their courtship display but failed to mate until they were 4 h old; newly emerged females were able to respond to males courtship display and mate Females attacked aphids in both light and dark conditions The number of eggs laid and parasitism (number of aphids parasitised) per oviposition bout (2 h oviposition period) were significantly greater in the photophase than in the scotophase

The reproductive response of Aphidius ervi Haliday to the density of pea aphid Acyrthosiphon pisum (Harris) was investigated in plastic cylinders (105 cm high x 85 cm diameter) Mean number of aphids parasitised and eggs laid by a single A ervi significantly increased with an increase of host density Numbers of eggs laid per parasitoid reached a plateau at host densities of 75 aphids/cylinder and above However the number of eggs laid in each parasitised aphid significantly decreased (from 29 to 13 eggs) with the increase of host density from 15 to 75 aphids/cylinder after which no further decrease occurred These results suggest that the parasitoid adjusts oviposition strategy in response to increasing host density through increasing parasitism and decreasing superparasitism The proportion of female progeny developed from fertilised eggs increased (up to 70) with the increase of host density from 15 to 50 or 75 aphids/cylinder after which it gradually declined suggesting that the sperm limit occurs when host density reaches 50 to 75 aphids/cylinder

The pests and the natural enemies were determined on the protected pepper in 1997 in the Izmir province of Turkiye. Spidermite [ Tetranychus urticae Koch. (Acar-ina:Tetranychidae)], aphids [ Aphis gossypii Glover, Myzus persicae Sulzer (Hom.: Aphididae)], whiteflies [ Bemisia tabaci Gern and Trialeurodes vaporariorum Westw. (Hom.:Aleyrodidae)], leafhoppers [ Asymmetrasca decedens (Paoli), Empoasca decipiens Paoli (Hom.:Cicadellidae)], thrips [ Haplothrips distingundus Uzel (Thys.:Thripidae)] andleafminers [ Liriomyza bryoniae (Kaltenbach) L.trifolii (Burges), L.huidobrensis Blanchard (Dip.:Agromyzidae)] were found to be the pests on the protected pepper. Aphid and leafminers densities were reach to the maximum at the beginning of the season. Whiteflies, spidermite and leaf hoppers were high in densities towards the end of the season. The population density of H.distingundus are high at the middle of the season. There was no treatment against any pests in the plastic tunnels. Therefore the beneficial were conserved and their populations increased at the begining of the season and suppressed the pest populations. Leafminerswere suppressed by the larval parasitoids, Diglyphus isaea (Walker)(Hym.:Eulophidae). The parasited aphids[( Diaretiella rapae (M'inst) Lysiphlebus fabarum Marshall, Aphidius matricariae Hal., Trioxys angelicae (Hal.) (Hym.:Aphidiidae)] were seen in the early vegetation. After the predators were seen in the plastic tunnels, the parasitism weren't recorded in the aphid population. Propylea quotuordecimpunctata (Goeze), Adonia variegata (Goeze)(Col.:Coccinellidae), Chrysoperla carnea (Steph.) (Neur.:Chrysopidae), Aphidoletes aphidimyza (Rond.)(Dip.:Cecidomyiidae), Sphaero-phoria scripta (L.)(Dip.:Syrphidae) were effective on aphid population. Stethorus gilvifrons (Muls.), Scymnus rubromaculatus (Goeze), S.apetzi Mulsant, S.interruptus (Goeze), S.frontalis (Fabricius)(Col.:Coccinellidae), C.carnea , Scolothrips longicornis Priesner (Thys.:Thripidae) were effective on spidermite population. Macrolophus caliginosus (Wgn.) (Het.:Miridae) were effective on whiteflies population.

Botanical preparations, usually from non-host plants, can be used to manipulate the behaviour of insect pests and their natural enemies. In this study, the effects of extracts of Chrysanthemum morifolium, a non-host plant of the diamondback moth, Plutella xylostella (Linnaeus), on the olfactory and oviposition responses of this phytophagous insect and on levels of parasitism by its specialist parasitoid Cotesia plutellae (Kurdjumov) were examined, using Chinese cabbage Brassica campestris L. ssp. pekinensis as the test host plant. Olfactometer tests showed that volatiles of chrysanthemum extract-treated host plants were less attractive to P. xylostella females than those from untreated host plants; and in contrast, volatiles of the chrysanthemum extract-treated host plants were more attractive to females of its parasitoid C. plutellae than those from untreated host plants. Oviposition preference tests showed that P. xylostella females laid only a small proportion of their eggs on chrysanthemum extract-treated host plants, while ovipositing parasitoid females parasitized a much higher proportion of host larvae feeding on the treated host plants than on untreated host plants. These results suggest that certain non-host plant compounds, when applied onto a host plant, may render the plant less attractive to a phytophagous insect but more attractive to its parasitoids. Application of such non-host plant compounds can be explored to develop push-pull systems to reduce oviposition by a pest insect and at the same time enhance parasitism by its parasitoids in crops.

Boivin, G., Hance, T. and Brodeur, J. 2012. Aphid parasitoids in biological control. Can. J. Plant Sci. 92: 1-12. Aphids are important pests of most cultivated crops worldwide. Among the natural enemies that regulate their populations, aphid parasitoids are commonly used in biological control programs in greenhouses and field situations. They belong to the Hymenoptera (Braconidae and Aphelinidae), and a few species are Diptera (Cecidomyiidae). Aphid parasitoids are themselves exposed to a variety of natural enemies including predators, fungi and hyperparasitoids. The most important impediment to the use of aphid parasitoids as biological control agents remains the production cost to mass-rear parasitoids. Rearing either aphids or directly aphid parasitoids in artificial media could be a solution to produce large quantities of aphid parasitoids at low cost, but such an approach still faces numerous challenges related to the nutritional and physiological requirements of developing aphid parasitoids.

Diaeretiella rapae is an important biological control agent of cabbage aphid Host searching handling and oviposition behaviour were investigated in relation to host age The parasitoid spent 61 of her foraging time searching for hosts Host handling time of the parasitoid decreased with increased number of host encounters The females were more successful in finding older hosts (7 days old) and spent more time (949 205 s/encounter) and did more stings (99 14/encounter) on them than the younger hosts They preferred to sting the abdomen rather than the thorax head or legs of the host The average number of eggs laid per host was highest (14 02 eggs) in 7dayold hosts When attacking 7dayold hosts they gained 42 success in ovipositing the host compared to 10 18 and 30 success in 1 3 and 5dayold hosts respectively Results suggest that D rapae may have adaptive preference for larger hosts and mass production could be more efficient by using 7dayold aphids

Aphidius gifuensis Ashmead is an economically important aphid parasitoid, particularly for pest Myzus persicae. The aim of the study was to feed M. persicae using a formulated artificial medium instead of tobacco to maintain parasitoid A. gifuensis in winter. The development, survival and reproduction of M. persicae fed with four artificial media (AM1-AM4), as well as the parasitism, emergence and longevity of A. gifuensis when reared on F3 M. persicae fed with AM1, were assessed. Over 15 days of the study, the survival rates of A. gifuensis for the AM1 and AM2 treatments were significantly greater than those for the AM3 and AM4 treatments. The highest fecundity of F1 A. gifuensis females was observed on AM1 feeding. No differences were noted in survival rate, development or nymph production between F2 and F3 M. persicae fed with AM1. No differences were recorded in the number of mummies, parasitism rate, adult longevity or proportion of A. gifuensis females between Treatment I (A. gifuensis parasitizing AM1-reared M. persicae) and the control. However, the emergence rate of Treatment I was lower than that of the control. The rearing of A. gifuensis on M. persicae fed with an artificial medium was found to be a feasible proposition. This could save time, space and cost compared with traditional production methods.

Once a minor pest, the pea aphid, Acyrthosiphon pisum has already become a major pest of grass pea ( Lathyrus sativus ), in Ethiopia, particularly in the northwestern region. The effect of two levels of chemical treatment on pea aphids and their natural enemies was investigated in a field experiment in Achefer, northwestern Ethiopia from September 2010 to March 2011. Plant height, plant density per 0.25 m2, number of pea aphids and parasitoids per plant, ladybird beetles per plot, and finally grain yield per plot were recorded. Based on the results of the ANOVA, plant height was significantly different between treated and untreated plots especially after the vegetative stage. The density of the plant did not significantly vary between treatments (P=0.99). Pea aphid population significantly varied between treated and untreated plots and between the different growth stages of the crop (P<0.0001). many of the natural enemies of pea aphid, i.e., ladybird beetles and parasitoids, were recorded on untreated plots. Generally, natural enemies increased as number of aphids increased. Significantly more yield was obtained from treated than untreated plots but there was no difference in yield between doses. Yield and aphid density were inversely related and grain yield loss due to pea aphids increased as high as 82.4%. This loss is very high necessitating appropriate control measures. Keywords: Food legumes, pea aphids, pest management, yield