Conséquences de l'élevage continu deLixophaga diatraeae [Dipt. Tachinidae] sur l'hote de remplacement:Galleria mellonella [Lep. Galleriidae]

Résumé L. diatraeae, parasite naturel des foreurs du genreDiatraea a été élevé au laboratoire en permanence surG. mellonella utilisé comme h?te de remplacement. Cet élevage a été comparé à celui effectué parallèlement surChilo sacchariphagus qui peut être considéré comme un h?te convenable pour le développement de cette Tachinaire. Les conséquences de l'exploitation deGalleria parLixophaga se sont traduites chez la tachinaire par une incapacité progressive des màles à s'accoupler et une fertilité moindre des femelles. Ces réactions ont eu pour conséquence de faire disparaitre, dès la 6^e génération, la souche deLixophaga élevée surGalleria. D'une fa?on plus générale ce mode d'action ?à long terme? contribe à expliquer les modalités de la spécificité parasitaire au même titre que les réactions ?à court terme? qui sont habituellement mieux connues parce qu'elles correspondent à des effets immédiats sur le parasite.

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Summary L. diatraeae, a natural parasite of the American borers from the genusDiatraea, has been reared continuously in the laboratory onG. mellonella. The results have been compared with those obtained on the Asian borer,C. sacchariphagus, which is a suitable host for the development of this Tachnid. Under these conditions, it became evident thatL. diatraeae could not maintain itself for more than 6 generations onG. mellonella. Indeed, the effect of adverse physiological factors onLixophaga during its larval stage is to reduce progressively both female fertility and the ability of the males to mate, even if there is no visible effect on the development of the larval and pupal stages. This phenomenon must be recognized because it affects the use of laboratory hosts for production of parasites for biological control. In this test the defensive reactions ofGalleria appeared progressively, generation after generation, but only on the adults (particularly on males) by widely known, that either prevent the parasite from penetrating into the host, or inhibit its subsequent development. In general, these results contribute to a better explanation of host specificity.

     

Biological control ofDiatraea saccharalis [Lep.: Pyralidae] in Florida by periodic releases ofLixophaga diatraeae [Dipt.: Tachinidae]

Lixophaga diatraeae (Townsend) parasitized 20 to 78% ofDiatraea saccharalis (F) larval populations within 3 weeks after release. The flies (4 to 6 days old) did not migrate from the release area, but the progeny dispersed as much as 3 km into adjacent untreated areas within 5 generations. Progeny dispersal, apparently during the prelarviposition period, resulted in 100% parasitization ofD. saccharalis larvae in some plots. In 2 of the 3 tests, the host population decreased after the releases. Percentage damaged internodes increased with distance from the release site.

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Résumé Des lachers de la mouche parasite, appelée vulgairement mouche de Cuba, dans les champs de anne, en Floride, ont limité les populations du foreur de la canne. La tachinaire a parasité 20 à 78% des foreurs. En outre, la descendance des parasites a été retrouvée à plus de 3 km des points de lacher. Les dégats aux cannes à sucre furent moindres dans les champs où les lachers ont été effectués que dans les champs voisins.

     

RearingGlypta fumiferanae [Hym.: Ichneumonidae] on a multivoltine laboratory colony of the western spruce budworm (Choristoneura occidentilis) [Lep.: Tortricidae]

Methods were developed for rearingGlypta fumiferanae Viereck on a nondiapausing laboratory colony of the western spruce budworm,Choristoneura occidentalis Freeman. Both host and parasite are univoltine and undergo diapause in nature. In this study, the parasite's voltinism was synchronized with that of a nondiapausing host.G. fumiferanae mated readily in the laboratory, and 5 consecutive generations were reared with an average generation time of less than 8 weeks-much less than the 23 weeks needed for 1 generation to develop in the field. Developmental times are reported, and some aspects of behavior described.     

Prédateurs et parasites d'Aphytis [Hym., Aphelinidae]

Summary Very few predators and parasites ofAphytis have been recorded. Among predators, only Coccinellids preying on Diaspine scale insects have been mentioned as damaging to the preimaginal stages ofAphytis on occasion, and a single case of a mitePyemotidae has been known to have destroyed the pupae. As to the parasites known, they are accidental and rare. There are cases where only the male lives as a parasite onAphytis, the female developing normally as a primary parasite onAphytis hosts. Two species harmful toAphytis have been found in Lebanon:Pyemotes herfsi Oudemans (Acarina, Pyemotidae) andApterencyrtus adeli n. sp. (Hymenoptera, Encyrtidae). P. herfsi is a polyphagous predator, and its increase in number might constitute a threat to theAphytis in the field and the insectary.A. adeli is the only example known so far of a true hyperparasite whose males and females develop onAphytis. It has been found abundantly on larvae ofAphytis mytilaspidis as well as on many other hosts.

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Extrait d'une thèse de Doctorat de troisième cycle (biologie animale) soutenue à la Faculté des Sciences de l'Université de Paris le 2 avril 1968.     

Release ofTelenomus remus [Hym. scelionidae] againstSpodoptera frugiperda [Lep.: Noctuidae] in Florida,U.S.A.

Telenomus remus Nixon, a scelionid egg parasite of Lepidoptera, was released against fall armyworm,Spodoptera frugiperda (J. E. Smith), near Homestead, Florida U.S.A. from May 1975 — May 1977. A small percentage (4.5) of the egg masses collected were parasitized byT. remus, however no recoveries were made in the months following the final release. An egglarval parasite,Chelonus insularis (=texanus) (Cresson), was reared from 50% of the larvae from eggs collected.T. remus apparently was not established in Florida.

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Résumé Telenomus remus Nixon, scelionide parasite des œufs de lépidoptères, a été laché contreSpodoptera frugiperda (J. E. Smith) près de Homestead en Floride, de mai 1975 à mai 1977. Un faible pourcentage des pontes récoltées (4,5%) se révélèrent parasitée parT. remus, cependant aucun parasite ne fut retrouvé dans les mois qui suivirent le dernier lacher. Un parasite ovo-larvaire,Chelonus insularis (=texanus) (Cresson) a été obtenu à partir de 50% des larves issues des œufs récoltés. ApparemmentT. remus n'a pas été établi en Floride.

     

Biological studies withChrysocharis parksi [Hym.: Eulophidae] a parasite ofLiriomyza spp. [Dipt.: Agromyzidae]

Biological studies withChrysocharis parksi Crawford, a parasite of agromyzid leafminers, were conducted.C. parksi successfully parasitized the following species in the genusLiriomyza Mik.,L. huidobrensis (Blanchard),L. sativae Blanchard,L. trifolii (Burgess), andL. trifoliearum Spencer. Successful parasite development was recorded from 8 plant families and 16 genera. Host plants which were suitable for leafminer development to the adult stage were also suitable for parasite development. Mean immature developmental period (egg to adult, usingL. trifolii as the host) at 21.1°, 26.7°, and 32.2° C was (for both sexes) 23, 14, and 14 days, respectively. Longevity of females provided only water was inversely related to temperature; significantly longer survival occurred at 21.1° C (5.0 days) compared to 26.7° C and 32.2° C (3.2 and 2.1 days, respectively). The addition of honey to the diet significantly improved longevity of both sexes at all temperatures. Adult female parasites which were provided an average of 33.0L. trifolii larvae per day produced an average of 135 offspring at a constant 26.7° C.C. parksi host-fed on ca. 3.7 leafminer larvae per day over an 11-day adult lifespan.      

Host recognition by the gypsy moth [Lymantria dispar] [Lep.: Lymantriidae] hyperparasite,Eurytoma appendigaster [Hym.: Eurytomidae] of cocoons ofCotesia melanoscela [Hym.: Braconidae]

Artificial and modified natural hosts were exposed to females of the gypsy moth [Lymantria dispar (L.)] hyperparasite,Eurytoma appendigaster (Swederus), to investigate its host recognition behavior on the primary host, which are cocooned larvae of the gypsy moth parasite,Cotesia melanoscela (Ratzeburg). Material(s) which caused drilling behavior by the hyperparasite on host cocoons were extracted with both polar and non-polar solvents. However, cocoons washed with large volumes of solvent still caused substantial drilling activities by females, suggesting that additional cues may be important. Results suggest that host recognition in this hyperparasite involves a variety of host characteristics.      

Release in Manitoba,Canada oftownesilitus bicolor [HYM.: Braconidae], an European parasite ofPhyllotreta spp. [Col.: Chrysomelidae]

Townesilitus bicolor (Wesmael), a parasite of some crucifer-infesting species ofPhyllotreta in Europe, was released in Manitoba Canada in 1978–83, in an attempt to reduce populations ofPhyllotreta cruciferae (Goeze) andP. striolata (Fab.). Releases totalled 1936 adults ofT. bicolor and approximately 2639Phyllotreta collected in Manitoba and parasitized in the laboratory. No evidence of establishment was found up to 1985 at either of the 2 release sites. The small numbers of parasite released, and dispersal of the host population twice each year, have reduced the probability of the parasite becoming established and of establishment being detected. Contribution n^o 1248     

Importance de la nutrition chezAphelinus sp. [Hym.Aphelinidae]

Résumé L'incidence de la nutrition sur la biologie des Aphélinides est étudiéc et analysée sous ses différents aspects: maturation sexuelle, spécificité parasitaire (adaptation à un nouvel h?te) et longévité. Les faits observés sont rapprochés de certains phénomènes d'adaptation à des facteurs du milieu connus chez d'autres groupes d'insectes. D'importants travaux ont été effectués sur un Aphélinide monophage,Aphelinus mali Haldeman depuis son introduction en Europe en 1929 pour freiner les pullulations du puceron lanigèreEriosoma lanigerum Hausm. Ce n'est que depuis une quinzaine d'années que les chercheurs américains ont orienté leurs recherches vers un autre Aphélinide,Aphelinus asychis Walker (=semiflavus Howard), susceptible d'attaquer un grand nombre d'espèces d'Aphides-h?tes. Cependant, la polyphagie de ce parasite fut très peu étudiée et c'est seulement en 1970 queRaney etal.,Manglitz & Schalk déterminant la fécondité du parasite en présence de divers h?tes, ont observé des différences de fécondité qui les ont conduits à considérer que certains h?tes étaient préférés par le parasite.

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Summary A study of polyphagous Aphelinids, parasites of aphids, revealed the existence of host conditioning. The physiology and behaviour of the female is influenced by the aphid species on which it feeds: sexual maturation, fecundity (measured by number of aphids mummified by one female) and longevity are impaired when this species differs from the one from which the female hatched. When females are fed with honey and water, longevity decreases (is reduced by about 15 days). Nutritive elements accumulated during larval life are used and eggs are progressively resorbed. This condition is not irreversible: if such females are reared with aphids, mature eggs can be observed after two days. Fecundity and longevity are decreased when one female (Aphelinus asychis), hatched from an aphid species A, is reared on an aphid species B. In the F₂ generation, the parasite is better adapted to the new host; in F₃ fecundity may be comparable with that recorded in females reared on aphid host A. However, if F₃ females hatched from species B mummies are now placed on aphid host A, the same kind of biological disturbances are observed as in the original transfer (A to B). After disproving the hypothesis of genetical selection of individuals adapted to the new host, the influence of nutrition on female physiology is demonstrated. This conditioning may be compared with that inAcrididae, attributable to a density factor, or that inNemeritis andDrosophila, to the odour of certain chemicals.

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Le présent article est extrait de la thèse de Doctorat d'état soutenue le 20 mars 1972 à l'Université Paris VI.     

Effects ofBlepharipa pratensis [Dip.: Tachinidae] on the pathogenicity of nucleopolyhedrosis virus in stage V ofLymantria dispar [Lep.: Lymantriidae]

The effects of myiasis caused byBlepharipa pratensis (Meigen) on the pathogenicity of 3 dosages (1.00×10⁴ PIB, 3.75×10⁴ PIB and 7.50×10⁴ PIB) of nucleopolyhedrosis virus (NPV) in stage V ofLymantria dispar (L.) were tested. When fed only NPV, 44% of the larvae fed the low dosage died, 67% of the larvae fed the mid-level dosage died, and 73% of those fed the high-level dosage died. At the low dosage, mortality was significantly lower than at the other dosages. The presence of the parasite significantly increased mortality due to NPV; 65% of the larvae fed the low dosage died, 77% of the larvae fed the mid-level dosage died, and 80% of the larvae fed the high-level dosage died. For biological control, the combination of NPV and parasite would increase mortality, but at the expense of the parasite.

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Résumé L'effet du parasitisme parBlepharipa pratensis sur la pathogénie de 3 doses (1.00×10⁴ PIB, 3,75×10⁴ PIB et 7,50×10⁴ PIB) du virus de la polyédrie nucléaire (VPN) chez le 5ème stade deLymantria dispar a été étudié. Nourries avec seulement la dose faible du VPN, 44% des larves ont succombé, 67% sont mortes de la dose moyenne et 73% des larves de la dose forte. La différence de mortalité obtenue avec la dose faible était significative par rapport à la mortalité obtenue avec les 2 autres doses. La présence du parasite a augmenté significativement la mortalité par virose; avec la dose faible cette mortalité a atteint 65%, 77% avec la dose moyenne et 80% avec la dose forte. Pour la lutte biologique, la combinaison du virus avec le parasite augmenterait la mortalité, mais aux dépens du parasite.

     

Lachers d'Opius concolor [Hym.: Braconidae] dans des populations de printemps deDacus oleae [Dipt.: Trypetidae]

Résumé Un lacher du braconideOpius concolor Szepl. a été effectué au printemps au cours de la première génération de multiplication de la mouche de l'oliveDacus oleae Gmel. dans l'oliveraie de Delphes. Il permet de constater que: le parasite s'installe normalement aux dépens des larves réceptives (troisième stade), il est apte à parasiter les larves deD. oleae présentes en haut et en bas de l'arbre, les pontes des femelles s'étalent sur deux semaines, le parasite est susceptible d'être hébergé par les pupes qui s'enfouissent dans le sol. La mortalité larvaire naturelle due à des causes non parasitaires est importante, notamment dans les olives tombées au sol et dans celles de la partie basse et ombragée de l'arbre.

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Summary A release of the braconid parasitoidO. concolor Szepl. was made during spring (May) against the larval population of the olive fruit flyD. oleae Gmel. in a grove containing some trees which had heavily infested olive fruits which had overwintered. The parasitoid developed normally in the 3rd instar larvae of this population. Although it was present throughout the tree, during the 1st days it was more active in the upper part where 51% of receptive larvae were parasitized than in the lower where 18% were parasitized. After one week, these figures were 20% and 44% respectively. They have been calculated from counts ofDacus larvae containing either eggs or larvae.O. concolor had almost completely disappeared from the tree 2 weeks after the release because of fruit fall following high winds, although it was still possible to find both eggs and larvae in the appropriate host stages on the soil. The emergingO. concolor population was dominated by male adults, making up 74% of the numbers. The natural mortality ofD. oleae larvae not induced by the parasite factor was important in the area, especially in the fruits fallen onto the soil in which 28% of young larvae and 14% of 3rd instar larvae died. Higher mortality occurred from these factors in the upper crown than in the lower: 16% of young larvae and 7% of 3rd instar larvae died in the former situation but 7% and 2% respectively in the latter. Almost no parasitism from indigenous parasites was recorded.

     

Identification des Régimes Alimentaires de la Larve D'un Insecte EntomophagePhanerotoma Flavitestacea [Hym.: Braconidae]

Résumé Les régimes alimentaires d'un insecte parasite entomophage,Phanerotoma flavitestacea, sont identifiés par examen histologique du contenu du mésenteron, au cours de ses 2 modes de vie larvaire successifs, endoparasite, puis ectoparasite. Lors de sa phase endophage, la larve se nourrit uniquement de l'hémolymphe des chenilles d'Anagasta kuehniella. Il n'y a pas de phase stéatophage. Au cours de sa phase ectophage, elle ingère tous les organes de son h?te, sans ordre apparent et sans choix. La digestion, commencée dès le repas achevé, est complètement terminée lorsque le cocon est tissé. L'existence de ces 2 phases et les régimes alimentaires du parasite sont discutés par référence à ce qui est connu chez d'autres Hyménoptères entomophages.

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Summary The alimentary diets of an entomophagous insect larva,Phanerotoma flavitestacea are identified by an histological examination of the mid-gut content, during its two modes of larval life: first endoparasite and then ectoparasite. In the phase as an endophagous larva, it feeds only on the haemolymph ofAnagasta kuehniella caterpillars. During its ectophagous phase, all the internal organs of the host are devoured without choice as well as without following any order in feeding. The digestion begins just after the end of feeding and it is completely finished when the cocoon is spun. The existence of these two phases and the alimentary diets of this parasite are discussed by refering to these phenomena already known in other entomophagous hymenoptera.

     

Establishment of the imported parasiteProspaltella perniciosi [Hym.: Aphelinidae] onQuadraspidiotus perniciosus [Hom.: Diaspididae] in Greece

Prospaltella perniciosi Tower was imported in Greece to aid in the biological control ofQuadraspidiotus perniciosus Comstock. Two to 10 years following release in apple trees the parasite was found well established onQ. perniciosus with low parasitism exceed to 2–5%. Parasitism by indigenous natural enemies, mostlyAphytis spp., was also low. Considering that these trees also suffer damage by other major pests, in order to obtain full benefit from the biological control ofQ. perniciosus compatible methods of supressing these pests are required.

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Résumé Prospaltella perniciosi Tower fut importé en Grèce pour la lutte biologique contreQuadraspidiotus perniciosus Comstock. Deux à 10 ans après son lacher dans des vergers de pommier, le parasite est trouvé bien implanté dans la population de Pou de San José, le taux de parasitisme oscillant entre 2 et 5%. Le parasitisme par des ennemis naturels indigènes, principalement parAphytis spp., était aussi bas. Tenant compte du fait que ces arbres subissent des dégats par d'autres ennemis importants et afin d'obtenir le maximum d'efficacité de la lutte biologique contreQ. perniciosus, des méthodes adéquates pour la répression de cet insecte sont exigées.

     

Osservazioni sulla biologica dellaProspaltella perniciosi Tow. nella valle Padana

Summary Investigations have been carried out in the Po' Valley (Italy) during 1964 to establish the number of generations of the San José scale and its parasiteProspaltella perniciosi Tow. It was found that the San José scale has three generations per year, while its parasite has six. The percent of parasitism attained in one year after parasite release was 60.Prospaltella hibernates as an egg in the first larval instar of its host.      

Field evaluation ofAllorhogas pyralophagus [Hym.: Braconidae], imported into texas for biological control of the stalkborerEoreuma loftini [Lep.: Pyralidae] in sugar cane

The external, gregarious, braconid parasite,Allorhogas pyralophagus Marsh was mass released into field cages enclosing sugar cane infested with the pyralid,Eoreuma loftini (Dyar) to examine factors affecting parasitism rates and to assess the parasite's potential contribution to borer larval mortality. Three field experiments were conducted in July, September, and December, 1984. Total parasitism was 25.2% for the study and was the single most important source of borer mortality. Borers were equally susceptible to attack in leaf sheaths, whorls, and stalks in general, but larvae tunneling deep within stalks were parasitized less. An interaction between tunneling behavior of the borer and attack strategy of the parasite was important for parasite success.A. pyralophagus is probably unable to effect complete control ofE. loftini in sugar cane becauseA. pyralophagus is physically unable to parasitize borers deep in the stalks. However, the parasite may be useful as part of an intergrated pest management program, acting in concert with other parasite species, or attacking the borer in small-stemed grasses that serve as alternate host plants.      

Mechanische und physiologische Abwehrreaktionen einiger Blattlausarten [Aphididae] gegen Schlupfwespen [Hymenoptera]

Summary It was known from earlier experiments thatRhopalomyzus ascalonicus (Donc.) encapsulated the eggs andRhopalosiphoninus staphyleae (Koch) ssp.tulipaellus Theob. the larvae ofAphelinus semiflavus How., but, on the other hand, the mechanical defence reactions of both aphids against the parasite appeared to be conspicuously weak. These experiments were now extended to the parasiteDiaeretiella rapae (M'Intosh) and to the aphidNeomyzus circumflexus (Buckt.). Also the eggs ofD. rapae were encapsulated byRh. ascalonicus without any exception. N. circumflexus only killed the larvae ofD. rapae andA. semiflavus by encapsulation, but some larvae of the second species remained alive. The defensive behaviour of this host during the approach and the attack byA. semiflavus was markedly less developped than that ofMyzus persicae (Sulz.) and was comparable to the behaviour of the two other aphid species. Probably, the defence behaviour of the investigated aphids was reduced when after phylogenetic development of the blood reaction it had become dispensable.      

Biology ofAgrothereutes tunetanus Haber. [Hym. Ichneumonidae] an ectoparasite ofOrgyia dubia Tausch. [Lep. Lymantriidae]

Résumé Les auteurs décrivent le cycle évolutif et le comportement de ponte de l'Agrothereutes tunetanus Haber. (Ichneumonidae, Cryptinae) dans les conditions de laboratoire (25°C et 50–60% H.R.). Le développement des œufs des larves et des nymphes, le comportement des stades larvaires, les habitudes alimentaires, l'accouplement et le comportement pendant l'oviposition sont décrits. A. tunetanus est un parasite de l'Orgyia dubia Tausch., attaquant le dernier stade larvaire de la femelle après que celle-ci ait tissé son cocon, mais avant la nymphose. Le même degré d'activité de ponte du parasite est provoqué par le dernier stade larvaire et la nymphe des femelles h?tes. Une moindre activité est suscitée par les femelles m?res dans les cocons et le dernier stade larvaire male, tandis que l'activité de ponte provoquée par les nymphes males est presque nulle. Le nombre moyen d'œufs pondus par une femelle durant une seule attaque (entre 3 et 4) ne dépend pas (de manière significative) du nombre de cocons présents. Le nombre d'attaques effectuées parA. tunetanus en 24 heures dépend de la quantité de cocons disponibles, les facteurs limitants sont le nombre d'œufs m?rs dans de la femelle gravide et la quantité d'œfus pondus pendant chaque attaque. Avec 6 cocons en 24 heures, une femelle, au maximum de sa fécondité, arive à une moyenne de 3,27 attaques. La fécondité d'une femelle est en moyenne de 308 œufs.

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Part of the M. Sc. thesis done under the supervision of the first author and submitted to the Department of Zoology of the Tel-Aviv University.     

The biology and behaviour ofIphiaulax varipalpis [Hymenoptera: Braconidae] as a parasite ofDirphya nigricornis [Coleoptera: Cerambycidae]

The ability of the braconid parasite,Iphiaulax varipalpis Cary to control the beetleDyrphya nigricornis Olivier was evaluated. Field collected samples and specimens reared in polyethylene paper tubes under laboratory conditions (23.0°C±1.0 at 70% r.h) were used. Field parasitism was low (10.72%) while laboratory parasitism was high (57.66%). The parasite detected the hosts very easily in the laboratory. This ability is minimised in thick canopies ofCoffea arabica L. Host colonization was brisk (90 seconds) and confined to a near absolute area of discovery, measuring 4.18±0.41 cm. The parasite reproduces gregariously with female lifespan being approximately double the male period. The parasites are very active at the age of 10 days. As they age their potential fecundity (232 oocytes) reduces drastically with oviposition.      

In vitro rearing ofTrissolcus basalis [Hym., Scelionidae] an egg parasitoid ofNezara viridula [Hem., Pentatomidae]

In vitro rearing of the egg parasitoidTrissolcus basalis (WOLL.) from eggs collected on the natural hostNezara viridula (L.) was initiated. Several oligidic diets containing insect material (Manduca sexta hemolymph or host egg content) were tested. Our initial medium with 50% hemolymph induced a high egg mortality, but by decreasing the hemolymph concentration, increasing the hen egg yolk concentration and adding 15% of free amino acids mixture, a hatching rate of 85% of the parasitoid eggs was obtained with 39% reaching the second instar and 33% the third instar. In a medium without hemolymph, but with 18% liquid from parasitized host eggs we obtained 90% to 100% hatching, 25 to 27% reaching the second instar and 8% the third instar. We did not obtain pupation from eggsin vitro, but did get pupae and adults from larvae rearedin vivo to second instar and transfered to anin vitro system.      

Introduction and establishment ofTrioxys pallidus [Hym.: Aphidiidae] in Oregon,U.S.A. for control of filbert aphidMyzocallis coryli [Hom.: Aphididae]

Hazelnut orchards in Spain, France, and Italy were searched for parasitoids of the filbert aphid,Myzocallis coryli (Goetze). A biotype ofTrioxys pallidus Haliday was found to parasitize the aphid throughout western Europe. Wasps were imported, quarantined, mass-reared, and released in Oregon orchards. The wasp successfully attacked and completed its development on Oregon populations of the filbert aphid. A greenhouse culture of the parasitoid was maintained continuously for over 50 generations, and approximately 30,000 adult wasps were released in western Oregon. Overwintering survival has been documented in at least 12 different locations. In 3 commercial hazelnut orchards, the parasitoids proved capable of reducing aphid population peaks by 33–48%.