Distribution and effectiveness ofAnaphes diana [=Patasson lameerei] [Hym.: Mymaridae], a parasitoid ofSitona spp. Eggs [Col.: Curculionidae] in the Mediterranean region

Surveys conducted from 1973 to 1984 showed thatAnaphes diana Girault was the predominant parasitoid ofSitona spp. eggs throughout the Mediterranean range of Spain, France, Italy, Greece, Bulgaria, Romania, Turkey and Syria. In each of these countries, the mean percentage parasitism of eggs fluctuated between 1.9 and 23.9%. The impact of the mymarid on its host increased considerably from autumn to spring. Two biotypes ofA. diana, one reproducing bisexually, the other being strictly thelytokous, occur sympatrically in the Mediterranean region. The origin of various consignments ofSitona eggs parasitized byA. diana shipped to Australia for field release of the mymarid is recorded. Egg parasitoids were found in the Damascus area (Syria) that may be adapted to and effective under the hot and dry climatic conditions of South Australia.     

The biology ofRoptrocerus xylophagorum [Hym.: Torymidae], with a note on its taxonomic status

The biology of the bark beetle parasitoidRoptrocerus xylophagorum (Ratzeburg) from Georgia, U.S.A., was studied under controlled conditions in Australia. Parasitoids were presented withIps grandicollis Eichhoff in the isolated bark ofPinus radiata D. Don. Females lived up to 24 days at 24°C, and could parasitize up to 11 hosts in a single day. Usually only 1 egg was laid on each paralyzed host. Both larvae and pupae were parasitized, but the former appeared to be preferred. The species was arrhenotokous, and tended to produce more males when parasitizing smallerIps larvae. Males and females required 158D^o and 179D^o respectively, above a threshold of 13.8°C, to complete development, and their size was dependent on the host stage. Insects in a 2nd culture ofRoptrocerus from California differed in appearance, although supposedly being the same species. A preliminary cross-breeding experiment provided evidence that the 2 cultures are reproductively isolated.     

Interactions within and between species at different densities of the bark beetleIps typographus and its predatorThanasimus formicarius

Interactions between the bark beetleIps typographus and one of its predators,Thanasimus formicarius, were investigated in caged spruce logs containing both species in eight different density combinations. Productively (offspring per female) ofIps was adversely affected by highIps gallery density as well as highThanasimus density.Thanasimus productivity was enhanced by highIps gallery density but negatively affected by highThanasimus density.Ips productivity andThanasimus developmental rate differed between tree individuals, probably owing to tree-related differences in phloem thickness. Relative predator-causedIps mortality was ca 20% higher at high gallery density (ca 300 egg galeries per m²) than at low gallery density (ca 100 egg galleries per m²), indicating that mortality was density dependent. This difference was due to the fact thatThanasimus larval density was positively related toIps gallery density. Mortality increased by ca 0.4% with each additionalThanasimus larva per m², independently of gallery density. Relative population levels ofIps andThanasimus were monitored with pheromone traps in two regions differing in theirIps typographus outbreak history. Absolute catch as well as theThanasimus/Ips catch ratio were ten times greater in the outbreak region than in the non-outbreak region. Coupled with the results in the caging experiment, this indicates thatT. formicarius responds numerically to changes inI. typographus numbers per unit bark area as well as toIps population changes at the regional level. The findings suggest that predation under bark may be a significant factor in supressingI. typographus outbreaks.     

New techniques of rearingAnagrus flaveolus [Hym.: Mymaridae], an egg parasitoid of the brown planthopper

A small cage was designed to study the biology and behavior ofAnagrus flaveolus Waterhouse, an important egg parasitoid of the brown planthopper,Nilaparvata lugens (Stal), a pest of rice. A method of rearing moderate numbers of parasitoids on planthopper eggs in the laboratory was developed. Though the mymaridAnagrus flaveolus Waterhouse, a common egg parasitoid of rice planthoppers and leafhoppers all over Asia, reduces pest populations, its biological control potential has largely been overlooked because of its minute size and the lack of suitable techniques to study and rear it in the laboratory.Ôtake (1968, 1969) described some techniques to study the development, longevity and fecundity of a related speciesAnagrus nr.flaveolus Waterhouse. The cages described herein are much simpler to build and more efficient to use compared with those developed earlier. Rearing this important parasitoid in large numbers in the laboratory has not been done before.     

Hymenopterous parasitoids of bark beetles [Scolytidae] in Israel: Host relation,host plant,abundance and seasonal history

Twenty six species of parasitoids were recorded from 15 species of bark beetles in Israel. Parasitoids were collected from infested cut branches of broadleaves and trap-trees of pine and cypress. Most of the parasitoids are oligophagous and range fromEcphylus caudatus, a monophagous species exclusive toHypoborus ficus, toHeydenia pretiosa, which develops on 11 species.Scleroderma domesticus, Agrilocida ferrieri andEupelmus nearurozonus are occasional parasitoids of bark beetles.Cephalonomia hypobori, Israelius carthami, S. domesticus, Entedon ergias, Cerocephala eccoptogasteri andRoptocerus xylophagorum are cryptoparasitoids and search for their host in the galleries. Known parasitoids are listed from 15 tree genera belonging to 8 botanical families. A typical range for the common parasitoids is presented with within-tree distribution of pine parasitoids. Relatively monophagous species are usually dominant parasitoids in a specific beetle population, whereas relatively polyphagous parasitoids vary in abundance among different host populations.Calosota spp., 2Eurytoma spp. andDendrosoter hartigii are usually present in small numbers. Information concerning the seasonal history of the parasitoids suggests that the major species may raise about 5 to 7 annual generations. Contribution from the Agricultural Research Organization, Bet Dagan, Israel N^o 1331-E, 1984 series     

Biological control of the weed,Chromolaena odorata [Asteraceae], byPareuchaetes pseudoinsulata [Lep.: Arctiidae] on Guam and the northern Mariana Islands

Chromolaena odorata L. is a major weed of tropical plantations and pasture lands.Pareuchaetes pseudoinsulata Rego Barros [Lep.: Arctiidae] was mass-reared and released to control the weed on the Mariana Islands of Guam, Rota, Tinian and Saipan in the western Pacific. One year following establishment ofP. pseudoinsulata on Guam, the weed was reduced 100% at 3 of 4 sites monitored with fixed quadrats. Seed production was prevented if defoliation occurred prior to the beginning of the flowering season. If defoliation occurred shortly after flowering began, the developing seeds were eaten byP. pseudoinsulata or there was a significant reduction in weight and germination of seeds that matured. Eighteen months after establishing on Guam,P. pseudoinsulata had defoliated approximately 25,000 hectares of the weed. This is the 1^st report on the quantitative impact of any control agent forC. odorata, and though the long term effect of the insect is still unknown, these results are encouraging.     

Hymenopterous parasitoids of bark beetles [Scolytidae] in Israel: Relationships between host and parasitoid size,and sex ratio

Information on parasitoids of bark beetles infesting conifers and broadleaves is presented to show the relations between host and parasitoid size, and parasitoid sex ratios. Sticky traps were employed to determine the sex ratios of parasitoid species operating on beetle-infested material. A wide range in body length was found for most species. Females ofCerocephala eccoptogasteri Masi,Cheiropachus quadrum Febr.,Eurytoma morio Boheman,Heydenia pretiosa Forster,Metacolus unifasciatus Forster,Rhaphitelus maculatus Walker andRoptrocerus xylophagorum (Ratz.) were usually significantly longer than their males, whereas the males of all fourDendrosoter spp. were significantly longer than the females. Body lengths of the males and females were almost identical inEntedon ergias Walker andEcphylus caudatus Rusch. The sex ratio varied markedly within most species; the mean ratio for 5 of them differed significantly from 1∶1. The sex ratio ofM. unifasciatus andE. morio was significantly related to host size. The sex-ratio of parasitoids trapped on sticky traps varied with time in relation to the phenology of the host beetle. Females were more numerous during the larvae development while males were more abundant between the pupal stage and emergence of the host. Male courtship behaviour ofDendrosoter caenopachoids Rusch.,D. protuberans (Nees),M. unifasciatus andR. xylophagorum is described. The effect of host size, the diversity in sex ratios, and possible interaction between parasitoid size and sex-ratio are discussed. Contribution from the Agricultural Research Organization, Bet Dagan, Israel. N° 1328-E, 1984 series.     

Parasitoids of the corn borerOstrinia furnacalis [Lep.: Pyralidae] in the Mariana Islands

A survey of the parasitoids of the Asian corn borer,Ostrinia furnacalis (Guenee), in the Mariana Islands showed that few of the borers were parasitized. Parasitoids were reared from only 30 pupae out of more than 4 500 sampled. Three species of pupal parasitoids were found:Xanthopimpla punctata (F.),Brachymeria albotibialis (Ashmead) andTetrastichus? inferens Yoshimoto. No parasitoids were reared from mature larvae. The only egg parasitoid observed wasTrichogramma chilonis Ishii. During the month prior to the sweet corn harvest, which was the peak period of moth oviposition, about 40% of the egg masses had at least one egg parasitized. An average of about 35% of the eggs within a mass were parasitized.     

Notes onPatasson lameerei [Hym.: Mymaridae], an egg parasitoid ofSitona spp. [Col.: Curculionidae] in the mediterranean region

Patasson lameerei Debauche is the most important of three egg parasitoids found onSitona spp. attacking lucerne and annual medics in the North-Western Mediterranean. The mymarids were lacking in eggs extracted from the soil in Morocco, Algeria and Tunisia. The biology and the behaviour of the egg parasitoid are described. In Central Europe, adults ofP. lameerei are recorded from May to September, but in the Montpellier region (Southern France), this species aestivates in the larval stage within the eggs of its hosts during the same period.     

Insecticide effects onEntomophthora muscae [Zygomycetes: Entomophthorales]

Studies were conducted to determine the effect of insecticide residues on germination of primary conidia ofentomophthora muscae (Cohn) Fresenius and to determine the relative susceptibility of healthy and infectedMusca domestica L. to insecticides. Primary conidia were discharged fromM. domestica cadavers onto glass microscope slides treated with insecticides. All insecticides significantly inhibited germination relative to control slides. Permethrin and naled had the least inhibition (36–40 %), while malathion and dimethoate almost completely inhibited germination (87–94 %). Tetrachlorvinphos/dichlorvos and carbaryl were intermediate (57–59 %). Healthy flies were not significantly different from infected flies in terms of susceptibility to naled, dimethoate, or permethrin. Infected flies exposed on the last day of pathogen incubation died on the bottom of the Petri dishes, rather than climbing and attaching as did untreated, infected flies. Both control and treated groups produced large numbers of primary conidia.     

Forest and laboratory evaluations of hybridizedApanteles melanoscelus [Hym.: Braconidae], a parasitoid ofPorthetria dispar [Lep.: Lymantriidae]

Hybrids ofApanteles melanoscelus (Ratzeburg) were produced from colonies originating from France, Yugoslavia, and Connecticut. All strains, as well as freshly collected “wild” Connecticut parasitoids of the same species were evaluated in the laboratory for developmental rate, host attack rate, and sex ratios. Development was significantly slower in all the laboratory strains compared to the progeny of forest collected Connecticut females. Progeny production was greater (almost 2X) for the “wild” females and the French-Yugoslavian-Connecticut hybrid than for the laboratory Connecticut strain. The proportion of females collected from the “wild” (Connecticut) strain was higher than that observed in any laboratory strain. A field test was conducted using the triple hybrid in 3 release plots with ca. 6000A. melanoscelus cocoons released per plot in central Connecticut, U.S.A. Weekly collections of gypsy moth larvae showed that the % parasitism was significantly higher in release plots than in the 3 check plots. These results suggest the value of inundative releases ofA. melanoscelus for reduction of sparse gypsy moth populations, but they did not show that hybridization of these strains produced a more effective parasitoid under forest conditions.     

Ecological requirements for hibernatingPropylea quatuordecimpunctata (L.) andCoccinella septempunctata [Col.: Coccinellidae]

During 3 successive winters, we studied the dormancy sites ofPropylea quatuordecimpunctata (L.) andCoccinella septempunctata L., 2 species of ladybirds which hibernate in leaf litter. Samples of litter were taken from several kinds of forest to study the influence of 3 variables (exposure; altitude; sampling place: edge or inner wood) on the abundance of ladybirds. We found the ecological requirements of the 2 species of coccinellids to be quite different:C. septempunctata prefers forest edges orientated towards the South and the West.P. quatuordecimpunctata prefers the inner wood and does not show a preference for station exposure. For each species, the number of ladybirds collected in the samples is positively correlated with station altitude. In addition, some observations were carried out to examine the main mortality factors just before and during dormancy. In maize fields near dormancy sites, the harvest is very harmful forC. septempunctata. During the winter,P. quatuordecimpunctata andC. septempunctata suffer fromBeauveria ssp. and some ladybirds have parasitoïds.     

Arthropods and nematodes co-occurring with the eastern larch beetle,Dendroctonus simplex [Col.: Scolytidae], in Newfoundland

Fifty-four species of insects, 5 of spiders, 5 of mites, 1 harvestman and 1 nematode co-occurred with the eastern larch beetle,Dendroctonus simplex LeConte, on tamarack,Larix laricina (Du Roi) K. Koch, at 2 localities in Newfoundland. The most abundant predators were the flyMedetera gaspensis Bickel and the beetleRhizophagus dimidiatus Mannerheim and the most abundant parasitoids were the HymenopteraSpathius canadensis Ashmead,Rhopalicus tutela (Walker) andRoptrocerus xylophagorum (Ratzburg).D. simplex is recorded as a new host for 9 predator and 3 parasitoid species.      

Biological control of the oil palm pestLatoia viridissima [Lepidoptera,limacodidae], in Cote d'Ivoire,by a new picornavirus

Among the major oil palm pest insects in the Côte d'Ivoire,Latoia viridissima Holland [Lepidoptera, Limacodidae] is the most frequently observed defoliator. During a pullulation of this species, a natural epizootic permitted us to demonstrate the occurrence of a small isometric RNA virus of 30nm in diameter. The buoyant density of the virus particles was 1.34. The virus capsid contained 2 major proteins with molecular weights of 30,000 (55%) and 31,000 (20%) and 3 minor proteins. One genome component was detected with molecular weight 2,9×10⁶. Agarose gel diffusion tests showed this virus was distinct from any other described insect Picornavirus. Trials with different doses of viral suspensions were tested on industrial oil palm plantation, allocated byL. viridissima, from ground level, using an automatic air carried sprayer. One week after the treatment, a mortality gradient, increasing from 11 to 61% according to the dose applied, was obtained. Two weeks after the treatment the mortality reached 92% of the larvae in the treated parcels. During the next generation, the number of caterpillars on the same parcel was very low.     

Host discrimination byChelonus insularis [Hym.: Braconidae], telenomus heliothidis [Hym.: Scelionidae], andTrichogramma pretiosum [Hym.: Trichogrammatidae]

The ability of female parasitoids (Chelonus insularis Cresson,Telenomus heliothidis Ashmead, andTrichogramma pretiosum Riley) to distinguish between parasitized and unparasitized tobacco budworm,Heliothis virescens (F.), eggs was determined in laboratory studies. All 3 species were relatively efficient at detecting eggs that were previously parasitized by conspecific females.T. heliothidis andT. pretiosum were able to discriminate on the basis of external examination of host eggs, whereasC. insularis appeared to examine hosts internally as well as externally. In interspecific tests, no species readily rejected eggs parasitized by the other 2 species.     

Superparasitism ofEpilachna varivestis [Col.: Coccinellidae] byPediobus foveolatus [Hym.: Eulophidae]: Influence of temperature and parasitoid-host ratio

Superparasitism ofEpilachna varivestis Mulsant larvae by the hymenopterous parasitoid,Pediobius foveolatus (Crawford), occurred under laboratory conditions. However,P. foveolatus avoided previously parasitized larvae in a manner which was directly related to the number of times host larvae were initially parasitized. Increasing the parasitoid-host ratio also increased percent host mortality and highest overall host mortality occurred at 15.6°C when the parasitoid-host ratio was 10∶10. Higher temperatures (22° and 28°C) and higher parasitoid-host ratios yielded higher numbers of parasitized larvae although a significant number of parasitoids failed to emerge at the highest parasitoid-host ratio. Higher temperatures along with increasing parasitoid-host ratios favored production of more male parasitoids.     

Host selection and larval interactions among three primary parasitoids ofPlathypena scabra (Lep.: noctuidae)

Three hymenopteran parasitoids that attackPlathypena scabra (F.) larvae often oviposit into consecutive instars of the host. We investigated host discrimination by adults and competitive interactions among larvae of these three parasitoid species. Avoidance of superparasitism byCotesia marginiventris (Cresson) andDiolcogaster facetosa Ashmead was tested. Females of each species were presented either withP. scabra parasitized by a different female of the same species 6 h earlier or unparasitizedP. scabra. Under these conditions,C. marginiventris attacked similar numbers of parasitized and unparasitized hosts.D. facetosa attacked 31% fewer parasitized than unparasitizedP. scabra. The avoidance of multiple parasitism byD. facetosa was studied in a similar bioassay. AlthoughD. facetosa females parasitized fewerP. scabra that had been attacked byC. marginiventris 6 h previously, the reduction in parasitism was only about 23%. In competition studies, immatureD. facetosa were better competitors than immatureC. marginiventris. Aleiodes (=Rogas) nolophanae (Ashmead) was an inferior competitor against bothC. marginiventris andD. facetosa when the duration between parasitism events was 1 h, but their competitive ability increased when they multiply parasitized hosts at least 32 h after the initial oviposition.     

Effects of parasite density and host availability on progeny production byBiosteres (Opius) longicaudatus, [Hym.: Braconidae], a parasite ofAnastrepha suspensa [Dip.: Tephritidae]

Progeny production ofBiosteres (Opius) longicaudatus Ashmead, a larvalpupal parasite of the Caribbean fruit fly,Anastrepha suspensa (Loew) was affected by host availability, previous ovipositional experience, and parasite density and age. Parasitization rates were evaluated in 24.5 cm³ ovipositional cages at parasite densities of 25, 125, and 250 male-female pairs by exposingB. longicaudatus adults to (a) 500A. suspensa larvae for a 24 h period or (b)ad libitum host larvae for each of the 14 days following eclosion. The mean numbers of parasite progeny produced at the 25, 125, and 250 densities were 1076, 1896, and 2038, respectively. The number of progeny produced per surviving female parasite was inversely proportional to the adult parasite density and relatively more female progeny were produced as the adult parasites aged. Host mortality was significantly higher among parasitized larvae. Maximum rearing efficiency was achieved at the 125 density.     

Seasonal history ofMacrocentrus grandii [Hym.: Braconidae] andEriborus terebrans [Hym.: Ichneumonidae], two parasitoids of the European corn borer,Ostrinia nubilalis [Lep.: Pyralidae]

The seasonal histories and phenological relationships of European corn borer,Ostrinia nubilalis (Hübner), and its 2 parasitoids,Macrocentrus grandii (Goidanich) andEriborus terebrans (Gravenhorst) were studied in southcentral Minnesota. Both parasitoids overwintered in mature borer larvae, broke diapause, completed development, and emerged at the same time as did borer adults. Thus the 1st generation parasitoids coincided with the peak abundance of their preferred larval instars of the 1st host generation. Both parasitoids had a 2nd generation, matching the bivoltinism ofO. nubilatis in Minnesota. The activity of 2nd generationE. terebrans was before the peak 2nd generation borer moth flight and was not synchronized with the peak abundance of 2nd generation borer larvae. The peak activity of 2nd generationM. grandii occurred after the peak 2nd generation borer moth flight and was fully synchronized with the peak abundance of 2nd generation borer larvae. Thus,M. grandii has both generations synchronized with the host seasonal history, and was the more effective of the 2 parasitoids.     

Hexamermis glossinae [Nematoda: Mermithidae] parasitizing tsetse [Diptera: Glossinidae] in Kenya

Glossina pallidipes Austen,G. brevipalpis Newstead andG. austeni Newstead were collected from 5 sites along the south Kenyan coast over a 2 year period. They were dissected and examined for nematodes. Three of the sites yielded tsetse parasitized by juvenile mermithids identified asHexamermis glossinae Poinar et al. Glossina pallidipes andG. brevipalpis are new host records for this parasite, whileG. austeni was captured infrequently and only at a site that failed to yield other parasitized tsetse. Parasite prevalence was low (0.16–0.61 %) and did not differ between male and female hosts. More tsetse than expected by chance harboured nematodes during the long rains season (April–August) than during the short rains (September–November) or dry season (December–March). Early juvenile stages (0.5–2.5 mm long) were recovered mainly from tsetse less than 50 days old, while late juvenile stages (35–85 mm long) were only found in flies older than 30 days. Late stages occurred singly while early ones usually occurred as two or more per host.