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.     

Alaboratory evaluation ofAnthocoris nemorum andA. nemoralis [Hem.: Anthocoridae] as predators ofPhorodon humuli [Hom.: Aphididae]

Anthocoris nemorum (L.) andA. nemoralis (F.) were reared on apterous hop aphids,Phorodon humuli (Schrank), at 20±0.5°C.A. nemorum andA. nemoralis killed an average of 255 and 174 aphids respectively during nymphal development, and the adults killed 37 and 33 per day respectively. Small anthocorid nymphs selectively killed small aphids but adult anthocorids and 5th instar nymphs killed aphids of every size. Mean development times from emergence to final moult were 22 and 16 days forA. nemorum andA. nemoralis respectively.     

Longevity and reproductive rate ofPatasson lameerei [Hym.: Mymaridae], a parasitoid ofSitona spp. [Col.: Curculionidae] eggs

Patasson lameerei DeBauche produced an average of 28.5 offspring under 2 temperature regimes usingSitona hispidulus (Fabricius) eggs as hosts. Although its fecundity was not affected by the temperature regimes,P. lameerei lived significantly longer at 6.7/18.3°C than at 21.1°C. When ample hosts were available,P. lameerei produced more offspring during the 1st few hours of its adult life than during any other comparable period. When the parasitoids were denied access to host eggs for 1,2, or 3 days after emergence, they still produced similar numbers of offspring during their 1st 24 h exposure to hosts.     

Evaluation of Greenbug and Yellow Sugarcane Aphid Feeding Behavior on Resistant and Susceptible Switchgrass Cultivars

Switchgrass (Panicum virgatum L.) is an emerging biofuel crop that serves as host for aphids. To discern the effects of plant age and possible resistance mechanisms, the feeding behavior of greenbugs (Schizaphis graminum Rondani.) and the yellow sugarcane aphid (Sipha flava Forbes.) was monitored on three diverse switchgrasses by the electrical penetration graph (EPG) technique. Callose deposition and genes associated with callose metabolism were also analyzed to discern their association with plant resistance. There was a strong host effect on greenbugs feeding on lowland cultivar Kanlow at the V3 stage of development, as compared to the greenbug-susceptible upland cultivar Summer and plants derived from Kanlow (♂) × Summer (♀) (K×S) crosses. These data confirmed that Kanlow at the V3 stage had antibiosis to greenbugs, which was absent in the Summer and K×S plants. In contrast, similar effects were not observed for yellow sugarcane aphids, excluding significant differences in the time to first probe on Kanlow plants at the V1 stage and reduction in time spent on pathway processes on Kanlow plants at the V3 stage. These data demonstrated that Kanlow plants may have multiple sources of resistance to the two aphids, and possibly some were phloem based. Microscopy of leaf sections stained with aniline blue for callose was suggestive of increased callose deposition in the sieve elements in Kanlow plants relative to Summer and K×S plants. RT-qPCR analysis of several genes associated with callose metabolism in infested plants was equivocal. Overall, these studies suggest the presence of multiple defense mechanisms against aphids in Kanlow plants, relative to Summer and K×S plants.     

Mass breeding of two species ofSaissetia [Hom.: Coccidae] for propagation of their parasitoids

Potato sprouts detached from soil are most suitable for mass rearingSaissetia oleae (Olivier),S. coffeae (Walker) and their parasitoids, since the duration of development of the coccids is short, and they can be grown easily with their natural enemies in closed containers under controlled conditions.S. oleae served for propagation ofMetaphycus affinisstanleyi Compere,M. helvolus (Compere),M. bartletti Annecke & Mynhardt,M. lounsburyi (Howard), whilstS. coffeae was better suited forScutellista cyanea Motschulsky. The ornamental plantAdhatoda vasica Nees, citron melon and squash fruits served for rearingS. coffeae, while oleander was used for breedingS. oleae and its parasitoids during the ebb of the culture on potato sprouts.     

Determination of host range in relation to systematics forPeristenus stygicus [Hym.: Braconidae], A parasitoid ofMiridae

Peristenus stygicus Loan develops inMirinae speciesLygus hesperus,Knight,L. lineolaris, (Palisot de Beauvois) andPolymerus basalis (Reuter),Orthotylinae speciesLabopidicola geminata (Johnston),Phylinae speciesPseudatomoscelis seriatus (Reuter) and partially develops in the mirineDichrooscytus sp. The parasitoids attackMicrophylellus maculipennis (Knight) (Phylinae) and another orthotyline species, but do not develop in these.Taedia johnstoni (Knight) (Mirinae), 2 species ofBrycorinae and 3 species ofLygaeidae are not acceptable as hosts. Olfactometer studies show the parasites are significantly more attracted to lygus nymphs whenPhaseolus vulgaris L. is present than either the nymphs or bean alone. Host color, mobility, size, previously infested plant material, and host plant species are rejected as host selection criteria.     

Interference between parasitoids [Hym.: Aphidiidae] and fungi [Entomophthorales] attacking cereal aphids

In field populations of cereal aphids parasitism levels declined through the season as fungal infection increased. In laboratory trials the fungusErynia neoaphidis Remaudiere & Hennebert took 3 to 4 days to kill the rose-grain aphid,Metopolophium dirhodum (Walker), whereas the parasitoidAphidius rhopalosiphi De Stefani-Perez took 8 to 9 days at 20°C. When aphids were infected by the fungus less than 4 days after being parasitized the parasitoids were prevented from completing their development. Conversely, when infection occurred more than 4 days after parasitization development of the fungus was significantly impaired. There was no histological evidence that the fungus invaded the tissues of the parasitoid when both attacked the same aphid. Interference between parasitoids and fungal pathogens must be taken into account when estimating the impact of these mortality agents on pest populations.     

Effect oforthogalumna terebrantis [Acari: Galumnidae] on neochetina eichhorniae [col. curculionidae] eggs and oviposition

Adult waterhyacinth mites,Orthogalumna terebrantis Wallwork, did not consume eggs of the mottled waterhyacinth weevil,Neochetina eichhorniae Warner, under 4 temperature regimes (viz. 5°–25°, 10°–30°, 15°–35° and 20°–40° C). Microscopic examination showed that mites did not feed or attempt to feed on weevil eggs and they starved when weevil eggs were the only source of food. At the same temperature regimes, 0, 50, 100, 150 and 200 mites were added to aluminium pans containing 3 pairs of adult weevils and a fresh waterhyacinth pseudolamina. Weevils laid more eggs/female (P≤0.05) in the presence of mites.     

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.     

Lethal temperatures of citrus blackflyAleurocanthus woglumi [Hom.: Aleyrodidae] and its parasite,Amitus hesperidum [Hym.: Platygasteridae]

Seasonally acclimatized citrus blackfly (CBF),Aleurocanthus woglumi Ashby, and its parasite,Amitus hesperidum Silv. were exposed to extreme temperatures for 3-hour periods and survivorship measured. In summer experiments, the LD₅₀ for CBF adults and 1st instar nymphs occurred between 40° and 45°C. The LD₅₀ forA. hesperidum adults occurred between 35° and 40°C and increased with decreased humidity, although some adults could continue to emerge from parasitized CBF up to 45°C. In winter experiments, the LD₅₀ for CBF eggs and adults occurred between ?5° and ?10°C and for other CBF stages between ?10° and ?15°C. The LD₅₀ for adultA. hesperidum, and survival and emergence of the parasites from CBF both occurred between ?10° and ?15°C. Comparing data from the 2 seasons shows that adults are the most temperature sensitive stage of CBF and the parasite is more temperature sensitive than CBF, especially at higher temperatures. Correlating lethal temperature data with field meteorological conditions shows that short-term temperature exposures cannot be expected to stop the potential spread of CBF orA. hesperidum through Florida.     

Development ofLydina polidoides [Diptera: Tachinidae] in relation to its hostChrysoteuchia topiaria [Lepidoptera: Pyralidae]

Lydina polidoides (Townsend) andChrysoteuchia topiaria Zeller were studied in the laboratory. The rate of development ofC. topiaria from eclosion to the diapausing prepupae was 55 days when larvae were exposed to long daylenghts (16 hr light, 8 hr dark) and 43 days when exposed to short daylengths (12 hr light 12 hr dark.) The same insects exposed to long days emerged as adults in 124 days, whereas those exposed to short days emerged in 156 days because short days prepared the prepupae for diapause but failed to maintain the diapause. When caterpillars (prepupae) ofC. topiaria parasitized by young larvae ofL. polidoides and non-parasitized caterpillars were removed from the field in January and exposed to long days at 21°C,C. topiaria emerged as adults in an average 55 days andL. polidoides in 106 days.Lydina polidoides is therefore univoltine andC. topiaria is probably the primary host of this Tachinid parasite.     

The parasitoids ofSpodoptera littoralis [Lep.: Noctuidae] and their role in population control in Cyprus

This paper is based on 20 months survey and laboratory studies of the parasitoids ofSpodoptera littoralis (Boisduval) (Lep.: Noctuidae) carried out in Cyprus in 1971–72. Regular sampling revealed the presence of 19 further macrolepidopterous members of the ecosystem, includingS. exigua (Hbn.),Heliothis spp. and “Plusia” spp. Attacking these were a complex of at least 37 named primary parasitoids and a single secondary parasitoid. The commonest were the ichneumonidHyposoter didymator (Thnb.) and the braconidsChelonus inanitus (L.),Meteorus unicolor (Wesm.) andMicroplitis rufiventris Kok. and notes on their hosts, hostplants and biology are given. Almost all of the parasitoids were polyphagous and this, together with a wide range of hostplants, appears to improve the carry-over of the parasitoids and permit for greater parasitism of the main pests,S. littoralis andS. exigua. The % parasitism is shown to vary greatly with the situation, being highest in unsprayed lucerne field and unsprayed market gardens, and lowest in potato fields and sprayed vegetable plots. Recommendations are made for possible reductions in crop spraying, permitting the growth of weeds, under certain conditions, mass-rearing and liberation of an endemic parasitoid (C. inanitus) and filling gaps in the parasite complex by the introduction of exotic parasitoids.     

Influence of temperature on the oviposition rate and longevity ofOpius concolor siculus [Hymenoptera: Braconidae]

The author has studied the influence of different temperatures (22°, 24°, 26°, 28°C) on oviposition and longevity ofOpius concolor siculus Mon., studying separately 13 couples at 22°, 15 at 24°, 100 at 26° and 11 at 28°C. The optimum temperature has been found to be 26°C. Differences have been observed betweenO. concolor Szepl. «African» andO. concolor siculus Mon. «Sicilian».     

Biology of the flea beetle,Altica carduorum [Col.: Chrysomelidae] on Canada thistle (Cirsium arvense) in South Dakota

A laboratory colony of 50 adults ofAltica carduorum Guérin-Méneville was established at South Dakota State University. Beetles reared in this colony had an average preoviposition period of 7 days when exposed to a regular cycle of 16 hr of light (24°C) and 8 hr of darkness (12.7°C). The laboratory reared females, whose longevity averaged 100 days, laid an average of 259.3±9.7 eggs. High temperatures and/or low RH are limiting factors to beetle survival. In the field eggs were laid throughout June on the underside of leaves along the edges of the veins. Adults fed throughout the summer and then over-wintered in the soil. Some of these beetles emerged the following spring and laid viable eggs. Factors limiting establishment in South Dakota, however, were high temperatures, low humidities, and the predators,Lebia viridis Say andHarpalus pennsylvanicus Degeer.A. carduorum originates from the Swiss Rhône valley where there is a relatively “continental” climate, but is limited to special habitats where comparatively high humidity occurs. South Dakota climate is characterized by cold winters, and hot, dry summers, therefore establishment would be most difficult.     

Parasitoids and hyperparasitoids ofZeiraphera diniana [Lep., Tortricidae] and their pole in population control in outbreak areas

There are 109 species of primary and secondary parasitoids associated withZeiraphera diniana Guénée in the Central European Alps. Ninety species are primary, 6 facultative secondary and 13 obligate secondary parasitoids. At family level, the composition of the complex seems to be the same in every outbreak area of the host, with ichneumonids predominating. In the Upper Engadine Valley (Switzerland), where intensive studies were conducted over a period of 3 consecutive outbreak periods (28 years), 65% of the complex is represented. The nomenclature ofZ. diniana parasitoids has been clarified as far as possible. Many species names cited in the literature are synonyms or misidentifications. The complex of parasitoids, together with the associated predators ofZ. diniana, is unable to slow down the rate of density increase of the host in outbreak areas. This fact has stimulated investigations on the most important parasitoid species, i.e.Phytodietus griseanae Kerr. (Ichneumonidae), Sympiesis punctifrons Thomson,Dicladocerus westwoodii West. andElachertus argissa Walker (Eulophidae) over a period of about 10 years. Recent research has demonstrated that immigration ofZ. diniana moths into the outbreak areas during the phase of host density increase is very important. The rate of increase of the natural enemies — which are univoltine —can never equal or exceed that of their host; consequently, control by these natural enemies alone is not possible.     

Duration of development and longevity inAphidius ervi andAphidius platensis [Hym.: Aphidiidae], two parasites ofMyzus persicae [Hom.: Aphididae]

Rate of development and longevity were studied inAphidius ervi Haliday andAphidius platensis Brèthes, two parasites of the green peach aphid,Myzus persicae Sulz. On paprika,A. ervi developed from egg to adult in 27.3 days (at 15°C) and 19.9 days (21°C),A. platensis in 19.9 days (15°C), 15.6 days (21°C) and 12.4 days (24°C). The period from oviposition to mummification was in both species roughly twice as long as the period from mummification to adult emergence. Males emerged slightly before females. Given water and honey,A. ervi lived 15.4 days (♂) and 13.1 days (♀) at 21°C. The effect of temperature on longevity was tested inA. platensis on this diet: at 15°C, 9.2 days (♂) and 7.9 days (♀); at 21°C, 12.0 days (♂) and 13.4 days (♀); and at 24°C, 7.4 days (♂) and 8.4 days (♀). When supplied only with water, both species lived for 1–3 days. When aphid-infested leaves were added, longevity increased by 3.5 days (A. platensis). The maximal longevity, obtained with water and honey, was somewhat reduced when leaves were added, probably due to mating and oviposition activities (A. ervi). Longevity was not significantly influenced by the different host plants during parasite development. Differences in longevity between the sexes were small and dependent on temperature and food.     

Spatial distribution of the gypsy moth [Lepidoptera: Lymantriidae] and some of its parasitoids within a forest environment

Aspects of the microhabitat distributions of the gypsy moth,Porthetria dispar (L.) (Lepidoptera: Lymantriidae), and some of its parasitoids were investigated in the field by means of sticky panels and gypsy moth egg masses exposed at different heights in trees, by egg masses exposed within forested and cleared areas, and by gypsy moth pupal collections from different heights in trees.Ooencyrtus kuwanai (Howard)(Hymenoptera: Encyrtidae), Apanteles melanoscelus Ratzeburg (Hymenoptera: Braconidae), and gypsy moths were caught most frequently on stickly panels placed in upper portions of trees. In contrast,Apanteles laeviceps Ashmead, a parasitoid of cutworms, was most often caught near the forest floor.O. kuwanai attacked equally egg masses exposed at different heights in trees, but parasitized those in a clearing less often than those within the forest prosper.Brachymeria intermedia (Nees) (Hymenoptera: Chalcididae) emerged mostly from pupae collected near the tops of trees and not at all from those collected below 5 m. The results are discussed as they relate to field sampling procedures, behavioral activities of gypsy moth and parasitoid adults, and integrated control possibilities for the gypsy moth.     

The establishment of two imported parasitoids of potato tuber moth [Phthorimaea operculella] in South Africa

Two parasitoids of the potato tuber moth (Phthorimaea operculella) (Zeller)[Lepidoptera: Gelechiidae], Copidosoma uruguayyensis Tachikawa andApanteles subandinus Blanchard, originally from South America, have been successfully established in South Africa. Recoveries many kilometers from the original release sites are common. In the Transvaal these two parasitoids have shown, by replacing the indigenous parasitoids, that they can possibly achieve better control of the potato tuber moth. The more efficient use of ridging and the complete discontinuation or reduction of insecticide applications to one or two carefully timed sprays could achieve better use of biological control.     

TheSitona [Col.: Curculionidae] species occurring onMedicago and their natural enemies in the Mediterranean region

TwentySitona species were found in the Mediterranean region during surveys on 17 volunteer and/or cultivated species ofMedicago. The distribution of the weevils was analyzed using the 3 concepts of abundance, constancy and dominance. EightSitona species were consistently recorded on lucerne and medics; of these, 3 were “constants” and only 2,S. humeralis Stephens andS. lineatus Linnaeus, also “dominants” in the sites investigated. Sixteen species of natural enemies were identified (table 4), including 3 egg predators, 3 egg parasitoids, 1 entomogenous fungus, 2 nematodes and 5 parasitoids of adult weevils. The effect of each organism on theSitona population numbers was slight, not exceeding in most cases an average mortality of 15%. At high host densities however, the braconidMicroctonus aethiopoides Loan which is the preponderant parasitoid, caused estimated mortalities up to 80% during a single weevil generation. Noticeable changes in the relative importance of the natural enemies were observed between the areas surveyed, with onlyM. aethiopoides and the mymarid egg parasitoidPatasson lameerei Debauche occurring widely. Moroccan, French and Greek strains of these 2 parasitoids were forwarded to Australia for the biological control ofS. humeralis there.     

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.