Within-field refugiums of Russian wheat aphid, Diuraphis noxia (Kurdj.) in cereals (Hom., Aphididae)

An analysis of the Russian wheat aphid (RWA) (Diuraphis noxia Kurdj.), overpopulated due to extraordinary weather conditions (2000) in the Czech Republic, enabled the identification of several within-field situations ouside of the routine approach. This group, classified as within-field refugium, includes variation due to field relief, some injuries caused by the use of machinery, the unharvested field margins and, last but not least, the volunteer plants. Differences between the RWA populations in these situations and the normal grove are presented and recommended to be taken into consideration in the research on RWA population dynamics and movement.     

Russian wheat aphid, Diuraphis noxia (Kurdj.) under adverse weather conditions (2001) (Hom., Aphididae)

Cool and wet weather in some periods of the season generally supressed the RWA (Diuraphis noxia Kurdj.) populations in the Czech republic in 2001. However, some sites manifested population levels ranging out of the population mean stated per area, and these sites were also apparently responsible for respective peaks of alate aphids sampled by suction traps. An analysis of these sites determined them to be attributed to some poor quality barley fields in a warmer area of the state. RWA is known to vary in all-over populations in different years, and the year 2001 illustrated its capability of its surviving even unfavourable periods and seasons, remaining well-established in the area.     

Increase of Russian wheat aphid, Diuraphis noxia (Kurdj.) in hot and dry weather (2000) (Hom., Aphididae)

Two hot and dry weather periods during mid-spring and early summer caused severe drought-stress to barley groves in many districts of the Czech Republic in 2000. Although not generally taken into consideration as an injury-increasing factor, the Russian wheat aphid (=?RWA), Diuraphis noxia (Kurdj.), was discovered to contribute significantly to injury in the ripening stage of spring barley as well as to the substantial decrease of yield (up to 30?–?40?% of the calculated mean, in some districts). RWA increased considerably not only in the lowland banker areas but also in the higher altitudes, values in the latter case then manifesting those found in the lowland banker areas in the previous years.     

Flight patterns of Russian wheat aphid,Diuraphis noxia (Kurdj.) during its expansion to Central Europe (Hom., Aphididae)

Flight patterns of migrant alate Russian wheat aphids (=RWA),Diuraphis noxia (Kurdj.) during its expansion from the south-east to Central Europe were determined. Samples were taken by Rothamsted-type suction air traps in Hungary (one location, 1990–1997) and in the Czech Republic (5 locations, 1994–1998). The results document a progressive expansion of RWA, and population variation in the individual years and periods of the season. A comparison of the evidence on RWA in the individual years since its detection in Hungary and in the Czech Republic supports the presumption on the occurrence of an expansion route from the south-east (Turkey) to Central Europe. This expansion is classified as an adventive route of the over-all expansion that has covered the whole West-Mediterranean (South Europe, North Africa).     

Suction air traps vs. crops in monitoring Russian wheat aphid, Diuraphis noxia (Kurdj.) in Central Europe (Hom., Aphididae)

Summary The Russian wheat aphid (=RWA), Diuraphis noxia (Kurdj.) is an exotic expansive aphid on the small grains determined in the Czech republic since 1993 (1995). Determination of RWA flight patterns by suction air traps (= SATs) between 1994-1998 indicated some banker, less important, or indicated RWA distribution areas. A comparison of the RWA monitoring by SATs and by crop samples in areas more or less distant from individual SAT locations manifested a high silmilarity of RWA evidence in its overall distribution and area-influenced population numbers. Owing to geographic area-dependent features of its life-cycle (holocycly) and host plant preferences, RWA seems to be most injurious to spring barley. In spite of the role of SATs in aphid forecasting, RWA samples are recommended to be taken also from the crops at the early ripening stage as the respective SAT evidence reflects only the emigration of the alate aphids originating from the decreasing populations. In general, RWA detection by SATs was either simultaneously or successively found to reflect the RWA presence in the more or less distant crops. The 30km perimeter of a SAT is agreed to be representative for mon-toring RWA populations in a sampled area.     

On-going expansion of Russian wheat aphid, Diuraphis noxia (Kurdj.) in central Europe (Horn.: Aphididae)

A supplementary research on Russian wheat aphid (= RVA), Diuraphis noxia (Kurdj.) between 1998-99 documented the pest distribution all over the Czech republic already. RVA abundance was proved to be significantly area-dependent within the state. The banker areas are in southern Moravia (district Znojmo, the frontier area near Austria) up to central Moravia. The determined RWA distribution area is much broader than presumed on grounds of climatic characteristics.The abundance of RVA generally decreases from the SE to the NW and N direction, as well as with the increasing altitude within the area.The highest altitude a.s.l. of RWA occurrence in the crop was 762 in. The re-classified main expansion route was determined to follow two directions (sourcing from Hungary and Austria) to southern-central-northem Moravia, and to southern Bohemia and further on to the central Bohemian lowland. The field information indicated the development of preference of RWA for barley.     

Distribution and Ecology of the Russian Wheat Aphid,Diuraphis noxia (Kurdj.), expanded to Central Europe (Hom.: Aphididae)

A part of the territory of the Czech Republic represents the up-dated northern limit of distribution (status 1997) which the Russian wheat aphid (=RWA),Diuraphis noxia (Kurdj.) has reached during its expansion from the southeast to central Europe. The newly defined area is classified as one of the adventive routes which may be derived from the main expansion of RWA from its native home (central-western Asia) into the broader Mediterranean area. Distribution and its history, and ecology (life-cycle, host plants, seasonal history, both native and introduced natural enemies) of RWA are presented on ground of field evidence and trials obtained in 1995–1997 in the Czech Republic. The origin of RWA, its distribution and establishment in the target area, as well as prognosis of its further expansion, are reviewed and discussed. Steps and approaches to RWA detection in the crop, as well as some notes on its management, are added.     

Adaptation of native syrphid flies to new exotic plant (Impatiens spp.)-aphidant associations in Central Europe (Dipt., Syrphidae; Hom., Aphididae; Hym., Formicidae)

Impatiens parviflora andI. glandulifera, two invasive touchme-not species of exotic origin were found to be associated with two aphid groups in Central Europe: a) Exotic species subsequently following their invasive plant hosts (Impatientinum asiaticum Nevsky), b) native species secondarily adapted to the new exotic hosts (Aphis fabae cirsiiacanthoidis Scop.). The species number (listed) of associated syrphid flies in the newly developed guilds was rather high, consisting of broadly oligophagous species. The plant phenology and adaptation of the aphids have resulted in associations which apparently represent seasonally significant sources of prey, their importance apparently increasing with the decreasing season. Antattendance was determined in both aphid species, and no adverse interference with the preying syrphid larvae was observed. In spite of an overall classification of the target plants as expansive weeds, they are classified positively as contributing to the enhancement of syrphid fly populations in the biocorridors in the cultivated landscape.     

The expansive Russian wheat aphid,Diuraphis noxia (Mordw.) detected in the Czech Republic

The Russian wheat aphid,Diuraphis noxia (Mordw.) has been detected in southern Moravia, the Czech Republic in June, 1995. Its location is related to its incidence in central Hungary. The further predicted area of distribution covers the grain-maize growing districts of southern Moravia (Czeck Republic), neigh-bouring parts of Austria, southern and south-eastern parts of the Slovak Republic. The aphid is classified as a species expanding to the north from its mediaterranean area of distribution, apart of extensive areas (North to South Americas, S. Africa, expected in Australia) which it has covered thorugh accidental introductions and further spread over the world.     

Über das Auftreten der Getreideblattlausarten (Hom., Aphididae) in norddeutschen Weizenanbaugebieten (1974/75)

The ocurrence of the different cereal aphids (Hom., Aphididae) in Northern German wheat growing areas 1974 and 1975 In July, 1974 and 1975,Macrosiphum avenae (F.) was the most common aphid on cereal fields in Northern German wheat growing areas.Rhopalosiphum padi (L.) was less abundant, whileMetopolophium dirhodum (Wlk.) was found very seldom.R. padi infested field edges only in most cases, while this was not true for all fields infested byM. avenae.     

Die Parasitoide der Blutlaus (Eriosoma lanigerum Hausmann) (Hom., Aphididae) und ihre Verbreitung in der Pfalz

Zusammenfassung Die Blutlaus kam zwischen September 1986 und Oktober 1987 in allen Apfelangebieten der Pflaz vor. Von insgesamt 50 untersuchten Orten mit Apfelvorkommen trat der Schädling in 22 von 28 bewirtschafteten Apfelanlagen, dagegen nur an 2 von 24 Orten mit wildwachsenden oder extensiv bewirtschafteten Apfelbäumen auf. Außer in der Westpfalz konnte überall auch gleichzeitig der einzige spezifische Parasitoid, die BlutlauszehrwespeAphelinus mali Hald. gefunden werden.NebenA. mali wurden aus mumifizierten Blutläusen 4 weitere Species aus der Überfamilie Chalcidoidea gezogen, wobei es sich um Hyperparasitoide der ArtenAsaphes vulgaris Walk.,Asaphes suspensus Nees undPachyneuron solitarium Htg. (Pteromalidae) sowie umAphidencyrtus aphidivorus Mayr (Encyrtidae) handelte.Um die Bedeutung der Zehrwespe bei der biologischen Bekämpfung der Blutlaus festzustellen, wurden in verschieden bewirtschafteten Apfelanlagen während einer Vegetationsperiode die Stärke des Blutlausbefalls über die Koloniezahlen und der Parasitierungsgrad durchA. mali über Präparationen von mehr als 63 000 Läusen ermittelt. Die Auswirkungen der zu dieser Zeit eingesetzten Pflanzenschutzmittel wurden berücksichtigt.Die Ergebnisse zeigen, daß in der Pflaz die biologische Bekämpfung vonEriosoma lanigerum mitA. mali in integriert bewirtschafteten Anlagen möglich ist, wobei der termingerechte Einsatz selektiver Präparate die Wirkung der Zehrwespe sinnvoll unterstützen kann. Die konventionell bewirtschafteten Anlagen waren dagegen besonders nach Einstellen der Insektizidbehandlungen viel stärker befallen und zeigten auch aufgrund vorangegangener Schädigungen der Wespe durch breitenwirksame Präparate deutlich geringere Parasitierungsraten.Eine Empfehlung an die Praxis wird gegeben.

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The parasitoids of the Woolly Apple Aphid (Eriosoma lanigerum Hausm.) Hom., Aphididae) and their distribution in the Palatinate, FRG

The Wooly Apple Aphid (Eriosoma lanigerum Hausm.) appeared during September 1986 and October 1987 in all greater areas with apple orchards in the Palatinate. From a total of 50 investigated places the parasite had been found in 22 of 28 treated orchards. On not or only extensive cultivated apple-trees it could have been only found in 2 of 24 places. With exception of the Western Palatinate, the only monophagous parasite ofE. lanigerum, Aphelinus mali Hald. appeared always sametimes.BesideA. mali, 4 other species of Chalcidoidea emerged from mummified aphids. These hyperparasites referred toAsaphes vulgaris Walker,Asaphes suspensus Nees,Pachyneuron solitarium Hartig (Pteromalidae) andAphidencyrtus aphidivorus Mayr (Encyrtidae).To determine the importance ofA. mali for biological control of woolly aphid, the infestation in different treated apple orchards has been investigated by counting the colonies during the season. The course of parasitism has been determined by dissecting altogether more than 63.000 aphids of all larval stages. The effects of pesticide treatments have been discussed.The results show, that in the Palatinate the biological control ofE. lanigerum by the parasitic waspA. mali is possible in apple orchards with selective treatment. In regular sprayed orchards the infestation by woolly aphid had especially after cessation of insecticide treatment been evidently higher, with lower rates of parasitism.A recommendation to the practice is given.

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Mit 7 Abbildungen und 2 Tabellen     

Influence of host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on some of the biological and ecological characteristics of the entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae)

The entomophagous Serangium parcesetosum Sicard (Col., Coccinellidae) is an effective predator of some whitefly species. However, information on the influence of the preys host plant species on its biological and ecological characteristics is still lacking in the literature. Therefore, the current study focuses on the possible influence of three greenhouse and two field host plant species of Bemisia tabaci (Genn.) (Hom., Aleyrodidae) on the number of eggs laid by S. parcesetosum. In addition, because of the economic importance and widespread planting of cucumber in greenhouses and cotton in the field, these plants were selected for further investigation into the development, mortality, longevity and reproduction of S. parcesetosum at a high temperature in the laboratory. Results showed that S. parcesetosum was able to lay eggs on all five host plant species of B. tabaci, whether greenhouse or field plants. However, among the three greenhouse plant species studied, S. parcesetosum females laid the highest number of eggs on cucumber followed by tomato and then sweet pepper. Of the two field plant species, significantly higher numbers of eggs were laid on tobacco than on cotton. S. parcesetosum could develop either on cucumber or on cotton as preferable host plant species for B. tabaci. There were significant differences in mean developmental duration of larval instars of the same sex between both host plant species; the duration was significantly shorter on cucumber than on cotton. There were no significant differences for mean total developmental duration from egg to adult emergence between both host plant species within the same sex; females showed a mean of 15.9 days and males of 15.1 days on cucumber, while on cotton the means were 17.2 days for females and 16.2 days for males. Total mortality percentage of S. parcesetosum during development from egg to adult stage was lower on cucumber than on cotton, 20.6 and 23.8%, respectively. Longevity of S. parcesetosum varied according to host plant species and sex with a mean of 63.4 days for females and 50.3 days for males on cucumber, and 92.4 days for females and 52.5 days for males on cotton. On cucumber, mean period of oviposition of S. parcesetosum was significantly longer than on cotton. Mean total fecundity was significantly higher on cucumber than on cotton, with means of 97.7 and 31.0 eggs/female, respectively.     

Über die Bevorzugung von Blatthaaren zur Eiablage bei Bemisia tabaci (Genn.) (Hom., Aleyrodidae)

Studies on the egg laying byB. tabaci showed this pest fixing its eggs at the basis of leaf hairs of cotton plants. The rejection of none hairy-leaved cotton varieties is apparently due to the lack of suitable egg laying sites. Moreover, the preference of the whitefly for leaf hair sites for egg laying explains reasonably why the hairy-heaved, jassid—resistant cotton varieties are more attractive to whitefly. The indiscriminate behaviour of egg laying mentioned byGameel (1974) may be possible on glabrousleaved host plants.     

Zur Taxonomie,Biologie und Ausbreitung der Tannentrieblaus Dreyfusia nordmannianae (Eckst.) (Hom., Adelgidae) in Tirol

Studies made in the inquirydistrict of Kufstein/Wörgl, Tyrol, showedDreyfusia normannianae (Eckst.) being the sole species of genusAdelges living on the firs. Observations on the phaenology of the generations at five different localities showed among other things that there was no summer-sistens-generation. The winter-mortality of the aphid on twigs and stems amounted to 7 till 9%. The rates of progrediens- and sistensgeneration as well as the number of eggs laid by sistens female were determined. At last experiments were made on the spreading. Within some weeks the youngA. nordmannianae progredientes and sistentes had a maximal migration distance of about three meters.     

Expansion of the aphid Myzocallis (Lineomyzocallis) walshii (Monell) on the red oak Quercus rubra, and adaptation of local parasitoids in the northeastern Iberian Peninsula (Hom., Aphididae, Calaphidinae; Hym., Braconidae, Aphidiinae)

An ongoing expansion of Myzocallis (L.) walshii (Monell) in the NE Iberian Peninsula was detected. The aphid species was recorded in Catalonia, Andorra and Navarra. Adaptation of local native parasitoids (at least Trioxys pallidus Haliday and T. tenuicaudus Stary) to the new immigrant was documented, together with background information on their host range in the native environments. The detection of parasitoids of M. walshii is the first published evidence in Europe. The new evidence for M. walshii in the NE Iberian Peninsula also supports the warning of the expansion of the aphid as a pest of Quercus rubra over Europe.     

Beeinflussung der Trieb- und Blattentwicklung von Eichen durch Gelege von Weichwanzen (Het., Miridae) und Zwergzikaden (Hom., Jassidae)

Zusammenfassung Es wurden im Burgenland (Österreich) Untersuchungen durchgeführt, um die Frage der Beeinflussung der Gesundheit von Eichen durch die massenhaften Eiablagen von Miriden und Jassiden an den bzw. in die Eichenknospen zu prüfen. Es wurden jedoch weder deutliche Strukturveränderungen in den Knospengeweben noch Einflüsse auf die Entwicklung der Knospen und jungen Triebe gefunden. Jedoch werden die von den Insekten geschaffenen kleinen Wunden möglicherweise von zahlreichen Pilzarten als Eintrittspforten verwendet.

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Effects on eggs laid by Miridae (Het.) and Jassidae (Hom.) on the development of the sheet and leaves of oaks

Studies were made in eastern Austria on the egg laying of jassids and mirids and their relations to the health of oaks. Neither distinct changing in the structure of tissues nor in the development of the buds which were injured by egg-holes were found. Probably the injuries made by the insects were used by different species of fungi attacking the oaks.

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Mit 5 Abbildungen und 3 Tabellen     

Die Reaktion von Getreideblattläusen (Hom., Aphididae) bei holozyklischer Überwinterung auf die Aussaatzeit von Weizen. Mit Beobachtungen zum Einfluß heftiger Niederschläge

On plots (25 m²) sown at different dates it was tested from 1982 to 1984 near Kiel (FRG) whether the sowing date would result in different levels of infestation of wheat by holocyclic cereal aphid populations. Aphids were too scarce to obtain results in 1982, and in the subsequent yearsSitobion avenae F. was the only species being abundant. In winter wheat (var. “Diplomat”), holocyclicS. avenae did not respont numerically to the sowing date. The maximum of attack, being equal in all sowing dates, occurred in growth stage 75. Small differences between sowing dates could be explained by the different abundance of natural enemies. In spring wheat (var. “Kolibri”) significant differences between sowing dates were observed, the earliest sown plots being attacked most heavily byS. avenae. The maximum of attack occurred in growth stage 71, mostly. Heavy precipitations proved to diminish significantly the numbers ofS. avenae per head at milky ripeness (GS 75), but not at GS 71. Numbers ofRhopalosiphum padi (L.) were not influenced significantly by the amount of precipitations falling during the observations. But precipitations and 8 other factors considered failed to explain the differences between sowing dates of spring wheat concerning the attack byS. avenae. It is assumed, therefore, that the physiological conditions of the wheat plant were gouverning the aphids' reproduction. The differences concerning the attack of winter wheat, apparently existing between holocyclic and prevailingly anholocyclic populations ofS. avenae, are stressed.     

Bionomics ofHaematoloma dorsatum (Hom., Cercopidae) in relation to needle damage in pine forests

The red-black pine bug,Haematoloma dorsatum, originates from the Mediterranean region, where it is known since long as a pest on pine trees. The insect has spread northwards during the last decades and it is now widely distributed in Europe. Within the West European region, however, severe pine needle damage is reported from The Netherlands only. Here, the nymphs suck on the roots of the grassDeschampsia (Avenella) flexuosa, which has expanded strongly in our pine forests, greatly due to atmospherical nitrogen deposition. The adults suck on the needles of several coniferous trees, primarily onPinus sylvestris. Due to the sucking, transverse rows of yellowish to brownish rings are formed around the needles. Later on, the needles become completely brown and drop off. These symptoms appear, when the adults already have left their host plants. Therefore, the symptoms could be wrongly attributed to other causes. A review of the literature is given on the infestations and bionomics ofH. dorsatum.With 6 figures     

Spring aphid-parasitoid (Hom., Aphididae,Hym., Braconidae) associations and interactions in a Mediterranean arable crop ecosystem,including <Emphasis Type="Italic">Bt</Emphasis> maize

Conspecific and heterospecific associations of aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) were used to determine the interactions between crops forming the main arable crop ecosystem (wheat, alfalfa, isogenic and [Bt Bacillus thuringiensis] transgenic maize) in an irrigated area in Catalonia, Spain. Species composition and instars of parasitized aphids (mummies) were used to detect the parasitoid population movements between the crops and proved interactions (alternation) between the crops, including transgenic maize. Parasitoid interactions were species-dependent, appearing in the movements between alfalfa-wheat-maize in the individual species. Aphidius ervi Hal., A. rhopalosiphi DeSt.-Perez, A. uzbekistanicus Luzh., Lysiphlebus testaceipes (Cress.) and Praon volucre (Hal.) were classified as key-stone species in the target agroecosystems in the area. No differences were found in aphid-parasitoid associations on Bt transgenic maize and isogenic maize for aphid species composition and associated parasitoid guild.     

Wirksamkeit des ParasitoidenEretmocerus debachi Rose und Rosen (Hym., Aphelinidae) gegenüber der Weißen FliegeParabemisia myricae (Kuwana) (Hom., Aleyrodidae)

Zusammenfassung Die Weiße Fliege,Parabemisia myricae (Kuwana) (Hom.: Aleyrodidae), stellt seit ihrer Verschleppung in die Zitrusanbaugebiete an der Südost-Mittelmeerküste der Türkei im Jahre 1982 eines der größten Probleme im dortigen Zitrusanbau dar. Zu ihrer biologischen Bekämpfung wurde im Jahre 1986 der spezifische Parasitoid,Eretmocerus debachi Rose und Rosen (Hym.: Aphelinidae) aus Kalifornien in die Türkei eingeführt. Der Parasitoid konnte sich nach Massenfreilassungen im gesamten Gebiet sehr gut einbürgern. In der vorliegenden Untersuchung wurde die Wirksamkeit vonE. debachi gegenüberP. myricae in zweijährigen Versuchen in natürlich befallenen Zitrusanlagen und auf künstlich infizierten und exponierten Zitrusjungpflanzen erfaßt.Innerhalb von zwei Wochen konnten auf den exponierten Zitrusjungpflanzen die ersten Parasitoiden festgestellt werden, wobei bis zu 10% derP. myricae-Nymphen und Puparien durchE. debachi parasitiert waren. In beiden Versuchsjahren und an allen 4 Standorten baute sich im weiteren Verlauf der Vegetation keine weitere Weiße-Fliegen-Population auf den Zitrusjungpflanzen auf. Die Populationsdichte vonP. myricae war auf den natürlichen befallenen Zitrusbäumen sehr viel geringer als auf den exponierten und künstlich infizierten Pflanzen. Dennoch traten mit den erstenP. myricae auch sofort durchE. debachi parasitierte Individuen auf. Die Parasitierungsrate erreichte teilweise 100%, so daß die Schädlingspopulation sehr schnell im weiteren Vegetationsverlauf abnahm und es zu keiner erneuten Gradation kam. Selbst auf sehr geringe Dichteerhöhungen derP. myricae-Population reagierte der Parasitoid mit einer erhöhten Parasitierung. Die Untersuchungen zeigten deutlich, daßE. debachi in der Lage ist, sowohl sehr hohe als auch sehr niedrige Populationen der Weißen Fliege in hohem Maße zu parasitieren und dadurch den Schädling erfolgreich zu bekämpfen.

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Efficiency ofEretmocerus debachi Rose and Rosen (Hym., Aphelinidae) in controlling the whiteflyParabemisia myricae (Kuwana) (Hom., Aleyrodidae)

The whitefly,Parabemisia myricae (Kuwana) (Hym.: Aleyrodidae) is a most serious problem in citrus since it was accidentally introduced into the Southeast Mediterranean region of Turkey in 1982. To control this pest biologically, the specific parasitoid,Eretmocerus debachi Rose and Rosen (Hym.: Aphelinidae), was imported from California to Turkey in 1986. The parasitoid settled very well after being mass released in the entire citrus growing area. In the present study the efficiencyE. debachi in controllingP. myricae was determined in naturally infested citrus orchards and on potted, artificially infested and exposed citrus seedlings over two years.Within two weeks, the first parasitods were determined on the exposed citrus seedlings at which 10% of theP. myricae-nymphal and-puparial stages were parasitized. In both years and at all four experimental sites no further population increase of the whitefly was observed on the citrus seedling over the entire vegetation period. TheP. myricae-densities were much lower on the naturally infested trees than they were on the exposed and artificially infested citrus seedlings. Nevertheless, the firstE. debachi were observed with the occurrence of the firstP. myricae. The parasitization rate reached sometimes up to 100%, so that the pest population decreased significantly in the following month to almost zero level. Even to smallest population increases ofP. myricae, the parasitoid reacted with increasing parasitization. The experiments proved, thatE. debachi was capable to parasitize high and low population densities of the whitefly completely and in consequence successfully controlled the pest.

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Mit 2 Abbildungen