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.     

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.     

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.     

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).     

Distribution and history of Russian wheat aphid, Diuraphis noxia (Kurdj.) in the Carpathian Basin (Hom., Aphididae)

The Carpathian Basin has been classified as one of the model areas of Russian wheat aphid (=RWA), Diuraphis noxia (Kurdj.), expansion from the southeast to Central Europe. Explorations in 2002 as well as the summarized information published earlier centered the evidence for RWA in the northern and northeastern parts of the area and its occurrence was detected and verified in the area up to the submountains of the Carpathian Mountain Range. The history and distribution peculiarities of RWA in the Carpathian Basin and area are reviewed and discussed.     

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.     

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.     

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

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.     

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.     

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.     

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.     

Spring aphid-parasitoid (Hom., Aphididae, Hym., Braconidae) associations and interactions in a Mediterranean arable crop ecosystem, including Bt 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 Wei?en FliegeParabemisia myricae (Kuwana) (Hom., Aleyrodidae)

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.     

Functional responses of the parasitoid,Ertmocerus longipes Compere (Hym., Aphelinidae) to densities of the whitefly,Aleurotuberculatus takahashi David et Subramaniam (Hom., Aleyrodidae) at different temperatures

The present study dealt with the functional responses of the parasitoid,Eretmocerus longipes Compere (Hym., Aphelinidae) to the densities of the whitefly,Aleurotuberculatus takahashi David et Subramaniam (Hom., Aleurodidae) at different temperatures under the laboratory conditions. The results showed that when the initial densities ofA. takahashi-3rd instar were raised from 10 to 320 ind./leaf, the numbers of parasitized nymphs increased as well, ranging from 7.0 to 23.1 at 20°C, 9.8 to 42.9 at 25°C, 6.7 to 39.9 at 30°C, and 1.8 to 8.3 ind./leaf at 35°C, respectively. The Holling Disk Equation was introduced to build up the models of functional responses. The response curves remained type II, although the numbers of parasitized nymphs were significantly different under different temperatures. The suitable initial densities of the host whitefly for parasitization were about 80 individuals per leaf. A negative relation was observed between the initial densities of the whitefly and the parasitization rates by the parasitoid. An increase in the initial densities ofA. takahashi-3rd instars ranging from 10 to 320 ind./leaf resulted in a decrease in the parasitization rate byE. longipes ranging from 70.0% to 7.2% at 20°C, 98.0% to 13.4% at 25°C, 67.0% to 12.5% at 30°C and 18.0% to 2.6% at 35°C with a value of 0.2877 was significantly smaller than that at 20°C with a vlaue of 1.3354, that at 25°C with a value of 1.6465 and that at 30°C with a value of 1.1199, respectively (p<0.01). The handling time (Th) forE. longipes was 0.1521 at 35°C, significantly longer than 0.0510 at 20°C, 0.0289 at 25°C and 0.0320 at 30°C, respectively (p<0.01). The maximum loading number (K) of the parasitized nymphs with a value of 34.5 ind./leaf at 25°C was similar to that with a value of 31.2 ind./leaf at 30°C, about 1.8 times as high as that with a value of 19.6 ind./leaf at 20°C and 4 times more than that with a value of 6.6 ind./leaf at 35°C. It was suggested that temperature affected the functional response by balancing searching rate and handling time. The optimal temperature range for the functional responses ofE. longipes to the densities ofA. takahashi-3rd instar was 25° to 30°C.     

大豆蚜阶段特异性经济阈值的制定

为制定大豆蚜Aphis glycines阶段特异性经济阈值,于2015—2018年连续4年开展田间试验,通过定点、定株调查和产量测定,运用回归分析法研究大豆4个特定生长阶段下不同密度大豆蚜侵染对其产量损失的影响。结果表明,在大豆4叶期—初花期阶段,大豆蚜侵染的累计蚜日及其种群增长率均最大,分别达到40 900头·日和0.184,大豆产量损失率也最高,达到了60.96%。大豆蚜的侵染密度与产量损失率在大豆出苗期—4叶期和4叶期—初花期阶段使用线性模型拟合的优度最高,在初花期—初荚期和初荚期—鼓粒期阶段使用对数曲线模型拟合的优度最高,并构建了各阶段的回归方程。基于反映市场价值和潜在产量变化的动态经济允许损害水平,得到大豆出苗期—4叶期、4叶期—初花期、初花期—初荚期和初荚期—鼓粒期阶段的平均蚜量阈值分别为79、227、323和460头/株;依据线性相关性转换得到更利于实际应用的阈值指标——有蚜株率和卷叶株率,如果提前3 d进行防治,则出苗期—4叶期阶段的有蚜株率阈值为17.88%,4叶期—初花期、初花期—初荚期和初荚期—鼓粒期阶段的卷叶株率阈值分别为4.78%、7.88%和12.59%。表...