Zsuzsa Basky

Abstract - Common ragweed (Ambrosia artemisiifolia L.) is native to North America; it was introduced into Europe by contaminated agricultural goods from the end of the 19th century. Since then due to its excellent ecological adaptability it has invaded whole Europe. Common ragweed is not only a noxious weed causing yield losses in agricultural crops; it invades disturbed urban areas and its highly allergenic pollen induces allergic rhinitis to sensitive people. In urban areas mowing is the most widely used mean of ragweed control.
Plants were mowed early (12 June) at  BBCH 33 (3 visibly extended internode), late mowed plots were cut off on (25 July) .inflorescence visible BBCH 51 Mowing twice happened on 12 June and 25 July. At mean plant density of 91 plant/m2 number of female flowers was 150/plant on an average, while that of the male inflorescences were 1676. Mowing treatments significantly decreased the above ground fresh biomass and plant height compared to the none-mowed control. The early mowing treatment did not decrease significantly the number of female flowers. Twice mowed and late mowed treatments significantly decreased the number of female flowers, that of the male inflorescences. Further studies are required to improve seed production decreasing effect of mowing treatments.

Survey of aphids on dicotyledonous herbaceous plants along the Hungarian highways on 33 sampling
points revealed the presence of four holocyclic Brachycaudus species. The monoecious B. lychnidis L. 1758
was the most frequently collected species. It colonised the perennial Silene alba (Mill.) E. H. L. Krause 1893
on the youngest highway section around Budapest (5 locations). The frequency of this species is due to frequent
occurrence of its host plant on this section compared to other host species. New record for the Hungarian fauna
is the occurrence of monoecious B. setosus Hille Ris Lambers 1948 on the biennial or perennial Tragopogon
orientalis L. 1753 on two locations on the southern part of the country. The heteroecious B. cardui L. 1758 was
found on biennial or perennial Senecio jacobaea L. 1753 in one location on north-western part of Hungary. On
the north-eastern part of the country the perennial Symphytum officinale subsp. bohemicum (F. W. Schmidt)
Čelak 1891 occurred on a damp area. The monoecious B. mordvilkoi Hille Ris Lambers 1931 colonised this
Boraginaceae species.

Sixty wheat lines were studied in Hungary and South Africa to determine their reaction to
Diuraphis noxia (Kurdjumov). Plants were infested with D. noxia at the two-Ieaf stage and
scored on a scale of one to ten for Russian wheat aphid damage after one, two and three
weeks. A score of one indicated very high resistance and ten extreme susceptibility. A free
choice test was conducted to evaluate antixenosis effect of the wheat lines. Antibiosis of 50
wheat lines was determined with the embryo count method. None of the Hungarian lines
proved to be resistant in Hungary or South Africa. Based on the damage rating scores, the
resistant lines were resistant in South Africa, but ali were susceptible in Hungary. They
showed characteristic leaf rolling and yellow stripes one week after infestation. The highly
resistant line Halt was most severely damaged with most plants dead three weeks after
infestation. Host plant choice tests did not reveal the presence of antixenosis in the lines
examined. In Hungary almost ali lines were incJuded in the group showing least antibiosis
except for MV Emma, MV 17, Gariep and Limpopo. In South Africa the susceptible MY
Magma and MV Magvas and the resistant Elands, Caledon, Gariep and Halt seemed to
possess some level of antibiosis.

Russian wheat aphid, Diuraphis noxia (Kurdjurnov) is a severe pest of cereals in South Africa and in the USA. In order to reduce D noxia damage, intensive resistance breeding pr'ograrns have been undertaken, resulting in D noxia-resistant cultivars that are now widely used in South Africa and in the USA. However, there appear to be differences in the ability of different populations of D noxia to darnage these resistant cereal cultivars. To deterrníne whether different biotypes of D noxia are present, daInage to eight wheat cultivars was compared when they were exposed to either Hungarian or South African aphid strains. It appeared that the Hungarian CVS MV Magdaléna, MV Magvas, and MV 17 were susceptible to D noxia from both Hungary and South Africa. The susceptible South African CV Betta was als o severely damaged regardless of the country of origin of the aphids. None of the cultivars resistant in South Africa (Caledon, SST 333, SST 972 and Halt) were, however, resistant to Hungarian populations of D noxia. These cultivars, which carry resistance genes originating from the breeding lines PI 262660, PI 137739and PI 372129, were severely damaged by the Hungarian D noxia. Apart from the highly resistant CV Halt, the resistant cultivars used in this study were developed in South Africa, with the biotype present there. DaInage to an cultivars tested was significantly more severe in response to Hungarian than to South African D noxia, indicating that a rnore damagíng aphid biotype occurs in Hungary. However, D noxia has not yet becorne a pest ofwheat in Hungary, possibly due to a difference in cultural practices.

[3erealsare grown on roughly 1.5
rnillion ha or about one third of
the arable field area in Hungary.
The first cereal aphid species reported in
Hungary was Schizaphis graminum Rondani
(Horváth, 1882). Sitobion avenae (Fabricius)
was reported in 1897 by Horváth. Sitobion
avenae is considered to be the most frequent
ce real aphid by Szalay-Marzsó (1970).
Kuroli and Német (1987) studied the abundance
of cereal aphids on wheat and in yellow
water pan traps. This study deals with
seasonal changes of cereal aphids and the
spatial distribution of newly occurred
Diuraphis noxia Mordvilko in Hungary.

During the observation period 12 predator species, belonging to four different insect orders, were reared or colleeted from Hyalopterus colonies living on peach, plum and reed. In our surveys the Syrphidae were the most abundant predators, although their number was high only at the time, when aphids were also abondant. Four hover fly species were reared colleeted from peach, 3 from plum and the most common 2 (Episyrphus balteatus Deg. and Metasyrphus corollae Fabr.) decimated the aphid colonies on reed too. The ratio of Coccinellidae was lower on each host plant than that of hover flies. Five lady-bird species were colleeted from peach, 4 from plum and 3 from reed. Chrysopidae were found in a small number on each host plant. The abundanceof Anthocoridae was the highest on reed, so they were the most important aphid predators on reed. The most frequent parasite was Praon volucre HALIDAY on each host pia nt. Five parasite species were reared from Hyalopterus colonies of peach, four from plum and two from reed.

The nuclcoiidc scqucncc of the cout protcin (CP) gene and the 3' non-translatcd region, in relation to aphid transmission of 7 potato tuber nccroiic ringspot isolales of Potato vitus Y (PVyNTN) were studied. Five isolales originatcd from diffcrcnt areas of potato ficlds in Hungary and two German isola tes servcd as controls. A 5' tail of the nuclcotidc sequences of the CP region and 3' non-rranslatcd region (NTR) were dcter-mincd. Scqucncc dala wcrc scm to the EMBL GeneBank Database. Hornelegy of nuclcotide and amino acid scqucnccs wcrc high among the studied PVY isolates. Aceording to the charactcristic rcgions, ali isolales belenged to thc PVyNT strain. Ali of the lested isolales could be transmiucd by the aphid Myzus persicae Sulzer to the test plant Nicotiana tabaCIIIII L. verifying the wide distribution oftuber necrene ringspot sirain in Hungary. Our data suggest that the high bomology found in the CP region of the differcru isolates. arc suitablc for development of coat protein mediated rosistanec against PVY in commercially importunt host plants like, e.g. potato.

GF 305 apricot seedlings as trap plants for aphids as weil as virus indicator plants of plum pox Potyvirus (PPV) were placed for a week exposition period into a plum orchard (in Karcag) totally infected by PPY. Serological (ELISA) tests showed that the time of natural PPV infection was the last decade of May in 1993. At the same time migration of winged aphids were followed by Rothamsted type sucking traps. A positive correlation was found between the migration of Hyalopterus pruni and the period of natural PPV infection. Migration of other vectors, as Aphis craccivora, Brachycaudus helichrysi, Myrus persicae, Phorodon humuli did not coincide with the time of natural spread of PPV. The role of Hyalopterus pruni in the natural distribution and spread of PPV in plum orchards needs more experirnental evidence. Abbreviations: PPV = plum pox Poryvirus

Plum pox virus (PPV) is the most frcquent viral pathogen of the stone fruit trees in
Hungary, cansing serious yield losses in piums peaches and apricots.
Migration of alate apluds was monitored by a Rothamsled type suction trap. The
intensive vector acuviiy penod of alata aphids was followed by GF 305 apricot
seedlings placed in a JOO % PPV infccted plum orchard for one week exposinon
period and replaccd by new ones everyweek. Apricor seedlings exposed to activity of
virus vector apluds were kept in aplud free greenhouse and two months later they
were tested for PPV infcstation by ELISA.
Jn 1993 the intensive vector activiry perrod start ed in the middle of May and was the
most intensive III the first week of June, it was almost sim tiar in 1994. It coincided
with the swarrmng peak of Hyalopterus prum (Geoffroy) in 1993 and 1995, while in
1994 with the swarming peak of the Brachycaudus helichrysi (Kaltcnbach).
During our transmissron expcriment Hyalopterus amygdali (Geoffroy) transmitted
PPV from apricot to apricot, Hyalopterus pnmi (Geoffroy), Phorodon humuli
(Schrank), Brachycaudus helichrysi, Aphrs spiraecola Patch, Aphis idaei van der
GON, Aplus sam buci L. transmitted PPV from plum to GF 305 apncot test plants.

Common ragweed, Ambrosia artemisiifolia (L.), is a widespread invasive weed species in Europe. In order to esti mate the hampering effect of native arthropods on the invasive ragweed, weekly insect collection was made by sweep net from May to September. Phytophagous insects found on ragweed were univoltine with high dispersal ability. Three polyvoltine aphid species with low dispersal ability colonized ragweed. The effect of these aphid species on plant development and pollen production was studied. Common ragweed plants grown in a greenhouse were artificially infested with five apterous individuals of either Aphis fabae Scopoli, Brachycaudus helichrysi (Kaltenbach) or Myzus persicae (Sulzer) at the 4-leaf stage. Feeding by ali three aphid species over a five week period significantly reduced plant height, the number of male inflorescences, the length of racemes, pollen emission and plant dry weight. Brachycaudus helichrysi produced the largest colonies, followed by A. fabae and M persicae. In a field experiment, the growth rate of A. fabae on caged ragweed plants was similar to that in the gre enhouse, but the final numbers of B. helichrysi and M persicae after 30 days was ten and seven times lower respectively than under greenhouse conditions. On exposed field plants, B. helichrysi was significantly more abundant than the other two species. However, no aphid species affected the height or dry weight of either caged or exposed plants during a 30 day period. However, longer exposure (83 and 112 days) resulted in significant plant height and dry weight decrease regardless of the aphid species. Résumé L'ambroisie, Ambrosia artemisiifolia (L.), est une mauvaise herbe envahissante tres répandue en Europe. Pour estimer I'effet néfaste des arthropodes indigénes sur cette piante, des insectes ont été collectés chaque semaine it l'aide d'un filet fauchoir de mai it septembre. Trois espéces d'aphidiens de plusieurs générations avec une faible capacité de dispersion ont colonisé I'ambroisie. L'effet de ces espéces d'aphidiens sur le développement des plants et la production pollinique a été étudié. Les plants d'ambroisie poussés en serre, au stade de 4 feuilles, ont été artificiellement infestés par 5 individus apteres soit Aphis fabae Scopoli ou Brachycaudus helichrysi (Kaltenbach) ou Myzus persicae (Sulzer). La consommation par ces trois aphidiens pendant une période de 5 semaines a significativement réduit la hauteur des plants, le nombre des inflorescences máles et leur longueur, I'émission de pollen et le poids sec des plants. B. helichrysi a produit les plus grandes colonies, suivi par A. fabae et M persicae. En expérimentation de plein air, le taux de croissance de A. fabae sur des plants sous cage a été similaire it celui en serre. En plein air, B. helichrysi a été significativement plus abondant que les deux autres espéces. Cependant, aucune espece d'aphidiens n'a affecté la hauteur ou le poids sec des plants soit en plein air soit sous serre pendant une période de 30 jours. Néanmoins, une exposition plus longue (83 ou 112 jours) a entrainé une diminution significative de la hauteur des plants et de leur poids sec quelque soit l'espéce d'aphidiens.

A yellow water pan trap was used to collect Diuraphis noxia (Mordvilko) in Central Hungary in 1989. In
1990 a Rothamsted-type suction trap colleeted 31 individuals. A D. noxia infestation was found in an
autumn-sown wheat field in October 1990. The D. noxia population that overwintered was holocyclic.
The life-span of fundatrices was 43.2 days at 18-22°C. The number of nymphs produced per fundatrix
was 46.6. Average progeny numbers of first-generation apterae and alatae were 29.4 and 21.4,
respectively. Second-generation apterae produeed an average of 48.8 nymphs; 35.9% of nymphs were
alatiform. The D. noxia population reach ed its peak on 3 July in the field, at which time the mean
number of individuals per wheat plant was 3953.6. By 20 July, the wheat plants had matured and the D. noxia colonies disappeared from wheet.

The common ragweed, Ambrasia artemisiifolia is a widespread invasive weed species in Europe. In order to esti mate the deteriorative effect of native arthropods on the invasive ragweed the effect of three indigenous aphid species on plant development and pollen production was studied. Common ragweed plants grown in a greenhouse were artificially infested with five apterous individuals of either Aphis fabae, Brachycaudus helichrysi or Myzus per-sicae at the 4-leaf stage. Feeding by ali three aphid species over a 5-week period significantly reduced plant height, the number of male intlorescences, the length of racemes, pollen emission and plant dry mass. Brachycaudus helichrysi produced the largest colonies, followed by A. fabae and M. persicae. In a host plant choice test, B. helichrysi showed significant preference for ragweed over sunflower. whereas A. fabae preferred sunflower and M. persicae did not show any preference. In a field experiment, the growth rate of A. fabae on caged ragweed plants was similar to that in the greenhouse, but the final numbers of B. helichrysi and M. persicae after 30 days was ten and seven times lower than under greenhouse conditions, respectively. On exposed field plants, B. helichrysi was more abundant than other species. However, no aphid species affected the height or dry mass of either caged or exposed plants during a 30-day period. Under controlled conditions aphids effectively hampered development and pollen production of ragweed, however , under Hungarian field conditions the development of ragweed was much more dynamic, therefore no deleterious effect of aphid feeding occurred.

Aphid flight has been monitored since 1990 by a Rothamsted type suction trap in the middle of the Great Hungarian Plain. Cereal aphids were the most abundant species found. The first individuals were caught in May, and abundance was greatest as cereals ripened between lO-June and 30-June for all species. The intensive summer flight period was the shortest in the case of Rhopalosiphum padi, longer for Schizaphis graminum and Diuraphis noxia, longest for Metopolophium dirhodum and Sitobium avenae. Apart from R. padi none of the cereal aphids had significant autumn flight activity. In four years the autumn peak of R. padi was higher than the summer peak. R. padi was the most abundant cereal aphid, except 1990 when S. graminum was the main species followed by S. avenae and M. dirhodum. The number of D. noxia increased over the period of sampling, rising from 31 in 1990 to 2030 by 1996.

Plum pox Potyvirus (PPV) is the most abundant viral pathogen of the stone fruit trees in Hungary, causing serious yield losses in plums, peaches and apricots. Flight of alate aphids was monitored by a Rothamsted type suction trap. The, intensive vector activity period of alata aphids was followed byGF 305 peach seedlings placed in a tetalív infected plum orchard for one week exposition period and replaced by new ones every week from 1st May tili 31 st August. Peach seedlings exposed to activity of virus vector aphids were kept in aphid-free greenhouse and two months later were tested for PPV infestation by ELISA. In 1993 the period of intensive vector activity started in the middie of May and was the most intensive in the first week of June. Similar tendency of natural infection was observed in 1994. The vector activity coincided with the swarming peak of Hya/opterus pruni in 1993 and 1995, while in 1994 with the gradation of Brachycaudus he/ichrysi. Other vector species as A. craccivora, A. fabae, and Myzus persicae had a maximal flight activity in the first decade of June. In our experimental conditions Hya/opterus pruni transmitted the PPV from apricot to apricot, Hya/opterus pruni, Phorodon humu/i, Brachycaudus helichrysi, Aphis spiraeco/a, Aphis idaei and Aphis sambuci (L.) from plum to GF 305 peach seedlings. Among these species A. ideae, A. sambuci and H. amygda/i, Myzus persicae and Sitobium avenae are new vectors. In our conditions 22 other species were unable to transmit the PPV.

Alate aphids were coJlected by Moericke-type yeJlow pan traps in cucumber and pepper fields. In the present paper the determination key of 95 species is presented. based on morphological characteristics visible with normal stereoscopic microscope. The foJlowing genera are inc\uded into the key:

Wheat plants, randomly chosen, were infected with Diuraphis noxia, Sitobium avenae, Rhopalosiphum padi and Metopolophium dirhodum, repectively, regardless of the presence or absence of other aphids. Half of the artificially infected plants were caged whereas the other half was left no caged. One month after artificial aphid infection plants were sampled weekly, and insects were counted. R. padi was the most abundant species, followed by S. avenae, M. dirhodum and D. noxia on caged tillers. Significant relationships were found between C. septempunctata and R. padi densities and between Aphidius ervi and S. avenae densities. Activity of parasitoids was hampered by hyperparasitoids. Chalcididae hyperparasitoids were more than twice as abundant as parasitoids. D. noxia was ca. ten to twenty times more frequent on no caged tillers, compared to other cereal aphid species. Populations of indigenous aphid species: R. padi, S. avenae and M. dirhodum were under the economic threshold on the n...

Szárbaindulás kezdetén történt drótkeretre feszített vektorháló anyaggal a 10-12 hajtást tartalmazó búzacsomók izolálása. Az izolátorok kihelyezését követően Diuraphis noxia, Rhopalosiphum padi, Sitobion avenae 5-5 szárnyatlan imágó egyedével történt a növények mesterséges levéltetű fertőzése. A puhaszemű Mv 17 fajta kalászhossza, kalászonkénti szemszáma, kalászonkénti szemtömege és a szemek átlagos tömege szignifikánsan csökkent kalászos hajtásonként 2-3 S. avenae táplálkozása következtében. A búzaliszt SE HPLC-vel meghatározott gliadin, glutenin és összes fehérje tartalma szignifikánsan nőtt a levéltetvek kártétele következtében. A gliadin és glutenin tartalom eltérő növekedése szignifikáns gliadin/glutenin arány csökkenést eredményezett, mely a sütőipari minőség egyik legfontosabb mutatója. A keményszemű Mv Magvas és Mv Magdaléna búza fajták kalászhossza és kalászonkénti szemszáma az utolsó év kivételével nem változott a levéltetű fertőzés hatására. A nagy egyedszámú D. noxia szi...

A potyvírusok levéltetű átviteléért a segítő fehérje (HC-Pro) és a köpenyfehérje (CP) három szakasza felelős: a HC-Pro amino-terminális végén található KITC motívum, a karboxi-terminális végén lévő PTK aminosav triplet és a CP DAG motívum. A burgonya Y vírus (PVY) általunk izolált, eltérő vektor hatékonyságú törzseit vizsgáltuk. A PVY-98, PVY-5 és PVY-111 törzsek HC-Pro és CP gének bázissorendjét meghatároztuk. A PVY törzsek HC-Pro fehérjéi nagyfokú hasonlóságot mutattak mind nukleinsav (98%), mind aminosav szinten (99%); a CP esetében a hasonlóság 91%, ill. 94% volt. A KITC, a PTK és a DAG motívum azonban teljesen megegyezett. Eredményeink azt bizonyítják, hogy a PVY levéltetű átvitelét szabályozó három aminosav motívumon kívül más tényezők is szerepet játszanak, mint pl. a HC-Pro és CP fehérje többi szakaszában talált aminosav különbségek. A PVY-5 és PVY-98 izolátumok HC-Pro génjét agrobaktérium vektorba klónoztuk és agrobaktériumba transzformáltuk. A zöld fluoreszcens proteinnel ...

Russian wheat aphid, Diuraphis noxia (Kurdjumov) is a severe pest of cereals in South Africa and in the USA. In order to reduce D noxia damage, intensive resistance breeding programs have been undertaken, resulting in D noxia-resistant cultivars that are now widely used in South Africa and in the USA. However, there appear to be differences in the ability of different populations of D noxia to damage these resistant cereal cultivars. To determine whether different biotypes of D noxia are present, damage to eight wheat cultivars was compared when they were exposed to either Hungarian or South African aphid strains. It appeared that the Hungarian CVS MV Magdaléna, MV Magvas, and MV 17 were susceptible to D noxia from both Hungary and South Africa. The susceptible South African CV Betta was also severely damaged regardless of the country of origin of the aphids. None of the cultivars resistant in South Africa (Caledon, SST 333, SST 972 and Halt) were, however, resistant to Hungarian populations of D noxia. These cultivars, which carry resistance genes originating from the breeding lines PI 262660, PI 137739 and PI 372129, were severely damaged by the Hungarian D noxia. Apart from the highly resistant CV Halt, the resistant cultivars used in this study were developed in South Africa, with the biotype present there. Damage to all cultivars tested was significantly more severe in response to Hungarian than to South African D noxia, indicating that a more damaging aphid biotype occurs in Hungary. However, D noxia has not yet become a pest of wheat in Hungary, possibly due to a difference in cultural practices.

ABSTRACT Cereal aphid flight was monitored by 12.2 m suction traps at Szolnok in the middle of the Great Hungarian Plain and at Rothamsted, UK. Flight activities of Rhopalosiphum padi, Metopolophium dirbodum and Sitobion avenae were compared by the cross correlation function (CCF) between Hungary and UK. There was significant synchrony between flight a-tivity in Hungary and UK of R padi, M. dirbodum and S. avenae based on the eight years weekly sample data. The peak flight occurred 1, 3 and 2 weeks later at Rothamsted than at Szolnok for the three species (the CCF values were at – 1 week lag, r = 0.854, – 3 week lag r = 0.809, – 2 week lag r = 0.883, P < 0.05 respectively). When the flights in individual years were compared within species and between places the syn-chrony was lowest for R. padi: – in 4 years out of 8 and there was no synchrony, in the other years when synchrony occurred the time lag varied between – 1 week and – 4 weeks. For M. dirhodum the time lag varied between 1 and – 5 weeks, the synchrony was the best for S. avenae the week lag varied between 0 and – 3 weeks. Our results show that flight activity of cereal aphids at Szolnok occurs 1-3 weeks earlier than at Rothamsted. The crop season is earlier in Hungary than in England.

... Növényvédelem 32 , 77–79. 22 Tóbiás, I., Maat, DZ, Huttinga, H., 1982: Two Hungarian isolates of cucumber mosaic virus from sweet pepper (Capsicum annum L.) and melon (Cucumis melo L.): identification and antiserum preparation. Neth. J. Plant Pathol. 88 , 171–183. ...

ABSTRACT Several life history parameters (nymphal development time, prereproductive
period, reproductive period, postreproductive period, total life span, total fecundity, and agespecífic
natalíty) of Diuraphis noxia (Mordvilko) from South Afríca and Hungary were compared
on 2 South Afrícan wheat varieties ('Betta', which is D. noxia-susceptible, and 'SST 333',
which is D. noxia-resistant) and 1 Hungarian spring barley variety (Tsís', which is D. noxiasusceptíble).
Nymphal development time, reproductive period, and total life span were signíficantly
longer in Hungary than in South Africa. South Afrícan nymphs developed to adults
between 9.3 and 9.7 d, whereas those in Hungary took 10.7-11.1 d (the ranges indicate
variation in mean values among host plant species). The adult reproductive period lasted 22.9-
24.0 d in South Afríca and 35.2-37.1 d in Hungary. Total life span was 41.7-45.2 d in South
Afríca and 52.0-52.2 in Hungary. Total fecundity was significantIy higher in South Afríca (67.1-
75.1) than in Hungary (53.0-{)2.2) on Betta, SST 333, and Isis. Hungarian D. noxia not only
produced fewer nymphs but took much longer to do so; therefore, it is possible that the
Russian wheat aphíd in South Africa would reach economic thresholds in the field sooner than
in Hungary

Transparent mulches, blue mulches and black mulches were used between rows on
seed cucumber fields to repel aphids. The incidence of virus in leaf samples collected at
random every 2 weeks was determined by mechanically-inoculating herbaceous indicator
plants. The virus percentage was significantly reduced by 70 and 77% on plots mulched
with transparent and blue plastic foils respectively as compared with the untreated plots.
There was no decrease when black plastic mulch was used. Two aphid-borne viruses,
cucumber mosaic virus and watermelon mosaic virus, were isolated from virus-infected
cucumber samples, 77% and 23%, respectively.

A survey of Pulsatilla grandis Wender revealed the presence of four aphid species colonizing Greater Pasque Flower in Hungary. Aphis pulsatillicola Holman, 1966 the monoecious Pulsatilla feeding aphid species is new record for the Hungarian fauna. The development of Cavariella theobaldi Gilette Bragg, 1918 on the isolated silky seed head proves that the host alternating aphid species (primary hosts are Salix species and summer hosts are Umbelliferae plants) was able to develop from nymph to alata on P. grandis. Winged forms develop in response to unsatisfactory quality of a host plant, while on suitable host apterae are produced. The polyphagous Aphis fabae Scopoli 1763 and Aphis gossypii Glover 1877 were able to overwinter and the progenies of fundatrices developed into wingless apterae on P. grandis.

Abstract The common ragweed, Ambrosia artemisiifolia
is a widespread invasive weed species in Europe. In order
to estimate the deteriorative eVect of native arthropods on
the invasive ragweed the eVect of three indigenous aphid
species on plant development and pollen production was
studied. Common ragweed plants grown in a greenhouse
were artiWcially infested with Wve apterous individuals of
either Aphis fabae, Brachycaudus helichrysi or Myzus persicae
at the 4-leaf stage. Feeding by all three aphid species
over a 5-week period signiWcantly reduced plant height, the
number of male inXorescences, the length of racemes, pollen
emission and plant dry mass. Brachycaudus helichrysi
produced the largest colonies, followed by A. fabae and
M. persicae. In a host plant choice test, B. helichrysi showed
signiWcant preference for ragweed over sunXower, whereas
A. fabae preferred sunXower and M. persicae did not show
any preference. In a Weld experiment, the growth rate of
A. fabae on caged ragweed plants was similar to that in the
greenhouse, but the Wnal numbers of B. helichrysi and
M. persicae after 30 days was ten and seven times lower
than under greenhouse conditions, respectively. On exposed
Weld plants, B. helichrysi was more abundant than other
species. However, no aphid species aVected the height or

The aphid transmissibility and within-plant movement of two PVY isolates belonging to PVYO and PVYN strains were studied. Potato plants were infected by Myzus persicae either 1 week after emergence or 30 or 45 days after emergence. Infected leaves, petioles of infected leaves, and different segments of the stems of plants infected 1 week after emergence were ELISA-tested 7, 11 and 14 days after infection. Segments of the plants infected 30 or 45 days after emergence were ELISA tested 30 days after infection. Normalised ELISA values were used for statistical analyses. Virus infection of progeny tubers was assessed by post-harvest inspection. The ability of 15 aphid species to transmit the virus isolates was also examined. There was no difference in the aphid transmissibility of the two isolates 7 or 11 days after exposure to M. persicae. However, normalised ELISA values were significantly affected by both isolate and sampling date 11 and 14 days after M. persicae transmission. The level of infection of different stem segments was significantly affected by both isolate and growth stage of the plant at infection. The proportions of infected leaves, stem segments and progeny tubers were all significantly higher for PVYN than for PVYO. PVYN was more effectively transmitted by a number of different aphid species than was PVYO. Newly described vectors of PVYN include Schizaphis graminum, Aphis fabae cirsiacanthoides, Aphis spiraecola, Myzus ligustri, Aphis fabae, Aphis spiraephaga, Myzus cerasi, Macrosiphum rosae, Diuraphis noxia, Aphis pomi and Rhopalosiphum padi, while those of PVYO include Aphis fabae cirsiacanthoides, Myzus cerasi and Myzus ligustri.