Showing papers on "Uroleucon published in 1999"

Host range and habitats of the aphid parasitoid Diaeretiella rapae (Hymenoptera: Aphidiidae) in Washington State.

Abstract: Host aphids of the parasitoid Diaeretiella rapae (M’Intosh,) are defined for Washington State, together with a listing of world findings. Specifics are given on host habitats frequented by the parasitoid, comparative population abundance, associated parasitoid species, and host switching. D. rapae is a common parasitoid of Brachycorynella asparagi (Mordvilko), Hayhurstia atriplicis (L.), Brevicoryne brassicae (L.), Diuraphis noxia (Kurdjumov), and sometimes Myzus persicae (Sulzer). In total, 19 species of aphids were positively linked with D. rapae and 6 are reported as hosts for the first time— Acyrthosiphon lactucae (Passerini), Phorodon humuli (Schrank), Dysaphis plantaginea (Passerini), Brachycaudus tragopogonis (Kaltenbach), Uroleucon ivae Robinson, and Braggia sp. D. rapae was shown to switch or alternate successfully between hosts, which suggests that certain host habitats might be used in conjunction with farmlands to enhance host opportunities for the parasitoid and improve its population stability. Two of its primary aphid hosts, B. asparagi and D. noxia, reached pest status shortly after their arrival in Washington but are less problematic today, in part at least because of host switching and acceptance by D. rapae.

Phylogenetics and evolution of the aphid genus Uroleucon based on mitochondrial and nuclear DNA sequences

Abstract: The genus Uroleucon, and the related genus Macrosiphoniella, represent a large Tertiary radiation of aphids, with a total of about 300 species distributed throughout the world, primarily on host plant species in the family Asteraceae. A molecular phylogenetic study was conducted to identify major clades within Uroleucon and to address the cladistic validity of current subgeneric categories, the evolution of host plant associations, the age of origin, and intercontinental movements in this genus. The seventeen study species included members of the three major subgenera of Uroleucon, species from Europe and North America, one member of Macrosiphoniella, and two outgroups. Data consisted of DNA sequences for three mitochondrial regions and the nuclear gene EF1alpha, for a total of 4287 sites. Nodes supported strongly in both parsimony and maximum likelihood analyses suggest that: (1) Nearctic Uromelan are a monophyletic group branching near the base of the genus and not related to European Uromelan, (2) the New World subgenus Lambersius is possibly monophyletic but is not a tightly related group and is not closely related to other North American species, and (3) Nearctic members of subgenus Uroleucon are a closely related monophyletic group not allied with Nearctic Uromelan or Lambersius. Instead they represent a separate colonization by an Old World ancestor, as they are nested within a strongly supported clade containing European members of both subgenera Uroleucon and Uromelan. Neither of these subgenera is monophyletic. Molecular clock calculations, based on calibrations of mitochondrial divergences from other insects, suggest that Uroleucon + Macrosiphoniella is a relatively recent radiation, probably no more than 5-10 million years old. Although largely confined to Asteraceae, this clade did not radiate in parallel with its host plants. Rather, lateral movement between lineages of Asteraceae must have occurred repeatedly.

Biotic potential of three coccinellid predators on six different aphid hosts

Abstract: Biotie potential of three coccinellid predators, viz., Coccinella septempunctata Linnaeus, C. transversalis Fabricius and Cheilomenes sexmaculata (Fabricius) was studied on six species of aphids, viz., Aphis craccivora Koch, A. gossypii Glover, A. nerii Boyer de Fonscolombe, Lipaphis erysimi (Kaltenbach), Rhopalosiphum maidis (Fitch) and Uroleucon compositae (Theobald). These three coccinellid predators accepted all the hosts, but U. compositae was the least preferred resulting in no egg production in C. septempunctata and C. transversalis. Developmental period on different aphid hosts, viz., C. septempuncata and C. transversalis varied from 16.5 to 21.4 and 15.2 to 18.0 days, respectively. C sexmaculata voraciously predated and bred well on all these hosts including U. compositae, indicating its wide host range. But, it developed faster on A. nerii (12.2 days) than other hosts and was more fecund on A. craccivora and A. nerii. A. craccivora was the most preferred host for all the coccinellids with higher rate of consumption and higher fccundity.