Cross-habitat usage by crop aphids and their parasitoids in the crop-noncrop interface in an organic vegetable farm

Abstract

Natural vegetation areas near cultivated land play an important role in maintaining insect diversity as well as interactions between insect communities and plants. Plant-aphid-parasitoid interactions and parasitism rates were assessed from February to September 2004 in adjacent cultivated and non-cultivated habitats in an organic vegetable farm in a chaco serrano woodland, Córdoba Province, Central Argentina. Seven aphid species present upon a total of eight vegetable species were found in the cultivated habitat. Macrosiphum euphorbiae was present on all vegetable species. Four parasitoid species were recorded, of which Diaretiella rapae was the most common. It was related to three aphid species, and provided 21.32% of parasitism on Brevicoryne brassicae. In the non-cultivated habitat, 36 plant species hosted a total of 22 aphid species and five parasitoid species. The aphid Myzus persicae was present on 17 plant species of eight different families. Macrosiphoniella artemisiae (present only on Artemisia abrotanum) was the most abundant aphid species, with the associated Aphidius sp. being the most abundant parasitoid. The maximum rate of parasitism of Aphidius polygonaphis (10%), related to Uroleucon aeneus on Carduus sp., was recorded in this habitat. Wild plants Artemisia abrotanum, Brassica nigra, Bidens pilosa, Capsella bursa-pastoris, Carduus sp., Chaptalia sp. and Chenopodium sp. were found to be important reservoirs of parasitoids D. rapae, Aphidius sp., A. polygonaphis, Aphidius ervi and Lysiphlebus testaceipes, which are potential controllers of many pest aphid species.