Effects of surrounding landscape on parasitism of alfalfa aphids in an IPM crop system in northern Catalonia
2013
Pons i Domènech, Xavier | Lumbierres i Bardaji, Belén | Comas i Angelet, Filipe | Starý, Petr
The parasitism (Hymenoptera, Braconidae, Aphidiinae) of alfalfa aphids (Hemiptera, Aphididae) was determined during three crop growing seasons. The highest rates of parasitism of Acyrthosiphon pisum Harris and of Therioaphis trifolii Monell occurred during the first-second and the fourth alfalfa intercuts, respectively. The landscape surrounding the fields affected only parasitism rates of A. pisum. During the second intercut the forest area had a negative influence on parasitism rates, whereas the bordering surfaces of alfalfa and winter cereals had a positive influence. Positive correlations were found between the rates of parasitism of A. pisum and the rate of aphid population increase in the first intercut. By contrast, negative correlations were found in the second intercut, when the aphid population peaked, suggesting that parasitoids contribute to the regulation of the aphid. This study stresses that regulation of alfalfa aphids cannot be explained solely on the basis of one functional group of natural enemies.
Afficher plus [+] Moins [-]This study was partially funded by the Cooperativa Pirenaica de La Seu d’Urgell (agreements CO8026 and CO9036 with the Universitat de Lleida, Spain). Thanks are due to Ramon Albajes for his criticism of the manuscript. We are also grateful to Antoni Ribes (Himenòpters de Ponent, Torres de Segre, Lleida) for identifying specimens of the genus Aphelinus and hyperparasitoids. The participating research efforts by P. Starý were partially funded by the Entomology Institute, Project AV0Z50070508 (Academy of Science of the Czech Republic). We would like to thank two anonymous reviewers for their valuable comments.
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