Étude prospective de la fondation, de l’immigration et des facteurs de mortalité des colonies de pucerons noirs de l’oranger Toxoptera aurantii Boyer de Fonscolombe (Hemiptera : Aphididae) au nord du Gharb

Abstract

Four hundred and eighty brown citrus aphid T. aurantii colonies from ten cohorts were followed and referred from middle of April to end of May in several citrus orchards in the Gharb area during 2006 et 2007 years. This pest would prefer to colonize the S1 and S2 citrus leaves stages but all other studied stages would be predisposed to be also colonized. The colonies of indeterminate foundation were the most important, followed by those founded by the apterous ones (e. g. summer colonies) and also those resulting from alatae one (e. g. spring colonies). Immigration of alates is also discussed. T. aurantii regulation factors are multiple (17 sources) and may act individually or combined. A significante difference of mortality level of T. aurantii colonies was noted and discussed between regulation's origins. Coccinellidae is the most efficient predators of T. aurantii, with A. decempunctata and i (Coleoptera : Coccinellidae). Impact of beneficial such as A. decempunctata, C. septempunctata, A. decempunctata in association with C. septempunctata on aphid regulation is respectively from 5 to 48.33% ; 5 to 16.7%, and 5 to 18.33%. Impact of other regulation’s origins such as temperature and old leaves on aphid mortality is respectively from 8 to 55% and 3.33 to 40%. Others predators such as Aphidoletes Aphidimyza Rond. (Diptera : Cecidomyiidae), Chrysoperla carnea Stephens (Neuroptera : chrysopidae) and Episyrphus balteatus DeGeer (Diptera : Syrphidae), affect also T. aurantii colonies. The impact of theses indigenous beneficial species, acting individually or with ladybird on colony survival is low, except for A. decempunctata in association with E. balteatus with a maximum of 10%.