OCCURRENCE AND POPULATION DENSITY OF APHIDS IN APPLE ORCHARDS OF SOUTH BULGARIA

Abstract

Abstract In a 2006-2008 study, seven aphid species (Hemiptera: Aphididae) were detected on apple trees in South Bulgaria: Rhopalosiphum insertum Walk. (apple-grass aphid), Dysaphis plantaginea Pass (rosy apple aphid), Dysaphis devecta Walker (rosy leaf-curling aphid), Macrosiphum euphorbiae Thomas (potato aphid), Aphis pomi De Geer (green apple aphid), Aphis spiraecola Patch. (spiraea aphid/green citrus aphid) and Eriosoma lanigerum Nausm. (wooly apple aphid). The dominant species were D. plantaginea, found in 97.8% of the surveyed orchards. Two green aphid species from the genus Aphis were both found in 96.4% of the orchards. The rosy apple aphid was a more important pest of bearing orchards, where infestation in spring always exceeded the economic injury level (1-2% of infested shoots). The green aphids were more important in young orchards and nurseries, where they developed during the entire vegetation period and infestation sometimes exceed 50-80% of shoots. A. pomi was still more widespread, but A. spiraecola was found throughout all of South Bulgaria. As pests of apple, the other species were less common, causing lower infestations and minor economic importance.