NATURAL ENEMIES OF APHIDS CALLAPHIS JUGLANDIS FRISCH. AND CHROMAPHIS JUGLANDICOLA KALT. (HEMIPTERA: APHIDIDAE) ON ENGLISH WALNUT (JUGLANS REGIA L.) IN PLOVDIV REGION

摘要

Two species of aphids attack Persian (English) walnut (Juglans regia L.) in the region of Plovdiv, Callaphis juglandis Frisch. and Chropmaphis juglandicola Kalt. (Hemiptera: Aphididae). Walnut aphids C. juglandis develops on the upper side of leaves and formed numerous colonies, which suck juice around the main vein.C. juglandis is much more common species, in comparison with the small walnut aphid, Ch. juglandicola, which settles and feeds on the underside of leaves. C. juglandis and Ch. juglandicola are potential pests of the Persian walnut in the region of Plovdiv. Present study was carried out to know the natural enemies of walnut aphids in the region of Plovdiv and their population dynamics and possibilities for biological control of aphids.The study was conducted in untreated walnut orchards of two different ecological regions - Plovdiv and Asenovgrad. Large number predators and parasitoids, belonging to the orders Coleoptera, Diptera, Neuroptera and Hymenoptera are found in the colonies of walnut aphids.Although these predators are considered to play an important role in the regulation of aphid populations, they did not prevent walnut aphid damages. Some possible causes for this ineffectiveness are discussed.