Current management of hazelnut diseases and pests.
The hazelnut agroecosystem is characterised by relative stability in space and time. Even in highly intensive cultivated areas, the pest and disease problems are the same. Bacterial blight, caused by Xanthomonas campestris pv. corylina, is considered the most serious disease in Turkey, Italy and the USA, which account for the bulk of the hazelnut production. Other pathogens cause more local economic damage. In Europe, the major pests are Phytoptus avellanae and Curculio nucum, but severe damage is also caused by a number of other species including Corylobium avellanae, Myzocallis coryli, Quadraspidiotus ostreaeformis, Archips rosanus, Operophtera brumata, Zeuzera pyrina, Anomala junii, Melolontha spp. and Agrilus viridis. Minor pests include Panonychus ulmi and Eotetranychus carpini. In the USA, Cydia latiferreana is the most important pest. Other major pests include Myzocallis coryli, Archips rosanus and Choristoneura rosaceana. It is suggested that infestations of at least 2 of these pests (M. coryli and C. rosaceana) was at least partially induced by the excessive use of insecticides. The hazelnut agroecosystem includes several groups of beneficial organisms which require protection. A limited number of pesticides have been registered for use in hazelnut orchards. It is suggested that some of these chemicals are highly destructive to beneficial organisms and should be avoided or used with more caution. The general and specific criteria for the management of hazelnut pests and diseases are discussed. This paper was presented at the 3rd International Congress on Hazelnut, held in Alba, Italy on Sep. 14-18th, 1992.