VIRUSES AND THEIR SIGNIFICANCE IN AGRICULTURAL AND HORTICULTURAL CROPS IN FINLAND

This paper reviews the plant viruses and virus vectors that have been detected in agricultural and horticultural crop plants and some weeds in Finland. The historical and current importance of virus diseases an d the methods used for controlling them in cereals, potato, berry plan ts, fruit trees, ornamental plants and vegetables are discussed. Plant viruses have been intensely studied in Finland over 40 years. Up to d ate, 44 plant virus species have been detected, and many tentatively i dentified viruses are also reported. Control of many virus diseases ha s been significantly improved. This has been achieved mainly through c hanges in cropping systems, production of healthy seed potatoes and he althy stocks of berry plants, fruit trees and ornamental plants in the institutes set up for such production, and improved hygiene. At the p resent, barley yellow dwarf luteovirus, potato Y potyvirus and potato mop-top furovirus are considered to be economically the most harmful p lant viruses in Finland.