7.02.04 – Phytoplasma and virus diseases of forest trees

There are not many studies on plant viruses of forest trees. But many diverse deciduous trees of any age do get infected by viruses which may cause degeneration and loss of vitality. Continuing surveys of forested areas, public greens and of young seedlings in nurseries seem to confirm the dispersal of viruses in many plants with virus associated symptoms. Viruses induce alterations in a tree's metabolism and alter plants predisposition. Any infected plant has to be considered as an infection source. Young  plants from nurseries might later be planted in public gardens and expand infections over a large area. From the economic point of view one should be aware that virus diseased plants may increase production costs because of the possibly decreased growth of infected stock plants and that may damage subsequent field performance.

The detection of viruses from decidiuous trees is difficult. The high amount of phenolic compounds, the irregular spread of pathogens in trees and the low virus concentration demand methodical adaption. Therefore more detailed diagnostic trails for the determination of individual known and unknown viruses have to be established referring to the presence of visible symptoms. The advance of virus diseases from many woody plants such as fruit crops, grape or citrus has shown that causal organisms can wipe out a tree species in a very broad region. Concern about this very real danger has provided much of the impetus for forest pathology and in particular virology research, but still investigations on viruses in the forest ecosystem are extremely rare as compared with viruses of the agricultural environment.