Gremmeniella abietina (lagerb) morelet: Distribution in Yugoslavia, significance and control

Abstract

Fungus G. abietina is one of the most dangerous pathogenic fungi inhabiting conifer plantations, and especially endangered species are the pines. Among the pines, the most susceptible species is Austrian pine, and endangered plantations are aged between 8 and 25 years. This fungus was detected in Serbia and Montenegro only on the mountains (Kopaonik, Vlasina, Go?, Durmitor). The fungus was identified on Austrian pine, Scots pine and spruce. In its development G. abietina forms both stages (anamorph and teleomorph). Its imperfect form i.e. pycnidial stage, is far more significant for the infection process, and mainly all infection is carried by conidia (=pycnospores). Infection of trees is possible throughout the year, but the critical period of infection is May-June. Conidia are transmitted by raindrops, and the infection is spread through the buds and bark of young shoots. Incubation period lasts for 9 months, i.e. if infection occurs in June of the current year, the first visible symptoms of infection occur in March of the following year. The symptoms of infection are visible at the base of buds (cross section), on the needles (initial orange discolouration at the base of the needles, and then the whole needle turns brown and drops) and on the bark of young shoots. Soon after infection symptoms, the fruiting bodies (i.e. pycnidia) appear on the necrotic tissues of the host. Apothecia form on the bark two years after tree dying. In the severely infested plantations, all dead trees should be felled and removed, and the remaining trees should be treated with copper fungicides. As this is a quarantine disease, care must be taken to prevent the spread of the disease to the new uninfected regions. This measure is imposed by the legal regulations on quarantine diseases.