OAK DECLINE AND THE STATUS OF OPHIOSTOMA SPP. ON OAK IN EUROPE

This paper brings together the individual reports of 11 countries on oak decline presented at an EPPO ad hoc Panel meeting at Lillafüred (HU) on 1989–06–20/22. Most countries (Austria, Czechoslovakia, FRG, Hungary, Italy, Netherlands, Poland, Yugoslavia) reported significant oak decline in the 1980s. However, none was reported in Denmark. In France, periods of decline mainly occurred earlier in the century, and only local decline was seen in the 1980s. In the United Kingdom, decline has never been considered a major problem and only local dieback occurs. In nearly all the countries with significant oak decline, water stress, due to severe drought in one or several years in the 1980s, is cited as the major cause. This predisposes trees to attack by various pests, of which the most frequently cited are Armillaria spp. (attacking the roots) and leaf‐feeding insects. Because Ophiostoma spp. have been cited in the literature as primary pathogens in eastern Europe, a search has been made in several countries for Ophiostoma spp. in declining oaks. The general conclusion is that they are found, but too rarely and irregularly to be of any primary significance. Several authors report Ophiostoma piceae , with which O. roboris is considered synonymous. Only in Czechoslovakia is it supposed that Ophiostoma spp. are pathogens, and then only with drought as the predisposing factor. Several other fungi are cited as pathogens of drought‐stressed oaks: in Italy, Quercus cerris and Q. pubescens are attacked especially by Hypoxylon mediterraneum; in the Netherlands, Pezicula cinnamomea is frequently found on Q. robur. In no country was it suggested that oak decline might involve an introduced or spreading pest, of possible quarantine significance.