AbstractIn southern England and Wales many cases of Phytophthora root-killing were reported on sizeable trees, including P. cinnamomi on yew, P. citricola on yew and Robinia × hillieri (the first record on R. sp.), and P. cryptogea on Lawson cypress (Chamaecyparis lawsoniana) and yew. A mixed consignment of transplants from the Netherlands in Nov. showed symptoms of severe P. damage and P. cryptogea was isolated from samples of beech (Fagus) and sweet chestnut. Microsphaera platani was again present on London plane (Platanus × hispanica) in central London but was less severe than in 1983. Erwinia amylovora was isolated from fresh small bark lesions on the stems of 10 to 15-yr old whitebeam (Sorbus aria) in Aug., this providing the first confirmation of direct bark infection. Diplodia pinea was identified on dying shoots of an Austrian pine (Pinus nigra var. nigra) in Hants, only the 2nd record of this fungus acting as a probable pathogen, the first being in 1951.
Common causes of injury in Scotland and northern England were extremes of climate and misuse of chemicals. Frequently recorded root pathogens were Heterobasidion annosum, Armillaria spp. and Meripilus giganteus. The occurrence of Pucciniastrum epilobii on common silver fir (Abies alba) is a new British record.
A survey of the incidence of resin top caused by Peridermium pini on Scots pine in Thetford Forest indicated that 2/3 of the old trees in the main block could be given a useful life expectancy of at least 12 yr.
Cumulative losses from Dutch elm disease (Ceratocystis ulmi) have increased from 8.7% in 1977 to 17.6% in plots monitored for regenerating suckers in southern England. All new infections in 1983 and 1984 were caused by the aggressive str. and none by the non-aggressive one. A trial evaluating Trichoderma as a curative and protective treatment on inoculated elms showed no significant differences between treated and untreated trees.
Foliage browning and shoot death in Sitka spruce (Picea sitchensis) and other conifers during winter 1983-84 was apparently not caused by 'acid rain' but probably by alternating periods of mild and cold weather accompanied by strong winds.