The meagre history of the study of the fungi of birchwoods in Britain is offered as an introduction to more recent studies in the British Isles and in continental Europe. Four categories of fungi (parasites, suspected mycorrhizals and lignicolous and humicolous saprophytes) are recognized and discussed. Examples of the most frequently found species-associations are given in relation to environmental factors.

The production of fruitbodies of mycorrhizal fungi associated with Betula spp. in an experimental site was observed to occur in a pattern ordered in time and space. Certain species of Inocybe, Hebeloma and Laccaria and Thelephora terrestris appeared in the first five years after planting: they were followed by species of Leccinum, Cortinarius and Russula. Usually more fungi were associated with B. pendula than with B. pubescens. More toadstools of Laccaria tortilis developed in association with one clone of B. pubescens than with another which favoured instead the development of Inocybe petiginosa.

The idea of a fungal succession is supported by below-ground observation of mycorrhizas. Early- and late-stage fungi formed mycorrhizas on seedlings growing in sterile conditions whether inoculated with mycelia or spores. However, only early-stage fungi formed mycorrhizas in unsterile conditions.

The concept of succession is based on observations made when treeless sites were planted with Betula spp. However, experimental planting of seedlings into soil with intact roots of older trees with mycorrhizas of Lactarius pubescens resulted in mycorrhizas on the seedlings: but no mycorrhizas formed if the roots of the older tree had been severed. This suggests that the pattern or sequence of mycorrhizal fungi associated with seedlings regenerating within natural stands is likely to differ from that associated with Betula spp. colonizing previously treeless sites.

Fungi reported as parasites of Betula in Britain are reviewed. Pathogens colonizing the major host organs: roots, stems, branches twigs and bark, foliage, flowers fruit and seed, together with those attacking seedlings, are assessed in turn. Other species of fungi not yet known from Britain, but having potential importance as disease agents are also discussed. The major stem decay pathogens and the occurrence of leaf rust in Britain and its significance as a major nursery disease are examined in detail. The status of the fungal parasites on birches in woodland and plantations, in ornamental plantings and in the nursery is considered.

The entomology of birch in Britain (and to a lesser extent in Fennoscandia) is reviewed in broad ecological terms. In particular, the size of the associated fauna, the kinds of geographical distribution patterns seen for birch insects in Britain, birch defoliators, and the conservation needs of insects associated with birch in Scotland are considered. A closing section briefly outlines additional literature on the ecology of birch insects.

Seven virus-like agents have been recognized naturally infecting birches in Europe or North America. Of these, only two have been studied in detail. Apple mosaic virus (AMV) infects Betula papyrifera and B. alleghaniensis in North America, and is associated with golden-white ring/line patterns in leaves. There is no evidence that AMV spreads between birches and no natural means of dissemination is known. In Europe, B. verrucosa and B. pubescens are naturally infected with cherry leaf roll virus (CLRV) which causes foliar mottle, pale yellow spots and bright green vein banding. In the United Kingdom, the prevalence of CLRV in unmanaged birch populations is less than in street trees. The virus is spread via birch seed and pollen which it infects and also contaminates. Sparse data suggest that the following viruses infect birch but their effects are unknown: yellow birch latent, tobacco rattle, tobacco necrosis, prunus necrotic ringspot and prune dwarf. There is a similar paucity of information concerning the cause of wood abnormalities that enhance the veneer value of affected timber: agents transmitted in soil or by grafting have been associated.

The authenticity of birch collections is always in doubt unless one has wild source material; even the collections of Forrest, Wilson, Rock et at. may be suspect in that labels and records have been lost or confused. Collections are best maintained from vegetative sources and clonal selection is discussed. Site tolerances, planting problems and after-care are given detailed coverage. Species, hybrids and cultivars in general cultivation are listed and a summary of representation in British arboreta is included.

Man has found a diversity of uses for birch at least since Mesolithic times. In the mediaeval period, it was used for all kinds of domestic and agricultural purposes and it is remarkable how early its beneficial effects in silviculture were appreciated. Similarly, its amenity value has been appreciated for centuries in the rural scene and today it is employed in urban improvement too. Its importance for fuel and charcoal goes back into the distant past. Its bark is unique, with a range of end products from trinket boxes in northern Europe to large canoes in Canada. The trade in birch products is very large in eastern North America, while in Finland the plywood industry is also important. Birch will continue to play a significant role in British Forestry, both as a nurse species and as the main amenity species for poor and exposed sites.