The continent of Europe is home to some 1500-2000 species of rust fungi (Pucciniales or Uredinales, Basidiomycota). All rusts are plant parasites. Some are the cause of major plant diseases, inflicting huge losses in agriculture (for example wheat, oat and barley rusts), horticulture (leek, rose and pear rusts) and forestry (pine, birch and willow rusts). Many others affect wild plants like sedges, anemones or orchids and some even damage weedy plants (e.g. dandelion or bramble), helping to control these.
Since many of them are of direct economical importance causing crop plant diseases, rust fungi have been studied for a considerable time in Europe as well as the other continents. Early records from Roman times describe the festivities surrounding the Robigalia, a celebration held in April to appease the gods of the wheat stem rust, Puccinia graminis, which still is a major plant pathogen causing substantial losses in wheat production every year.
Rusts parasitise all major species of higher plants, including ferns. Rusts are normally host specific - each rust species only affects one or few species of host plants. However, many rusts also require two unrelated host plants to complete their life cycle. A famous example is the wheat stem rust mentioned above, which lives for part of it’s life on wheat and part on barberry (Berberis vulgaris). This link was only discovered and ascertained in the nineteenth century, and barberry hedges were subsequently banned from wheat growing areas, significantly reducing stem rust infection of wheat. Similarly, the rust of rowan trees completes its life cycle on juniper bushes, leading to noticeable infection foci where the two hosts grow near one another.
Once arrived on the host plant, rust spores germinate and invade the plant, producing a fungal network of cells (mycelium) inside their hosts and causing disruption of host plant metabolism and resource flow. They obtain their energy by tapping into their host plants' cells using a specialised organ known as haustorium. After relatively little time (10-14 days) the rusts produce a new generation of spores to infect other plants. The spores are normally wind or animal dispersed, but modern travel and plant trade has greatly widened the geographical range of many rusts. See, for example the story of Cronartium ribicola, the White Pine Blister Rust.
Rust specimens at RBGE are kept in our herbarium collection on their host tissue. Although this is not encouraged, many plants in the living collection also have rust infections; as an example look out for bright orange spots on rowan (Sorbus aucuparia) leaves from June onwards or the purple spots on bramble (Rubus fruticosus) leaves. To view images of the herbarium collection here and at other major European herbaria please go to the EURED website.
webpage updated 3 December 2012