Taxonomic name: Ophiostoma ulmi (Buisman, 1932), Nannfeldt; Ophiostoma novo-ulmi Brasier, 1991
Synonyms: Ceratocystis ulmi
Common names: dutch elm disease (English), Schlauchpilz (German)
Organism type: fungus
Dutch elm disease (DED) is a wilt disease caused by a pathogenic fungus disseminated by specialised bark beetles. There have been two destructive pandemics of the disease in Europe and North America during the last century, caused by the successive introduction of two fungal pathogens: Ophiostoma ulmi and Ophiostoma novo-ulmi, the latter much more aggressive. The vector is represented by bark beetles, various different species of scolyts living on elm trees. These beetles breed under the bark of dying elm trees. The young adults fly from the DED infected pupal chambers to feed on healthy elm trees. As a consequence, spores of the fungus carried on the bodies of these beetles are deposited in healthy plant tissue. Ophiostoma ulmi sensu lato can also spread via root grafts.
natural forests, planted forests, urban areas
Hosts: Host trees include all the Euro-American native elms as field elm (Ulmus minor), wych elm (Ulmus glabra), european white elm (Ulmus laevis), American elm (Ulmus americana), red or slippery elm (Ulmus rubra), rock elm (Ulmus thomasii), and cedar elm (Ulmus crassifolia). Asian elm species are generally much less susceptible than Euro-American native elms. The Chinese elm (Ulmus parvifloia) is occasionally infected by the disease but is much less susceptible than American elm. Vectors: O. ulmi is vectored by a number of bark beetles, the efficiency of which is dependant on thei body dimension. In America the main species are Hylurgopinus rufipes, the American elm bark beetle and Scolytus multistriatus, the introduced smaller European elm bark beetle, while in Europe the main vector is the large European bark beetle Scolytus scolytus, and S. multistiatus, S. pygmaeus and S. kirschii are also active (see also Webber, 2000).
Stack et al. (1996) notes that the observable symptoms and the progression of Dutch elm disease differs among trees that are inoculated through beetle feeding and those that are infected through root grafts. Trees infected by beetles first show wilting, curling and yellowing of leaves on one or more branches in the upper portion of the tree. Large trees may survive and show progressively more symptoms for one or more years. In addition, because of their position, the infections arising from native elm bark beetle inoculations have a head start in spreading through the tree. Frequently, by the time first symptoms are noted, the fungus has already reached scaffold branches or the main trunk of the tree. Once the fungus is established within a tree, it spreads rapidly via the water-conducting vessels. The tree forms gums within these vessels in response to the presence of the fungus, causing the tree to wilt and eventually die. Trees infected through root grafts wilt and die rapidly; this frequently occurs in the spring soon after the trees have leafed out and progresses from the base of the tree upward.
Ophiostoma ulmi s.l. was first discovered and studied in the Netherlands by seven women researchers, hence the name Dutch elm disease (Partridge, 1997).
Native range: The origin of the fungus Ophiostoma ulmi, the causal agent of Dutch elm disease, remains unknown but it is probably native to Asia.
Known introduced range: O. ulmi was introduced in Europe around 1910 (Brasier, 1999) and from here was introduced into America, where it arrived around 1930. O. novo-ulmi was first recognized in Britain in the early 1970s, but probably began more or less simultaneously in the 1940s at two locations: eastern Europe (the novo-ulmi subspecies) and the southern Great Lakes area of North America (the americana subspecies). The latter was introduced in Britain during the 1960s and later spread in continental Europe (Brasier, 2000). The disease is prevalent in Canada and has been controlled in New Zealand.
Introduction pathways to new locations
Other: Spores of the Dutch elm disease fungus are carried on the bodies of beetles and deposited in egg galleries and tree wounds (Stack et al., 1996).
Local dispersal methods
On animals: O. ulmi is spread by beetles to surrounding trees (Partridge, 1997).
Other (local): When elms are growing near each other, the fungus may spread when their roots come in contact in the soil and graft together (Stack et al., 1996).
Transportation of habitat material (local): If infected wood is to be used as firewood, it should first be debarked (Stack et al., 1996).
Preventative measures: According to Stack et al. (1996), Dutch elm disease cannot be eliminated once it begins. A year-round community sanitation program is the key to slowing the spread of the disease. The most available control is removing infected trees and promptly destroying the wood. If infected wood is to be used as firewood, it should first be debarked. Trenching to disrupt root grafts is also recommended to protect healthy elm trees near diseased ones. In urban situations, insecticide spraying of high value trees has been effective in keeping bark beetles from attacking susceptible trees. In ornamental plantings, suggested control measures include planting trees further apart to prevent root grafts or choosing mixed tree species. The use of resistant selections for new plantations is strongly recommended.
The American Phytopathological Society (APS) offers on its website illustrated lessons to introduce the symptoms and signs, pathogen biology, disease cycle, epidemiology, disease management, and scientific, economic and social significance of major plant diseases. Please follow this link
Dutch elm disease for details.
Ophiostoma ulmi s.l. has three asexual phases: a yeast phase, a Sporothrix -like stage, and a Graphium stage (Anacker, 2001).
This species has been nominated as among 100 of the "World's Worst" invaders
Reviewed by: Dr. Alberto Santini Forest Pathologist PhD Istituto per la Protezione delle Piante. Italy.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Thursday, 18 March 2010