One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.
Please consider upgrading your browser to the latest version or installing a new browser.
More information about modern web browsers can be found at http://browsehappy.com/
E. harknessii rarely produces spermogonia, which are commonly produced by heteroecious Cronartium spp. From May to July, orange-yellow spores are produced on the surface of newly produced galls. Galls grow each year and spores are produced on the gall surface every year for many years unless the gall tissue dies. Small galls on young twigs are frequently pyriform and sometimes produce a small witches broom. For more information, see Boyce (1961), USDA (1963), Hepting (1971), Ziller (1974), Hiratsuka and Powell (1976), Sinclair et al. (1987) and Hiratsuka (1987).
The autoecious nature of the rust makes control difficult. Removal of infected trees may be economical in certain silvicultural situations. Nurseries should be established well away from infected stands of pine.
Several non-rust fungi have been reported in association with and acting as natural biological control agents of E. harknessii. An aggressive mycoparasite, Scytalidium uredinicola, has attracted particular interest (Tsuneda et al., 1980; Cunningham and Pickard, 1985) and the possibility of biological control using a rust-feeding beetle (Epuraea obliquus) as the carrier of this parasite has been proposed (Hiratsuka, 1991; Currie 1995; Currie et al., 1995).
Resistance to E. harknessii exists in Pinus contorta var. latifolia and Pinus banksiana (Yanchuk et al., 1988; Burnes et al., 1989; White et al., 2000).
Since symptoms may not be apparent for several years after infection, the only practical phytosanitary measure is to prohibit entry of live planting stocks of Pinus species which are known to be hosts (see List of Hosts) from countries where E. harknessii occurs (OEPP/EPPO, 1990). As E. harknessii survives in living tree tissue alone, only live plants should be regarded as a phytosanitary concern.
E. harknessii is damaging in its effect on form, lumber content and growth rates of Pinus, and kills smaller individual trees, although it is not known to wipe out whole stands. Galls on the main stem of young trees can lead to the death of the tree, but galls on branches of older trees cause little loss (Gross, 1983). Severe outbreaks on seedlings of P. ponderosa and P. contorta have been recorded in north-west Canada as well as serious damage to young natural stands of P. banksiana and P. sylvestris plantations in Quebec. However, P. sylvestris has been reported to be much less susceptible than P. contorta (Van der Kamp, 1989). In North America, damage in commercial stands occurs chiefly to P. contorta in the Rocky Mountains (Ziller, 1967, 1974). When compared with 'blister rusts' (e.g. Cronartium comandrae) on P. banksiana and P. contorta in northern Canada, E. harknessii was found not to be as aggressive on dominant trees, but to attack intermediate or suppressed trees which would disappear in any case (Hiratsuka et al., 1988).