Christmas Tree Pests and Weeds - Fungal Pests and Diseases

Fungal Pests and Diseases

Christmas trees are also vulnerable to large scale infestations from various fungal pathogens. In 2002 concern in the U.S. Pacific Northwest arose over the spread of a relatively new fungal disease called annosus root rot (Heterobasidion annosum or Fomes annosus). The disease is spread by airborne fungal spores and was first discovered in Northwest Christmas tree farms in 1983.

The plant pathogen, Phytophthora ramorum, which causes sudden oak death (SOD), is a fungus-like protist which was identified in the early 1990s. By 2002, sudden oak death had been reported along the California coast and the Oregon Coast, and two species of conifer were identified as hosts of the pathogen, Douglas fir and coast redwood. Between 2003 and 2005 P. ramorum was detected in Douglas fir, grand fir, white fir and California red fir on Christmas trees in Santa Clara County. Camellias imported from California to British Columbia in 2003 and early 2004 caused a significant SOD scare in the horticultural and Christmas tree industries. The detection of P. ramorum led to plant recalls in Canada, and a series of steps meant to quarantine the disease before it spread. The 2003–2004 SOD scare extended to Washington and Oregon nurseries and farms.

Douglas-firs are vulnerable to the two plant pathogens that cause Rhabdocline needlecast, Rhabdocline pseudotsugae, and Rhabdocline weirii. R. weirii affects only Douglas-fir trees. The pathogen often makes Douglas fir trees unsalable as Christmas trees and affects the Christmas tree farming industry. Douglas firs are also affected by Phaeocryptopus gaumanni which causes Swiss needlecast.

Red band needle blight is a fungal disease which affects coniferous trees, particularly pine, with a worldwide distribution. The disease is caused by the fungi Mycosphaerella pini, also known as Dothistroma pini (formerly D. septospora). Since the late 1990s its appearance in the United Kingdom has increased, among the most affected species is Corsican Pine and the disease has been a significant problem in Thetford Forest. Though the disease spread rapidly during September 2007 Christmas tree growers remained confident that Christmas tree crops would be unaffected.