Christmas tree pests and weeds 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 "Dothistroma septosporum". 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
Fraser Filter Fraser Filter A Fraser Filter, named after Douglas Fraser, is typically used in geophysics when displaying VLF data. It is effectively the first derivative of the data. If formula_1 represents the collected data then formula_2 is the average of two values. Consider this value to be plotted between point 1 and point 2 and do the same with points 3 and 4: formula_3 If formula_4 represents the space between each station along the line then formula_5 is the Fraser Filter of those four values. Since formula_6 is constant, it can be ignored and the Fraser Filter considered to be formula_7.