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
Tree automaton three statements are equivalent: Tree automaton A tree automaton is a type of state machine. Tree automata deal with tree structures, rather than the strings of more conventional state machines. The following article deals with branching tree automata, which correspond to regular languages of trees. As with classical automata, finite tree automata (FTA) can be either a deterministic automaton or not. According to how the automaton processes the input tree, finite tree automata can be of two types: (a) bottom up, (b) top down. This is an important issue, as although non-deterministic (ND) top-down and ND bottom-up tree automata are