User:Ka Faraq Gatri/sandbox2

Phytophthora lateralis is a soil-borne oomycete plant pathogen that causes cedar root disease in Port Orford cedar trees in Northern USA. It is alien to the USA and was first noted to cause disease in around 1920.

It was originally thought that it was pathogenic only to the genus Chamaecyparis and that of those Port Orford trees were the most susceptible. However, recent work has found that the Pacific Yew can also be infected and killed by P. lateralis, although it is less susceptible. Spreads by zoospores and only under exceptional circumstances does aerial spread occur. "Infection takes place primarily in the roots, which may be healthy and intact when invaded by the fungus. The inner bark and cambium are killed as the fungus gradually grows up the roots toward the base of the tree. In diseased roots, a dark-brown zone, sharply delimited from healthy tissue, is present in the bark. Often a dark--almost black-- resinous band is visible in the inner bark close to the cambium. The zone of killing may extend upward in the main bole 2 to 5 feet aboveground before external symptoms become apparent. The first external evidence of the disease is a slight paling of the foliage.  Next, the foliage gradually takes on a yellowish, withered look. This occurs a few days or weeks after the appearance of the first external symptoms. Then progressive color changes occur: first to a more pronounced yellow, then bright red, then red brown, and finally brown.  Trees are usually completely defoliated 2 to 3 years after death. 

As of 2006 P. lateralis is known to be distributed in North America, with sporadic reports of infection in France, the Netherlands and New Zealand. The centre of origin of P. lateralis is currently unknown, however, based on the resistance of Asiatic species of Chamaecyparis to infection some scientists have suggested that it may originate from this region. The recent isolation of P. lateralis from a Chamaecyparis forest in Taiwan seems to support this hypothesis.

P. lateralis is capable of surviving in frozen organic matter for at least six weeks. . Vegetative growth is inhibited by temperatures greater than 30°C. P. lateralis has a lower optimal temperature for growth and sporulation than many other Phytophthora species. P. lateralis is homothallic.

Current disease management programmes employed by the USDA Forest Service consist of attempting to reduce the spread of P. lateralis and trying to breed Port Orford cedar trees which are resistant to the pathogen.