Softwood or coniferous trees can be harmed or killed by disease-causing organisms called pathogens. The most common tree diseases are caused by fungi. Fungi lack chlorophyll and derive nourishment by feeding on (parasitizing) trees. Many fungi are microscopic but some are visible in the form of mushrooms or conks. Also some tree diseases are caused by bacteria and viruses. Pathogens can infect many different tree species with similar disease symptoms. These are the ones I want to address here:
Needle Cast Tree Disease:
Needle cast is a group of tree diseases that cause conifers to shed needles. The symptoms of needle cast tree disease first appear on needles as light green to yellow spots, which eventually turn red or brown. Growth of the fungi from the spots on the needle will cause death of the entire needle. Tiny black fruiting bodies form on the surface of the needles before or after the infected needles are shed.
Find out how to prevent and control needle cast tree disease of conifers
Needle Blight Tree Disease:
This group of needle blight tree diseases, including Diplodia, Dothistroma and brown spot, attack conifers at the needles and on twig tips. Infected needles often fall from the tree, creating a denuded look. Blight can result in dramatic browning of the foliage, beginning on the lower branches. Repeated annual cycles of infection can result in dead limbs and eventual loss of any meaningful ornamental value.
Find out how to prevent and control needle blight tree disease of conifers
Canker Tree Disease:
The term "canker" is used to describe a killed or blistered area in the bark, the branch or the trunk of an infected tree. Dozens of species of fungi cause canker diseases.
Find out how to prevent and control canker tree disease of conifers
These are wood-decay diseases. They may get in through wounds in the lower part of the tree or penetrate roots directly. They involve the roots and in some cases the butt also. These fungi can travel from one tree to another using airborne spores and soilborne infested stumps and root systems.
Find out how to prevent and control root and butt tree disease of conifers