WHAT IS IT?
Dothistroma Needle Blight (DNB) is a fungal disease caused by the fungus Dothistroma septosporum. The disease causes needles to brown and drop prematurely and can significantly slow the growth of the infected tree.
DNB affects all species of coniferous trees.
HOW TO IDENTIFY:
The most distinguishing sign of DNB can be seen in the needles of an infected tree. An infected needle will turn brown at the tip while remaining green at the base. The brown and green sections of needle are separated by a reddish-brown band. Eventually the entire needle will turn brown and fall off. Older needles which are closer to the trunk of the tree tend to be more severely affected by DNB.
The fungus lives through the winter within its host tree. Come spring the pathogen is transported via rain or through direct contact with needles. Once exposed to the new host needle, the fungus germinates and penetrates the new host needle. At this point the needles will begin to show the signs of infection. Once this occurs (usually during spring or early summer) the pathogen produces its fruiting body known as stromata.
IF LEFT UNTREATED:
If an infected tree goes several years without being treated for DNB, it is very likely that tree death will occur. The defoliation of an infected tree will increase every year until the tree is killed.
To treat for DNB, we treat the soil around the tree with a fertilization treatment, and the trunk of the tree is injected with a fungicide. This treatment will last for three years.