Small black fruiting bodies of the fungus are formed on this dead tissue. Conidia are produced in these structures and when moisture is present masses of conidia will ooze out to form tendrils or horns. The conidia are spread by rain and various other means such as mechanical disruption and insects. The fungus enters the plant through wounds as well as unbroken tissue. The browning of the needles and twigs begins at the tips and progesses downward toward the stem.
Moisture is an important factor in disease spread and severity.
Nurseries and Christmas tree plantations that utilize overhead irrigation usually have more severe disease problems because wetting of the foliage results in earlier spread of the conidia. Good sanitation is important in reducing disease occurence in nurseries. Clean cultivation, good drainage and roguing are important techniques that should be followed. Fungicides are usually applied as protectants and a regular schedule of funigcide sprays must be applied to prevent the penetration of the fungus into the plants. Homeowners are encouraged to use at least two sprays, one when the disease is first noticed and another 10 to 14 days later.