Pitch canker caused by the fungus Fusarium subglutinans f.sp.
Infection typically occurs in the upper portion in the crown in early winter to spring.
At the site of infection pitch flow occurs as the tree responds to the fungus' presence. Infection will progress down the stem and this results in the flagging or reddening of shoots. The fungus is spread via the wind and rain and likes cool, moist conditions. Infection therefore takes place in the late winter to early spring of the year. Here is a canker that is producing the characteristic resin flow.