If not controlled, over a period of years it will kill the tree. The most obvious symptom is the browning and stunting of the needles of the new growth. The needles are retained on the tree. Excess resin flow builds up on the dead twigs and needle bases. The pimples are the fruiting bodies of the fungus.
Infection usually begins on the lower branches and moves up the tree.
Diplodia tip blight may be confused with pine tip moth damage but in the case of the later the fungal fruiting bodies will not be present, and moth larvae and tunneling in the shoots will be evident. Life Cycle Infection is most common in spring from April to mid-June when the young emerging needles are soft and tender. They are most vulnerable for the two weeks when the buds first open. They are dispersed throughout the year. Under very moist, humid conditions, the spores germinate and infect the needles.