 The two major diseases are root rot, cyanosis, and blister rust. Or in the case of a sugar pine tree in the Stanislaus National Forest. The spores landed on the needle, grew down the needle, grew into the branch, grew into the main stem, and girdled the main stem. No water will get past the girdle, and everything above that will die. All the cones that were produced at the tips of the branches will die too, so there will be no seeds produced.