1. Dothistroma needle blight: I’ve always referred to this one as the “wedding ring” disease, in that one of the common symptoms is the presence of several tan to brown lesions that cross and surround the needle in several locations. In advanced cases, the browning extends to the end of the needle. Though this disease may make the tree unsightly, only severe infections that occur year after year are life-threatening. Cover sprays in mid-spring usually will interrupt the disease cycle.
2. Diplodia tip blight: Also referred to as sphaeropsis tip blight, this disease is more potentially damaging than dothistroma, as it kills the new shoots needed for the growth and development of existing stems and to fill in voids left by damage to others. Terminal shoots that appear to have died during expansion – usually a third of the size of unaffected shoots – and black dots (pycnidia) on the bottom of the cones are clues that diplodia is present.
3. Pine needle scale: Scales are tiny insects covered with a waxy coating; in this case, a white shell with a brown head. During most of the year, pine needle scales shield nymphs from predators and weather events, but are vulnerable and easy to control in mid-spring when nymphs hatch from eggs and crawl out looking for a suitable site to establish residency. During this roughly two-week period, many insecticides will control the scales. Horticulture oils and insecticidal soaps are particularly effective. Using a magnifying hand lens will help determine when the crawler stage begins.
4. Zimmerman pine moth: This pest causes damage when the larvae colonize the vascular system of the tree. First noticeable by the presence of white to light-pink globs of pitch in the tree crotches, Zimmerman pine moth is particularly damaging due to the interruption of the flow of water and nutrients. The pitch masses usually occur on the underside of the junction of the branches and the trunk in the branch collar area. Bark spray applications in early spring and late summer offer effective control.
5. Pine wilt: Pine wilt could be renamed “sudden pine disease,” in that trees often show few symptoms in spring, then, as the season progresses, the foliage exhibits a progressively lighter color. Pine wilt has a complex life cycle, involving feeding by pine sawyer beetles, the exit of pine wilt nematodes from their bodies, the entry of the nematodes through the feeding wounds and eventual clogging of cambial tissues, causing quick decline in health and vigor. Pine wilt is common on Scotch and jack pine; as such, identification of the pine species is helpful in diagnosis. Removal of affected trees is the recommended control method in most cases.
6. Pine tip moth: Another pest that affects the new shoots of pines is the pine tip moth. In the case of the southwestern pine tip moth, larval-stage feeding damages new growth after emergence from eggs laid in early spring. The tiny larvae bore into the fresh young tissues and, as they grow and develop, cause pine tips to die back beyond the feeding sites. Other species such as the common tip moth cause similar damage in mid-summer. The key to control is watching for damage to the shoots and inspecting for the presence of boring insects when symptoms are present. Cover sprays prior to boring activity are effective for control.