Sphaeropsis blight

Diplodia tip blight, also known as Sphaeropsis blight, is a widespread disease affecting conifers caused by an opportunistic fungal pathogen, Diplodia sapinea. It is found in “both hemispheres between the latitudes 30° and 50° north and south". The diseases symptoms include: damping off and collar rot of seedlings, stem canker, root disease, and, most commonly, shoot blight. These symptoms have caused significant economic loss to nurseries and pine plantations. In a nursery in the north-central United States, losses of 35% have been reported. Shoot blight and eventual die back can cause a reduction of marketable volume in timber by 63%. Infection of terminal shoots can result in dead-top which significantly limits the usable length of the tree trunk. The presence of the pathogen in concert with severe weather conditions can lead to extreme loss. Following a severe hailstorm in South Africa, nearly 5,000 acres of pine plantation were infected with Diplodia tip blight. It was necessary to prematurely harvest large swaths of the plantations resulting in a loss of 45%. Areas that were not harvested prematurely still suffered an average timber loss of 11%. Hosts and symptoms Diplodia tip blight is a common disease among conifers, especially pines.Scots pine, red pine, Mugo pine, Ponderosa pine, and Austrian pine are especially susceptible. Some spruce, fir, and cedar species are also vulnerable to infection. The disease can infect trees of all ages, though trees that are physiologically stressed through water or nutrient deficiencies or wounded via extreme weather or insect damage have a higher incidence of infection. The hallmark symptom of Diplodia tip blight is stunted, brown needles and stems, particularly of new shoots. The needles of infected shoots typically remain attached, are shorter than average and are tan colored. In particularly severe cases, entire branches can become infected. Resinous cankers can form on the stems, leading to disfigurement and sometimes death of the tree. In addition to the symptoms of the disease, signs of the pathogen are also evident in the late summer and fall as the fungal survival structures, pycnidia, are formed. The pycnidia appear as small black dots and can be found at the base of the needles, on the scales of the seed cones, and on the bark of the tree.