Disposal of a Scots Pine infected with Diplodia

Asked October 6, 2016, 4:17 PM EDT

We have two large Scots pines that died this summer. Although the inciting event may be due to a number of things, we do know the pines were infected with diplodia and that the cambium does have staining associated with dipoldia. The question is: What are the best management practices for disposal of a pine infected with diplodia? Bruce Labno

Washington County Minnesota

1 Response

We haven't been able to find any specific guidelines regarding the disposal of diplodia affected trees. The following Morton Arboretum description of the diplodia organism's life cycle suggests that it's advisable to remove diseased wood and needles before spring when new growth on healthy pines is susceptible to infection.

A fungus called Diplodia pinea causes the disease. The fungus overwinters in pycnidia (fungal fruiting bodies) in infected shoots, bark, and seed cones. Tiny spores called conidia erupt from the pycnidia in wet weather. Although they are produced from spring to early fall, they are especially abundant in spring and early summer, when the new shoots (candles) are expanding. Candles can only be infected by the fungus while they are elongating in the spring. After the needles have fully expanded, the shoot can no longer be infected by the fungus. Wind and rain disseminate the conidia. When the conidia land on a susceptible plant part, they infect it by penetrating the plant through wounds or stomates, usually in mid- to late spring. Once the fungus penetrates the plant, it quickly spreads throughout the needles, then to the stem and into nearby needles and cones. The needles begin to die several weeks after infection. Later in fall after the needles have died, the pycnidia appear on the base of the needles or on second year seed cones."

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