Diplodia (Sphaeropsis) Tip Blight of Pine: Symptoms and Control

Diplodia tip blight, caused by Diplodia pinea (formerly Sphaeropsis sapinea), affects Austrian, Scots, ponderosa, mugho, red, and other 2- and 3-needled pines. The disease kills shoot tips and branches, reducing aesthetic value and tree health.

Fruiting bodies on cone scales

Symptoms

• Browning of needles on new shoots as they emerge from the fascicle sheath; shoots die.
• Early sign: small drops of resin ooze from shoot buds as growth begins in early spring.
• Infected buds stop growing, remain undersized.
• Replacement buds also become infected.
• As disease progresses, whole branches may die but needles remain attached.
• Small black fruiting bodies (pycnidia) erupt through needle surfaces, especially below the sheath at the needle base, and on second-year cone scales.
• Thousands of spores ooze during wet weather and are splashed throughout the tree.
• Lower branches usually infected first.

Disease Cycle

The fungus overwinters in black fruiting structures on dead shoot tips and infected cones. Trees of all ages are susceptible, but severity increases after 20–30 years. Predisposing factors include drought, insect damage, mechanical injury (hail, frost), and high nitrogen fertilization.

Management

• Promote tree vigor by protecting from environmental stresses, insects, and injuries.
• Avoid high nitrogen fertilizers on pines.
• Apply fungicide to entire crown, especially lower branches, as buds begin to swell (bud break) and again 2 weeks later. Sprays at other times are ineffective.
• Do not plant healthy 2- or 3-needled pines near older infected pines.
• If pruning infected branches, disinfect tools between cuts to prevent spread.

References

• Hudler, G. W. and W. A. Sinclair. 1978. Diplodia tip blight of pines. Cornell Tree Pest Leaflet A-7.
• Nichols, L. P. 1978. Diplodia tip blight of pines. Penn State Ornamentals and Turf Newsletter 2(1):1-3.

Diplodia symptoms on tree and twig.

Prepared by Gary W. Moorman, Professor of Plant Pathology