Cause Sphaeropsis sapinea (formerly Diplodia pinea), a fungus. Has become more of a problem in Idaho and Oregon on ponderosa pine. Also is a problem on Austrian, Scots, red, and mugo pine. The disease normally does not kill trees but allows other organisms (such as pine beetles) to gain entry, which may kill the tree. Generally a problem on older trees. Trees that are stressed because of poor site, drought, snow damage, or insect activity are very susceptible. For example, trees found in the transition area between high desert and foothills in central Oregon. Tree wounds are an entry for the fungus. Spores produced on infected plant debris spread to new shoots during wet spring weather. Infections may remain latent (symptomless) for many years. Under low water conditions, latent infections of red pine seedlings were released with rapid symptom development.
Symptoms Stunted, discolored needles develop on new spring growth. The shoot tip continues to die back to the main stem, killing older needles as the season progresses. Several branches or whole portions of the tree may be affected. Dead needles often remain on the branch through the next spring. Small, black fruiting bodies (pycnidia) may form in fall on twigs, needle bases, or cones.
- Prune out infected branches. Best to wait until dry weather in late summer so insects such as pitch moth are not attracted to pruning wounds.
- Landscape trees-keep trees well watered and stress free. Also, do not overfertilize.
- Forest trees-thinning stands is helpful.
- Christmas trees-do not shear in wet or very humid weather.
Chemical control Apply from budbreak though shoot elongation.
- Bravo Weather Stik at 2 to 3.5 pints/A. 12-hr reentry.
- Concert at 22 to 35 fl oz/100 gal water. My cause injury to buds, blooms or tender new growth especially foliage of 'Knock Out' and 'Double Delight' roses. Landscape use only. A Group 3 and M5 fungicide. 12-hr reentry.
- Eagle 20 EW at 6 to 12 fl oz/100 gal water is registered for a few pine species in the landscape, greenhouse and nursery. 24-hr reentry.
- Echo 720 at 2 to 3.5 pints/A. 12-hr reentry.
- Propiconazole-based products.
- Banner MAXX at 5 to 8 fl oz/100 gal water. 12-hr reentry.
- ProPensity 1.3 ME at 5 to 8 fl oz/100 gal water. 24-hr reentry.
- Quadris at 6 to 15.5 fl oz/A for Christmas tree use. Do not apply more than twice sequentially. 4-hr reentry.
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 and M5 fungicide. 12-hr reentry.
- Thiophanate-methyl-based products. 12-hr reentry.
- AllBan Flo at 14.5 to 20 fl oz/100 gal water.
- Cleary's 3336 WP at 16 to 24 oz/100 gal water.
- Halt (by ferti-lome) at 2.5 teaspoons/gal water is registered for home use. H
- OHP 6672 4.5 F at 14.5 to 20 fl oz/100 gal water.
- Topsin 4.5 FL at 20 fl oz/A plus another fungicide with a different mode of action.
- Tourney 50 WDG at 1 to 4 oz/100 gal water. 12-hr reentry.
References Schnepf, C.C. 1992. Diplodia Tip Blight on Ponderosa Pine, Current Information Series Publication 946. Moscow: University of Idaho Extension Service.
Stanosz, G. R., J.T Blodgett, D.R. Smith, and E.L. Kruger. 2001. Water stress and Sphaeropsis sapinea as a latent pathogen of red pine seedlings. New Phytologist 149:531-538.