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Sphaeropsis Tip Blight of Pines

Ned Tisserat Extension Specialist, Plant Pathology


	Figure 1. Sphaeropsis tip blight of Austrian pine

Disease

Although pine trees are not native to Kansas, they have been widely planted for ornamental and windbreak purposes. Many of the pines, including Scots (Pinus sylvestris), Austrian (P. nigra), and ponderosa (P. ponderosa) are reasonably well adapted to growing conditions in Kansas. Unfortunately, these pines may be subjected to one or more foliar or shoot diseases that can cause premature defoliation of the needles, shoot and branch dieback, and even death of the tree. Among the most common and serious of these diseases is Sphaeropsis (formerly Diplodia) tip blight.

Pine trees may be seriously damaged or killed by Sphaeropsis tip blight. Austrian, ponderosa, Scots, and mugo (P. mugo) pines all are susceptible to the disease. In Kansas, tip blight is most severe on mature (30 years or older) Austrian pines, although the disease can occur on susceptible pines at any age. Tip blight primarily causes the death of new shoot growth in the spring. However, repeated infections over a period of several years can result in the death of large branches or even the entire tree.


Figure 2. Resin-soaked, blighted shoots caused by Sphaeropsis sapinea.		Figure 3. Black fruiting structures (pycnidia) of the Sphaeropsis fungus on cone scales.

Symptoms

Symptoms of Sphaeropsis tip blight first appear in late May or early June. New, developing shoots (candles) fail to elongate properly and turn yellow or tan. Small droplets of resin often form on the stunted needles. Normally, all infected needles remain attached to the branch. Dead shoots are more common in the lower portion of the tree crown; however, trees which have had repeated infections over several years can have dead shoots and branches throughout the crown.

In late summer or fall, small black fruiting structures of the fungus are formed at the base of the stunted, current-season needles. These structures are easily visible with a 10X handlens, but may be partially hidden by the sheath-like needle fasicle. The fruiting structures also are formed on the scales of two-year-old cones and are much easier to find there than those produced on the needles.

Sphaeropsis tip blight can be confused with winter damage or injury sustained from the pine tip moth. Remember that tip blight results in stunted, yellow to tan shoots in late spring after needle elongation has begun, and that black fruiting structures are visible on both needles and cones in the fall and winter. Winter damage normally results in death of shoots before needles emerge in the spring and the injury may be restricted to one side of the tree. Shoots damaged by the tip moth have hollow buds and may have the larvae present inside the shoot whereas those damaged by tip blight remain solid and resin-filled.

Cause

The fungus Sphaeropsis (Diplodia) sapinea survives from year to year in dead shoots, branches, and in pinecone scales. The small, spore-bearing structures (pycnidia) of the fungus are produced both on needles and cones. The spores are dispersed by water and require a high relative humidity for germination and penetration of the host tissue. New shoot growth is very susceptible to infection, and thus most infection occurs in the spring when the candles are elongating. Older shoots or larger branches may become infected if these tissues are injured by hail, insects, or other types of mechanical damage. Recent research also suggests that the fungus may cause incipient infections on pine shoots and other tissue,then remain quiescent for a period of time without causing shoot blighting or canker development. These latent infections may then become active during periods of tree stress and result in branch dieback.

Control

Currently there are no sources of resistance among Austrian pine selections to Sphaeropsis tip blight. Scots and white pine are less susceptible to tip blight. Nevertheless, these pine species suffer from other disease and environmental problems that limit their use in our state.

Removal of dead shoots will improve the appearance of diseased trees, but it will not necessarily prevent infection since much of the inoculum is produced on cones that remain attached to the tree. Similarly, spacing trees more than 10 to 15 feet apart will allow for greater air circulation and decrease blighting. Trees attacked by tip blight should be adequately watered and fertilized.

Control of Sphaeropsis tip blight is aimed at protecting the susceptible, expanding shoots from fungal infection in early spring. Tip blight can be controlled with two to three applications of an appropriate fungicide if the chemical is applied at the right time. The first application should be made approximately the third week in April just as the new buds are elongating. The trees should be sprayed a second time 10 to 14 days later. A third application in late May or early June may be required in wet springs.

Fungicide timing may need to be adjusted slightly depending on pine shoot development in the spring. Spraying after the critical period of bud break and elongation will not be effective in controlling tip blight. Thiophanate-methyl (Cleary’s 3336, Fungo, Fertilome Halt), propiconazole (Banner MAXX) and some copper-containing fungicides, including Bordeaux mixture, Kocide 2000, and Tenn-Cop 5E, are registered for control of tip blight. Thorough coverage of the foliage with the fungicide, especially in the lower two-thirds of the crown, is essential for adequate disease control. A trombone sprayer or a motorized high-pressure sprayer may be required to deliver the fungicide to the tops of very tall trees. Unfortunately, the fungus has the potential to cause infections every year. Therefore, severely blighted trees will probably require yearly applications.

In recent years, there has been interest in the possibility of controlling tip blight by injecting trees with systemic fungicides. Research trials on this technique have been inconclusive. Therefore, injections are not currently recommended.

Symptoms and Control of Sphaeropsis Tip Blight
Disease	Pine Hosts	Symptoms	Time of Symptom Development	Chemical Control	Time of Chemical Application
Sphaeropsis tip blight	Primarily Austrian, also Ponderosa, Scots, and Mugo	Dieback of current year’s shoots	Late spring to early summer	thiophanate-methyl (Cleary’s 3336, Fungo, Feritome Halt, Green Light Systemic Fungicide) propiconazole (Banner Maxx) copper-containing fungicides (Bordeaux, Kocide 2000, Tenn-Cop 5E	Third week in April. Second application in 10 to 14 days

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