Conifer Diseases and Disorders

Note: product label supersedes all other recommendations, * chemicals require a commercial applicator.

Common name:   Brown spot                    
Scientific name:   Scirrhia acicola, a fungus
Species affected:   Primarily Scots pine, particularly short-needle varieties
Where it occurs:   primarily in southeastern South Dakota
Symptoms:   Symptoms are very similar to Dothistroma, but occur in July.
Control Recommendations:   Chlorothalonil (Daconil) with the first treatment when needles have expanded, second 3-4 weeks later.

Common name:   Cedar-apple rust                
Scientific name:   Gymnosporangium, a fungus
Species affected:   Primarily eastern redcedar, Rocky Mountain juniper and creeping juniper
Where it occurs:   occurs throughout the state
Symptoms:   The red-brown galls form over two years.  The mature galls produce gelatinous tendrils (horn) during moist spring weather.
Control Recommendations:   Treatments are rarely applied, however, mancozeb (Dithane M-45) can be applied every three weeks from early June to late July to reduce gall formation.

Common name:   Cytospora canker                
Scientific name:   Leucocytoma kunzei, a fungus
Species affected:   Primarily blue spruce, but Black Hills spruce may also be infected.
Where it occurs:   occurs throughout the state
Symptoms:   The  needles on the lower branches turn brown in the spring.   These branches generally have spots or streaks of bluish resin (black fruiting bodies may be found beneath these resin patches).
Control Recommendations:   Prune out all the infected branches before the spring rains.  Disinfect pruning tools between cuts.  Maintain tree health by mulch, irrigation, and fertilizing.

Common name:   Diplodia tip blight
Scientific name:   Diplodia pinea (Sphaeropsis pinea), a fungus
Species affected:   Primarily Austrian pine, but also found on ponderosa, Scots, and mugo pine.
Where it occurs:  throughout the state
Symptoms:  Symptoms occur in late spring with new shoots becoming brown and stunted, the new needles have similar symptoms.
Control Recommendations:   Thiophanate (Cleary 3336F) apply just before bud break with two more treatments spaced 10 days apart.

Common name:   Dothistroma needle blight                                                            
Scientific name:   Dothistroma pini, a fungus
Species affected:   Primarily Austrian and ponderosa pine.
Where it occurs:   rarely seen in the state
Symptoms:   Symptoms occur in the fall, and are first seen on the lower crown.  Needles have yellow and tan spots with green to brown water-soaked bands.  The base of the needles remain green.
Control Recommendations:   Bordeaux (Bordeaux) with one treatment after new growth expands.

Common name:   Elytroderma needle cast    
Scientific name:   Elytroderma deformans, a fungus
Species affected:   Ponderosa and lodgepole pine
Where it occurs:   occurs in the Black Hills
Symptoms:   Symptoms occur in the spring when groups of year-old needles turn reddish-brown except for the base.  Needles usually drop by October.  Often confused with Diplodia, check for brown lesions in the inner bark (but not always present for Elytroderma).
Control Recommendations:   There is no effective chemical control.  Remove heavily infested trees.

Common name:   Juniper blight                    
Scientific name:  Phomopsis, Cercospora, or Kabatina, caused by one of these fungi
Species affected:  Eastern redcedar and Rocky Mountain juniper
Where it occurs:   occurs throughout the state
Symptoms:   Cercospora blight symptoms occur in early summer with the oldest needles on the lower branch turning yellow and dropping.  Phomopsis and Kabatina blight affect shoot tips so the tips of the plants turn reddish-brown.  Kabatina symptoms occur on new growth in the spring, Phomopsis symptoms can occur at any time during the growing season.
Control Recommendations:   Bordeaux (Bordeaux), mancozeb (Diathane M-45) or thiopanate (Cleary 3336F) applied at 7 to 10 day intervals during active growth (if weather remains wet). Mancozeb is the only fungicide recommended for kabatina tip blight.

Common name:   Lirula needle blight                                
Scientific name:   Lirula macrospora, a fungus
Species affected:   Black Hills spruce is the most susceptible
Where it occurs:   rarely found in the state
Symptoms:   First sign is yellow bands on the needles that turn purplish-brown and extend over the entire needle by fall.  Infected needles may remain attached for several years.
Control Recommendations:   Chlorothalonil (Daconil), first when needles half elongate and the second when needles are fully expanded.

Common name:   Naemacyclus (Cyclaneusma) needle cast
Scientific name:   Naemacyclus minor, a fungus
Species affected:   Primarily young plantations of Scots pines
Where it occurs:  occurs primarily in southeastern South Dakota
Symptoms:   Symptoms occur in the fall on second year needles.  Small light green spots first appear with the entire needle turning a dusty yellow (confused with 3rd year needle drop).
Control Recommendations:   Chlorothalonil (Daconil) - four treatments beginning in April and ending in October, may not be economical.

Common name:   Pine wilt                                    
Scientific name:   Bursaphelenchus xylophilus, a nematode
Species affected:   Scots pines in windbreaks and Christmas tree plantations
Where it occurs:  found only in the extreme southern part of the state.
Symptoms:   Symptoms begin in midsummer with foliage yellowing the browning.   Tree usually dies before spring.
Control Recommendations:   Vector is a Cerambycid beetle - remove and burn infested trees before May 1.  Dead and dying branches should be removed to reduce attraction.

Common name:   Rhizosphaera needle cast                
Scientific name:   Rhizosphaera kalkhoffii, a fungus
Species affected:   Primarily mature Colorado spruce
Where it occurs:   occurs primarily East River
Symptoms:   Symptoms occur in midsummer with the needle turning yellow then purplish-brown in late winter.  Small black fruiting bodies emerge from stomates in the spring.
Control Recommendations:   Chlorothalonil (Daconil), first when needles half elongate and the second when needles are fully expanded.

Common name:  Western gall rust                                
Scientific name:   Endocronartium harknessii, a fungus
Species affected:   Primarily ponderosa pine, Scots pine, and mugo pine are sometimes infected
Where it occurs:   primarily in the Black Hills, but can be found throughout the state
Symptoms:   A round gall on the branches of the tree.  The woody gall will produce masses of orange spores each spring.
Control Recommendations:   Resistance varies from tree to tree.  The galls may be pruned from small infested trees but this treatment has very limited effectiveness.

Common name:   Winter burn (browning)                                    
Scientific name:
Species affected:   all evergreens
Where it occurs:
Symptoms:   Needles turning brown or reddish-brown.  This is desiccation due to the needles transpiring due to warm, windy conditions but water uptake is limited by cold or frozen stems or soils.
Control Recommendations:   Plant susceptible plants such as yews in areas they will not be exposed to winter sun.  Make sure that evergreens do not undergo moisture stress in late summer/early fall.  Watering just before freeze-up is of limited benefit.

Common name:   Winter kill
Scientific name:
Species affected:   all evergreens
Where it occurs: 
Symptoms:   Needles turning brown or reddish-brown.  The inner bark of twigs and branches also have brownish streaks.  This is due to an usually drop in temperature as the plant is entering or leaving dormancy.
Control Recommendations:

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This page was last updated November 15, 2006