Environmental
Injuries

Pathological
Disorders
Shoot Blights
Branch & Stem Diseases

Contents

Pathological Disorders –
Foliage Diseases

Several diseases cause spotting, browning, and/or premature casting of needles of pines and spruces in North Dakota including ponderosa pine, red pine, Scots pine, Colorado spruce and Black Hills (white) spruce. Needle diseases seldom kill trees, but the reduction in healthy foliage lowers vigor. Spots, bands or discoloration on needles may be symptoms of needle disease infection, but may also occur in response to insect or mite injury, air pollution (including herbicides), cold temperatures, drought stress, or aging. The diseases discussed have not all been found in North Dakota, but have all been found in nearby states.

Pine Needle Blights

DOTHISTROMA NEEDLE BLIGHT caused by Dothistroma pini can infect all two or three needle pines, but only ponderosa and Austrian pines are highly susceptible. Early symptoms appear in late summer or early fall as deep green bands with a water-soaked appearance and as yellow or tan spots. The spots and bands turn brown to reddish-brown. The ends of infected needles gradually die and turn brown. Tiny black fruiting bodies develop near the infection band in late fall or the following spring. Infected needles drop prematurely. In the western United States, where the infected spots or bands are more red than in the Great Plains, this disease is called red band disease.

BROWN SPOT NEEDLE BLIGHT caused by Scirrhia acicola causes symptoms and damage similar to Dothistroma, including spots, bands, dead needle tips and fruiting bodies. Neither Dothistroma nor Brown Spot are serious in North Dakota.

CYCLANEUSMA NEEDLE CAST, caused by Cyclaneusma minus (formerly Naemacyclus minor), can infect ponderosa and Scots pines. Needles of all ages are susceptible. Infection can occur during any season, most often in the spring. First symptoms appear as small, light green spots which gradually lighten and coalesce, turning the entire needle a dusty yellow, often with distinct transverse brown bars. Symptoms on most infected needles develop in fall but can develop at any time. Needles are normally cast from the branches a few months after developing symptoms. In North Dakota, fruiting bodies (apothecia) usually develop after needles are cast. They appear as raised, off-white areas on dry needles and as swollen, yellow, waxy areas on moist needles (top illustration - A) (52KB color jpg). Damage is caused by the presence of yellow needles and defoliation. The development of yellow needles in the fall is often confused with natural needle senescence. Presence of transverse brown bars on discolored needles and the development of typical fruiting bodies are diagnostic for Cyclaneusma. Economical chemical controls are not currently known.

LOPHODERMIUM NEEDLE CAST can infect ponderosa, red, and Scots pines. First symptoms are yellow to brown spots or bands on needles. Infected needles die and may drop before the normal time. Characteristic black, football-shaped fruiting bodies develop on dead needles (bottom illustration - B) (52KB color jpg). Several species of Lophodermium occur in North Dakota or nearby states. Control measures taken depend on which species is present. Long-needled Scots pine varieties are more resistant to some species than short-needled varieties.

PINE NEEDLE RUST caused by Coleosporium solidaginis can infect all our pines but seldom causes severe damage. Infection of needles occurs in early fall. White fruiting structures (51KB color jpg) erupt through the surface of needles in late spring. Heavily infected needles die and drop. Less heavily infected needles may produce fruiting structures again the following spring. Since this disease needs two hosts to complete its life cycle, control is by removal of nearby weedy alternate hosts (goldenrod, aster).

Spruce Needle Blights

LIRULA NEEDLE BLIGHT caused by Lirula macrospora can infect all species of spruce. White (Black Hills) spruce is most commonly affected in North Dakota. All ages of needles are susceptible. Sporulation of the fungus is from late May through August, with peak releases from early June to mid-July. First symptoms appear as yellow bands which gradually become purplish-brown and expand over the entire needle in the fall, 15 to 17 months after infection. Large, smooth, black fruiting bodies (75KB color jpg)(hysterothecia) develop along the length of the then reddish-brown needles the next spring, 23 to 25 months after infection (top illustration -A) (60KB color jpg). Infected needles slowly lose color, become pale or tan and hysterothecia gradually mature and release spores the next spring and summer, 35 to 39 months after infection. Gray-tan needles with old hysterothecia may remain attached to branches for several years after sporulation. Damage is caused by the presence of discolored needles and reduced foliage, which reduce growth and aesthetic value. Lirula can be controlled by two properly timed applications of fungicide in each of three consecutive years.

RHIZOSPHAERA NEEDLE CAST caused by Rhizosphaera kalkhoffii can infect several spruce species, but is primarily a problem on Colorado spruce in North Dakota. All ages of needles are susceptible. Needles are infected in late spring and early summer. Infected needles usually turn yellow and then purplish-brown in late winter. The following spring tiny fuzzy black fruiting bodies (pycnidia) (bottom illustration - B) (60KB color jpg) appear. In mass, they may form characteristic black lines along the length of needles instead of the normal white lines. Infected needles drop off by mid to late summer of the year following infection. Damage is caused by the presence of dead discolored needles and reduced foliage. Rhizosphaera needle cast is currently the most widespread foliage disease of spruce in North Dakota. Rhizosphaera can be controlled by two properly timed applications of fungicide in each of two consecutive years.

Control of Pine and
Spruce Needle Blights

Foliage diseases often occur in characteristic patterns. They can usually be distinguished from physiological or environmental problems because they occur mostly on the lower portion or on the north side of trees where needles remain wet longer. Usually the disease builds up on lower or inner parts of the tree before damaging the upper portions (Table 1).

To determine the cause of needle spots, bands or discoloration due to disease, it is necessary to find fruiting bodies of the particular fungi. Often these are hard to find or only appear at certain times of the year, and laboratory diagnosis is needed. Presence of colored spots or bands alone is not sufficient evidence to diagnose disease. Insect or mechanical damage can also result in such symptoms.

Cultural controls are often sufficient to prevent serious damage by needle diseases. These include maintaining tree vigor, planting resistant varieties when available, and promoting good air circulation around trees. Crowded, dense plantings create environmental conditions favorable for needle diseases. The needle disease fungi described here are often inhabitants on senescent older needles where they cause no problem. Only when they infect younger needles is there reason for concern.

Chemical controls may be needed if serious damage occurs. Spray materials and schedules are available for many of these diseases but identification of the needle disease involved is necessary for proper timing of protective sprays.

Table 1. Foliar symptoms and signs of common spruce problems.

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		           Disease/Disorder
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  Rhizosphaera   Lirula 	  Cytospora 	    Environmental
  Needle Cast 	 Needle Blight    Branch Canker     Injury
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Symptoms:  

  Needles turn   Needles turn     Whole branches    Needles turn 
  red-brown or   tan to light     die. All needles  brown in winter 
  purple-brown   brown in fall,   turn gray-yellow  or after 
  in winter,     remain attached  then brown. 	    drought.
  drop by early  for 4-5 yr,  	  Abundant resin 
  summer.	 becoming gray.   flow.
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Affected part:  
 
  Older needles, Older needles,   All needles on    Most exposed 
  current year   current year     a branch equally  parts and 
  needles 	 needles remain   affected. Indi-   youngest needles
  remain green.  green. 	  vidual branches   show greatest 
				  scattered in      injury.
				  lower part of	
				  tree affected 
				  first, later on 
				  all lower branches.
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Most severe on: 
       
  Lower 	 Lower branches,  Lower branches    Exposed or 
  branches,      shady areas,	  on crowded or     droughty sites, 
  shady areas,   Black Hills 	  stressed trees,   newly planted
  Colorado 	 Spruce.	  Colorado Spruce.  trees.
  Spruce. 	 	
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Look for physical presence 
of fungus (signs):   

  Tiny  	 Long (1/2 in.)   No signs on 	    No signs on 
  (1/100 in.)    black lines 	  needles. Under    needles.
  round black    demark hyster-   bark surface      (Dead needles 
  pycnidia  	 othecia in 	  are round black   may support 
  emerge from    older 	          structures 	    mold growth 
  needle         (3rd yr) dead    (stromata) 	    in wet 
  stomates 	 needles.	  containing 	    weather.)
  (white areas)  	          pycnidia. 	
  in April-June. 	 	  
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Controls:  

  Promote air circulation and 	   Avoid crowding;   Water deeply to 
  avoid crowding. 		   thin out plant-   promote good 
  Fungicide sprays may help but    ings by 	     roots. Water
  timing is critical. 		   removing poor     during droughts. 
  Plant spruce trees in full       trees. Prune off  Protect newly 
  sun. 			           infected branches transplanted
				   in winter. Don't  trees from 
				   cultivate under   wind and sun.
				   spruce. Promote 
				   vigor. 	
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N E X T | B A C K | C O N T E N T S

Environmental Injury
Pathological Disorders - Shoot Blights
Pathological Disorders - Brach and Stem Diseases