White Pine Decline versus White Pine Root Decline: What's the Difference?

Decline of White Pine

Decline is common among white pine in Kentucky.  Two distinct diseases with similar names are often confused, but they are distinctly different.  Note that white pine decline is an abiotic malady that leads to slow decline, while white pine root decline is a fungal disease that causes sudden plant death.  More details follow:

White Pine Decline

Symptoms

White pine decline causes needle s to yellow and drop prematurely, causing a noticeable thinning of the canopy (Fig 1).  Other symptoms include unusually shorter needles; needle tips may become brown.  Bark of individual branches may become shriveled and needles on those branches become wilted or limp (Fig 2).

Figure 1.  White pine decline, an abiotic malady, is caused by environmental conditions.  Symptoms include thinning needles and reduced plant vigor.

Cause

White pine decline is not caused by a pathogen.  Symptoms are induced by environmental conditions such as

·         high soil pH

·         high soil clay content

·         restricted root-growth

·         compacted soil

·         mechanical disturbances that cause root injury  

Figure 2.  Wrinkled bark is common on trees suffering from white pine decline.  Needles above damaged bark become wilted and drop.

Disease Management

The best way to manage white pine decline is through prevention. Select sites with the following characteristics:

• acidic soil (pH of 5.5 and not above 6.5)
• sandy or loamy rather than clay soils
• large area for root development

·         loose soil free from soil compaction

·         sufficient soil moisture (regular irrigation and mulch)

·         vigorous plants (control insect pests and fertilize trees regularly)

Once decline begins, it may be difficult to reverse.  However, the following practices may be implemented.

·         lower soil pH by applying granular sulfur according to soil test results

·         aerate soil by vertical mulching or other means

·         fertilize and water to eliminate stress

White Pine Root Decline

Symptoms

Trees may be infected for several years without showing symptoms.  However, once symptom development begins, homeowners often notice delayed bud break and reduced candle elongation in spring.  Mature foliage then fades, droops, and turns brown rapidly (Fig 3-4).  Conversely, nearby trees may appear healthy; mortality appears quite random with a few trees dying each year. Resin flow (pitch) is visible at the tree base and is associated with a dark brown girdling canker under the bark (Fig 5).  The trunk may be flattened on the affected side.

Figure 3.  White pine root decline, a fungal disease, causes rapid wilting of white pine. 

Cause

White pine root decline, is caused by the fungus, Leptographium procerum that infects inner bark and sapwood of roots and lower trunks of white pine.  Although the disease is most serious on white pine, the fungus also can infect Scots and Austrian pines.  Losses within an infected planting range from 20 to 50%.

Figure 4.  Rapid wilting is often followed by rapid browning (needles intact) when trees are suffering from white pine root decline.

Trees planted on wet sites are more susceptible to infection, although other stresses may also cause trees to become susceptible to the disease.  Once infection occurs, the fungus may be spread from tree to tree by contaminated insects as they move from diseased trees to healthy trees nearby.  Galleries of insects such as the pine root collar weevil may be found in cankers and provide a place for the fungus to sporulate.  Weevils and other bark-infesting insects may serve as vectors for this disease.

Figure 5.  Pitch is often associated with trunk cankers caused by white pine root decline.

Disease Management

Cultural practices help reduce disease spread by insect vectors. No fungicide is available for disease management.

·         avoid  wet sites

·         do not replant eastern white pine among stumps of recently killed trees

·         remove and destroy infected trees including stumps,

·         collect samples for diagnosis by removing tissue from the canker face (bark removed) and shipping in a plastic bag.

 

Revision of original by John Hartman.