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).
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Figure 1. White pine
decline, an abiotic malady, is caused by environmental conditions. Symptoms include thinning needles and reduced
plant vigor.
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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
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Figure 2. Wrinkled
bark is common on trees suffering from white pine decline. Needles above damaged bark become wilted and
drop.
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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.
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Figure 3. White pine
root decline, a fungal disease, causes rapid wilting of white pine.
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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%.
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Figure 4. Rapid
wilting is often followed by rapid browning (needles intact) when trees are
suffering from white pine root decline.
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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.
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Figure 5. Pitch is
often associated with trunk cankers caused by white pine root decline.
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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.
