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.

Win the Battle Against Powdery Mildew

Powdery mildew is one of the most easily recognizable diseases of landscape and garden plants.  While most fungal pathogens are favored by wet weather, powdery mildew pathogens favor high humidity but not wet conditions.  Shady areas, areas with poor air circulation, and low areas that trap damp air are ideal environments for disease development.

Powdery fungal growth is an easily recognizable symptom of powdery mildew disease.

A wide range of plants are susceptible to powdery mildew:  annuals, perennials, shrubs, ornamental and fruit trees, small fruit, and vegetables.  While symptoms appear similar on most plants, powdery mildew fungi are usually host-specific.  For example, powdery mildew of dogwood cannot infect pumpkins or cucurbits, and powdery mildew of cantaloupe will not infect phlox or rose. 

Typical symptoms of powdery mildew include dusty fungal growth on surfaces of leaves and on young succulent plant tissue (Photo 1 & 2).  Powdery mildew may occur as isolated blotches or cover entire leaves, stems, buds, or flowers.  Early infections can lead to leaf stunting, curling, or other deformation (Photo 2).  Infected fruit may become disfigured or fall prematurely (Photo 3).  In the fall, small fruiting structures that resemble pepper flakes may be visible to the naked eye (Photo 4 & 5).  These structures contain overwintering spores that serve as inoculum for the following year.

Infection of young growth may result in stunted or deformed tissue.

Management of powdery mildew begins with prevention.  Plants should be properly spaced and thinned for improved air circulation and more rapid leaf drying.  Resistant cultivars are available for crabapple, dogwood, phlox, zinnia, cucurbits, and several other plants and are an excellent means of disease prevention.

Fruit infections ultimately lead to yield loss.

Fungicides usually are not warranted when cultural practices are implemented.  Early season infection, however, may require one or more applications of effective fungicides.  Homeowners have a wide range of fungicides available.  However, they should carefully read labels to confirm that the selected fungicide may be used legally on select plants or that the fungicide is suitable for edible plants.

Fungicides effective against powdery mildew include:

·         Chlorothalonil – broad spectrum protectant; ornamentals, some fruit and many vegetables

o   Bonide Fungonil concentrate or Fungonil RTU

o   Ortho MAX Garden Disease Control

o   Sevin Daconil

·         Myclobuanil – systemic; ornamentals, most fruit and vegetables

o   Spectracide Immunox (only Immunox Multi-purpose Fungicide Concentrate is labeled for use on fruit and vegetables)

·         Propiconazole – systemic; ornamentals, some fruit

o   Bonide Fungonil RTS (different from other Fungonil products, which contain chlorothalonil)

o   Bonide Infuse

o   Fertilome Liquid Systemic

·         Tebuconazole – systemic; ornamentals only

o   Bayer Advanced Disease Control

o   Bonide Rx Systemic

·         Triflorine – systemic; ornamentals only

o   Ortho Rose Pride Disease Control

Late in the growing season, powdery mildew fungi produce small, black overwintering structures that can serve as inoculum the following year.