White Pine Woes

Posted by Annie Napier on 11/01/2017

Blue-green Limber pines typically grow 20-30’ tall with a pyramidal habit maturing over time to a more rounded form. However, in exposed high alpine sites at or near tree line, it may also be seen growing in very dwarf shrubby shapes twisted and contorted by the extreme elements.

We like to use ‘Vanderwolf’s Pyramid’ because of it's closely spaced, twisted, silvery blue green needles.

pyramidal evergreen with blue green needles

When days shorten and temperatures drop, the spores of fungus, Cronartium ribicola, produce short hair-like structures (called telia) on the lower surface of its summertime hosts:

  1. Ribes (red, white, and black currants and gooseberries), 
  2. Castilleja spp. (indian paintbrush), and
  3. lousewort, which is native to the continental United States.

Fall's cool, moist atmospheric conditions have triggered the transfer of this white pine blister rust to 5-needled pines by infecting needles, then creating stem cankers which girdle and kill branches and goes on to infect upper shoots, and eventually the entire trunk. 

Fall symptomsIf you have a white or limber pine, what you will notice this Fall are: 

  • needles on one or more branches that turn yellow, then rusty red

  • cankers - swollen areas with discolored and/or cracked bark on branches &/or oval or diamond shaped cankers on main trunks, often with a dead branch in the center

  • sticky, white sap that exudes from the canker and drips from the branch or runs down the trunk

 

Next Spring you can expect to see blisters at the edge of the cankers and release of powdery orange spores.

In the Summer you will see gummy, orange droplets containing spores along the canker.

Culturally, you can: 

  1. Be intentional with plant selections.  Plant resistant cultivars of the Ribes host, or place the 'Vanderwolf' in an area with plenty of air circulation, avoiding low lying areas and cold pockets.  The right plant in the right place is a principle to strive by. 
  2. reduce moisture on the needles by redirecting irrigation systems, 
  3. remove branches with cankers at a branch union or where the branch meets the trunk.  Be sure to remove at least 4" of healthy wood beyond the visible symptoms of disease.  Sanitize your pruners/loppers afterward.  

 

Love this limber pine, but see signs of infection or know that you have a host species lurking? One option is to replace it with another of our favorite pines, the 'Oregon Green' Austrian Black pine, (10-20' T & 10' W) which has shown promising resistance to the common pine issues in Oklahoma.

Some of our favorite (non-pine) evergreen trees for central Oklahoma include:

  • Atlas cedar 
  • Alaska cypress 
  • Arizona cypress
  • Oak leaf holly
  • 'Nellie Stevens' holly
  • Upright Yaupon holly
  • 'Canaerti' juniper
  • Colorado spruce - for morning sun or shady micro-climates
  • 'Green Giant' Arborvitae - for wetter areas
  • 'Little Gem' Magnolia
  • Cedar of Lebanon

Call us for an estimate on planting some year round interest with evergreens for your project. We look forward to working with you to make your outdoor space something to be grateful for! 

 

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