Plant Disease Watch List

• Pine Wilt

  Pine wilt is a disease caused by the pinewood nematode, Bursaphelenchus xylophilus. This nematode is spread by the pine sawyer beetle. By itself, the beetle does little damage to a tree beyond some minor stress, but it is the primary vector of this nematode, which enters the trachea of the insect at larval stage and is spread during feeding after the insect spreads to other trees as an adult. This disease is established in Eastern Kansas but has yet to establish in most of Western Kansas at this point.

  Pine wilt disease usually kills pine trees relatively quickly, within a few weeks to a few months. Mature pine trees (10+ years old) are more susceptible than young ones. Because of this, it is not a serious threat to Christmas tree farms. However, this makes it a prime threat to windbreaks as pine trees are frequently used as windbreaks across the state.

  How do I recognize it?

  Symptoms include color change in needles from green to grayish green, then to brown. If you remove a limb, it is usually characterized by a lack of resin, as the nematodes multiply and clog up the xylem which stops resin flow. Needles do not drop immediately but may stay on a dead tree’s branches up to a year.

  What to do if I find it?

  To prevent the spread of pine wilt, it is imperative to remove dead pines promptly. They must be burned, buried, or chipped, as they may harbor insects and promote spread of the nematode. Do not use the wood for firewood, as the insects may still emerge from firewood logs. When planting evergreens, select resistant trees, such as white pine, spruces, firs, and junipers. Susceptible pines include Scots pine, Austrian pine, Mugo pine, jack pine, and red pine. No effective nematicides exist at this time.

  If you suspect a pine tree of having pine wilt, a sample of wood is necessary. Take a disk of wood or branch at least 1 inch thick and 3 to 4 inches wide and submit it to the Kansas State University Plant Disease Diagnostic Lab in Manhattan, Kansas. If a pine tree dies it is important to know whether pine wilt was the cause, as it is important to dispose of the tree properly to avoid spread of the nematode.
  
  
  
  
  For more information:

  • Pine Wilt Fact Sheet
  • Pine Wilt vs Pine Tip Blight

• Boxwood Blight

  Boxwood blight is a destructive disease caused by the fungus Calonectria pseudonaviculata, first detected in the UK in 1994. It spread to Connecticut and North Carolina in 2011 and Kansas in 2014. Since then it has spread across the United States, Europe, and parts of Canada.

  Early detection and eradication work are ongoing. In addition to boxwood, the disease attacks pachysandra, sarcococca, and other species in the family Buxaceae. Proliferation of the disease causes severe defoliation and leads to crop loss in nurseries and planted landscapes.

  Why is it important?

  Boxwood is a popular evergreen bush in Kansas because they are low-maintenance and tolerate a wide variety of environmental conditions. If allowed to spread, this disease could be devastating to the Kansas boxwood industry and landscapes.

  How to recognize it?

  Symptoms of boxwood blight include light brown leaf spots with dark borders, which coalesce and form brown patches and black streaks on green and woody stems. These symptoms cause defoliation and death of the plant. In conditions of high humidity, white growth may be visible on the undersides of the leaves.
  
  For more information:

  • Boxwood blight pest alert
  • Purdue boxwood blight page