Posted by: Curtis Utley, Jefferson County Extension Plant
Diagnostic Clinic
Have you ever seen an established pine in your neighborhood
just up and die? I received some branch samples last week from a Scots pine (Pinus sylvestrus) that “just died this fall”.
Now this is alarming to a homeowner and a diagnostician alike. There are many
possible causes for woody plants to die outright.
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| Dead Pinus mugo. |
One of the causes of rapid death I screen for in exotic pines is the presence of pine wilt nematodes (Bursaphelenchus xylophilus). Exotic pines are those species not native to North America such as: Scots (P. sylvestrus), Austrian (P. nigra), mugo (P. mugo) , and red pine (P.densiflora).The nematodes are vectored to perfectly healthy pine trees during maturation feeding by the pine sawyers (Monochamus spp.); long horned beetles which carry the nematodes within their bodies from an infested pine tree the beetles, as a grubs, called home the year before.
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| Wood chips bubbling in a beaker |
The screening process
starts by taking branch samples cut close to the trunk, or better yet, trunk
wedge samples. These samples are cut into ¼” inch cookies. These cookies are
then cut into tiny blocks. The cubes are then put into a beaker full of
distilled water and air is bubbled through the water and chips overnight. The next
morning I pour the wood soup through a #45 sieve stacked on top of a #325
sieve.
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| Wood chips poured on top of a #45 sieve stacked on top of a #325 sieve. |
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| Material trapped by #325 sieve. |
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| Petri dish containing material trapped by #325 sieve. |
All of the larger wood material is captured on the #45 sieve while the
nematodes, if present, are washed through and captured on the #325 sieve.
All
of the material captured on the #325 sieve is then transferred to a Petri dish
and observed microscopically. If nematodes are present they can be seen
swimming through the aqueous saw dust. Pine wilt nematode is confirmed by the
structure of the male genitalia.
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Pine wilt nematode Bursaphelenchus
xylophilus. Sandra Jensen, Cornell University, Bugwood.org
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So interesting, Curtis! You guys do all the cool stuff at the JeffCo Plant Clinic. I never knew how you actually detected for the nematodes, so thanks for the detailed info.
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