Mycorrhizal fungi and seedling survival

dwheeler at dwheeler at
Wed Sep 16 00:30:31 EST 1998

Early this year I mailed some dried mycorrhizal fungi which are fairly simple
to grow to a forest consultant nearby. Last week I looked at a new 50-acre
plantation which had been treated with these mycorrhizal fungi. Trees were
mostly Douglas fir, with some Grand fir, Ponderosa pine, and Lodgepole pine
for variety. Trees were planted at about 9 foot spacings in irregular rows
into a field that formerly was a wheat field.

I remember telling the consulting forester that mycorrhizal fungi should
assist in tree survival, but strongly suggested he do three different
inoculations over a period of 6 weeks, beginning with initial planting.

I don't think the two additional inoculations got done.

The trees have been in the ground since about April, and were assisted by the
wettest May Oregon has had on record.

Nonetheless, when I saw the site last Wednesday, September 9 I was amazed at
the lack of noticeable tree mortality. With only a limited time to look, I
eyed about 1.5 acres, or about 3,000 trees. I found 2 fatalities, both of
which were immediately adjacent the entrance to the field. It may even be
that these two trees were killed by being run over by pickups, etc.

As I recall, the mycorrhizae sent were Rhizopogon truffles. Supposedly a
single dip-inoculation of these in a very dilute solution will colonize about
60 percent of the trees.

While average tree fatality is between 5 and 15% normally, the fatality on
this stand was considerably lower: less than 1%. I believe the Rhizopogons
cost $25- $30, and treated 120,000-plus trees, or a cost per tree of less
than 1 cent per 40 trees.

Do you think it was worth it?

Daniel B. Wheeler

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