A FUNGI CALLED "MYCORRHIZAE"
Stephen B. Maul
phc-mti at platinum.nb.net
Tue Mar 19 12:47:20 EST 1996
Response to "A fungi called 'mycorrhyzae'"
A recent posting regarding mycorrhizal fungi and inoculants in general
and Plant Health Care, Inc. in particular, made exaggerated and
unbelievable claims about the nature and use of these products. The
posting was not issued from Plant Health Care's scientific arm, or its
subsidiary, Mycorr Tech, Inc. Rather, the unapproved posting
originated from a novice in Plant Health Care's sales office. For
this, we apologize. Anyone in the scientific field who deals with
sales and marketing personnel know the problems associated with
reining in an enthusiastic sales force. Often, well established
scientific facts are retranslated into oversimplified, catchy slogans
which can start an avalanche of embellishment under which the truth is
often buried. As a result of this posting, Plant Health Care has
taken steps to insure that future statements about its mycorrhizal
inoculant products are properly screened and accurate prior to their
issuance. Regarding the posting in question, a few clarifications are
First of all, there is no such fungus called "mycorrhyzae" and
mycorrhizal fungi do not comprise a "family of fungi". Rather the
term "mycorrhiza" refers to the specialized root-fungus structures
which are formed as a result of the association. Species from various
subdivisions of the Fungal Kingdom can form beneficial associations
with plant roots, although there are significant differences in the
structures of the various plant-fungus associations. However, there
is a relative lack of specificity between plants and fungi
contributing to the same type of association. Plants that form
ectomycorrhizae can do so with many fungi which form ectomycorrhizae,
while plants that form endomycorrhizae, especially
vesicular-arbuscular mycorrhizae (VAM), will do so with a wide variety
of fungi contributing to the compatible endomycorrhizal form.
Fungi that form mycorrhizal associations with plants are worldwide in
their occurrence, and the vast majority of the world's plants do form
these associations. However, in the aforementioned posting, the
ubiquity of mycorrhizal fungi is clearly overstated. Indeed, if
mycorrhizal fungi were on "every grain of sand and every gram of
soil", then there would be no need to sell inoculants. In natural
settings, mycorrhizae are the rule for plant roots. But trees and
other plants are rarely planted (by man) into mature forests where the
soil environment is already rich in mycorrhizal fungi. Rather, these
plants are typically transplanted into disturbed,
mycorrhizal-deficient sites, like mined sites, residential properties,
and degraded forest lands, and in mycorrhizal-deficient fumigated
nursery beds and artificial potting media. Hence, in such situations,
introduction of the appropriate mycorrhizal fungi is beneficial to
successful establishment of the trees or plants being introduced.
Dramatic results are often obtained under these circumstances with
reduced mortality, increased growth, and cost savings.
While there is evidence that the occurrence of certain root diseases
caused by nematodes or fungi is reduced in plants bearing mycorrhizae
compared to those that do not, it is certainly not true that these
fungi "can prevent all root pathogens and damaging nematodes from
attacking the root." While it is widely accepted that mycorrhizal
fungi are quite beneficial to plants, they are certainly no panacea
affording unlimited protection or unlimited plant productivity. We
think our products are second to none in the trade, and each of them
can stand on its own merits without added embellishments. We have
research to back up our current knowledge and claims about our
products, but no product exists that will do everything for everybody
everywhere all of the time.
The current scientific staff of Plant Health Care Inc. and its
subsidiary, Mycorr Tech Inc. is composed of Drs. Donald H. Marx, C.
Edward Cordell, Stephen B. Maul, and Michael J. Kernan.
Plant Health Care, Inc.
440 William Pitt Way
Pittsburgh, PA 15238
Fax (412) 826-5445
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