Page 16 - 2025 GM spring

u FEATURE u DR. TOM HSIANG, UNIVERSITY OF GUELPH
An Update on
and Fusarium
Figure 1 Figure 2
The fungus which causes pink snow
mold, Fusarium patch, and
Microdochium patch was first
reported in 1825, and after several
reclassifications (e.g Lanosa nivalis,
Monographella nivalis, Gerlachia
nivalis, Fusarium nivale), it is now
most commonly referred to as
Microdochium nivale.
Although M. nivale can be found
year round in most regions
supporting grass growth, the disease
it causes is only considered severe on
turfgrass in cool, wet, temperate
areas such as Northwestern Europe
(British Isles, Scandinavia, the
Netherlands, Belgium, and northern
Germany), the Pacific Northwest of
North America (coastal parts of B.C.,
Washington and Oregon), and parts
of ‘Down Under’ (southern coastal
parts of New Zealand and Australia).
Microdochium nivale can attack a
variety of hosts in the family Poaceae
(grasses) such as commercial wheat
and barley, as well as a number of
economically important turfgrasses,
such as creeping bentgrass, annual
bluegrass and perennial ryegrass
with varying degrees of susceptibility
among species and among cultivars.
WHAT’S THE DIFFERENCE
BETWEEN MICRODOCHIUM PATCH
AND FUSARIUM PATCH?
Microdochium patch, Fusarium
patch, and pink snow mold are all
caused by the fungus, Microdochium
nivale. There was an attempt in the
late 1990’s to change the names of all
these diseases to pink snow mold,
whether on grasses or cereals. This
caused an awkward situation for
regions that very seldom experience
snowfall yet were having outbreaks
of what was being called a snow
mold disease.
More recently, there has been a
trend to use the name Microdochium
patch to refer to the disease
symptoms on grasses caused by
Microdochium nivale, both with and
without snow cover. The name ‘pink
snow mold’ is still the name for the
disease on winter wheat and other
cereals that overwinter. Under snow
cover, Microdochium nivale on low-
cut grasses causes circular patches
up to 20 cm across (Figure 1).
In the absence of snow cover,
and with cool wet weather,
Microdochium nivale generally
causes irregularly shaped patches
that are less than 5 cm across (Figure
2) unless there is a prolonged
outbreak when patches may merge.
The issue then is whether these
should be considered separate
diseases or a single disease. I
personally prefer to retain the
previous distinction of pink snow
mold (Figure 1) vs. Fusarium patch/
Microdochium patch (Figure 2) as
referring to separate diseases, rather
than combining them into a single
disease name, Microdochium patch.
However, the name Microdochium
patch may gradually replace the
name Fusarium patch, as generations
of turf managers become familiar
with the newer name.
So, with these definitions in mind,
Microdochium patch and pink snow
mold may be different if they refer to
two different diseases, or may be the
same if you regard them as a single
disease. And Fusarium patch may
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