Page 23 - 2025 GM spring

Avoid Fungicide Resistance
Fungicide resistance can occur after
repeated applications of fungicides
with the same mode of action and
can pose significant challenges to
effective disease management.
Resistance occurs when fungal
populations develop genetic
mutations or adaptive mechanisms
that reduce their sensitivity to
fungicides, rendering standard
treatments less effective or even
obsolete. As resistant strains survive
and reproduce, reduction in disease
control duration and control failures
can become more common. To
combat the development of fungicide
resistance, several integrated disease
management strategies are
recommended, including using
fungicide with different modes of
action (rotating applications and in
tank mixtures), following fungicide
application labels, and implementing
cultural practices where possible.
Currently, the dollar spot
pathogen has exhibited the potential
to develop resistance to
benzimidazoles (FRAC group 1),
dicarboximides (FRAC group 2),
demethylation inhibitors (DMIs,
FRAC group 3) and more recently,
succinate dehydrogenase inhibitors
(SDHIs, FRAC group 7). Monitoring
and early detection of resistance is
key to mitigate the impact of
fungicide resistance on turf health
and performance.
Long Term Use of DMIs
Research over the past three decades
on Clarireedia jacksonii has revealed
a progressive increase in resistance
to the DMI fungicide propiconazole,
which is the active ingredient in some
commonly used fungicides such as
Quali-pro and BannerMaxx. This
prompted us to develop a kit for
detecting fungicide resistance that
can be used by golf course
Superintendents in the field.
This kit can enable rapid, on-site
detection of resistant fungal strains,
providing crucial and timely infor-
mation to guide dollar spot
management practices. End-user
testing of a preliminary kit, encom-
passing samples from 20 sites across
southern Ontario, has been con-
ducted to validate the field kit’s
sensitivity to detecting resistant
isolates.
This research not only highlights
the escalating challenge of fungicide
resistance but also displays the
development of practical tools and
strategies for turf managers to
monitor and manage resistance
effectively. GM
The OTS is hosted by the Guelph Turfgrass Institute, Sports Turf Canada, the Ontario Recreation Facilities Association, the
Nursery Sod Growers Association of Ontario, and the Professional Lawn Care Association of Ontario. All event profits are
reinvested into these non-profit organizations to benefit our shared stakeholders.
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GreenMaster • CGSA •
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