Download Managing tobacco blue mold in 2015: a

Managing
tobacco
blue mold
in 2015:
a
proactive
fungicide
approach
ANR Agents’ Special Training
Emily Pfeufer1 and Bob Pearce2
University of Kentucky
Departments of Plant Pathology1
and Plant and Soil Sciences2
Managing tobacco blue mold in 2015:
a proactive fungicide approach
• Pathogen biology and
history of blue mold in KY
• Fundamentals of disease
management
• Resistance to fungicides
• Blue mold fungicide
options and modes of
action
• Blue mold spray program
Subtle yelloworange spots
on tops of
leaves
Blue
sporulation on
underside of
leaf
Seebold, 2006
Pathogen biology
• Sporangiospores are the
main infectious agent
• Free water on leaf surface
required for germination
• 5-7 days later, symptoms
develop on leaves
• When symptoms develop,
secondary sporulation
occurs
• Optimal sporulation
conditions: at least 1.5 hrs
darkness, 95% humidity,
59 - 74°F
• Peronospora tabacina, a
water mold pathogen
As many as
1 million spores!
Modified from C.E. Main, North Carolina State University.
History of blue mold in KY
• Prominent disease of high density tobacco production
• 1979: early blue mold confirmations and wet, cool summer
resulted in over $56 million in losses in KY1
• 1980: blue mold is identified early in KY, but due to hotter,
drier summer, did not result in significant losses2
• Ridomil also labeled that year for blue mold management
• Resistance to Ridomil developed within 5 years of its labeling3
• Sporadic epidemics since, primarily due to poor protective
sprays combined with conducive conditions
• Several years with early threats, but never materialized into
epidemics due to weather and/or prevention
1. Nesmith, W. C. 1984. Plant Disease 68:933-936. 2. Davis et al., 1981. Plant Disease 65:508-512.
3. Nesmith and Jones, 1984. Phytopath. 74:631.
Disease management: a 3-step process
Blue-gray sporulation
on underside of leaf
1. Prevention – occurs prior
to pathogen introduction
to crop
2. Monitoring & diagnosis –
scout for early, accurate
disease detection
Seebold, 2005
3. Cultural and chemical
management – disease
has already arrived, and
steps are taken to reduce
its impact
Preventative tactics
Blue mold throughout transplants
In the floatbed: starting resistant
varieties, regular mowing with
effective clipping removal,
floatbed fungicide applications
Seebold, 2006
At transplant: crop rotation,
preplant fertility, plant spacing,
at-transplant fungicide
applications
In season: weed management,
sucker control, fungicide
applications
Early lesion
Palmer
Resistance to fungicides
Natural population
of blue mold fungus
in environment
. .
. . .. ..
.. . .
. .. .
.. .. . .
. .. .
.
More resistant
fungi in population
Fungicide
application
Fungicide
application
.
..
.
Fungal escapes
from fungicide
.
.
.
Spores released
from escapes,
causing new
infections
... .
. . .
. ..
Fungal
escapes
Resistance to fungicides
• Resistance to metalaxyl
(Ridomil) in the blue mold
pathogen after 5 yrs
• Key to preventing
development of populations
with fungicide resistance is
to alternate modes of action
(“rotate” fungicides)
• Some fungicides are more
prone to resistance
development than others
Blue mold fungicides available today
Product
Active ingredient
Mode of action
FRAC group
Actigard
Acibenzolar-S-methyl
Systemic acquired
resistance inducer
21
Manzate ProStick
Mancozeb
Multi-site, contact
fungicides
M3
Agri-mycin 17, Ag
streptomycin, Harbour
Streptomycin
Protein synthesis
inhibitor
25
Forum, Revus
Dimethomorph,
Mandipropamid
Inhibit cell wall
formation
40
Quadris, Satori,
AzoxyStar, Azoxy 2SC
Strobilurin
Inhibit cellular
respiration
11
Presidio
Fluopicolide
Disrupts cell integrity
43
Mode of action – the mechanism by which a pesticide, drug, or
other biologically active chemical functions (from apsnet.org)
Activity of fungicides listed here
• Contact fungicides (must
be on plant surface prior to
pathogen arrival): Manzate
ProStick, streptomycin
• Systemic fungicides
(applied prior to arrival,
but actually enter plant
tissue): azoxy products,
Revus, Forum, Presidio
• Actigard – a different
kind of systemic
fungicide
Bost
More about Actigard
Ivors and Mila
• Not directly toxic to pathogen
as most other fungicides are
• “Primes” plant’s own defenses
against infection by pathogens
• Must be applied
preventatively for full
effectiveness
• Very low risk of resistance
development, no residues
• KY data suggests 50% reduction in blue mold compared to
untreated control, when Manzate was alternated weekly with
Actigard starting 4 days post-transplant (Pearce)
Blue mold fungicide program: early season
• EVERYONE: Any unset floatbed plants should be treated
now with either Manzate ProStick or Quadris (if not
sprayed with Quadris already)
• For fields with blackshank pressure, Ridomil or Presidio
may be applied in setter water. No blackshank and high
risk for blue mold, apply Manzate or Forum/Revus over
the top
• Actigard when plants are 18-inches or taller, followed by
Manzate, Forum/Revus, Presidio, or azoxy product over
the top
• 10 days after Actigard application, reassess risk level
based on regional blue mold pressure
Blue mold fungicide program: late season
• Continued moderate to high risk: Apply a second
Actigard application followed by another fungicide
spray (azoxy product, Manzate, Presidio, or
Revus/Forum)
• If high pressure persists or blue mold is present in field,
select another fungicide to approach end of season
with. Fungicide PHIs:
•
•
•
•
•
Azoxy products: 0 day
Forum: 0 day
Presidio: 7 days
Revus: 7 days
Manzate: 30 days
Plant with systemic blue mold. Palmer
Blue mold fungicides to have on-hand
• Manzate ProStick (at least
2 applications’ worth)
• Actigard (at least 1 app)
• Azoxy compound OR
Presidio (2 app)
• If Presidio, apply no later
than 7 d preharvest
• Forum OR Revus (2 app)
• If Revus, apply no later
than 7 d preharvest
C. Johnson, VA Tech
P. Bertrand, UGA
Summary
• A proactive approach
will minimize losses to
blue mold
• 6 modes of action are
available to help
manage blue mold
• A typical grower should
have 3-4 different
fungicides on hand for
most effective
management
Sporulating blue mold lesion. Seebold, 2005.
Blue mold lesion on upper surface of leaf.
Questions?