Managi ng tobacco blue mold in 2015: a proactiv e fungicid e approac h ANR Agents’ Special...
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Transcript of Managi ng tobacco blue mold in 2015: a proactiv e fungicid e approac h ANR Agents’ Special...
Managing
tobacco blue mold
in 2015:
a proacti
ve fungici
de approa
chANR Agents’ Special Training
Emily Pfeufer1 and Bob Pearce2
University of KentuckyDepartments 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 Seebold, 2006
Subtle yellow-orange spots on tops of leaves
Blue sporulation on underside of leaf
Pathogen biology
Modified from C.E. Main, North Carolina State University.
• Peronospora tabacina, a water mold pathogen
• 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
As many as 1 million spores!
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
1. Prevention – occurs prior to pathogen introduction to crop
2. Monitoring & diagnosis – scout for early, accurate disease detection
3. Cultural and chemical management – disease has already arrived, and steps are taken to reduce its impact
Seebold, 2005
Blue-gray sporulation on underside of leaf
Preventative tacticsIn the floatbed: starting resistant varieties, regular mowing with effective clipping removal, floatbed fungicide applications
At transplant: crop rotation, preplant fertility, plant spacing, at-transplant fungicide applications
In season: weed management, sucker control, fungicide applications
Blue mold throughout transplants
Seebold, 2006
PalmerEarly lesion
Resistance to fungicides
..... ....
.. .
Natural population of blue mold fungus in environment
Fungicide application .
. .
Fungal escapes from fungicide
.. ... .. ...
Spores released from escapes, causing new infections
Fungicide application
.. ..
More resistant fungi in population
.. ... ....
. . .. .
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 todayProduct 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
• 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
More about Actigard
Ivors and Mila
• 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?