Download What is Botrytis cinerea?

Botrytis cinerea
Dealing with Grey rot infection
In the Vineyard
• Outline the pathogen
• Review the disease cycle
• Identify Control and management strategies
In the Winery
• What are the changes in fruit composition after a
Botrytis infection?
• What impacts can these changes have on the must
and wine produced?
• What can we do to minimize the damage?
What is Botrytis cinerea?
• Necrotrophic fungus
• Causes damage to its host to obtain nutrients
• Has a variety of hosts and is considered Ubiquitious
Primary Infection - Sources of Innoculum
• Most inoculum develops from over-wintering in
vineyard material.
Inoculum can come from:
• Dried fruit structures called mummies.
• Within dormant buds, foliage, or bark.
• Dark, dried, hardened, disc like, structures called
Sclerotia. (Sclerotia may be present on the on the
foliage, canes, or mummies)
Infection
• Given the right conditions, both mycelium and sclerotia
will sporolate
• Most spores are asexual conidia.
• Conidia have the ability to germinate between the
temperatures of 1-30 degrees C.
• They also require free water, or in the absence of free
water, a relative humidity of greater than 93%
Infection
Infection - Continued
Penetrates the host either by passive or active means.
Passive
• stomatal openings
• wounds
• previous sites of infection by other pathogens
Active
• enzyme mediated; enzymes break down host tissue
Disease Cycle
Symptoms - Leaves
V-shaped area of dead brown tissue; yellow margins.
Symptoms - Early Shoot Infection
Infected shoot turns brown and dries out
Infection - Flowering
Blossoms may dry out or rot.
At the end of bloom, withered caps and stamens may be
seen; berries may abort.
Early berry/Bunch infection
• Rachii and pedicels targeted at flowering. This can
ultimately lead to the inoculation of young berries.
• Inoculum can also remain trapped within the cluster
after bunch closer.
Activation of Latent infection
Why do latent infections activate?
• Reduction of fungi-toxic compounds
• Foliar nitrogen applied post verasion
• Conditions
Extended periods of humidity
Late Season Infection
• Disease cycle can occur every 3-4 days
• Prolonged wet conditions encourage continued
infection
• At 15 degrees, wetness lasting 15-20 hours may be
enough for infection to occur.
• Damaged berries an easy target. Disease can spread
from there.
Disease Cycle
“Noble Rot” vs. “Gray Rot”
• Latent infections become active near the Skin
• Fungal mycelia reach the skin. Hyphae perforate it.
• Cells greatly modified and the berry loses its ability to
regulate hydration.
“Noble Rot” vs. “Gray Rot”
Noble Rot
• If the conditions are warm and dry, the berry begins to
dehydrate.
• High osmotic gradient causes fungal growth to cease
Gray Rot
• If the conditions are wet and humid, the berry can not
dehydrate.
• Fungal growth continues and spreads.
Prevention Strategies?
Vineyard Sanitation
Promote injury reduction
• Keep powdery mildew in check
• Bird control
• Insect control if necessary
Promote an open canopy
• Vigor reduction
• Leaf removal
• Shoot positioning
Prevention Strategies?
Assess varietal susceptibility
• Skin thickness
• Cluster compactness
Chemical control - Timing, Treatment, Technique
• Spray at the right time
• Use appropriate chemicals
• Ensure adequate spray coverage
Chemical Control
Chemical Control
• “Lance” prior to flowering
• Chemical spray 80-90% capfall
• Chemical spray (different group) pre-bunch closure
• Saranade max at verasion?
• Rovral as pre-harvest if required.
Rotten Grapes in the Winery
The year turned ugly. You have Gray rot in the
vineyard and want to salvage something.
Depending on the amount of rot in the harvest, a sound
wine may still be produced.
…Wait a minute…why worry anyways?
What does Botrytis do to my fruit?
Botrytis SEVERELY changes fruit composition:
• Consumes sugars
• Degrades grape acids
• Degrades grape proteins
• Consumes Nitrogen and Vitamins
• Produces anti-biotic compounds
• Produces gluconic acid
• Produces mucic acid
• Produces polyols
• Produces glucose polymers (glucans)
• Produces many destructive enzymes
Major Consequences – Enzymes Produced
Oxidize aromatic compounds and aroma pre-cursors
• Esters hydrolysed
• Terpenes freed and then oxidized
• Thiols bound or destroyed
Laccases oxidize Phenolic substances
• Browning in white wine
• “Oxidative Breakdown” in red wines
Laccase is fairly resistant to SO2 and Bentonite
Major Considerations
Just how rotten is the fruit?
• Easy to see on White grapes
• Not so easy on Red Varietals
• Botrytis may be active inside the berry even though no
rot is seen the outside
LACCASE can be monitored
• Test kits that quantify “Laccase units”
• or can do simple test…
Dealing with Laccase
More rot means more Laccase:
Botrytis Development
Healthy grapes
Full rot with no Conidiophores
Laccase Activity
Units/ml
0
1-2
Conidiophores
15-20
Shriveled and rotted grapes
20-70
Dealing with Laccase
Flash pasteurization or Thermovinification
• Heat the must to destroy the enzyme
Addition of Enological tannins
• Combine with the enzymes to fine them out
Protection of the must using SO2 (PROPER USAGE)
• More SO2 is required than if the must were clean (10g/hL?)
• Many more molecules bind SO2 in must made from rotten grapes
• Free SO2 protects wine from Oxidative breakdown
• Ascorbic Acid can compliment SO2 treatment
Maintenance of free SO2 eventually destroys enzyme
Laccase - White Wine Considerations
Minimize Mechanical damage
• Whole bunch press
Cooling
• Cooling juice lowers Laccase activity
(Cryoextraction?..)
Inert gas protection – minimize O2 dissolution
• Dry ice at press pan and while settling
SO2 solution (10g/hL) mixed in properly to juice as it is pressed
(ascorbic?)
Check for potential browning (Laccase activity) while juice is settling
Laccase – Red Wine Considerations
Good SO2 addition while filling tank
• Want homogenization
Minimize pre-ferment maceration
Yeast Inoculation shortly after tank is filled
• Bad idea to Co-inoculate?
Check for oxidative breakdown potential:
• If wine sensitive to breakdown run off early
• Addition of SO2 at run-off
Ferment Considerations - Nutrition
Botrytis may have consumed much of the Nitrogen
• Test for Yeast Assimilable Nitrogen(YAN)
• If below 140mg/L  supplement near the end of 1/3rd ferment
Add Nitrogen depending on the Brix level of the must
(YAN table)
Use a product that also adds vitamins (Thiamine and Pyridoxine)
**Remember healthy yeasts are best. Oxygen during
development and fermentation.
Ferment Considerations
Stuck Ferments can occur
• Not enough Nutrients
• Competition with other Yeasts
• Presence of anti-microbial substances
• Build-up of other substances toxic to yeasts (fatty acids)
• Possible late season vineyard spray contamination
A stuck ferment can be a big issue!
Ferment Considerations – Stuck Ferment
Monitor your ferment
• Stuck ferment can usually be predicted…
What can be done?
• Yeast hulls or inactivated yeasts
Still no go?
• Restart Ferment…
• Red must should be pressed and lightly sulfited
• White must can be lightly sulfited as well.
• Bacterial contamination not wanted at this time!
Lysozyme is also an option…
Other issues?
Clarification problems are likely
• 1,3- and 1,6- glucans are produced
• These molecules aggregate together (ethanol in wine)
• Filterability is dramatically reduced
Test for filterability
• If needed add enzyme to break down glucan molecules
Other instability
• Mucic acid will be present up to 2g/L
• Can form Calcium Mucate
• If de-acidifying using Acidex or CaCO2 be careful
• may precipitate out of the wine at a later date…
Questions?