Presentation on theme: "Botrytis cinerea Dealing with Grey rot infection."— Presentation transcript:
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 - 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
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.
“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
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 DevelopmentLaccase Activity Units/ml Healthy grapes0 Full rot with no Conidiophores1-2 Conidiophores15-20 Shriveled and rotted grapes20-70
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 1/3 rd 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…