GREY ROT Flashcards
Also known as
Vaalrot
Causative organism
Botrytis cinerea
Where does it occur?
all viticultural regions excepts for dry regions
When do you see Grey rot in the vineyard?
- rain during the ripening stage
- followed by cool periods
- ten days, bunches
How does grey rot work?
- moisture are lost during evaporation and the berries then shrink.
- colour change from light to golden brown
- berries shrivel and change into a soft raisin
- the sugar concentration in the sap increases
Dry hot periods after infection?
- contamination limited to only a few berries on a bunch
- these berries shrivel, turn brown or toughen
or the infection is followed by the development of other harmful secondary organisms
Why is the severity of botrytis lower in warmer, dry regions?
These areas have low relative humidity and this is restrictive on the infection
Factors that determine onset and course of infection?
-cultivar resistance
-cultivation practices
vine and bearer spacing, trellis system, canopy management - suckering, leaf thinning
How progressed to noble rot?
cool conditions, high RH but not wet conditions. Can make wine (late harvest or noble wines).
fine cracks in skins and bunches, they are left on the vine until late season
How is progression regulated
climatic conditions
How does grey rot happen?
hot, moist conditions
How does botrytis spread?
hibernation occurs through the formation of specific structures in infected shoots and berries and dead organic material in the vineyard.
Favourable conditions promote sporulation
These spores land on berries and undergo successful germination in the presence of free run-off and eventually penetrate the skin
Infection during flowering
pathogen remain until the onset of ripening, chemical control should be applied in areas with conductive climatic conditions)
First signs of grey rot
- during ripening
- light brown and dull skin discolouration
- little pressure will cause the skin to slip away from the underlying tissue
Later harvest wines
dry autumn periods
