N E W Z E A L A N D W I N E G R O W E R S FA C T S H E E T
MANAGING BOTRYTIS
KEY NOTES
• Botrytis is the major bunch rot affecting winegrapes in New
Zealand.
• Botrytis fungicide residues are persistent and detectable in wines.
• Controlling Botrytis requires an integrated approach involving
vigour control, canopy management, fungicide application and
reduction in Botrytis inoculum.
CONDITIONS FAVOURING BOTRYTIS
Botrytis in Sauvignon Blanc (photo by Tim Robinson,
Agrivet Services Ltd).
There are two key periods when Botrytis infections are likely
to occur: (1) flowering to bunch closure, when Botrytis infects
senescing flower parts (such as flower caps and aborted berries);
and (2) veraison to harvest, when ripening berries become
susceptible to infection. Botrytis infections are favoured by warm
wet weather. Disease pressure tends to be higher and more
frequent in northern and western areas of the North Island, with
lower pressure in eastern areas. Disease pressure is generally
lower in the South Island, although Botrytis outbreaks may occur
following warm rainfall at the key infection periods.
MANAGING BOTRYTIS
Slipskin Botrytis in Chardonnay (photo by Trevor Lupton).
Botrytis control requires an integrated approach involving vigour
control, canopy management, fungicide application and reduction
in Botrytis inoculum.
Reduce Botrytis Carryover from one season to the next by pruning
out and mulching the previous season’s rachii (bunch stems),
petioles and tendrils.
Avoid High Vine Vigour: swards such as chicory and fescue reduce
growth of overly vigorous canopies. High nitrogen will increase the
risk of Botrytis: nitrogen use in lower vigour sites should be on a
“little and often” basis.
Maintain an Open Canopy: dense canopies reduce spray
penetration and delay drying after rainfall. Use shoot thinning and
leaf plucking to maintain 70% bunch exposure from pre-bunch
closure to harvest.
Use Water Sensitive Papers to confirm sprayer coverage of
bunches at the key Botrytis fungicide applications of 80% capfall
and pre-bunch closure.
Watch the Weather: Botrytis fungicides are protectants, which
should be applied prior to an infection period.
BOTRYTIS FUNGICIDE APPLICATIONS
JUNE 2010 | NZBOT100 | BOTRYTIS MANAGEMENT
Flowering to pre-bunch closure
The two key application timings are 80% capfall and one month later
at pre-bunch closure. Applications at these growth stages target
senescing flower parts and aborted berries following flowering. For
recommendations on fungicides, refer to NZ Winegrowers Export
Wine Grape Spray Schedule, Sustainable Winegrowing Guidelines,
N E W Z E A L A N D W I N E G R O W E R S FA C T S H E E T
Botrytis on left of bunch, with sour rot on right (photo by
Tim Robinson, Agrivet Services Ltd).
and your winery as fungicide choice may be determined by preharvest interval for specific markets and/or resistance management
strategies, and changes occur from time to time.
Bunch closure to veraison
Following bunch closure, berries are relatively resistant to Botrytis
infection, and hot dry summer weather conditions are generally
unfavourable for infection. If warm wet weather occurs, consider the
use of a fungicide such as captan or a “soft” fungicide (described in
the following section).
Veraison to pre-harvest
Berries become more susceptible to Botrytis infection as ripening
progresses. Conventional fungicide options at this stage are limited
due to the likelihood of residues being detected in the finished
wine. Products based on biological control agents, such as Bacillus
spp, Trichoderma spp and others, chitosan or fatty acids offer
Botrytis control without risk of residues. These products are likely
to be less effective and of shorter persistence compared to the
fungicides available at flowering to pre-bunch closure.
Recently several products based on chlorine dioxide, chlorine
bromide or peracetic acid have been registered for Botrytis
control. These products have a “sanitiser” effect on Botrytis, killing
on contact but having no residual effect or residues. Previously,
Potassium metabisulphate (PMS) has been used in this way.
SLIPSKIN BOTRYTIS AND SOUR ROTS
Slipskin Botrytis is an aggressive infection that can occur following
warm wet weather when Brix levels are high and the crop is within
days of harvest. Symptoms include blotchy marks on the skin of
the fruit and infection developing from the pedicel (point of berry
attachment to the bunch stem) with the skin sloughing off when
rubbed. Berries often fall off when the vine is shaken or harvested.
Early detection of slipskin and prompt harvest is advisable.
OTHER SOURCES ON THE WEB
• New Zealand Winegrowers
www.nzwine.com
• Sustainable Winegrowing New Zealand
www.nzwine.com/swnz/
• Marlborough Wine Research Centre
www.wineresearch.org.nz
• HortNet
www.hortnet.co.nz/
Contact:
New Zealand Winegrowers
www.nzwine.com Telephone 09 303 3527
JUNE 2010 | NZBOT100 | BOTRYTIS MANAGEMENT
Sour Rots are associated with micro-organisms other than
Botrytis, such as the fungus Rhizopus, yeasts or bacteria, such
as Acetobacter. Symptoms include a vinegar smell, and infected
berries may be an orange-red colour. Sour rots may infect bunches
following Botrytis, bird or wasp damage. In varieties with tight
bunches, sour rots may develop from berries rupturing as bunches
become over tight. As with slipskin, sour rot control is difficult.
Prevention of bird damage and the use of varieties and clones with
looser bunches is recommended.
ACKNOWLEDGMENT
This fact sheet was written by Trevor Lupton, Lewis Wright Valuation & Consultancy Ltd., and includes information gained by the
Grape Futures Project, co-funded by the Sustainable Farming Fund
and Sustainable Winegrowing New Zealand.
DISCLAIMER While care has been used in compiling this fact sheet New Zealand
Winegrowers gives no prediction, warranty or assurance in relation to the accuracy
of or fitness for any particular purpose, use or application of any information
contained in this document. To the full extent permitted by law neither New Zealand
Winegrowers nor any of its employees shall be liable for any cost (including legal
costs), claim, liability, loss, damage, injury or the like, which may be suffered or
incurred as a direct or indirect result of the reliance by any person on any information
contained in this document.
© New Zealand Winegrowers 2010. All Rights Reserved.