Let's talk about Botrytis!

Monday, July 9, 2012

Hi Folks!

Thanks to everyone who came out to a great evening vineyard walk on June 28th, and most of all thanks to our host Gaspereaux Vineyards.  Stay tuned, the next vineyard walk is in the works for later this month! 

I have gotten a few calls about Botrytis Bunch Rot control and thought I'd give a little bit of information here on the disease and the products that are currently registered.  Botrytis is caused by several different organisms but Botrytis cinerea is the most common in regions with cool to moderate temperatures.  Leaves may show symptoms (large, irregularly shaped, brown lesions) following periods of heavy rain in the spring.  The first diseased berries are usually visible shortly after veraison, and once established infections can spread quickly from berry to berry during the pre-harvest period, especially in tight clustered varieties. Varieties like Seyval Blanc and some of the vinifera varieties may be especially susceptible.    There's a good factsheet from BC Ministry of Agriculture which rates the susceptible varieties, click here to see it!  

It is recommended to apply fungicides to prevent Botrytis bunch rot at the following timings:  Late Bloom; Pre-bunch Closure; Veraison, and Pre-Harvest (days to harvest will depend on product’s PHI).  We are at or just past the 'late bloom' stage and quickly approaching the ‘pre-bunch closure’ timing.  The application at 'pre bunch closure'  is a very important application as it is the only opportunity to ensure that all of the berry surfaces are protected before the cluster closes!!!  There are a number of products registered for Botrytis in grapes and I've listed them in the table below.  Make sure you rotate products from different chemical groups for resistance management purposes.  

Botrytis Bunch Rot
Direct spray to the fruiting zone of the grape canopy.  Use at least 1000L of water to provide good coverage.  Susceptible cultivars, vinifera and hybrids may require more than 1 application during the bunch closing period.  If late summer, early fall weather conditions are wet and humid, additional fungicide applications may be required to control botrytis during this period (especially important for late harvest for ice wine)
Fenhexamid (group 17)
Elevate 50WDG
Use Agral 90 at 200ml/1000L of water (.02%v/v) with Elevate in the tank.  Do not apply if rain is expected within 6hrs after application. 
Iprodione  (group 2)
Rovral 50WP
Do not apply more than 2 times per year.  Alternate with other fungicides.
Cyprodinil (group 9)
Vanguard 75WDG
Do not apply with 30m of lakes, streams, and ponds. 
Boscalid + pyraclostrobin (groups 7 & 11)
Pristine WG
420-735 g/ha
Use high rate when disease pressure is high.  Do not apply more than 6 applications per growing season.  Do not apply to concord Fredonia and like cultivars due to possible injury.  21 day REI for hand labour tasks
Pyrimethanil (group 9)
Scala SC
Maximum of 3 applications per year.  Alternate with other fungicides. 
Bacillus subtilus (group 44)
Serenade Max
3-6 kg/ha
Use the high rate and short spray intervals when conditions favour disease development.  Complete coverage is required use a minimum water volume of 500L/ha
Cyprodinil + Fludioxanil (groups 9 & 12)
Switch 62.5G
775-975 g/ha
Begin applications at early bloom, on additional application may be made at berry touch, veraison, or preharvest.  Application interval is 21 days.  For resistance management do not apply more than 2 consecutive applications of fungicides from the same class (group 9, 12) in a season, and then alternate with two applications of a fungicide with a different mode of action. 7 day PHI.  2 day REI for hand labour tasks. 

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