Friday, September 7, 2012

Home stretch!

I think many of you are either harvesting or getting ready for it.  We harvested our Chardonnay and Merlot yesterday. (Of course most of them are damaged due to our fungicide trial, but there are a few left...)

It seems like we are expecting some rain over this weekend.  The question is what to do in terms of the last minute disease management.  If you have clean vineyard without major rot issues, and you only have only a few days to go, you probably not need to take action. 

If you have clean vineyard, but you still have more than 10 days to go, it may depends on the condition of the berries.  If you notice any wounding on berries (by birds, hornets, sun damage, etc), then you may want to consider captan before this rain because many of late season rots take advantage of these wounds.  If you have nice clean berries, then, you may able to wait and see.

If you have some rot issues, again captan is a nice tool.  It is effective against variety of pathogens, and it has a very short PHI (0-day) (but remember that REI is 48-72 hours, depends on the formulation).

If you have some downy mildew issues, it is probably a good idea to mix a phosphonate (phosphorous acid, such as Prophyt, Agri-Fos, etc, 0-day PHI) with captan.  Sine we have experienced a frequent rain events and humid nights that were very conducive for downy mildew development in the past few weeks, please make sure to scout your vineyards for downy mildewIt tends to appear on younger leaves on the top of the canopy first.  You may or may not see yellow "oil spot" on the top surface of the leaves, so, make sure to flip leaves over to look for downy mass of spores.  I know you are probably focused on your clusters now, but leaves are also important!  Downy mildew cannot get to berries at this time of the season, but heavy infection on leaves can defoliate leaves.  Your vines will need these leaves to mature berries and also to store carbohydrate for winter survival. 

The vine on the right hand side is defoliated due to lack of protection against downy mildew.  You don't want this to happen to your vines!

Monday, September 3, 2012

Today's disease risks

After yesterday's post, Winchester area received measurable rain.  ;)  The estimated wetness duration was 14 hours with 72F.  It was long and warm enough for Botrytis and Downy mildew.  

It looks like we are expecting a few more rain events in next few days due to the effect of a tropical depression Issac.  We will see...

Sunday, September 2, 2012

disease risks from today's rain

We are having a very humid day today in Winchester area.  There have been several rains passed since early morning, but only a few of them were enough to be recorded at weather station (it need to be more than 0.25 cm/0.01 inches).  Plus, even though the RH has been high, it was not higher than 70% in most of the day.  Thus, if anything, there were a low risk for downy mildew infection event.

I imagine many of you are preparing for harvesting now.  I am hoping not seeing too many rains!