Sunday, January 3, 2010

Mummies.

Do not be afraid, Vinoland has not been overrun by marauding, undead creatures with names like Kharis, Imhotep and suchlike. Having said that, there are indeed mummies ominously lurking amongst the vines.
My New Year's Day walk through the vineyard was delayed due to rain. Today was sunny, an almost balmy 57 degrees, and was the perfect day to get out in my wellies with the Vinodogs and have a look-see in the vineyard in order to evaluate the pruning to be done. Everything looked good, but now that all the grape leaves are on the vineyard floor the mummies hanging about, in the tangle of last year's wood, could be clearly seen. Oh no...the curse of the bunch rot!
The primary pathogen causing bunch rot is the fungus Botrytis cinerea. Botrytis overwinters in the vineyard in a structure called a sclerotium which is associated with mummified clusters of grapes left over from the previous harvest, and thus can be an important source of inoculum in the spring. In a well-managed vineyard (mine), these mummies are completely removed from the vines at pruning time. The mummies fall to the vineyard floor where soil microorganisms attack the sclerotia and kill them. Yikes, that actually does sound a little scary!
I saw perhaps a dozen such clusters in the Cabernet sauvignon...no big deal. The best control of Botrytis is achieved through good vineyard sanitation and the disposal of grape mummy clusters in the winter dormant period...which is now.
Mummies! Spooky!

12 comments:

Thomas said...

Hello Vinogirl,

I have been under the impression that Botrytis cinerea is airborne and so it is just about always around at fruit set but requires a break in the skin to do its work.

Have I been wrong about that?

Thud said...

Eat em!

Vinomaker said...

It is true that there is often an abundance of spores released by the conidiophores in the spring after overwintering in mycelium masses or sclerotia. The timing of the release corresponds to flowering and fruit set so both wind and rain can promote contact with the grapes. It does require an entry point on the grape skin but that usually does not occur, if at all, until late in the growing season, at least in California. As a precaution, removing infected grape clusters is a useful, but often time consuming task. Thankgoodness they don't do that with the Sauterne and Tokaj grapes!

Vinogirl said...

Thomas: You would be correct...but it just doesn't live in the air, it has to be 'born' somewhere. Botrytis survives the winter by forming sclerotia on the surface, or within colonised plant tissue (in this case mummies are the pefect incubator.) Under certain climatic conditions the sclerotia germinate (sporulate) and produce conidia which are spread by air currents...especially problematic at bloom. It is then that they can infect grape flowers, succulent young stems, and even young leaves. When the sugar content of the berries increases and the skin begins to soften during maturation, the grapes themselves become susceptible to infection, (this again is quite dependent on climatic conditions...fruit first has to split due to osmotic uptake etc.) These physiological stages are however down the road (bloom in these parts approx mid May, maturation Aug/Sept depending on varietal of course.) It is now, winter, that concerns me, and the mummies loitering in the vineyard!

Thud said...

Oh my God...trainspotters!

Vinogirl said...

Thud: Hush up! You just concentrate on drinking the stuff! I'm putting up with your architectural salvage trainspotting afterall!

monkey said...

who left them grapes on there to be wasted???!!!

Vinogirl said...

Blame it on Thud...that was one of his rows!

The villager: said...

57 degrees does sound positively balmy !

Thud said...

Nah...that was one of the geriatric rows.

Wartime Housewife said...

I've bloody done it! I've finally worked out how to comment on Blogger. Small triumphs and all that.

Vinogirl said...

Villager: It was a little unseasonable, I think I'd prefer some of your snow for January.

WH: Congratulations. If there was an award for 'posting persistence' you'd get it. Welcome!