News Feed Forums Fruit and Nuts Powdery Mildew appearing on grape clusters only, not on new leaf growth Reply To: Powdery Mildew appearing on grape clusters only, not on new leaf growth

  • Ann-Marie Saunders

    August 1, 2021 at 11:45 pm

    Hello Bill,

    Thanks for your suggestions and I am in agreement with your comments. We have been applying calcium, manganese, copper plus other trace minerals since fruit set.

    The vines are quite vigorous this year, I suspect due to all the rain as well as our efforts (2nd year now with AEA products) in improving vine health. Fruit set and cluster formation went very well with 2 full bunches and in some cases 3 per cane. I was hoping that each vine’s accompanying large and full canopy would be drawing enough photosynthetic energy to support the fruit it has set.

    My concern is that there has been so much vegetative growth this year that the fruit development/sugar accumulation has been slower leaving the berries susceptible for a longer period of time. Today I went through and “hedged” the cane tops that were towering over the trellis on half of the affected Chardonnay block. This was my attempt, culturally, to refocus the vine towards fruit/seed and root growth instead of shoot tip growth so we’ll see what happens as I compare both halves of the block.

    It’s still curious why some clusters on a particular vine, or even some berries on a particular bunch get powdery mildew while other other bunches on the same vine are seemingly untouched. Is the nutrient flow somehow diminished in these cases?

    I am familiar with mineral oil and have used it in the past, more so in the earlier part of the season and it can be effective, especially on foliage. However, since I’ve been including kumulus sulphur in the spray mixes, in order to change to oil I would need to wait at least 2 weeks. By this time veraison will be starting, the grape brix will be a lot higher and powdery won’t be an issue on the bunches. Also, applying oil to the clusters later in season has the potential to interfere with the natural “bloom” development on the berries…we’ve encountered this before.

    Would be great if the vines were always able, at the right times to produce their own oils, lipids, proteins etc. putting themselves in the best position to fend off diseases such as powdery mildew.

    Looking forward to the day!