On some of my largest, older cab franc leaves (basal), I am noticing what appears to be a slight burning on the tips of the leaves. Otherwise the leaves look good. Good color. Good size, etc.
Any ideas to suggest what might cause this? A deficiency of some sort? "General Viticulture" has a paragraph that suggests high sodium, but I'm not sure how that would happen.
Regards Jeff Chorniak
Hi: Browning at the edges of grape leaves usually signifies potassium deficiency. I would spread about l/2 pound of potassuium chloride per plant. It should be applied in a straight line (concentrated) about one foot on each side of the trunk. It can be applied any time. Potasium chloride is usually sold at the fertilizer distributors as potash muriate.
Joe.
If potassium deficiency is the problem, wouldn't potassium phosphate or potassium nitrate be more appropriate? I'd expect that the nitrogen or phosphorus would be more useful to the plants than chloride.
Tom S
Jeff,
I had a similar problem where the leaves took on a purplish outline as well. Like Joe, I also figured on potassium deficiency, and saved my fireplace ashes that winter. A large cupful scattered under each vine every few years keeps the problem at bay. It works for the small vineyard.
[Thought I posted this several days ago. Sorry.]Jeff,
If the burn is only at the tip of the leaf I would suspect your fungicide spray was mixed too strong. The spray has a tendency to flow down to the end of the leaf and if it is too concentrated , will burn the tip. I also think it's too early for potassium deficiency to show but I don't know where you live. Also, if it is potassium deficiency, mulching the vine after giving it ALOT of water will help the roots absorb the potassium out of the soil. THe vine like all plants needs moisture to get the nutrients out of the soil. It's why potassium deficiency is more likely on sandy soils. I have basically eliminated any potassium defifiency symptoms from my vineyard just by making sure I mulched the area of the vineyard that was driest which also coincided with P symptoms. I didn't use any P fertilizer or ashes.
Hope this helps.
Bob
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