Grapes brown blotches (forum)

Alvine starts with ...
Wondering if someone can solve my problem. I sprayed my Red Globe vine with wettable Sulphur before budburst, then Phos Acid since fruiting. Yet the bunches are starting to display brown blotches like on the attached pic, that eventually take over the fruit. The affected area of the fruit shrinks inwards, like the moisture is being drawn out of it until all that's left is a shriveled up "mummy". There is no sign of fungal presence on the leaves or the shoots, which makes me think more of some deficiency. The soil here is nothing but sand and I've been using a basic fruit fertilizer. Maybe not enough?
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Picture: 1

Time: 26th November 2013 2:45pm

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Original Post was last edited: 26th November 2013 2:44pm

About the Author Alvine
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yrt says...
Botrytis, I think.

Time: 26th November 2013 4:32pm

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About the Author yrt
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Alvine says...
Thanks for your thoughts yrt.
I'm not sure it's Botrytis though. All the info I find about Botrytis eventually shows a "mildewy" growth on the fruit and true "bunch rot" formation, whereas this starts on the outside of the affected fruits and seems quite random in occurence. Hence my suspicion of some mineral deficiency, perhaps, maybe...

Time: 26th November 2013 5:58pm

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jakfruit etiquette says...
How about spray injury from phos acid, sunburn, or combination, ie water drops act like a lens on the fruit skin ??
Is there any pattern to the damage, ie all on the sun side, or from the direction you spray ?

Time: 26th November 2013 9:02pm

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About the Author jakfruit etiquette
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Diana says...
It looks like sunburn to me- the same side of each one is cooked (then rots, infecting the rest of the fruit).

Diana.

Time: 26th November 2013 10:36pm

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About the Author Diana
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Alvine says...
Thanks Jackfruit & Diana. No relationship with sun exposure and not consistent with Phos acid spraying. Last year, when it seemed the vine might actually be ready to produce for the first time after about 12 years of total neglect, I fertilized it after a few bunches had formed. It then put out quite a few more. I never treated it and all the "secondary" bunches got affected with these blotches and dropped, while the handfull of original ones got to maturity. By the end, the leaves were showing signs of powdery Mildew. So this year, I really looked after it. Bear in mind, this is Perth: very dry and probably the poorest soil anywhere in Australia.

Time: 26th November 2013 10:54pm

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Mike Tr says...
Chemical burn, sun burn and wind burn can all look like that. Whatever it is heavy mulching, macro and micro nutrient without chlorides and an organic fertilizer would help.

Time: 26th November 2013 11:10pm

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Alvine says...
I've given it another dose of fertilizer and I'll keep an eye on it. Thanks again to all who offered advice. If anybody else believe they have a definite, feel free!

Time: 27th November 2013 10:45am

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Alvine says...
Update for those interested: It was suggested it might be Potassium deficiency so I applied a Potash foliar spray about one week ago. And the problem has shown no progression since then so I think I've got it solved. Thanks again to all who contributed.

Time: 4th December 2013 11:15am

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amanda19 says...
That's interesting...I was going to say sunburn or boron deficiency myself...
What do the leaves look like tho..?


Time: 4th December 2013 5:57pm

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About the Author amanda19
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Alvine says...
Hi Amanda, Definitely not sunburn. Boron? I guess it could be though the fertilizer I had been using did contain trace elements. Perhaps not enough in view of the sandy soil.
Looking hard, I did find leaves with the border starting to die and some with yellowing between the veins. But like I said, I had to look hard. I imagine the problem with deficiencies, is that they combine, making it hard to diagnose accurately. But it looks like I'm on top of it! Thanks again.

Time: 6th December 2013 4:13pm

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