Hello again, Alex.
Well, your question proved to be rather an interesting one to
research. As you'd probably discovered before you came to us, the
gardening sites are of little use; offering all the advice in the
world about roses and hostas (or peas and carrots) but little to do
with grapes of any kind.
Fortunately, the "Superior Seedless" variety you are growing comes
with an unseen extra which is rare in the agricultural world:
In my efforts to locate an authoritative source for information, I
tracked down the company which developed and owns the "Superior"
seedless cultivar. They are Sun World International, who also
developed the popular "Red Flame" seedless grape (we see "Red Flame" a
lot, here in Canada). I sent an e-mail to their customer service
feedback address, outlining your problem.
I received a reply today from David Marguleas of Sun World. To my
surprise, he informed me that the company maintains a technical
support staff for just such issues. Their support people correspond
directly with the grower to determine the cause of their problems, and
to suggest the most effective solutions available.
Mr. Marguleas asked me to pass along his e-mail address to you.
Simply send him a message, letting him know that you're "the Google
Answers guy," and that you're in Israel. He, in turn, will connect
you with a support person responsible for growers in your region. His
e-mail address is:
Initially, I'd tried various combinations of keywords such as "grape
cultivation" "troubleshooting" "FAQ" "tips" etc; but to little effect.
Searching on "Superior Seedless" and "cultivar", however, brought me
to Sun World's website after exploring a few false trails. Their main
site is found at
In the past, I've combed through mountains of contradictory advice on
a wide variety plants. It's been a chore, at best, and deciding which
information was reliable was sometimes difficult. I'm happy I was
able to locate authoritative assistance for you, and who better than
the developers of the cultivar?
Good luck with next year's crop!