UNIVERSITY OF FLORIDA
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UNIVERSITY OF FLORIDA
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
B CenURGtr Science
7) GIBBERELLIC ACI ACIAPPLICATION SEp 1990
John A. Mortensen
The best time to apply gibberellin is 2 weeks after Orlando Seedless
grapevines reach full bloom. Full bloom is defined as 50% to 70% open blooms
on 50% of the clusters of the vine.
The most commonly found source of Gibberellic Acid is called Pro-Gibb
(Abbott Laboratories). It is marketed in liquid form at 3.91% concentration.
Quantity of concentrate needed
Desired application rate (ppm)
per 100 gal.
* 1 teaspoon of liquid equals approx. 5 ml
Parts per million (ppm) is figured by multiplying the 3.91% by 10,000
(3.91% = 39,100 parts per million). For application to the vines you need
about 100 ppm instead of the 39,100 ppm in concentrated Pro-Gibb; thus you
need 39,100 100 = 391 ml of water for every one ml of Pro-Gibb concentrate.
A gallon of water has 3,785 ml in it, so divide this by the 391 ml of water to
obtain 9.68 ml concentrate per full gallon of water. 9.68 ml is approximately
2 teaspoons (see table above, opposite 100 ppm). This type of figuring can be
used with any concentration of liquid Gibberellic Acid (simply multiply the
percentage concentration by 10,000, etc.).
For increased effect, repeat the application of 100 ppm of gibberellic
acid one week after the first application. This results in larger berries and
softening of any gritty seed remnants in the berries. Do not exceed the
amounts shown as limits on the product label.
Leesburg CFREC Research Report LBG 90-14
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