Evaluating Blueberry Pollination

Many factors can detract from good pollination: poor weather, unhealthy or poorly managed bees, beekeeper fraud, and pesticide misuse, among them.

Following is some information on bee pollination from Dr.
Gary Pavlis of Rutgers Cooperative, quoted in the SMALL FRUIT IPM MESSAGE, MAY 13, 1999, Prepared by Sonia Schloemann , UMass Extension Small Fruit Specialist:

"In fields where poor pollination is feared, because of poor bee activity,
visual symptoms should be checked before investing in gibberellin sprays to
promote set of berries. If a large percentage of flowers are turning
purple instead of dropping, while still white, this is a sign of poor
pollination. Lack of rapid growth of the ovaries and their discoloration
also are indicative of pollination failure. Already, "re caps" are
beginning to fall from Weymouth and Earliblue bushes. This is a
designation given to unpollinated berries which turn reddish and/or
yellowish and then drop. A small amount of drop is expected and occurs
even with good crops. If your estimate of the number of unpollinated
flowers (purple flowers plus red caps) is less than 20 percent it may not
be profitable to spray with gibberellin. It is almost always profitable to
use this spray on varieties which are not attractive to honeybees:
Earliblue, Coville, Berkely, Stanley, 1316-A and Concords. The best timing
is when two thirds of the blossoms have dropped. This spray (Pro Gibb - 80
oz. per acre with sticker, or Gibrel) is absorbed through the skin of the
ovary making it unnecessary for the flower and pistil to be attached.

The following guidelines may be helpful in determining whether Gibberellin
is needed:
1. Bee activity has been consistently poor. Unless at least an
average of 20 bees can be seen actually entering flowers in a 10 minute
period, pollination will be below normal.
2. Flowers are hanging for long periods and turning purplish (wine
colored) before dropping. When pollination is progressing well, blossoms
drop while still bright white in color. A vigorous shaking of canes should
cause a shower of white corollas dropping to the ground.
3. Ovaries are rapidly swelling soon after flowers drop and are
staying green -- not turning yellowish or reddish in color."

Article by Jim Cane, on rabbiteye pollination with solitary bees.

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