Georgia’s unpredictable winters and late freezes can prove
deadly to blueberries and the
more than 200 Georgia farmers who depend on them.

Blueberry plants flower in late February to March. That’s
usually past south Georgia’s
freeze-danger point, said Scott NeSmith, a University of Georgia
horticulturist.

“But in one out of every eight or 10 years, there will be a late
freeze that causes
significant damage,” NeSmith said.

“Blueberries are like peaches,” he said. “You can’t cry and do
it over. If they don’t
bear fruit, you just end up with a pretty green plant and zero
income until next year.”

After a late freeze last winter, though, NeSmith and UGA
extension scientist Gerard
Krewer showed growers something that can let them rest a
little easier this year.

They told growers to use a growth regulator called gibberellic
acid on their
freeze-damaged blueberry flowers. As a result, nearly 4 million
pounds of blueberries
survived the late freeze.

G.A. is a natural plant hormone first used in the early ’60s to
improve fruit set.

“The drawback to G.A. is that it’s inconsistent,” NeSmith
said. “It had basically been
sitting on the shelf for 30 years because everyone viewed it as
unreliable.”

In the early ’90s, NeSmith and Krewer developed a spray program
for applying G.A.
to blueberries with consistent results. By 1995, their efforts
had helped Georgia
blueberry production grow from 3.5 million pounds per year to 13
million pounds.

In 1993, farmers reported they’d saved fruit from a late frost
after applying G.A. In the
past, blueberry growers had little hope of saving their crops
after a late freeze.

Based on the growers’ reports, NeSmith and Krewer began testing
the benefits of using
G.A. on freeze-damaged flowers. Using growth chambers, they
subjected plants to low
temperatures during flowering periods. Then they applied G.A.

“We needed to find out the lowest temperature limit at which
G.A. will work,”
NeSmith said.

They found out G.A. works when applied after freezes from 25 to
31 degrees.

“Natural pollination declines at these temperatures,” NeSmith
said. “But G.A. can take
over and set fruit from freeze-damaged flowers. But below 24
degrees, we know that
not even G.A. would help.”

Before studies were complete, the 1996 late freeze hit. NeSmith
and Krewer were
forced to make a decision.

“Before we knew everything we wanted to, we had to tell people
to use it,” NeSmith
said. “We had to take the chance. We just decided whatever we
get, we get. It had to
be better than losing the entire crop.”

It was. Most south Georgia blueberry growers credit NeSmith,
Krewer and gibberellic
acid for saving 3.5 million to 4 million pounds of berries with
a value of $5 million.