Deep Freeze Nears

January 14, 2009

I'm sure that everyone has been keeping a eye on the weather situation
that has developed. A strong arctic cold front is moving into Alabama
and will be bringing sub-freezing temperatures across Alabama. Lows on
Thursday, Friday and Saturday will be in the teens in many areas with a
few areas slightly above 20 and some single digits during one or more days.

The warm weather the last half of December brings some concern as
plants lost some of their acclimation to cold temperatures. I'm hopeful
that since we have had the opportunity to be cooling down more gradually
prior to these sub-freezing temperatures that damage will not be severe
on most of our fruit crops.

However, we do have locations that due to the higher accumulation of
chill hours coupled with the warm temperatures have begun activity on
the cellular level and in some cases a visible level. Damage would be
expected.

On February 4 to 6th, 1996 we got into the single digits at my location
and observed severe fruit bud damage to peaches. Chill hour
accumulation at that time was close to 900 hours, about 250 hours higher
than where we are this year at the Chilton Research and Extension Center
when this hits.

Not much can be done in our orchards but, it will be very helpful to
decisions that growers will have to make in fertilization and other
practices if we are able to quickly assess the overall situation to
fruit crops following the freeze.

For crops like peaches select shoot samples across the chill hour ranges in your area. Starting at the base of the flower bud cut with a single blade razor mid-way through and observe for browning. Then it's a matter of damaged buds divided by total buds to calculate percent damage.

Considerable variation of damage occurs in fruit trees based on shoot
location and orientation. A good representation would be 2-3 shoots
(12" to 15" long) from 3-4 feet height and 2-3 shoots from 6-8 feet
height. Using 10-12 shoots per variety and orchard location will mean
you might have 150 - 200 buds to cut per combined sample.

Damage to Pistil in Peach Bud

Peach Bud Without Damage
I will put this information together and report back my findings by the end of next week.