Frost Puts Produce At Risk

Frost Puts Produce At Risk

Ohio fruit and vegetable crops are at risk for freeze or frost injuries, but growers do have some options to protect them. An extended period of unseasonably warm weather in March led vegetation to reach growth stages more than a month earlier than normal.

From row covers to wind turbines, Ohio fruit and vegetable growers are weighing their options because they still have several weeks to deal with the potential of a frost or freeze event. Fruit crops are in various stages of bloom and freezing temperatures are a concern, says Brad Bergefurd, an Ohio State University horticulture specialist,  noting that the temperature at which fruit buds are injured depends primarily on their stage of development.

"One really cold night could do many growers in," Bergefurd says. "A lot of our fruit growers aren't sleeping well and are a little edgy until we get through April and through the bloom period.

Frost Puts Produce At Risk

"Being as far advanced as we are now in the growing stages, the potential for freeze injury exists, which could result in misshapen fruit or low-quality fruit or the total death of the blossom. You can get frost or freeze injury at 33 degrees."

As flowers swell and expand into blossoms, they become less resistant to freeze injury, he said. Not all blossoms on a tree are equally tender. Resistance to freeze injury varies with plant types as it does between orchards, fruit crops and cultivars. Buds that develop slowly tend to be more resistant.

As a result, some buds can be killed at higher temperatures, while others are resistant at much lower temperatures, Bergefurd says.

The issue is significant, considering Ohio's vegetable crops were valued at $212.1 million in 2010, says Richard Snead, an agriculture statistician with the U.S. Department of Agriculture National Agricultural Statistics Service's Ohio Field Office in Reynoldsburg.

The state's fruit and nut crops were valued at $64.5 million during that same time period, which is the most recent data available, Snead said. In 2010, Ohio's apple crop was valued at $26.8 million, strawberries at $9.5 million, peaches at $9.4 million and cabbage at $6.7 million.

The financial impact for growers could be devastating, Bergefurd says.

"We could lose an entire crop or have a reduced crop load depending on when or if a frost or freeze happens," he says.

But there are measures growers can take to protect their crops from frost or freeze, including:

* Sprinkler Irrigation - Growers can use sprinklers to prevent freezing injury by using the energy that water releases when it freezes and changes from a liquid to a solid, to keep the temperature in the ice right at the freezing point - 32 degrees. As long as growers keep the ice wet, the ice temperature will stay at 32 degrees. If the ice dries out and water starts to evaporate from the ice, the ice will get colder than the air temperature as it evaporates.

* Row Covers - Growers can use row covers to shield plants from the effects of cold and wind. The covers can add an extra 5 to 10 degrees of warmth under the blanket to keep frost off tender blooms or blossoms.

* Tractor-mounted Frost Control Machines - Growers can mount large fans with propane heaters onto tractors and drive throughout the orchard to circulate warm air through the orchard by blowing streams of hot air to both sides which are aerodynamically clean, without turbulence so they penetrate the cold air mass, forming a warm air layer at the height of the trees or crops

* Wind Machines - Growers can use wind turbines with 20-foot propeller blades stationed throughout the orchard to circulate air and raise the temperature in orchards by circulating warmer air down to crop level through the orchard.

* Fog - Growers can create fog using a smudge pot as a frost-protection method. The idea is to duplicate the greenhouse effect, using a "cloud" to blanket the crop area to decrease radiative cooling and stop the plant from dropping to the critical temperature.

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