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WI fruit growers battle freezing temperatures

Gloria Hafemeister
Correspondent
These unopened blossoms on this Macintosh tree were spared the impact of frost during the cold snap last week.

Last week’s freezing temperatures presented a scare for fruit growers in the state, particularly in the southern third of Wisconsin.

Steve Louis, a fifth generation owner of Oakwood Fruit Farm at Richland Center is the president of the Wisconsin Apple Growers Association. He says, “We did see quite a bit of damage in our orchard this weekend. Some areas we have seen about 40% damage and other areas we are seeing as much as 90%. Not much we could do to prevent or protect the blossoms from the damage.”

His family’s farm is diversified and besides raising 20 varieties of apples they also have an on-farm store with apple products, grapes, homegrown grass fed beef, cheese and sausage.

Laura Tisch of Munchkey Apples, Mout Horeb, says, “Our apple tree blossoms were at the beginning of pink stage when temperatures were very low on Saturday morning. Temperatures below 28 degrees is when you will start to lose some flowers.”

She notes, “We have a frost fan that circulates the air through the orchard and can bring the warmer air back down that rose up in the evening. Our frost fan ran all night and I really feel that it made a big difference. To lose some flowers is okay because a lot of the time the trees have too many fruit and we are removing them so we can have better quality fruit and not stress the trees out by over cropping them.”

She adds, “As of now we are still planning on having our Wisconsin Apple Grower Association field days here unless things change due to COVID 19.  I am sure if we cannot have it here this year, we can have it in 2021." 

Tisch says they plan to discuss the use of a frost fan, picking machines for harvest and hedging the farm's apple trees to make a fruiting wall.

Amaya Atucha, assistant professor in the department of Horticulture and the Fruit Crop Extension Specialist at the University of Wisconsin-Madison, told the Wisconsin State Farmer there was a wide range of damage throughout the state, especially in the southern part of the state were the trees were approaching bloom.

“In northern parts of the state the apple trees were not as advanced and there was only a little damage to the tips of the leaves but the flowers were not yet coming out,” she said.

After speaking with colleagues in the Door County Penninsula research station regarding to cherry blooms, she said the damage reports across orchards varied depending on the variety. While some varieties were already budding out, others were not that far along. Damage also varied according to the geographical location of the orchard and whether wind reached the trees.

As for the damaged apple trees she said, “I always tell apple growers that we only need eight to ten percent of the flowers to have a full crop of apples. It is much the same for cherries.”

Atucha pointed out that Wisconsin had a good winter and trees did not experience stress from cold temperatures or ice. Weaker stressed trees will be more susceptible to damage in spring than healthy trees.

She says growers won’t really know the true results for a couple of weeks but is confident that frost damage will be minimal.

Anna Maenner works with fruit grower organizations in Wisconsin and was busy the days after the frosty nights surveying fruit growers about the extent of the damage. She said grape growers in the state reported little or no damage to their crops.

Part of the reason is the Wisconsin growers have varieties that are better able to handle Wisconsin’s weather extremes. Also,in most cases the grapes were not quite far enough along in their spring growth to suffer damage.

Blueberries, on the other hand, may have had some damage as the flowers were exposed.

Maenner said most apple growers she talked with said they didn’t have quite as much permanent damage as might have been expected. Those who had damage indicated it was only to a portion of the clusters and they now plan to adjust their spring thinning accordingly.

Strawberries at Mayberry Farm at Mayville were protected from damage by a layer of ice provided by the Clark’s irrigation system throughout the nights of freezing temperatures last week.

Strawberry growers faced the same challenges as other fruit producers with buds appearing in early May for June production.

Danielle Clark of Mayberry Farms in Mayville says they maintain an irrigation system on their farm, not so much for providing moisture in summer but rather for protecting the tender plants from frost in spring.

“Frost protecting is a normal part of growing strawberries in Wisconsin,” she says."We had been fortunate last year with the late spring and the frosts ended before the plants came out of dormancy and began to set buds. The buds are the cream of the crop,”

She says buds emerge from the crown and slowly extend to the canopy where they will eventually open into blossoms and extend above the canopy.

"The degree of freezing penetrates deeper into the canopy and poses a threat to the buds,” Clark said.

She says it isn’t only the buds but all of the plant tissue that is subject to burn and mortality from freezing temperatures. This spring the freezing temperatures came at a crucial time and they were happy to have the irrigation system set up.

“A constant water supply during sub-freezing temperatures generates heat as it transforms into ice," Clark said. "That heat keeps the plant at or above 32 degrees. As long as the process continues, ice keeps building and the plant stays protected.”

According to Clark, the challenge is to make sure the process isn't interrupted. 

Her husband was kept busy every night making sure nothing changed the water flow rate from pump to sprinkler head. 

“For us, that is over 115 sprinklers this season – the most we have had with our business,” she says. “We inspect the irrigation 4-5 times per evening, each inspection taking 20-30 minutes. The biggest difference for this growing season is the amount of sustained cold temperatures we have experienced.”

Clark says that six nights of temperatures at or below freezing in May is not ideal for June-bearing strawberries.

"A few of these nights brought temperatures down to the low-20’s with nighttime temperatures below freezing for 8 or more hours," she said. "It takes a lot of water and management to protect a crop for that long.”

Unlike some crops, there aren’t any crop insurance products for strawberries, she notes, except for the USDA Non-Assurable Crop “NAP” program that steps in to provide catastrophic coverage in the event of an adverse event. Frost is not typically considered an adverse event unless it is really unusual and extreme.

Joe Zimbric, Dodge and Fond du Lac County UW-Extension crops and soils agent says there were not a lot of soybeans planted yet in the state and the fields that were planted were barely out of the ground. In cases where corn or soybeans did suffer from the few days of below freezing temperature, he says farmers will be able to replant those spots because it is still early enough in the season.