May 9, 2017

Michigan small fruit takes a hit from frost

West central Michigan has seen a number of days with temperatures dropping to the low 30s causing significant damage to small fruit crops, mainly to blueberries and to some extent to strawberries.

Until Sunday 7, 2017, temperatures in west central Michigan remained cold but well above the freezing point in most of the region. This drop in daily temperatures gave some pause to small fruit growers that were concerned with the rapid plant growth and development resulting from high temperatures observed during early spring. Although there were some localized freeze/frost events affecting some strawberry fields, no major problems were reported for other crops like blueberries. It was until the early hours of Monday 8 and Tuesday 9 when temperatures dropped below the freezing point substantial damaging blueberries and other small fruit crops.

The first important freeze/frost event of May 8 lasted from around 3 AM to 7 AM and temperatures dropped as low as 28 degrees Fahrenheit. However, some growers, both strawberry and blueberry producers reported temperatures of up to 22 degrees Fahrenheit. The second event on May 9 affected mainly counties north of Van Buren. This event lasted from 2 AM to 7 AM and temperatures dropped below the freezing point, 30-31 degree Fahrenheit.

This sudden change in the current weather conditions was unexpected because overcast conditions of the previous days did not signal a potential risk of spring frosts.

Growers with overhead irrigation have been able to avoid significant crop losses by turning on the sprinkle irrigation system in some of the at risk blueberry fields. Unfortunately, some growers did not have enough water to protect their fields and ran out of water before the freeze/frost was over. This may have increased the frost damage considerably.

A preliminary evaluation of the damage to blueberries at Ottawa, Allegan and Van Buren counties showed that most damage occurred at Van Buren and fields at the southern part of Allegan County. Most affected fields were those fields with early varieties like Brigitta, Duke and Bluecrop that were left unprotected. In Brigitta for example, 100 percent of the flowers were damaged. In Bluecrop the first bloom, and all flowers that were already open were also damaged. Blossoms that were in late pink stage or at earlier stage were not damaged.

At Ottawa County and north Allegan, the damage is less significant. The blueberry bloom period was one week behind that of Allegan or Van Buren County. Thus, less flowers were already opened. However, in comparison to Van Buren and other southern counties, counties north of Allegan have sustained two continuous days of freezing temperatures. This may increase the damage caused by spring frosts. A more complete evaluation will be conducted once field conditions allow.

– Carlos Garcia, Michigan State University Extension