West central Michigan small fruit update – May 19, 2020

Recent light frost events did not affect small fruit crops in west central Michigan despite freezing temperatures ranging from 28 to 30 degrees Fahrenheit.

Strawberry plant
Strawberry plant with flower bud and new leaf emerging from the crown at Hudsonville, Michigan. Photo by Carlos Garcia-Salazar, MSU Extension.

Cool and wet conditions prevailed during the past week with some late spring frost events occurring on Tuesday and Wednesday, May 12 and 13. However, for the past seven days, average daily minimum temperatures were 43 degrees Fahrenheit and the average maximum was 62 F. So far in west central Michigan, growing degree days (GDD) base 50 F accumulated since March 1 are only at 127 GDD. In addition to low temperatures, four days with precipitation ranging from 0.5 to 2.5 inches left a total accumulation of 4.2 to 4.5 inches of rain in the area.

We are continuously monitoring the effect of low temperatures on blueberries and strawberries in west central Michigan. Field inspections conducted during the past seven days indicated that no further damage to crops occurred because of the past freeze/frost events of May 12 and 13.

Strawberries were still in the new leaf growth stage with flower buds emerging from the crown (see photo). According to Barclay Poling from North Carolina State Extension, at this critical stage strawberries can sustain temperatures in the 20 to 25 F range without suffering much damage. As of May 19, bloom just started in west central Michigan, although growth and development has been delayed for more than a week due to prevailing low temperatures. No major insect or disease problems has been reported by growers.

Blueberries, on the other hand, are entering the early pink stage. Despite some damage observed from the polar air mass passing on May 8 to 11, light spring frost events on May 12 and 13 did not caused further damage. In those early bloom stages, most varieties in west central Michigan can stand temperatures in the 28-30 F range without suffering damage.

It is important to notice that we are observing new shoot growth frost damage in Bluecrop and Duke blueberry fields. However, Elliott and other late season varieties are not affected.

Damaged tissue is always a port of entry for fungal diseases like mummy berry and Phomopsis. According to the Michigan State University Extension article, “Mummy berry springs into action: How to manage this disease,” frost injury increases susceptibility of the shoots to infection, and fungicide applications within 24 hours of a frost event significantly reduced shoot strike incidence. Recommended fungicides to prevent mummy berry infections after a spring frost event include Indar, Prolin and Quash among others. Check the “2020 Michigan Fruit Management Guide” (Extension Bulletin E0154) for more products and doses.

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