West central Michigan small fruit update – May 14, 2019

Bloom of small fruit crops has been delayed due to persistent cold and damp conditions. However, this arrested development has prevented significant bloom damage by isolated spring frosts.

Blueray blueberry variety.
Blueray blueberry variety at Fennville, Michigan. Photo by Carlos Garcia-Salazar, MSU Extension.


This past week, low temperatures and rainy conditions continued across west central Michigan delaying the flowering of strawberries and blueberries. However, the only effect of those conditions was to holdup development of the blueberry bloom period, which prevented potential damage by isolated late spring frosts. Although most of these isolated events were not registered by our Michigan State University Enviroweather network, in some locations it was possible to observe icy patches on the grass during early morning hours.

No hours below freezing were reported in west and southwest Michigan, except at Lawrence, Michigan. The Teapot/Dome Enviroweather station reported 30.6 to 31.6 degrees Fahrenheit from 3 to 7 a.m. on Saturday, May 11, and Tuesday, May 14.  

Other than those isolated evens, the daily minimum temperature around west central Michigan has been on average 38 F and the daily maximum around 59 F. Rainy conditions left 0.8 to 1.06 inches of rain in the area. So far, total precipitation accumulation since Jan. 1 ranges from 10.5 to 13.9 inches. Most rain occurred in southwest Michigan. Because of these cold and damp conditions, growing degree day accumulation (GDD, base 50 F) since March 1varies from 134 GDD at West Olive to 200 GDD in Grand Junction area.

Bluecrop blueberries
Bluecrop blueberry variety at Fennville, Michigan. Photo by Carlos Garcia-Salazar, MSU Extension.

Crop conditions

Due to prevailing low temperatures, strawberries are in early stages of development and leaves are still developing and emerging from the crown. Although there have been some nights with temperatures near freezing, no problems have been reported by growers.

Blueberries continue to develop although very slow. Currently, the variety Bluecrop and Blueray are in the late pink stage, and Jersey is in the early pink stage (see photos). However, this week’s forecasted temperatures will reach the upper 70s, so we are expecting the first flush of flowers by the end of the week, especially around the Allegan-Grand Junction area.

Based on these preliminary observations, it seems that Michigan will have a very good harvest if no other weather-related events occur in the near future.

Jersey blueberries
Jersey blueberry variety at Fennville, Michigan. Photo by Carlos Garcia-Salazar, MSU Extension.

As we enter the blueberry bloom period, the need for monitoring the two major pests of blueberries, cherry fruitworm and cranberry fruitworm, increases. There have been reports of early emergence of overwintering cranberry fruitworm moths around the Grand Junction area. Therefore, if you have not deployed your pheromone traps for cranberry fruitworm and cherry fruitworm monitoring, do it immediately. You need information on the arrival of fruitworm moths to your crop for timing insecticide applications to control these pests on time and prevent significant fruit damage. Visit MSU Enviroweather to check the cranberry fruitworm and cherry fruitworm phenology models to target the moth oviposition period to suppress the first generation of fruitworm larvae as they emerge from their eggs.

Below are the current forecasted events on the life cycle of both cherry fruitworm and cranberry fruitworm. Use this information as a guide to program your fruitworm control program.

Current GDD accumulation (base 50) since March 1 in west central Michigan is 140 GDD around the West Olive-Fennville area. Around the Grand Junction area, it is already 200 GDD, and cranberry fruitworm moths are already detected.


First adults

First eggs

Current GDD accumulations as of May 14, 2019

Grand Junction


West Olive

Cherry fruitworm

238 ± 30

432 ± 15




Cranberry fruitworm

375 ± 20

460 ± 20




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