West central Michigan small fruit update – May 23, 2017

Spring frosts caused some damage to blueberries and strawberries, but no significant impact was observed on most berry crops in west central Michigan.

For the past two weeks, weather in west central Michigan was cold with light rains and a continued threat of spring frost damage to blueberries and strawberries. However, overcast conditions and rains during this period prevented temperatures from going below freezing. Daily temperatures for the past seven days have been, on average, 59 degrees Fahrenheit with an average minimum temperature of 50 F and a maximum of 59 F.

Present weather conditions are slowing down plant and insect growth and development. So far, growing degree-day (GDD) accumulation (base 50 F) since March 1 varies from 340 GDD around West Olive, Michigan, to 420 GDD around Grand Junction, Michigan.

Blueberries are in full bloom in counties north of Allegan County and at petal fall in southwest counties such as Van Buren and Berrien counties. Major concerns for blueberries are preventing mummy berry shoot strike and the transmission of the pathogen to flowers (that may result in fruit infections later on), and insect pests. Recommended fungicides to prevent mummy berry infections and Phomopsis twig blight include Quash (2.5 ounces per acre), Proline (5.7 fluid ounces per acre) and Quilt Xcel (14-21 fluid ounces per acre). For a complete list of recommended fungicides, consult the “2017 Michigan Fruit Management Guide,” Michigan State University Extension bulletin E0154.

Other concerns in blueberries are fruitworms. Due to low temperatures prevailing for the past two weeks, insect pest phenology was delayed and no adult fruitworm flight was reported until last week. Cherry fruitworms started flying in blueberry fields in Allegan and Van Buren counties. We can use trapping data collected last week to set the biofix for our cherry fruitworm model (check the Enviroweather website).

Last week, we observed the first pick of cherry fruitworm flight around the Grand Junction, Michigan, area. Therefore, growers with early season varieties already at petal fall should be ready to apply the first insecticide application against cherry fruitworm.

Likewise, cranberry fruitworm is already out. Accordingly, the biofix date to program the insecticide application around Grand Junction should be May 19. However, growers should use their own fruitworm trapping information to set the biofix date for their particular fields.

To adjust the predictions for the beginning of the cherry fruitworm or cranberry fruitworm egg-lying period at your farm using your own trapping data, go to Enviroweather and enter the day when you observed the first adult cherry fruitworm or cranberry fruitworm in your traps in the corresponding box. This will be your biofix date to start the prediction for the date when the egglaying period will start at your farm.

Below is a table with the predicted degree-days when we are expecting the emergence of cherry fruitworm and cranberry fruitworm adults, as well as their egglaying period. It also includes current degree-day accumulation for key weather stations in west Michigan.

Predicted degree-days for cherry fruitworm and cranberry fruitworm emergence


First adults

First eggs

Current degree-day accumulation (5/23/2017)

Grand Junction


West Olive

Cherry fruitworm

238 ± 30

432 ± 15




Cranberry fruitworm

375 ± 20

460 ± 20




* Adults already started emerging around Fennville and Grand Junction area.

2017 systems approach to manage spotted wing drosophila (SWD): IPM training for berry growers

MSU Extension will conduct the first 2017 Spotted Wing Drosophila Workshop from 9 a.m. – 4 p.m. Monday, June 5, in the training room at MSU Trevor Nichols Research Center, 6237 124th Avenue Fennville, MI.

In 2015, 50 percent of growers attending similar trainings reported the following benefits after applying what they learned: one or two applications less than in 2014; and average pest control expenses of $175 versus $375 per acre in 2014. In addition, in 2015, those attending the training reported crop losses due to SWD averaging 9 percent of their crop versus 18.5 percent in 2014.

We recommend growers participate in this training since controlling SWD remains a major issue for most of the industry. Learning to adjust their pest control program according to changing conditions of weather, plant and insect phenology is critical to save money, resources and obtain a successful SWD control.

For the full agenda and to register online, go to 2017 Spotted Wing Drosophila Workshop.

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