West central Michigan small fruit update - May 17, 2022

The big spike on daily temperatures from past days accelerated blueberry bloom and the emergence of overwintering populations of cherry fruitworm and cranberry fruitworm in west Michigan.

Adult cherry and cranberry fruitworms.
Left, an adult cherry fruitworm (CFW). This is a small, brownish gray moth with a median gray band on the forewings and a dark spot at the base of the hind wing. Right, an adult cranberry fruitworm (CBFW). CBFW adults are about 11 mm in length. Forewings of CBFW are grayish brown with two identifying whitish triangles. Photos by Carlos Garcia-Salazar (left) and Chrissy McClaren, BugGuide.net (right).

Michigan west coast experienced a sudden change in daily temperature during the past seven days. Daily minimum and maximum temperatures passed from the lows 40 to the upper 50s, and from the low 50s to the 90s degrees Fahrenheit. Over the past seven days daily minimum temperatures were on average 56 degrees and the daily maximum averaged 74 degrees Fahrenheit. Those temperatures allowed an increase in the daily degree-days (GDD) accumulation. On average there were approximately 18 GDD (base 50 F) accumulated per day. In addition to the increase on daily temperatures there was a reduction in the amount of precipitation. Over the past seven days there were not more than 0.18 inches of rain accumulated in the region.

Regarding plant growth and development, blueberries in west central Michigan are in bloom. However, the percentage of open flower buds goes from full bloom in south Allegan and the Grand Junction area to 50% bloom at Ottawa County and counties up north.

On major activity for this week is to monitor blueberry fields for the beginning of the Cherry and Cranberry adult emergence and the management of fruit rots, mainly the mummy berry and anthracnose fruit rots.

Blueberry fruitworms

At this time of the season monitoring and control of the cherry fruitworm (CFW) and cranberry fruitworm (CBFW) is critical (see photo above). According to the MSU phenology models for both insects (see table below), the CFW is already flying. CFW adults have been already trapped around Fennville’s blueberry fields but in very small numbers. According to the phenology models, we are expecting to find the first CFW eggs by the end of this week around the Grand Junction area. For the Ottawa County area, we expect the first CFW eggs at the end of next week.

On the other hand, the CBFW adults should be flying at the end of this week in Van Buren County, around Grand Junction, and at other southern counties. At Ottawa and Muskegon counties the CBFW flight should begin at the end of next week. For an extended forecast on the phenology of these fruitworms please visit the MSU Enviroweather (fruit) and select your nearest weather station to obtain a forecast for your location.

Table 1. Fruitworm phenology model forecast for the next seven days at west central Michigan.


First adults

Second eggs

Current Degree Day accumulation (5/17/2022)

Grand Junction, MI

Fennville, MI

West Olive, MI

Cherry fruitworm


432 ± 15




Cranberry fruitworm






2022 Pre-bloom Blueberry Meeting

The pre-bloom blueberry meeting is Wednesday, May 18, 2022 from 1:00 to 4:30 p.m. at the Trevor Nichols Research Center in Fennville, Michigan. Please register online. The meeting agenda is below.




1:00-1:10 p.m.

Welcome and Industry Update

1:10-1:30 p.m.

2021 Blueberry IPM evaluation: Results and recommendations for 2022 crop season.

1:30-2:00 p.m.

Disease management: Mummy berry and Anthracnose, and Research Projects

2:00- 2:30 p.m.

 Navigating MSU Enviroweather’s New Website: Tips and Tricks for Blueberry growers.

2:30-2:35 p.m.


2:35-3:00 p.m.

Fruitworm and Blueberry Stem Gall Wasp  management recommendations

3:00-3:20 p.m.

Honey bee and pollinator stewardship

3:20-4:30 p.m.

Blueberry irrigation scheduling to improve fruit quality and yield

4:30 p.m.

Questions and adjourn

This event is free. There is not cost for attending but online pre-registration is required.

Register for the 2022 Pre-Bloom Blueberry Meeting

We very much appreciate your participation in this event since this is an opportunity to hear your comments and suggestions to improve our programing for better serving our blueberry industry.

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