West central Michigan small fruit update – April 25, 2017

Preparing for an early arrival of fruitworms and spotted wing Drosophila is important for minimizing fruit damage and pest control expenses.

This year's small fruit growing season had an early start in west Michigan thanks to high temperatures in March and April. Currently, west central Michigan continues to enjoy temperatures above freezing and for the past seven days, average minimum temperatures have been around 41 degrees Fahrenheit and the daily maximum averaging 66 F. No significant precipitation has been reported except for a small amount on Thursday, April 20, that left less than 1 inch of rain in the area. Accumulated precipitation registered in the area since Jan. 1 is 10.47 inches.

Crop conditions for blueberries continue advancing. Early season varieties are already in the tight cluster and early pink bud stages. So far, no spring frost or other events are affecting the bloom period. However, there are important issues associated with the early portion of the plant growth in blueberries that need attention.

Issue No. 1 is preventing shoot and fruit infections by key diseases of blueberries like mummyberry shoot strike and fruit rots. These diseases require preventive treatments from bud break to the green fruit stage. Although current dry weather conditions are not conducive for important outbreaks of mummyberry or other fungal diseases, alternaria and anthracnose need to be treated now.

Growers that did not have dormant applications against mummyberry and fruit rots need to make sure their fields are sprayed before the bees are in the field. That will ensure a good fungicide cover and prevent negative effects on pollinators.

If you delayed your fungicide treatments and the bees are already in your field, please take the following steps recommended by Meghan Milbrath and Jacquelyn Albert from Michigan State University Extension.

  • Avoid fungicide applications during crop bloom whenever possible.
  • Spray after sunset or before sunrise, or when the temperature is below 50 F.
  • Use integrated pest management (IPM) practices to reduce fungicide applications and increase treatment efficiency.
  • Use drift reduction practices.
  • Develop a pollination contract and bee safety plan with your beekeeper.
  • Establish bee-friendly habitat away from crops and protected from sprays.
  • Keep up-to-date on current research and new strategies to protect bees on your farm.
  • Communicate with beekeeper.

Insect IPM

Currently degree-day (DD) accumulation base 50 F in west central Michigan is approximately 140 DD. Therefore, attention is needed to trap placement for monitoring the emergence of the overwintering generation of cherry fruitworm and cranberry fruitworm. Below is a table with the current degree-day accumulation for key MSU Enviroweather stations in west Michigan and the predicted degree day accumulation at which adults and eggs of both species will show up in the field as predicted by our cherry fruitworm and cranberry fruitworm degree-day models (check MSU Enviroweather for more stations and details).

Predicted degree-days for cherry fruitworm and cranberry fruitworm emergence


First adults

First eggs

Current degree-day accumulation (4/25/2017)

Grand Junction


West Olive

Cherry fruitworm


432 ± 15




Cranberry fruitworm






From this table, it is important to notice trap deployment in the Grand Junction, Michigan, area is this week.

Next twilight meeting

Please make sure you attend our next twilight meeting on Thursday, April 27. The meeting is in South Haven, Michigan, from 5:30 to 7:30 p.m. at Haven Harvesters, 165 Veterans Drive, South Haven, MI 49090. For more information, see “Two blueberry management meetings scheduled before bloom.”

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