West central Michigan small fruit regional report – April 26, 2016

It’s time to prepare your integrated pest management program for the 2016 blueberry season.

It is time again to start looking at our integrated pest management (IPM) program for the 2016 blueberry season. Growers should develop their 2016 IPM program to include the pest complex dealt with in 2015 and the progress made in reducing insect damage and crop loses. Last year was a difficult year for Michigan’s berry industry. The harsh temperatures that occurred at the end of the winter caused substantial damage to blueberry fields across the state. That extensive damage caused a considerable drop in the size of the 2015 blueberry crop that, according to the North American Blueberry Council, reached only 85 million pounds of blueberries. That is approximately 25 percent less than what was expected.

Under those circumstances, for growers with a good crop, controlling insect and disease problems was critical to ameliorate the impact of winter damage. A 2015 Michigan State University Extension survey indicated that 52 percent of surveyed growers considered winter damage as the main reason for crop losses in their farms. Insect pest control was a problem for only 31 percent of growers. However, this response may be misleading because many growers reporting winter as their main production problem had no crop at all and those that had a crop were able to deal with insect pests with relative success. Insect pest population pressure was considerably lower than in other years due to the harsh winter conditions experienced by insect pests in 2015.

So, what do we expect for the early portion of the 2016 season? As of April 26, temperatures remain cooler with minimum temperatures averaging 46 degrees Fahrenheit and maximum temperatures averaging 68 F. However, those temperatures allowed for a growing degree-day (GDD) accumulation of 145 GDD base 50 F since March 1. In addition, during the past five days we had some precipitations that amounted to 1 inch in some areas. Total precipitation accumulated in west central Michigan as of April 26 is 9.6 inches. Although temperatures have been below the 70s, they have allowed enough degree-day accumulation to advance plant growth and development for small fruit crops.

Blueberries are showing different flower bud development stages. In Allegan and Ottawa counties, bloom stages go from tight cluster in Elliott to early pink bud in Bluecrop and other early varieties. Considering the milder winter conditions of the present season, we expect insect pests to return to their “normal” population patterns. The same can be said for the blueberry plant phenology.

In 2015, cherry fruitworm and cranberry fruitworm appeared in Allegan and Ottawa counties between the last week of May and the first week of June. This delayed emergence was the effect of winter conditions experienced by fruitworms in 2015. However, because of the 2016 milder winter conditions, we expect their emergence taking place much earlier.

In the following table we can see the present development of fruitworms according to our phenology models.

Fruitworm development in Michigan according to phenology models


First adults

First eggs

Current degree-day accumulation (4/26/2016)

Grand Junction


West Olive

Cherry fruitworm


432 ± 15




Cranberry fruitworm






Considering the current GDD accumulation, fruitworm traps should already be out, especially in the Grand Junction, Michigan, area. In Ottawa County, traps should be set up this week. Taking in consideration the extended weather forecast for the Grand Junction, Michigan, area, the first cherry fruitworm adults should start emerging by the middle of next week.

One special recommendation for fruitworm trap placement is to avoid putting cranberry and cherry fruitworm traps side by side. There is an interference effect between the pheromone of those two insects that will cause low or no catch of insects in those traps. To avoid this problem, set the traps at least 20 feet apart from each other.

For Ottawa, Muskegon and Oceana counties where the stem gall wasp is a serious problem in Jersey fields and other susceptible varieties, consider integrating this insect pest into your early fruitworm IPM program. That may include using insecticides such Intrepid or Confirm for the first application against fruitworms at 50 percent petal fall, and Lannate, Assana XL or Danitol for the second application right after the removal of the bees from the field. For doses and recommendation for protecting bees and natural enemies from non-target impact of insecticides, consult the 2016 Michigan Fruit Management Guide (E0154). You may also get assistance from your local MSU Extension office, or you may contact me at 616-260-0671 or garcias4@msu.edu.

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