West central Michigan small fruit regional report – September 2, 2014

Blueberry harvest has proceeded with better yields than expected. Spotted wing Drosophila continues to be the main concern, and growers need to check fruit before harvest and before and after any insecticide application.

Weather conditions in west central Michigan are typical of Michigan’s summer. There has been some light rain in the area during most of the week, which left more than 1 inch of precipitation. Temperatures, on the other hand, continued without much change. Daily maximum temperatures averaged 78 degrees Fahrenheit and daily minimum temperatures averaged 62 F. These conditions caused a high relative humidity that favored the presence of fruit rots in blueberries, raspberries and strawberries.

Fall raspberries are actively being harvested throughout west Michigan. Berries are of excellent quality, but have some fruit rot problems due to rain and high temperatures occurring during the past week. Regarding strawberries, there are still a few day-neutral strawberries being harvested with fruit of very good quality, but also with a few fruit rot problems.

Blueberries are the main small fruit crop actively being harvested, but are getting closer to the end. In blueberry fields south of Allegan County, most of the early and mid-season varieties are finished and only Elliott and other late-season varieties are hand- or machine-harvested at this time. Due to the winter damage that most varieties suffered, the harvest season in 2014 will be shorter. In southwest Michigan, it is possible that in two or three more weeks the harvest will be over, and in northern counties it may be possible that the harvest will extend until the end of September.

Most late-season blueberry varieties are harvested for fresh pack due to relatively good market prices that allow a better return for growers trying to maximize the limited labor available. Another factor is that at this time, Michigan is the main provider of fresh blueberries in the country and hand-harvest is preferred over mechanical harvest for processing.

Regarding insect and disease problems for all berries, the major problem at this time is the continuous presence of spotted wing Drosophila (SWD). Numbers of flies in monitoring sites continue to increase, but we are still below the number we observed last year. So far in west central Michigan, the maximum number of flies in a site with history of SWD has been 22 flies. In 2013, the same site had up to more than 50 flies per week.

As it was anticipated, in blueberries the detection of larval infestations in fruit loads has increased as the season progress. Most growers with access to technical assistance through their association or through pest consultants have been able to maintain good SWD control. However, the cost of controlling this pest remains high, and so far, there have been few loads with worms that have been downgraded or rejected.

A conscious sampling of fruit before harvesting and before and after any insecticide applications should be conducted to avoid fruit infestations at harvest time. If SWD larvae are found in samples of fruit taken before harvest, Michigan State University Extension recommends using a “rescue” application with any of the insecticides that have demonstrated good larval control such as Mustang Max. Also, check the weather and if the daily temperatures or rainy conditions may affect the durability of the insecticide you applied, repeat the application with a different insecticide. For insecticides and doses for blueberries, see “SWD Management Recommendations for Michigan Blueberry.” For insecticides and doses for raspberries, see “Spotted Wing Drosophila Management Recommendations for Michigan Raspberry and Blackberry Growers.”

Contact your nearest MSU Extension county office or Carlos Garcia at 616-260-0671 or garcias4@msu.edufor assistance.

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