West central Michigan small fruit regional report – July 29, 2014

Red raspberry and blueberry harvest continues. Spotted wing Drosophila is the main concern for berry growers in west central Michigan and has showed up in small numbers in several counties.

Weather conditions in west central Michigan have remained without major changes. Maximum daily temperatures for the past seven days averaged 76.5 degrees Fahrenheit and the minimum 55.5 F. Both temperatures were only 0.5 degrees higher than the previous week. Rain accumulation on the other hand remained almost without change. Only less than 1 inch of precipitation accumulated during this period. This prompted blueberry growers to supplement their fields with irrigation. However, conditions are conducive for maintaining a good fruit quality during the harvest season.

As of today, July 29, our scouting activities in blueberries, raspberries and strawberries indicate that spotted wing Drosophila (SWD) is already well-established in west central counties in all small fruit crops: strawberries, raspberries and blueberries. Spotted wing Drosophila populations still are small, but there has been an increase in the number of flies trapped at our monitoring sites during the past seven days. Small fruit crops in Allegan County are the places where the highest numbers of flies were trapped during this sampling period.

Despite the increase in specimens caught in Michigan State University Extension’s monitoring network, no fruit infestations have been reported by growers. This is quite different from the previous year when we received multiple complaints from growers that were finding fly larvae in harvested fruits. Currently, we do not have information on any blueberry loads rejected at the processing plant.

In comparison to 2013, we are seeing a decrease in the number of insecticide applications against SWD. This is due in part to the small numbers of flies that are showing up in our crops this season. Also, the SWD integrated pest management program, emphasizing early detection and control of the first generations of SWD, has provided good results in fields where growers have detected the pest.

In spite of this relative success, it is important to remain vigilant and follow our recommended protocol for dealing with this pest:

  • Monitor with traps baited with a yeast and sugar solution or the TRECE commercial lure
  • Apply insecticides as soon as the flies are detected in the traps
  • Before and after any insecticide application, sample the fruit in search of worms using a salt or sugar solution to evaluate the effectiveness of your SWD control program.

Remember to make sure you take in consideration the weather conditions at the time of the application and during the expected protection period. High daily temperatures greater than 90 F tend to reduce the effectiveness of pyrethroids. The same is true for Malathion. 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, see “SWD Management Recommendations for Michigan Blueberry.”

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

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