West central Michigan small fruit regional report – July 21, 2015
Blueberry harvest continues with excellent quality and better yields than expected. Spotted wing Drosophila are increasing in southern counties and showing up in raspberries.
Berry harvest season in west central Michigan is in full swing for blueberries and red raspberries. Benign weather conditions that have prevailed for most of the growing season are favoring excellent fruit quality. For example, during the past two weeks, average temperatures remained below the 70s with an average minimum temperature of 58 degrees Fahrenheit and a daily maximum of 79 F. Rain, on the other hand, has been present, but has not interfered with blueberry harvest. The amount of rain accumulated during the past week reached 1.75 inches.
Regarding insect and disease problems during blueberry harvest, spotted wing Drosophila (SWD) and fruit rots, including Anthracnose and Alternaria, are the main concerns. So far, SWD have been under control for the most part. Growers are learning that early control of arriving SWD populations secures good management of the pest throughout the harvest season. Currently, most growers have maintained a strict control of SWD populations, and SWD captures in monitoring traps have remained below the numbers of flies captured last year in the same fields. In addition, the increased use of weather information and understanding of the characteristics of recommended insecticides for SWD control is making a difference. So far, no blueberry SWD fruit infestations have been reported to Michigan State University Extension, neither by growers or packers and shippers.
Based on the extended weather forecast for the next week, which indicates daily maximum temperatures averaging 86 F with less than 50 percent chance of rain, growers needing to spray against SWD may use Imidan (three-day pre-harvest interval or PHI), Mustang Max (one-day PHI) or Malathion (one-day PHI). However, avoid using Malathon if the daily temperature rises above 90 F or the chance of rain is higher than 70 percent for the next 48 hours after the application. For more options and recommendations, please consult the “2015 Michigan Fruit Management Guide,” or the “SWD Management Recommendations for Michigan Blueberry” factsheet.
Finally, before making the decision to spray, please check the MSU Enviro-weather advanced weather forecast to select the best insecticide for the forecasted conditions of temperature and probability of rain.