West central Michigan small fruit regional report – August 2, 2016
Overripe fruit and labor shortage for hand-harvest may increase the risk of spotted wing Drosophila fruit infestations in blueberries.
West central Michigan remains under high temperatures with some precipitations that alleviated the summer drought that has prevailed for the past 30 days. During the past week, daily temperatures reached the upper 80s under moderated drought conditions. On average, daily minimum temperatures during the past seven day were 63 degrees Fahrenheit, and the daily maximum averaged 82 F. There were some scattered thunderstorms that left between 0.75 and 1.5 inches of rain in the area. That helped blueberry growers to alleviate the severe drought that was affecting the quality and yield of fruit being harvested.
Harvest of summer raspberries and blueberries continues in the area with some problems related to the summer heat, lack of consistent rain, the presence of the spotted wing Drosophila (SWD) and limited availability of labor for hand-harvest.
In raspberries, SWD remains the main problem. This is a difficult situation for raspberry growers because most of the raspberry fields in west central Michigan are small U-pick operations. The characteristics of these restrict the options for SWD control. Currently, the following insecticides are considered safe for U-pick operations: Grandevo, Entrust, Delegate and Malathion. These insecticides are not restricted-use products and have a one-day pre-harvest interval. Please check Michigan State University Extension bulletin E0154, “2016 Michigan Fruit Management Guide,” for recommended doses. Brigade is also recommended for raspberries, but this is a restricted use pyrethroid insecticides with a three-day pre-harvest interval.
In blueberries, the prevailing drought conditions and high temperatures caused fruit drop and soft fruit in blueberry fields ready for harvest. Daily high temperatures caused a rapid ripening of the fruit putting pressure on growers to harvest as quickly as possible. However, shortage of hand labor presents a problem for some growers unable to obtain enough picker to hand-harvest their fruit, and prevent fruit overripe and SWD fruit infestations. Mechanical harvest is becoming the only available option if no labor for hand-harvest is available.
In addition to weather problems, SWD populations continue increasing in blueberry fields as more ripe fruit is available for the reproduction of the fly. We continue trapping large numbers of flies in blueberry fields with deficient management, fields surrounded by woods or neighbors with problems controlling SWD. Also, fruit leftovers remaining on the bushes in fields already harvested are becoming a SWD breeding ground. If you have finished harvesting an early variety and next to it there are blueberries in the process of ripening, spray both fields to prevent SWD buildup that will impact your berries not yet harvested.
Growers should make sure they are making the right choice of the insecticide they are using against the SWD at this time. It is necessary to take in consideration the current weather conditions, especially daily temperatures and the presence of rain. During the past week, temperatures in southern counties reached the mid- and upper 90s and most insecticides are affected by high temperatures and sunlight. Before making the decision to spray, check the weather conditions for the next 24-72 hours via MSU Enviro-weather and select the appropriate insecticide accordingly.