West central Michigan small fruit regional report – July 20, 2016

Lack of precipitation continues affecting small fruit crop quality and yield. Spotted wing Drosophila presence is reaching high numbers in blueberries and raspberries.

As of July 19, 2016, the summer drought affecting Michigan’s central region remains the main issue for small fruit crops, especially blueberries. Weather conditions for the past seven days have remained unchanged, with scattered thunderstorms and rain showers with temperatures reaching the upper 80s. However, the average daily minimum temperature has been 62 degree Fahrenheit and the maximum 82 F. Except for a storm that left 1.5 inches of precipitation on Monday, July 11, no substantial precipitation has occurred in the central region so far. The extended weather forecast for the next five days indicates that the chances of substantial precipitation are less than 55 percent. All small fruit crops require supplemental irrigation at this time.

Other than drought and the presence of spotted wing Drosophila (SWD), blueberry and red raspberry harvest continues without incidents. Red raspberries are being harvested in Ottawa and Allegan counties. SWD is the major problem. To prevent the buildup of large populations of SWD, which are difficult to manage at the end of August and beyond, a continuous monitoring program is needed. Fruit infestation has already been observed and insecticide applications are already in progress. In raspberries and blackberries, recommended insecticides effective against SWD at this time are: Brigade 2EC (three-day pre-harvest interval), Delegate 25WG (one-day pre-harvest interval), Malathion 8 F (one-day pre-harvest interval) and Mustang Maxx (one-day pre-harvest interval, see the label for dose). For a complete list of recommended insecticides and doses for SWD control, check the “2016 Fruit Management Guide,” Michigan State University Extension bulletin E0154.

Blueberry harvest is in progress for early and mid-season varieties. Unfavorable weather conditions are causing fruit shriveling and soft fruit problems at harvest. In addition, limited labor availability is creating problems for small fruit growers unable to find enough people to hand-harvest their fields. Under these circumstances, mechanical harvesting is their main option to harvest in time and prevent fruit loses and SWD fruit infestations.

We are observing another large emergence of SWD, especially in blueberry fields with history of low insect pest management or surrounded by woods with large presence of wild blackberries. The number of flies trapped at those places went from 27 to 46 flies per trap. On the other hand, traps at well-managed fields or far from wild SWD hosts are catching less insects; zero to no more than seven flies per trap.

At this time, we recommend constantly monitoring your fields for SWD presence. Reduce the trap checking interval from once a week to twice a week if you are actively harvesting, and take immediate action as soon as the flies are observed in the trap.

Before making the decision to spray, check the weather conditions for the next 24-72 hours (visit MSU Enviro-weather) and select the appropriate insecticide accordingly. If you are actively harvesting, the recommended insecticides effective against SWD at this time are: Brigade 10 WSB (one-day pre-harvest interval), Mustang Maxx 0.8 EC (one-day pre-harvest interval), Delegate 25WG (one-day pre-harvest interval) and Malathion 8 F (one-day pre-harvest interval). If you are more than three days from harvesting you may use Lannate or Imidan.

Clarification on report from July 12, 2016

In my small fruit report from July 12, 2016, it was mentioned that Brigade had a three-day pre-harvest interval. That is true for Brigade on raspberries and blackberries. For blueberries, the pre-harvest interval is one day. Although Brigade is recommended for blueberries and cane barriers, the formulations are different. In blueberries, the MSU-recommended formulation is Brigade WSB, and for raspberries and blackberries, the formulation is Brigade 2EC, and with a three-day pre-harvest interval. However, both formulations are registered for use in blueberries and canebarries.

For a complete list of recommended insecticides and doses for SWD control, consult MSU Extension’s “2016 Michigan Fruit Management Guide” (E0154) or contact your local MSU Extension office for assistance. You may also contact me at 616-260-0671 or garcias4@msu.edu.

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