West central Michigan small fruit update – June 26, 2018

Summer insect and disease management in blueberries and other small fruit is fast approaching. Cane collapse and fruit rots in blueberries and the beginning of the spotted wing Drosophila (SWD) flies arrival should be the main focus of growers’ IPM program

Small fruit crops, especially blueberries and raspberries, require particular attention from now on. That is particularly important in blueberries, since the harvest may start at the end of this week with early varieties.

Current weather condition in west central Michigan are dry with only a few rain showers that produced less than one inch (0.11 to 0.5 inch) of accumulation during the past seven days. Daily temperatures over the same period have been below the 80s for the most part. On average, the daily minimum temperature in the area was 60 degrees Fahrenheit and the daily maximum was 75 F, although temperatures have remained around the upper 70s.

Regarding blueberries, the lack of substantial rain is creating stressful conditions for fields with light soils or with limited supplemental irrigation. As a result of these conditions, fields with a history of cankers occasioned by injuries produced by mechanical harvesting or by previous infections of phomopsis and other fungal diseases, are showing multiple plants with collapsed canes. Those canes should be removed as soon as possible now that they are easy to spot. Infected material should be collected and removed from the field and burned to prevent further infections on healthy plants. Follow up with a fungicide treatment to prevent new cankers from developing. Recommended fungicides for this problem are: Aliett (no more than four applications, and 12 h PHI), Pristine (0 days PHI) and Quash (7-day PHI). For other products and doses please check the 2018 Michigan Fruit Management Guide (MSU Extension Bulletin E0154).

The other concern is the arrival of spotted wing Drosophila. During the past seven days, SWD flies have started to arrive in blueberry fields in west central Michigan. In Allegan County, around the Fennville area and in the southern portion of the county, the number of flies trapped during the past seven days varied from five to 28. That sudden increase of SWD flies at monitoring sites could be associated with temperatures and relative humidity from previous days (On June 10, precipitation reached 1.6 inches in this area.). Even though weather conditions have been dry for the most part, rain showers from the past seven days have provided enough relative humidity for the flies to prosper.

It is important to deploy monitoring traps now for early detection of the arrival of SWD flies. Blueberry fields with more than five percent fruit in the blue stage or that just started coloring are at risk of early SWD attack if flies are undetected or unattended. Detecting the early fly arrival is critical for a successful SWD management.

Growers need to be aware that knowing when to spray, what to spray based on the characteristics of recommended insecticides, plant conditions and the prevailing and forecasted weather conditions is basic for a successful SWD management. If growers require assistance with their SWD management program, please visit the nearest MSU Extension office or call Carlos Garcia at Ottawa County Extension 616-994-4580 for assistance.


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