West central Michigan small fruit update – July 27, 2021

Blueberry harvest is in full swing in west central and southwest Michigan. Bluecrop, Jersey and other mid-season varieties are being harvested. Yields and fruit quality are excellent.

People hand-harvesting blueberries in a field.
Hand harvesting blueberries for fresh packing in West Olive, Michigan, July 2021. Photo by Carlos Garcia-Salazar, MSU Extension.

The blueberry growing region has been passing through a period of relatively good weather conditions characterized by daily minimum and maximum temperatures ranging from 62 to 88 degrees Fahrenheit, respectively. Some scattered rain showers left a rainfall accumulation ranging from 1 to 1.71 inches of rain.

These good weather conditions are allowing for harvesting without many delays due to rain or other weather events. Although at the beginning of the season, daily temperatures were unseasonably cold, delaying plant growth and development for several days (more than one week in some cases), warmer temperatures from the past weeks are bringing things back to normal. As of July 27, the growing degree days (GDD) base 50 accumulation in the region is ranging from 1,630 to 1,870 GDD.

Regarding crop conditions, all blueberry varieties are ripening very fast, compressing the harvest period and creating problems for growers unable to secure enough labor for hand-harvesting. The labor shortage is compelling growers to bring foreign workers, and this season we are seeing more H2A pickers in blueberry fields than in past years. Growers unable to find labor for harvesting for fresh are machine harvesting for processing. 

In comparison to other years, there have been a few problems in blueberries. Spotted wing Drosophila (SWD) arrived late in west central and southwest blueberry fields. That delay allowed growers to establish a good SWD control that so far has remained in place.

Our regional SWD monitoring network indicates that pest populations remain low although in some fields near to wooden areas, SWD captures have increased substantially but nothing compared with the high populations we observed during the past season. This is good news for growers because up until now we have not received any reports of SWD infested fruit loads rejected or downgraded at packing facilities. The benefits of an improved SWD control also means saving in pest control and in the number of insecticide applications required to manage the SWD in 2021.

Despite the present success in managing the SWD, our recommendation is to maintain a permanent surveillance of the pest population fluctuations. SWD is a very aggressive insect pest with a reproduction potential that can change thing in a matter of days. Therefore, monitor the presence/absence of flies in your fields is critical.

For monitoring, use commercial lure in your traps and check the presence of SWD twice a week, and after every insecticide application. Also, before harvesting, take several fruit samples and used the salt test to check for the presence of larvae in the fruit to make sure your IPM program is working and your fruit is clean.

If you need to spray, check the 2021 Michigan Fruit Management Guide (Michigan State University Extension bulletin E-154) for insecticide recommendations, and check the current weather conditions to select the best product according to temperature and rain fastness. 

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