West central Michigan small fruit update – June 19, 2018

Small fruit crops in west central Michigan were in the middle of a heat wave with only scattered rain showers, increasing the need for supplemental irrigation.

For the past week, west central Michigan was under a heat wave that affected all small fruit crops. Temperatures during the past seven days reached the upper 80s with little rainfall, leaving a little more than 0.5 inch of rain. During this period, average minimum temperatures were 62 degrees Fahrenheit and the maximum averaged 83 F.

According to meteorological information, during the past 15 days there was only a small amount of precipitation in the area. Rainfall accumulation ranged from 0.8 inch in Ottawa County to 2.7 inches in Allegan County. However, accumulation in Allegan County is skewed by a single rain event on June 10 when precipitation reached 1.6 inches. Only 0.74 inch of rain has been registered after that. High temperatures and low relative precipitation is creating the need for supplemental irrigation for all small fruit crops, especially for strawberries and blueberries.

Due to intense heat and dry weather conditions, strawberries are at the end of the harvest season with potentially two more weeks of harvest. Yields are lower than expected due to winter and spring frost damage. In some cases, the flavor has not been the best.

All blueberry varieties are growing at a good rate. They are in the late green fruit stage and harvest of early varieties is expected by the first week of July. So far, no major issues have been reported. However, winter damage will result in some crop yield reduction in fields away from the Lake Michigan shorelines, especially in Bluecrop and Elliott fields. Also, there was some hail damage around the Fennville-Grand Junction, Michigan, area. Damage could be mistaken for fruitworm damage, so before thinking about applying insecticides, affected fruits need to be cut to see if fruitworm feeding is present.

Maintain a good fruit rot control program. Remember, prevailing high temperatures and high humidity conditions favor Anthracnose and Alternaria fruit rot. So far, the predictive model for Anthracnose indicates a low to moderate risk for Anthracnose infections. Symptoms might already be present in some early cultivars. Recommended fungicides to control these diseases are Abound and Switch. Please check Michigan State University Extension bulletin E154, “2018 Michigan Fruit Management Guide,” for recommended rates and other recommended fungicides.

For insects in blueberries, cranberry fruitworm and cherry fruitworm flight is over, and so far no fruitworm damage has been reported. Deploy spotted wing Drosophila (SWD) monitoring traps for early detection of the arrival of overwintering SWD flies in blueberry and other small fruit crops. Detecting the early fly arrival is critical for a successful SWD management. So far, MSU Extension SWD monitoring network in blueberries has not shown flies in west central counties, but its presence in cherries in northwest counties has been already reported.

Knowing what and when 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. Although we have completed two SWD workshops in 2018, we are willing to offer another workshop if enough growers are interested in the training.


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