Northwest Michigan fruit update – Sept. 1, 2020

Apples are sizing up nicely, and the predicted weather conditions look favorable for improving color.

Weather report

Fall feels like it is in the air, and summer is coming to an end. Many people are eagerly awaiting the fall, and apples are looking terrific. The temperatures in the forecast, both day- and nighttime, will continue to be similar to the past few days. Daytime highs will be in the low to mid-70 degrees Fahrenheit; however, there are some daytime highs that are predicted to only reach into the low to mid-60s. Nighttime temperatures will mainly be in the mid-50s range—again, good for coloring up fruit.

Our growing degree day (GDD) base 42 are right on target with our 30-year average: 3,055 GDD base 42. Our GDD base 50 are higher than our average; for 2020, we have accumulated 2,083 GDD base 50 compared with 1,994 GDD base 50.

Growing degree days (GDDs) through Aug. 31, 2020








30 Yr. Avg.

















Crop and pest report

Recent cooler nights are helping to color up apple fruit, and good color is now visible on many apples. At the Northwest Michigan Horticulture Research Center, Gala trees are showing the most red fruit, and Honeycrisp are just starting to transition from a yellow-green to a pink hue. Lighter set blocks have some bitter pit showing up.

We started to test apples for maturity last week but will really dive in this week. If you would like samples tested, please drop off fruit at the back lab door of the Northwest Michigan Horticulture Research Center by noon on Tuesdays. We will plan to collect fruit on Tuesday mornings and run samples in the afternoon. Our fruit team apple maturity calls are held on Wednesday mornings, and we will publish apple maturity reports with local and statewide updates to the MSU Extension website around noon on Wednesdays.

At this time, most of the more common varieties are still hard and not yet ripe. However, apple season feels right around the corner, and we are officially in September! Growers did a nice job thinning this season, and fruit is sizing well. Growers are starting up with plant growth regulator applications.

Apple pest activity was slower over the last week as a result of cooler temperatures. However, we have observed San Jose scale crawlers settling on fruit at the station and have received isolated reports of this pest on fruit in commercial blocks. Last week, we reported the first detections of brown marmorated stink bugs in traps adjacent to an apple block at the station. This week, we are continuing to find low numbers of brown marmorated stink bugs in traps with a total of eight bugs detected at the station so far this season.

Lastly, we are starting to receive calls about testing harvest crews for COVID-19; if you have questions, please contact Nikki Rothwell at 231-342-4094 or We are working with other government regulators on getting this information out in a more formal way in the coming days.

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