Northwest Michigan fruit update – July 8, 2025
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EmailSweet cherry harvest will begin this week. Growers have been busy managing ripening fruit for American brown rot and spotted wing drosophila.
Weather report
The weather was hot on Saturday, July 5, and the daytime high at the Northwest Michigan Horticulture Research Center hit 89 degrees Fahrenheit. On Sunday, July 6, we hit a high of 71 F and had variable rainfall across the region. The Northwest Michigan Horticulture Research Center Enviroweather station recorded a total of 0.31 inches of rain yesterday, July 6. At the East Leland weather station, that region received 0.25 inches on July 5 and another 0.57 inches on July 6. Eastport Enviroweather station recorded 0.12 inches on July 5 and 1.0 inches of rain on July 6. Kewadin, Elk Rapids and Williamsburg received no rain on July 5, but 0.15 inches, 0.34 inches and 0.34 inches respectively for July 6. Old Mission received 0.08 inches and 0.28 inches on July 5 and 6. Northport Enviroweather station received 0.26 inches and 0.73 on July 5 and 6. Benzonia and Onekama received a trace of rain on July 5, and a quarter inch of rain on July 6.
Despite the variable in actual rainfall accumulation, the relative humidity at all stations recorded over 90% on Sunday. The wet weather moved out to start the work week, and Monday was still on the cooler side with a daytime high of 72 F. July 8 is predicted to be in the high 70s and sunny. Although it feels less humid, the relative humidity is predicted to be in the 70% range for the remainder of the week. Growers will need to be actively managing for spotted wing drosophila and American brown rot, both of which can develop rapidly under the forecasted conditions.
The weather this year has been warm, cool and everything in between. Despite the constantly changing weather, we are almost on par for growing degree day (GDD) accumulations compared to our long-term average. For 2025 at the Northwest Michigan Horticulture Research Center, we have accumulated 1545.4 GDD base 42 and 942.7 GDD base 50. We are almost spot on to our 35-year average this week: 1554.0 GDD base 42 and 945.8 GDD base 50.
Crop report
Sweet cherry harvest will begin this week in northwest Michigan. Some growers that harvest for the stem-on market have already started harvesting. There was also demand for u-pick sweet cherries over the Fourth of July weekend, and many growers opened their markets for the tourists excited for sweet cherries. The Black Pearls at the Northwest Michigan Horticulture Research Center are still on the red side, and this variety is a fairly early cherry. They are harvesting both sweet and tart cherries in west central Michigan this week.
Tart cherries are coloring up, but there is significant variability in ripeness between sites. I sampled a block of tart cherries north of Omena, and most fruit on the trees was still green. On the other hand, cherries at the station are certainly straw color to red. For growers with a small crop, they will start to put ethrel on their tarts later this week. Gala and Honeycrisp fruit size are 34 millimeters (mm) and 36 mm, respectively.
Disease report
Apple scab. According to the Enviroweather scab model, we are at 100% mature spores and 99% dispersed spores. They have called the end to primary scab in southwest Michigan and on the Ridge. West central Michigan still has not called the end to primary scab because they have not had daytime rains. Northwest Michigan has called the end of primary scab. Some growers have reported scab as a problem in particular blocks.
Here are the following links for RIMpro outputs from July 8, 2025:
Powdery mildew is apparent in our blocks at the Northwest Michigan Horticulture Research Center. For powdery mildew control, single site fungicides should be used at this timing: SHDIs (Miravis, Tesaris, Merivon), QoIs (Flint Extra) and DMIs (Rhyme). Many of the materials growers will be using for scab control will also control powdery mildew. We have not seen powdery mildew in tart cherry this season. To look for powdery mildew in cherries, look for the suckers growing on the inside of the tree. This disease often shows up there before other places in the canopy.
Cherry leaf spot. We have had seven leaf spot infection periods since the first of June. Two of those infection periods were considered high risk. We have substantial leaf spot in our untreated checks in the efficacy trial.
American brown rot. We have significant American brown rot infections in sweet cherries at the research station (Photo 1). In reflection, we had a somewhat loose spray program in the sweet cherries, the level of infection reflects the long intervals between sprays. In most commercial blocks in the region, growers have done a good job controlling American brown rot. However, we are not out of the woods yet, and growers will need to remain diligent in controlling this disease through harvest. This disease is more problematic in sweet cherry than tart cherry, but we have seen American brown rot be a problem in both species. However, American brown rot control in sweet cherry is critical as this disease can go from a few infected fruit to an epidemic level is less than 24 hours.
We have had favorable weather for American brown rot as this disease is favored by warm and wet conditions, both of which we have had in the past few weeks. Tighten up intervals if American brown rot infection is present in the orchard. Luna Sensation, Merivon, Tesaris, Miravis and Cevya are all labeled good to excellent for American brown rot control. As sweet cherries are ripening, the sugar content in the fruit is high and the fungus needs sugars to grow.
Additionally, we have seen bird pecks in fruit, and these areas of damage are excellent ways for American brown rot to get a foothold on infection. Lastly, we have seen spotted wing drosophila stings in fruit, and these oviposition and/or exit holes are another way American brown rot can more easily infect fruit.
Pest report
American plum borer. We caught an average of five moths this week.
Lesser peachtree borer. This pest was caught for the seventh week, with an average of 18 moths per trap.
Greater peachtree borer. This pest was caught for the third week, and the numbers jumped up to an average of 12 moths per trap.
Obliquebanded leafroller. This is the third time we have caught this pest this season. We caught at average of 11 moths per trap. This pest can be seen flying on or near porch lights at this time of year. The moth is orange and distinctively bell shaped.
Black stem borer. We caught an average of 1.5 this week.
San Jose scale. We caught no males in traps at the station this past week. We have had many instances of low trap counts but significant crawler activity with this pest this season.
Plum curculio. This insect only has one generation per year, and we expect to see adult beetles in the orchards soon. This pest does occasionally feed on cherries before harvest if the populations are high.
Codling moth. We caught an average of two moths per trap. We have caught codling moth at the Northwest Michigan Horticulture Research Center for five weeks in a row, and we set our biofix for June 3. Based on the codling moth model and the June 3 biofix date, the model predicts we will be seeing the emergence of adults on July 14. “Codling moth management options for Michigan apples” from Michigan State University Extension is a good article on codling moth.
Spotted wing drosophila. Numbers are down at the Northwest Michigan Horticulture Research Center and at all the grower sites where we trap. This decline in adult flies in traps is due to ripening cherries; the traps become less attractive to adult flies as all the fruit in the orchard competes with the trap. We have had ideal weather for spotted wing drosophila, and growers need to be managing for this pest now.
Not unlike fungal diseases, weather conditions also favor spotted wing drosophila development—these pests like warm and humid weather, and they can have a generation every seven days under ideal conditions. We have seen lots of infested fruit, both sweet and tart cherries, at the Northwest Michigan Horticulture Research Center. We have also had reports of infestation in commercial farms from growers and scouts. Both sweet and tart cherries are susceptible for spotted wing drosophila egglaying now.
Based on a May 15 bloom date at the Northwest Michigan Horticulture Research Center, the spotted wing drosophila model is predicting high risk and has been predicting high risk since July 1. We have seen new stings and exit holes in fruit, which shows that this pest has been around at least a week. Growers need to be protecting both sweet and tart cherries from spotted wing drosophila infestation. With the shortage of fruit in the orchard, growers will need to protect what is left from infestation; with a light crop, the spotted wing drosophila pressure will increase. “Managing Spotted Wing Drosophila in Michigan Cherry” from Michigan State University Extension is a good resource on spotted wing drosophila management. Growers will need to be diligent about keeping spray intervals tight to prevent infestation before harvest.
