MSU Extension Fruit & Nuts

Weather report 

The weather has been warm and humid for the last week, but the forecast for this coming week is predicted to be dry. At this point, there is no rain in the weather forecast until Sunday, July 6. This stretch will be the first week without multiple days of rain in the forecast. The relative humidity is predicted to remain in the high 70s and low 80s, but the winds today are helping to reduce the humidity. The warmer and drier weather is a welcome relief as fruit is ripening. American brown rot and spotted wing drosophila populations can increase exponentially in weather conditions that are warm and humid with ample rainfall.

The forecast for the week of July 1 is predicted to be in the low to mid-80s with full sun. On Saturday, July 5, just in time for the National Cherry Festival parade, the Traverse City weather forecast is predicted to be 95 degrees Fahrenheit.

For 2025 at the Northwest Michigan Horticulture Research Center, we have accumulated 1344.6 growing degree days (GDD) base 42 and 797.9 GDD base 50. We are almost spot on to our 35-year average this week: 1362.9 GDD base 42 and 810.3 GDD base 50. With the recent warm weather, we have accumulated close to 200 GDD base 50 in the last week. This heat has accelerated cherry ripening.

We have had rain on and off since June 21. At the Northwest Michigan Horticulture Research Center, we received 1.62 inches of rain on June 21. We received another quarter inch of rain on June 26, and another 0.10 inches of rain on June 27. We had more rain on June 29, accumulating 0.12 inches, and on Monday, June 30, we received just under a half-inch of rain at the Northwest Michigan Horticulture Research Center. A pretty wet week and a half, and growers have been actively managing for fungal diseases given these conditions.

Crop report

Sweet cherries are definitely coloring up this week. The sweet cherry crop is variable, but overall, sweets have a better set than tart cherries in northwest Michigan. There is some variability in crop size in sweet cherries, and variety plays a big role in this variability. Golds are at 17 millimeters (mm), and Ulster and Emperor Francis are at 23 mm. In addition to color, sweet cherry sugar content is going up. We ate some Coral Champagne sweet cherries this week, and they tasted good. Bird damage is also showing up in sweet cherry blocks, a sure sign of ripening fruit. Some growers have put ethrel on sweet cherries this past weekend and others are applying this product around July 4. Sweet cherry harvest will start within the week for some growers.

Tart cherries are also starting to color. With a small crop on the trees, these cherries will ripen more quickly than trees that set a large crop. We have more tart cherries at the Northwest Michigan Horticulture Research Center than we initially thought, but our overall crop is still quite light. However, we are working in grower blocks where the crop looks good. The crop size for northwest Michigan is estimated to be 35 million pounds.

Gala and Honeycrisp fruit size jumped since last week when they were 30 mm and 31 mm. Apples have reached a size where they are too big to thin. We have had reports of over thinning in some apples while other growers will have to hand thin. The apple crop is shaping up nicely, and the estimate for Michigan is about 27 million bushels. According to the Michigan Agricultural Cooperative Marketing Association newsletter, the report for Michigan is as follows: “Southwest – June drop has ended; more significant than expected. Thinners worked randomly. Some hand thinning taking place on select varieties. Average crop in the area. Quality and size good. Ridge – Honeycrisp off slightly; Jonagold, Red Delicious, Fuji also down from last year. June drop still occurring. Some hail in the Sparta area; growers debating what will be harvested. West Central – Hot temperatures during bloom caused pollination issues. Crop varies by variety and location. Most thinning complete; apples at 12-15 mm. North – Gala and Honeycrisp at 26 mm. Some hail in the region. Crop variable due to cold temperatures in late April.”

Disease report

Fire blight. Shoot strikes are showing up in susceptible varieties as a result of the recent hail that came through the region last week. Growers should cut out these strikes 8-12 inches below the symptoms, and cuts should be made when the weather is warm and dry. This week’s forecast looks like a good time to cut out fire blight strikes.

Two treatments of the Apogee and Actigard combination provides excellent suppression of fire blight. Treatments of 2 ounces of Apogee and 1 ounce of Actigard per acre applied starting at king bloom petal fall and then again 10 days later suppressed fire blight lesion development. This strategy is critical to successfully control shoot blight, especially in high density orchards.

Apple scab. According to the Michigan State University Enviroweather scab model, we are at 100% mature spores and 99% dispersed spores. They have called the end to primary scab in southwest and on the Ridge. West central Michigan has not called the end to primary scab because they have not had daytime rains. Northwest Michigan also called the end to primary scab after last week’s rain, but growers that were concerned with calling it last week can surely call it this week after we received another half-inch of rain June 30. We have heard concerns about scab in certain blocks where growers have not been able to get this disease under control. If there are active scab lesions on the leaves, protect the fruit from infection.

Here are the following links for RIMpro outputs from June 24, 2025:

• Williamsburg 
• Benzonia 
• East Leland 

Powdery mildew is showing up on terminals in apples at the station. Once the white mycelium is evident on leaves, this disease is difficult to eradicate. If powdery mildew is showing up in the orchard, use fungicides to protect new tissue from infection. This disease does not need rainfall for activity—hot and humid conditions are optimal for powdery mildew infections. 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 yet this season. To scout 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. These drier conditions will be good for keeping cherry leaf spot at bay. There are definite lesions in the untreated areas of the efficacy trial at the station. Unlike scab, leaf spot will need to be managed through harvest. Most growers still apply a post-harvest spray to keep leaves on from this disease.

Pest report

American plum borer. We caught two moths this week. The flight for this pest is likely over for the first generation. Second generation flight will happen later into the summer.

Lesser peachtree borer. We caught this pest for the sixth week, with an average of 20 moths per trap. We caught an average of 23 moths last week. This pest is at peak flight now.

Greater peachtree borer. We caught this pest for the second time this week, but numbers are very low.

Obliquebanded leafroller. This is the second time we have caught this pest this season. The numbers went up from last week, catching an average of 25 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 four this week.

San Jose scale. We are catching very few males in traps at the station this year. This week, we only caught an average of one per trap.

Plum curculio. With the recent rains and warm weather, plum curculio activity is now on the downswing. The females move into orchards in the spring and lay eggs into developing fruit. We were concerned that this pest’s activity may be longer than in most years due to the start and stops of warm and cold weather. However, we have officially hit summer weather, and plum curculio egglaying is likely over at this time of the year.

Codling moth. We caught an average of 2.3 moths per trap. We have caught codling moth at the Northwest Michigan Horticulture Research Center for four weeks in a row, and we set our biofix for June 3. Based on the codling moth model and the June 3 biofix date, we are at peak egglaying for the first generation now. We are actively managing for codling moth at the station. “Codling moth management options for Michigan apples” from Michigan State University Extension is a good article on codling moth.

Rose chafer. This pest is on the downswing. Although they are hard to control, this pest is short-lived in most years. We managed for them in our young orchards this year, but we have not seen many in the past week in the orchard (or in our flower bed!).

Spotted wing drosophila. Numbers are on the rise at the Northwest Michigan Horticulture Research Center. Last week, we caught an average of eight flies per trap. This week, we caught an average of 36 flies per trap. In three different traps, we caught 13, 31 and 35. We also found more flies in traps at our grower sites this week than last week. In a managed Leelanau Orchard, we trapped 450 flies in 12 traps. In a tart cherry orchard in Antrim County, we trapped 132 flies in 12 traps.

This pest can infest fruit even if trap numbers are low—we have seen this in many years where we trap few adult flies in an unsprayed block but end up with significant infestation. Based on a May 15 bloom date at the Northwest Michigan Horticulture Research Center, the spotted wing drosophila model is predicting high risk today, July 1. This means that the fruit are ripe enough for females to oviposit their eggs.

The model is based on fruit development, not the spotted wing drosophila fly. The flies are likely ubiquitous in the orchard, but the fruit is only susceptible for infestation once fruit is ripe enough—we are at that point! Growers need to be protecting both sweet and tart cherries from spotted wing drosophila infestation. With the shortage of fruit in the orchard, protect what is left from infestation; with a light crop, the spotted wing drosophila pressure will increase.

Despite this dire warning above, growers may be getting a bit of a break with the weather. This pest thrives when weather conditions are warm and wet. The forecast for the next week is predicted to be warm, even hot and dry. This pest does not do well in hot and dry, so the activity will likely drop. These conditions do not mean that we are out of the woods for spotted wing drosophila control, but with reduced relative humidity and higher temperatures, this pest is slightly less of a threat with this weather. Just like a fungal pathogen, spotted wing drosophila can increase exponentially under warm and wet conditions.

Ethephon. Some growers have started to apply ethephon in sweet cherries, and those with small tart crops will also start soon. “Ethephon on cherries” is an older article that is still important today about using ethephon to loosen cherries. Watch the temperatures as we have seen ethephon cause phytotoxicity if it gets too hot. The current forecast is predicting Saturday, June 5, to be 95 F.