West central Michigan tree fruit update – June 17, 2025
Print
EmailWarm weather and scattered showers are forecasted across the region this week. Some early sweet cherry varieties are starting to turn red.
Weather update
This week began with hot and dry conditions across the west central and Grand Rapids, Michigan, regions. Fruitlets are growing steadily, and the window for chemical thinning of apples is coming to a close in some orchards. Tart cherry, sweet cherry, peach, pear and apple are sizing well (Figure 1). June drop is starting in sweet and tart cherry.
Highs in the west central region will be in the mid- to upper 70s this week. Highs in the Grand Rapids region will be in the upper 70s and low 80s. Nighttime temperatures will be in the 50s and low 60s according to the Hart and Sparta Enviroweather stations. Based on the Hart Enviroweather station for June 16, current degree-day (DD) accumulation is 996 DD42 and 527 DD50. For the Sparta Enviroweather station, current DD accumulation is 1180 DD42 and 662 DD50. Across the regions, growing degree days are behind the 5-year average.
Get the full weather update from Jeff Andresen
Weather data was gathered from Enviroweather.
Very little rain has fallen across the regions over the past week. For the Hart Enviroweather station, precipitation was 0.01 inch on June 12. For the Sparta Enviroweather station, precipitation totaled 0.20 inch for June 12-13. This week, storms are forecasted to bring over an inch of rain which will help replenish soil moisture. Soil conditions have been very dry, especially for the west central region.
For the Hart Enviroweather station on June 16, maximum soil temperatures were 79.6 degrees Fahrenheit at 2 inches and 75.2 F at 4 inches. Maximum soil moisture was 5.4% at 4 inches and 6% at 20 inches. For the Sparta Enviroweather station on June 16, maximum soil temperatures were 91.2 F at 2 inches and 84.8 F at 4 inches. Maximum soil moisture was 46.9% at 0-12 inches and 55.6% at 12-24 inches, similar to last week.
More information and reports on normal weather conditions and departures from normal can be found on the NOAA Climate Prediction Center website, NOAA U.S. Climate Normals website, NOAA Climate Normals Quick Access Page (which may be searched by region) and Midwest Regional Climate Center website.
Crop update
Apple varieties in Oceana County range are sizing well. Fruit size for early varieties is about 30-38 millimeters (mm). In Hart, Zestar have an average fruitlet size of 36 mm, and Idared have an average fruit size of 30 mm. Honeycrisp have an average size of 25 mm. Some June drop is occurring in early varieties, and results of chemical thinner applications are becoming more apparent.
If fruit has grown past the size for effective chemical thinning and hand thinning is needed or if crop load is being evaluated to decide if another chemical thinner is needed, consider using tools to determine optimal crop load such as the Equilifruit disc or the trunk gauge. This Equilifruit disc was developed in France as a hand-thinning gauge for centrifugal systems, but research at Penn State University showed it is also an effective tool for tall spindle systems with renewal type pruning. The disc can be placed on a limb at 3 centimeters (cm) from the tree trunk using the notch size that fits snuggly around the branch. The corresponding F-value on the selected notch shows the number of fruit that should be left on the limb of that size using limb cross sectional area (cm2, LCSA) after hand or chemical thinning.
If the number of fruit is greater than the F-value, additional thinning is necessary. To adjust crop load on an entire tree, start at the lowest limb on the tree and systematically work to the top of the tree.
A trunk gauge developed by researchers at Cornell University and Valent can also be used to adjust tree crop load and indicate how many fruit a young tree can carry for a given trunk size. The trunk gauge measures cross sectional area (cm2, TCSA). It also provides guidance for varieties with biennial bearing tendencies like Honeycrisp and Fuji and more annual varieties like Gala, Empire, McIntosh and Delicious.
For more information about using the Equilifruit disc and other hand-thinning tools, check out these articles from Penn State and Washington State:
- Penn State University: Apple Crop Load Management - A Hand-thinning Gauge
- Washington State University: Green Fruit Thinning with the Equilifruit Disc
Using these tools can enhance fruit size and quality. These are also helpful gauges to train crews and recalibrate crews who are doing tasks like hand thinning to see what the target crop load should be for your blocks and varieties.
Sweet cherry are growing steadily, with average fruit size at 22 mm. Average fruitlet size for tart cherry was 16 mm. June drop is occurring in some blocks of sweet and tart cherries.
Peaches are differentiating by size. Fruit that is persisting is about 14 mm in diameter for Venture peach at the West Central Michigan Research and Extension Center.
Apricots are growing steadily, and average fruit size is 32 mm in Oceana County.
Plums have a good set for European and Japanese varieties. Stanley plums measured 18 mm on average.
Pear fruitlets are growing. Average fruitlet size was 20 mm for Bartlett pear at the West Central Michigan Research and Extension Center.
Pest and disease update
Diseases
Insect activity has been fairly mild so far this season. There will be risk for apple scab and cherry leaf spot this week with the chances for rain. Primary apple scab spores are still being monitored in the Grand Rapids area and in New Era. With little to no rain recently, the last of the primary apple scab spores have not yet been recently. The Enviroweather apple scab model for Hart and Sparta is predicting that 100% of spores are mature and 97% of spores have been released in Hart and 98% of spores have been released in Sparta.
With the hailstorm last week in the Grand Rapids region, there may have been infection by the fire blight pathogen, Erwinia amylovora, to cause trauma blight. Fire blight symptoms could start showing up in orchards nine or 10 days after a trauma event, so fire blight symptoms could start showing up later this week. Be diligent about scouting orchards and removing shoot strikes quickly as the fire blight pathogen can move rapidly through shoots at about 2 inches per day in some instances.
Insect pests
In Oceana County, no green fruitworm or redbanded leafroller were caught. Oriental fruit moth was trapped with an average of 2.5 moths per trap.
American plum borer was trapped at the West Central Michigan Research and Extension Center (0.3 moths per trap). One moth per trap was found in Mason County. Lesser peach tree borer was trapped in Oceana and Mason counties with an average of 0.3 borers per trap at the West Central Michigan Research and Extension Center and in Mason County.
Codling moth was trapped in Oceana and Mason counties with an average of three moths per trap. One lesser apple worm was trapped this week.
In Sparta, codling moth was trapped at 24 moths per trap. No oriental fruit moth were trapped. Obliquebanded leafroller adults were observed this week for the first time in Sparta with 25 moths per trap. Dogwood borer adults have not been trapped.
European red mite is active in warm and dry conditions, which are favorable for egg hatch and larvae activity. Scout for European red mites in apple and pear.
Green apple aphid nymphs and adults were observed feeding on the underside of leaves this week. Scout to determine if management is needed. Many aphid predicators such as lady beetles and lacewings can help keep aphid populations in check. In general, established orchards can sustain thresholds of an average of three to four infested leaves on terminals before fruit damage occurs.
Green peach aphid may be present in orchards this week. Adults and nymphs cause leaf curling and yellowing from feeding on the undersides of leaves. Monitor orchard blocks to determine if treatment is needed.
Scout for rose chafer adults on leaves and fruit where rose chafer typically feed. Damage can be more severe in sandy locations near the orchard edge and grassy areas.
Rosy apple aphid and woolly apple aphid are common pests in our region. Scout for colonies of rosy apple aphid nymphs in fruit clusters. Woolly apple aphids have been observed in orchards this week.
Twospotted spider mites are active in hot and dry weather like we have right now. Scout for twospotted spider mites in addition to European red mites. Check for necrosis or bronzing of leaves and webbing on the underside of the leaf. Twospotted spider mites can impact leaf health in combination with European red mite and plum rust mite if feeding is heavy. “Firing” in tart cherry has been associated with this mite complex and can cause branch die back in hot and dry conditions.
For more information about regional reports, please visit the Michigan State University Extension website.
