West central Michigan tree fruit update – June 9, 2026
Print
EmailFruitlets are rapidly growing. It will be hot and humid this week before a cool down into the weekend.
Weather update
Conditions this week have been hot and wet so far in the west central and Grand Rapids, Michigan regions. Hot weather has rapidly advanced phenology and fruitlet size for tree fruit crops such as cherry, peach and apple (Figure 1). Current degree-day (DD) accumulations as of June 9 are 990 DD42 and 555 DD50 at the Hart Enviroweather station and 1,144 DD42 and 669 DD50 at the Sparta Enviroweather station.
Storms over the past several days brought much-needed rainfall across the region. Hart received 0.69 inches of rain June 5-6 and 1.61 inches June 8-9. Sparta received 0.61 inches June 5-6 and 0.27 inches June 8-9.
More rain is expected June 9 and through the rest of the week. With hot weather over the next few days, more storms are in the forecast which will include potential for high winds, rain and severe storms. Highs will be in the 80s through Thursday, and temperatures will cool slightly into the weekend into the 70s
The NEWA apple irrigation model is a helpful guide to determine how much water is needed for your planting.
Listen to the weather update from Jeff Andresen, MSU climatologist, at the Fruit & Nuts Weather page from MSU Extension.
Weather data was gathered from MSU Enviroweather.
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.
Crop update
Weather over the past few days has advanced tree phenology quickly. Fruitlets have been growing rapidly, over 0.5 millimeters (mm) per day for some varieties.
Apple varieties in Oceana County range from 15-30 mm fruitlet growth stages depending on the location in the county. On June 8 in Hart, average fruitlet size was 31.6 millimeters (mm) for Zestar and 27.7 mm for Idared. Among later-maturing varieties, average fruitlet size was 19.3 mm for Gala, 22.7 mm for Honeycrisp, 20.9 mm for Jonagold and 22.9 mm for Minneiska. Scout block by block to assess early fruit set to determine potential crop load and thinning needs. Scouting is critical this year to best optimize crop load.
Some varieties have lighter fruit set this season such as Empire, Golden Delicious, Fuji and Red Delicious, but even set of these varieties differs by block and location. These varieties may not need thinning or may need some light chemical thinning or follow up hand thinning. Other varieties that have heavier set include Gala and Honeycrisp, although this also varies from block to block. Fruit set is variable across the region, and early evaluation is thinner efficacy has also been variable. Some blocks will need additional thinner applications, and other blocks may simply need some touch up with hand thinning. For Oceana County, this is likely the last week for a good chemical thinning window before fruit reaches 25-30 mm. For the Sparta area, some varieties are already past the chemical thinning window and over 30 mm. Temperatures this weekend and into next week will be in the 70s and up in the 80s, which will enhance thinner efficacy. However, if temperatures are above 85 F, do not apply a chemical thinner.
More information about general apple thinning recommendations and decision-making tools for apple can be found at: Honeycrisp crop management - Apples (msu.edu).
Apple scab pressure is continuing, and primary scab spores are still being trapped in low numbers. From the rain events on June 5-6, nine and eight spores per rod were counted respectively, and for the rain event on June 8-9, there were 16 spores per rod. Rimpro and MSU Enviroweather models showed infection periods for these rain events. Rain is forecasted again this week from June 9-12, and the Hart and Sparta Rimpro models are predicting an infection during this time. Wetting events this week have had extended wetting periods and with the warmer temperatures, fungal spores will grow quickly. Only 9 wetting hours are needed for infection when the temperature averages are between 61-75 F. Enviroweather is predicting 100% of the spores are mature and 95% of them have been released for Hart.
Similar conditions are predicted for Sparta. Amy Irish-Brown with Valent counted three spores per rod from the June 5-6 rain event and 2.5 spores per rod for the June 8-9 rain event. Enviroweather is predicting 100% of the spores are mature and 97% have been released.
Continue scouting for fire blight symptoms from infection during bloom. Remember that nectria blight can also look like fire blight symptoms with shoot dieback. However, nectria blight starts at the base of the shoot and moves toward the shoot tip, and the wood has an orange color due to fruiting bodies that appear at the nodes.
Tart and sweet cherry fruitlets are growing rapidly in Hart, and some red color is starting to show. For early sweet cherry varieties such as Ebony pearl, average fruitlet size was 20.1 mm this week. Bacterial canker symptoms, blossom blast, have been observed in Oceana County on sweet cherry where fruiting spurs are dying back (Figure 2). Dead branches should be cut out to prevent canker formation. Pruning is recommended during the summer during dry periods when the bacteria is not as active.
Average fruitlet size for tart cherries is 14.2 mm. There have been a couple cherry leaf spot infection periods on June 5-6 and 8-9 in Hart. Continue rotating fungicide chemistries to manage resistance. Captan and copper containing products are effective against cherry leaf spot. Chlorothalonil is also an effective material, but the 10-day re-application restriction may be limiting. Another fungicide application may be needed prior to the end of the 10-day re-application timing, so use a different fungicide such as Captan or copper products during that timing if needed.
Peaches are growing quickly. Average fruit size for Venture peach at the West Central Michigan Research and Extension Center in Hart is 21.1 mm. Rusty spot (powdery mildew) and bacterial spot management is needed in peaches, particularly if disease pressure was high in 2025. For the MSU trapline, oriental fruit moth were trapped this week at the West Central Michigan Research and Extension Center with four per trap. A biofix date has been set for Hart for May 11.
Populations around the county are declining for this first generation, and trap counts at other farms in the county were zero this week for oriental fruit moth. At the West Central Michigan Research and Extension Center, peak egglaying was predicted on June 4. The second generation biofix is predicted to be around June 15.
Plum fruitlets are growing rapidly in west central Michigan. If needed, manage for black knot. Average fruitlet size for Castleton plums is 25.4 mm.
Apricots have an average fruit size of 39.2 mm. Fruit set was very light this year, likely due to cold damage and poor pollination weather during bloom.
Pear fruitlets are also growing. Average fruitlet size of Bartlett pear at the West Central Michigan Research and Extension Center is 19 mm. Similar to last week, applications to manage pear scab are needed to cover new green tissue similar to apple scab. Pear scab symptoms have been observed in the region. Pear psylla adults have been observed in the Bartlett pear block at the West Central Michigan Research and Extension Center.
Additional pest and disease information
No green fruitworm adults were trapped this week in Oceana County. Pest activity has been high with the warm weather. Aphids were observed again this week on shoot terminals. Plum curculio adults have not been observed in traps in Oceana County, but some damage has been found in apple. At the Trevor Nichols Research Center, 0.3 plum curculio per trap was observed this week.
Other pests to scout for include obliquebanded leafroller, American plum borer, lesser peachtree borer, rose chafer, green peach aphid, European red mite and white apple leafhopper. Obliquebanded leafroller larvae were observed this week in apple and were feeding on leaves and fruitlets (Figure 3). At the Trevor Nichols Research Center, 16.7 adults per trap were caught. Dogwood borer were also trapped at the Trevor Nichols Research Center this week with 30 borers per trap.
American plum borer and lesser peachtree borer were trapped again this week at the West Central Michigan Research and Extension Center. Trunk bores can be difficult to manage, especially once bores and larvae are inside the trunk. Without the use of chlorpyrifos, there are other insecticide options that should be considered to manage borer populations. See more information on alternative management options. Research from MSU shows that chlorantraniliprole (Altacor) is an effective alternative to chlorpyrifos. Acetamiprid has shown some efficacy but with mixed results in Michigan.
For more information about regional reports, please visit the Michigan State University Extension website.
This work is supported by the Crop Protection and Pest Management Program (grant no 2024-70006-43569) from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
