Southwest Michigan fruit update – June 4, 2024

Fruit development is 10-plus days ahead of normal.

Grape bloom
Concord juice grapes are starting to bloom in southwest Michigan. Photo by Mike Reinke, MSU Extension.


Warmer than normal temperatures this spring have pushed fruit development 10-plus days ahead of normal. Rain over the past week ranged about 0.5 inch or less in the Allegan County area. Amounts close to 2.5 inches in central and lower Berrien County over the same period made spray coverage difficult to apply and maintain. Some rain and moderate temperatures are expected for the coming week.

Southwest Michigan GDD summary from March 1 – June 3, 2024


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMREC)




Lawton (Lawton)




Fennville (TNRC)




Grand Junction




Average for the SW region




A weather report by Michigan State University meteorologist Jeff Andresen is available online

Tree fruit

Examination of female San Jose scales at the Southwest Michigan Research and Extension Center revealed crawlers soon to hatch. Active crawlers have been detected elsewhere in lower Michigan.

Peach and nectarine fruit are 40-plus millimeter (mm) in diameter, with pits still soft. Protection against plum curculio and tarnished plant bug is still needed if there is a crop. Flagging of branch tips by oriental fruit moth larvae damage has been showing up over the past two weeks in Berrien County. Trap catches of oriental fruit moth have decreased, indicating the first generation flight is ending. Rusty spot spray coverage period is from shuck split to pit hardening for susceptible varieties. The Trevor Nichols Research Center trap line has recorded moth catches for the lesser and greater peachtree borers for the past four and two weeks, respectively. Assail trunk sprays and pheromone disruption are the strategies for managing borers with the unavailability of Lorsban.

In cherries, Montmorency tart fruit have resumed growth now that pit hardening is complete. Cherry leaf spot symptoms continue to show up in area orchards. Scouting for symptoms of cherry leaf spot is recommended now to judge effectiveness of your fungicide program.

In plums, Shiro Japanese plum fruit are 30 mm and Stanley European plum are 27 mm in diameter in Berrien County. Plum curculio egglaying is winding down, but feeding can continue. The critical time for fungicide control for black knot is petal fall to approximately late June when new growth slows. Some plum varieties show significant amount of leaf shotholes, presumably due to reaction to fungicides, sometimes from captan applied under cool, slow drying conditions.

Apple fruit at the Southwest Michigan Research and Extension Center near Benton Harbor range from 34 to 45 mm in diameter. Fruit drop over the past week has been significant. Gala and Jonagold appear to have a light crop in many area orchards. Small amounts of terminal shoot blight due to the bacterial disease fire blight have been reported. Overwintering apple scab ascospores catches continue to drop in number, averaging 10 per sample rod for the last two rains in a Berrien County orchard. Scab symptoms are easy to spot in some locations. Continued management of powdery mildew and juniper rust is needed for susceptible apple varieties. Symptoms for sooty blotch and flyspeck are expected to start showing up in a few weeks. Codling moth larvae hatch has been predicted to start about 10 days ago in central Berrien County.

Gala apple fruit hanging from a tree.
Gala apple fruit cluster with smaller fruit soon to drop due to chemical and natural thinning. Photo by Bill Shane, MSU Extension

Pear (Bartlett) fruit are up to 33 mm and Harrow Sweet 26 mm in diameter at the Southwest Michigan Research and Extension Center. Hand thinning will be starting soon. The primary scab season is nearly over. Pear psylla are causing gumming and sooty symptoms on fruit and leaves in some orchards.

Small fruit

In grapes, Concord and Niagara bloom continues in much of the area on surviving primary shoots. Hybrid wine grapes bloom is becoming more widespread. Vinifera wine grapes are close to bloom. Expect bloom in these varieties to begin in the next week or so.

Early phomopsis infections have been common this year. With the regular rains we have been seeing this spring it can be challenging to maintain spray coverage for phomopsis and early downy mildew infection concerns. Powdery mildew is being reported in other crops, so be prepared to protect against this disease as well.

Now that we are at or near bloom the focus should expand to include the spring concerns and the bunch rots: phomopsis, black rot, anthracnose, downy mildew, botrytis bunch rot and powdery mildew.

If you experienced damage from the spring frost on April 25, an article on dealing with frost-damaged vineyards by Rufus Isaacs and Tim Miles of Michigan State University is available.

In blueberries, green fruit are developing with earlier varieties showing hints of blue. Fruit set looks good. Some farms are reporting poor foliage growth on Bluecrop and other varieties. The cause is unknown so far. Disease focus should be on early fruit rot management. Cranberry and cherry fruitworm have been caught.

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Strawberry harvest is underway in Berrien and Van Buren counties. All the leaves are out by now. Maintain fungicide coverage to protect the leaves and help prevent botrytis as fruit begin to show. Growers are suspecting the upcoming wet, warm weather to shorten the harvest season. Once harvest is over, it will be time to renovate perennial strawberry beds.

Upcoming meetings 

Our weekly Monday Night South Michigan Fruit IPM Meetings will are a hybrid format. The meetings will be held in-person at the Southwest Michigan Research and Extension Center, 1791 Hillandale Rd, Benton Harbor, MI 49022, with virtual attendance available online. Our next meeting is Monday, June 10, at 5:30 p.m. No advanced signup is needed for attending in-person. The meetings are free, and one pesticide applicator credit is available for each meeting.  

The MSU Controlled Atmosphere (CA) Clinic on July 17 in Muskegon, Michigan, is organized by the MSU Department of Horticulture every other year to pass on new information relating to CA storage and warehousing of apple and other temperate fruit. This will be of primary interest to apple growers and storage operators.  

The meeting this year features four internationally recognized leaders in apple postharvest science: Christopher Watkins (New York), Jennifer DeEll (Ontario), Carolina Torres (Washington State University) and David Rudell (U.S. Department of Agriculture Agricultural Research Service – Wenatchee) and Randy Beaudry (MSU). Sign up here. 

The 2024 Michigan Viticulture Field Day is back for its 35th year. It will be held at the Southwest Michigan Research and Extension Center on July 31. Come for the education, stay for the steak dinner and local wine tasting. New this year, we are adding a second day for just the wine makers. The Michigan Enology Experience will be down the street from Southwest Michigan Research and Extension Center at the Lake Michigan College Welch Center the day after Viticulture Field Day on Aug. 1. We will talk wine production and tour some local wineries and see how they manage some of the challenges of winemaking in Michigan. Registration is available online. More information can be found in the article, "The 35th annual Michigan Viticulture Field Day and inaugural Michigan Enology Experience are approaching."


This work is supported by the Crop Protection and Pest Management Program [grant no 2021-70006-35450] 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.    

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