Southwest Michigan fruit update – May 7, 2024 

Bloom is finishing up in many of the major crops.

Some beehives in rows.
A cluster of beehives in Van Buren County. Photo by Cheyenne Sloan, MSU Extension.


The past week in southwest Michigan, temperatures have ranged from mild to warm, with daytime highs reaching into the 60s and 70s and nights generally staying above freezing. Precipitation has been intermittent, providing essential moisture for soil hydration, but can make sprays more frequent or difficult to plan.  

Southwest Michigan growing degree days (GDD) summary from March 1 – May 6, 2024 


GDD 42 F 

GDD 45 F 

GDD 50 F 

Benton Harbor (SWMREC) 




Lawton (Lawton) 




Fennville (TNRC) 




Grand Junction 




Average for the SW region 




 Watch the latest weather report from Michigan State University meteorologist Jeff Andresen.  

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Frost on April 25 resulted in failure of many Montmorency tart cherry blossoms to form fruit. Photo by Bill Shane, MSU Extension. 

Tree fruit 

Cold temperatures on April 25 caused damage to fruit buds of plum, cherry and some apple varieties. Catch of San Jose scale adult males was first reported this week at the Trevor Nichols Research Center trapline in Fennville, Michigan. Crawlers from this generation are expected at 400-450 degree-days base 51 degrees Fahrenheit after this biofix. Scale has become an increasingly troublesome pest on fruit trees with the loss of Lorsban insecticide treatment as an option. Treatment of this generation of crawlers is important to limit potential exponential population growth in later generations and tree damage. 

Apricot fruit are 0.75 inches in diameter. Crop potential is generally poor due to earlier freezes. There have been no reports of plum curculio damage, but protection is needed now against this insect pest.  

Peach and nectarine are out of the shuck. Most of the few remaining fruit in central and lower Berrien County have dropped due to cold damage. Crop potential is still decent in parts of northern Berrien County, Allegan County and northwards. Peach scab symptoms are showing up on twigs infected last summer.  

Peach leaf curl disease symptoms are obvious in orchards where fungicide treatment for the pathogen last fall or spring was inadequate. Infection probably took place on April 12 during a long, cool wetting event. If trees have been severely affected by peach leaf curl, provide adequate water and fertilizer to help keep them from further stress.  

Protection against plum curculio and tarnished plant bug is needed now if the crop warrants the expense. According to the Enviroweather model, oriental fruit moth egg hatch should be underway—this generation can cause tip dieback of branches if uncontrolled.  

Spectacular symptoms of peach leaf curl are being seen in the region. Photo by Bill Shane, MSU Extension. 

In cherries, low temperatures on April 25 further reduced crop potentials in much of the region. Sweet cherries are 13 millimeters in diameter and tart cherries are 10 millimeters. Managing cherry leaf spot and plum curculio are the major concerns now.  

In plums, Shiro Japanese plum fruit are 14 millimeters and Stanley European plum are at 10 millimeters in Berrien County. Crop potential was further reduced by the April 25 freeze event. Fruit should be protected against plum curculio and plant bug attacks. Critical time for fungicide control for black knot is petal fall to late June (10-inch new shoot growth).  

Apple fruit range from 5 to 11 millimeters in diameter. Most of the lingering blossoms are too old for new fire blight infections. The fire blight infection on April 28 is estimated to begin showing symptoms on May 13, based on forecasted temperatures. Apple scab ascospores are still being released in significant numbers during rain events. Continued management of powdery mildew and juniper rust is needed for susceptible apple varieties. First trap catches of codling moth were reported this week by the Trevor Nichols Research Center in Fennville, Michigan. 

Pear (Bartlett) fruit are up to 11 millimeters in diameter. Lingering bloom generally looks too old for new fire blight infection. Continued scab sprays are needed to protect green tissue against infection.  

Small fruit 

Grape damage from the April 25 freeze is becoming more noticeable. While the damage is widespread, many fields show variable damage levels. Many primaries are growing well on vines near woodlots where the nearby trees helped protect from freeze damage. In these locations, juice grapes have primary shoots up to 6 inches long with clusters lengthening. In the vineyard interiors, damage is more pronounced with very few surviving primaries. In these locations, secondaries have their first leaf unfolding. Vinifera buds that survived the Jan. 15 cold event are at first leaf to 3-inch shoots. Variable budbreak is common with several blind nodes being seen on cordons. If these conditions persist, vines in these conditions should have a decent partial crop, but rebuilding the cordons in subsequent years will be necessary to get back to full production.  

Blueberry bloom is here. We are reaching full bloom in Allegan County and entering petal fall from Berrien County into Van Buren County. Apply fungicides to protect open flowers from mummy berry infection. Flowers are most susceptible to both infection and pollination after opening. Fungicide applications are focused on early bloom and mid- or full bloom to protect newly opened flowers, which are most at risk.  

At the end of bloom, disease control refocuses on both mummy berry infections in late bloom and anthracnose infections to young green fruit. Applying pesticides during bloom should be done in the early morning or at night when bees are unlikely to be foraging. Check out this article about pollinator stewardship during fruit crop bloom 

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A bee on its way to pollinate a blueberry flower in Ingham County. Photo by Guy Sloan. 

Strawberry flowers have emerged. With bloom and bee activity, do not use insecticides. Cool, wet conditions can favor angular leaf spot, a bacterial disease. The only effective bacterial controls are copper formulations. Growers are looking at early season herbicides to control overwintering weeds and are finishing up spreading straw. Check the preharvest interval when selecting an herbicide. 

Bramble buds have separated from the cane and are starting to open. Some early varieties have expanded leaves. Once you have leaves, you can start scouting for leaf-eating insects like sawflies and leafrollers and diseases like rust.  

Upcoming meetings 

Our weekly Monday Night South Michigan Fruit IPM Meetings will once again be 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, May 13, 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 Unconventional Fruit Working Group 01: Orchard and Vineyard Floor Management will be May 29 from 12:30 - 1:30 p.m. via Zoom. This is a virtual meetup group for fruit farmers who grow fruit using non-conventional practices, including organic farmers. Each 1-hour meeting has a theme, with the first meeting theme being "orchard and vineyard floor management." After a short educational presentation, farmers can share their experiences and listen to the experiences of other farmers. Sign up here. For more information, contact Derek Plotkowski at 

The MSU Extension blueberry team will be hosting a Blueberry Pollination Meeting on May 15 the Trevor Nichols Research Center in Fennville.   

Additional information and surveys  

Michigan State University is running a pollinator survey this spring and summer to understand how people interact with pollinators in natural, urban and managed landscapes. The survey is anonymous and takes only 10-15 minutes to complete.  

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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