Southwest Michigan fruit update – June 18, 2024 

Hot weather means thirsty plants.

Blueberries with varying degrees of ripeness.
Growers in Van Buren County are expecting to begin picking this week. Photo by Cheyenne Sloan, MSU Extension.


This week is expected to be hot and humid with scattered cloud cover. Temperature highs are expected to be in the low and mid-90s with lows in the 70s. The potential for evapotranspiration (PET) this week will be higher than normal, which means irrigation will be needed in many crops. There are chances of scattered showers and thunderstorms throughout the week with most of them expected over the weekend.  

Southwest Michigan GDD summary from March 1 through June 17, 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 (MSU) meteorologist Jeff Andresen is available online.   

Tree fruit 

Spotted wing drosophila flies have been detected in traps and various soft fruit over the past few weeks, so protective insecticide sprays should be ongoing where appropriate. San Jose crawlers have been active for several weeks, so new scales should be showing up on fruit and limbs in problem orchards. Brown marmorated stink bug numbers are still low but could be significant in isolated areas close to overwintering sites such as buildings and near woods. Scouting of these areas for insect activity is recommended. The best brown rot fungicide options close to harvest for stone fruit are the SDHI fungicides Miravis and Merivon, and the second generation DMI Cevya.  

Peach and nectarine predicted harvest dates in southwest Michigan are about five days earlier than normal (e.g., July 28 for Red Haven in central Berrien County). Pits are now hard in Berrien County, indicating fruit susceptibility to rusty spot and bacterial spot diseases should be reduced. Oriental fruit moth trap number are still low but should be increasing soon for the second generation flight. Assail trunk sprays and pheromone disruption are the strategies for managing lesser and greater peachtree borers with the unavailability of Lorsban.  

Harvest of sweet cherry varieties is underway. Some harvest of Montmorency cherries has begun for local sales. Tart cherry brix is relatively high and fruit pull force is relatively low (fruit are loosening), indicating fruit are maturing rapidly. Mechanical harvest of tart cherries is scheduled to begin next week in Berrien County for processors. Birds are feeding on both sweet and tart cherries. Spotted wing drosophila larvae are showing up in low numbers in area fruit, so insecticide protection is important. Brown rot and cherry leaf spot control continue to be the primary disease management concerns now.  

Apple fruit hand thinning is still underway. Predicted apple harvest dates (full report coming next week) look to be a week to two weeks ahead of normal, depending on the variety. Calcium treatment for suppressing bitter pit should be ongoing for susceptible varieties. Low-rate NAA treatments for encouraging return bloom are being applied now. 

The model for sooty blotch and flyspeck  predicts symptoms could start showing up now in some area orchards. Orange-yellow leaf spots due to juniper rust are showing up in some orchards. Protection against codling moth larvae should be ongoing. Oriental fruit moth trap catches are expected to increase soon with the start of the second generation flight. Apple maggot flies are showing up in yellow sticky traps and will start to be a concern in the next few weeks for sandy sites. 

Orange-yellow juniper rust symptoms are showing up on apple leaves. Photo by Bill Shane, MSU Extension. 

Pear insect concerns are pear psylla and obliquebanded leafroller. Pear fruit are generally too hard for this generation of codling moth to be a problem.  

Small fruit 

Grape bloom is complete in most juice grape and hybrid varieties. Bloom continues in some vinifera wine grape blocks. With bloom complete it is possible to perform some early season crop load estimates. In many locations, juice grape crop load looks to be about 1 ton per acre or lower. Some good locations are better. Wine grapes are generally close to a 50% crop.  

With the heat and humidity over the next week, powdery mildew is a concern. With the low rain chances most days, it may be possible to extend spray intervals for rain-dispersed diseases like downy mildew and black rot, but powdery mildew likes humidity without rain. Be sure to have coverage for powdery mildew. 

A grape plant infected with tumid gallmaker. Photo by Cheyenne Sloan, MSU Extension. 

Blueberry harvest of early season cultivars are beginning this week in Van Buren County. Disease focus should be on early fruit rot management. Phomopsis cane collapse continues to appear. In these hot, dry conditions, you need to irrigate. If you have overhead irrigation, focus on protecting against anthracnose. See “Blueberry growers need to focus on Anthracnose fruit rot as bloom ends” from Michigan State University Extension. Consider irrigating at night when the temperatures are cooler rather than the day, so the wetting periods occur during cooler periods. Use systemic fungicides, which are absorbed into the plant, reducing fungicide washoff from sprinkler applications. Cranberry fruitworm, cherry fruitworm, spotted wing drosophila and blueberry maggot have all been caught.  

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Strawberry harvest is done in Berrien and Van Buren counties. It is 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, and final, meeting is Monday, June 24, 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."  

Planning ahead for hot weather  

The following information is from the MSU College of Human Medicine. 

With a hot Michigan summer upon us, it is important to be mindful that hot weather can be dangerous while working outside. The heat produced by your body while working plus high outdoor temperatures makes it more likely for your body to overheat. To prevent overheating, do the following: drink plenty of fluids; take frequent breaks in the shade, and if possible, reschedule high energy tasks for earlier or later in the day. 
Call 911 immediately if severe symptoms of overheating occur such as confusion, slurred speech, fainting, nausea/vomiting, rapid pulse, seizures, hot dry skin, or heavy sweating. Then, move the person to a cool place and help lower their temperature with a cool wet cloth and/or cool bath. Do not leave the person alone. Death can occur if the body does not cool down, so it is essential to have a plan before such symptoms occur.  

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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