Southwest Michigan fruit update – May 31, 2022

June drop of tree fruit has begun. Apple thinning is almost finished. 

Fruit continues to size up. June drop has begun. Here, Harrow Sweet pear is the right size to be a good target for plum curculio. Photo by: Bill Shane, Michigan State University Extension.


Last week again started mild with high temperatures near 70 degrees Fahrenheit and lows in the upper 40s. The temperatures slowly rose through the week then shot up to near 90 F on Monday. The rains on Wednesday brought a quarter to half inch of rain to the region. A major storm system passed to the north of the region on Friday. The northern parts of our area received around 2 inches from the southern edge of the system while other parts of the region saw less than a tenth of an inch.  

The coming days will be consistent with last week. Today’s high should be close to 90 degrees. A line of storms will pass through the southern part of Michigan this evening and overnight. The system will bring cooler weather. The rest of the week, we should see highs in the 60s, rising to the mid 70s over the weekend. After tonight, the best chance of rain will be Sunday or Monday.  

With the warm finish to last week, we picked up an above average number of degree days, 168 growing degree days (GDD) base 42, 112 GDD base 50. Soils are beginning to dry out. 

Southwest Michigan GDD Summary from March 1 through May 31, 2022 


GDD 42 F 

GDD 45 F 

GDD 50 F 

Benton Harbor (SWMREC) 




Lawton (Lawton) 




Fennville (TNRC) 




Average for the SW region 




Average last week 




Peach crop is looking good. June drop is underway. Photo by: Bill Shane, Michigan State University Extension.

Tree fruit

Tree fruit crops are beginning their natural June drop. With the sunny weather and high evapotranspiration rates this past week, trees in drought prone areas may start showing stress as the soils continue to dry out.  

Newly planted trees may have bloom which are attractive to bees and other pollinators. Be cautious with sprays, avoiding when possible, and spraying at night when necessary to avoid harming pollinators. Plum curculio egg laying damage on fruit has slowed with the recent cool weather and the ending of the reproductive cycle of the current generation. 

Codling moth is being caught in traps in higher numbers than last week. Oriental fruit moth flight is ending. Obliquebanded leafroller flight should begin this week.   

Apricot fruits are at 1 to 1 1/8 in in diameter.    

Peach and nectarine fruit range from 17 to 21 mm in diameter, with some natural drop starting. Oxytetracycline should be used instead of copper for bacterial spot to reduce chances of phytotoxicity. Rusty spot management is needed after shuck split for susceptible peach varieties. Peach scab management is needed now. Peach leaf curl symptoms started showing up about two weeks ago. Some green peach aphids are causing leaf distortion. 

In cherries, sweet cherries are at 15mm, tarts are at 10 to 11mm diameter. Tart cherry crop potential looks good for SW Michigan. ProGibb treatment for suppression of bloom on young trees generally starts about 3 weeks after bloom. Cherry leaf spot control should continue. 

In plums, Japanese plum are up to 20 mm and European plums are mainly around 15 to 18mm. Plum curculio oviposition has been seen in both types. Continue black knot management on susceptible cultivars until terminal growth is generally halted.  

Apple  varieties range from 15 to 22mm in diameter.  Natural June drop is starting. Scab sprays are needed during the primary scab season from March to early June to protect against ascospores released in rains. Powdery mildew symptoms are appearing on buds infected in 2021. May 16th was a fire blight infection period. Symptoms from this infection should start appearing approximately May 29th. Tarnished plant bug and green fruitworm damage has been seen in the area. Tarnished plant bug becomes active when we see temperatures above 70. Treatments after bloom are typically common for this pest. Codling moth egg hatch is likely underway. Egg hatch is when treatments typically start for this pest.  

Pears are at 18 to 20mm in diameter. Pear psylla adults are present in some blocks.  Powdery mildew symptoms are present on terminal foliage of pears. This is the same strain commonly found on apples, but rarely on pears. 

Bloom has begun today in early hybrid wine grape varieties such as Marquette, Geneva Red, and Biranna (seen here). Bloom should be expected soon in other hybrids and juice grapes. Wild grape bloom began late last week and over the weekend. Photo by: Mike Reinke, Michigan State University Extension.

Small Fruit

Grape shoot lengthening continues. Juice grapes and many hybrid wine varieties are close to bloom. The early blooming varieties, Marquette, Geneva Red, and Brianna started blooming today at the Southwest Michigan Research and Extension Center. Pre-bloom management of phomopsis, black rot and powdery mildew are the primary focus at this time. Wild grape bloom was noticeable throughout the southwest region this past weekend; many areas reached 50% bloom somewhere between Friday and Monday. Wild grape bloom is used as the biofix for grape berry moth management later in the season.  

Blueberries are mainly at petal fall with some later varieties still blooming. The disease focus later in bloom shifts away from mummy berry and to fruit rot management. Cranberry fruitworm are being caught in pheromone traps. Cherry fruitworm moth catch is expected as well. According to Enviroweather, egg laying should be underway for both species. Fruit are required for egg laying and damage, so management usually begins after fruit set when egg laying begins. 

Strawberry bloom continues. Red fruit are beginning to be seen. Harvest should begin soon. All the leaves are out by now: maintain fungicide coverage to protect the leaves and help prevent botrytis as fruit begin to show. With fruit beginning to form, western flower thrips populations should be monitored and appropriate insecticides used as needed. 

Bramble bloom has begun in raspberries and blackberries. Raspberry sawfly scouting should begin. This insect causes leaf damage that can stress the plant, potentially reducing the crop potential.  

Hops  are up to 6 feet tall at this time. Downy mildew spikes are showing up more often. Early season management is important to stay ahead of this disease in hops.  

Paw Paws bloom continues

Upcoming meetings

Our regular SW Monday Fruit IPM Updates has moved to a hybrid format. The meetings are being held in person with virtual attending also available online. Our meetings are on Mondays beginning at 5:30 pm. You do need to register to receive the Zoom link and password for these meetings. A link is emailed each Monday morning for that evening’s update. The webinars are free of charge and two pesticide applicator credits and certified crop advisor credits are available for each meeting.  Recordings are available for viewing online 

Join MSU Extension on June 9 for our blueberry preharvest meeting! We will hear from MSU researchers and educators and have a few updates from industry leaders. We will send out more information as the program schedule is finalized. This program will be offered in person and virtually at no cost so make sure and sign up today! It will take place in person at the Van Buren ISD in Lawrence Michigan from 5-7 on Thursday June 9. We look forward to having you there! 

Related Articles 

2022 Fruit insecticide registration update 

Southwest Michigan fruit update – May 24, 2022 

Michigan grape scouting report – May 25, 2022 

Southwest Michigan fruit update – 2021 review 

Managing bacterial canker in sweet cherries: What are the options? 

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.

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