Southwest Michigan fruit update – May 2, 2023

A series of mornings below freezing this past week has caused sporadic damage to some crops, but prospects are still good in most locations.

Niagara grapes.
With the cold weather this past week, some damage is being reported. Here, Niagara grape buds were injured. The injury is inconsistent with healthy buds on the same cane as damaged ones. Photo by Mike Reinke, MSU Extension.


Due to website maintenance, last week’s fruit report was not posted to the Michigan State University Extension system. Here is last week’s southwest Michigan fruit report that was posted earlier this week: Southwest Michigan fruit update – April 25, 2023.


We had another cool week last week. A series of mornings below freezing started Monday, April 24, and continued through Thursday morning, April 27. Mixed cloud conditions and consistent breezes kept temperatures near 30 degrees Fahrenheit for most of these mornings. Thursday morning was the coldest. Clear skies and calm conditions were favorable for a radiation freeze with temperatures in the mid- to upper 20s F throughout the region mainly in the low elevations where cold air collects.

A warm front passed over southwest Michigan on Thursday bringing mid-60s F for highs and upper 40s F for lows until Saturday evening. A low-pressure system entered the region that has lingered over the area, finally exiting today (May 2) with cooler temperatures and widespread light rain. Total rainfall amounts are 0.5 to 1 inch.

The region saw few growing degree days (GDD) last week, 30 GDD base 42 and 10 GDD base 50, respectively.

Southwest Michigan GDD summary from March 1 – May 1, 2023


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMREC)




Lawton (Lawton)




Fennville (TNRC)




Average for the SW region




Average last week




Cool conditions are expected to continue through Wednesday. A warming trend begins Thursday and will continue into next week. Expect high temperatures in the low 70s by the end of the weekend or beginning of next week. The only precipitation expected is scattered showers beginning Monday.

Tree fruit

Temperatures last week had multiple days with lows in the 30s F and in the upper 20s F on Thursday. Crop damage evaluation is underway. Temperatures and rain have been generally poor for bee activity and pollen tube growth. See the Michigan State University Extension article, “What can fruit growers do if a freeze is coming?” for more information.

Oriental fruit moth catch is still very low to none due to cool temperatures. Tarnished plant bug and plum curculio are expected to be very active when evening temperatures start to climb. Brown rot treatment could still be needed for stone fruit during petal fall to prevent colonization of flower tissue.

Apricots fruit are emerging from the shuck. Crop prospects are still good.

Apricots are emerging from the shuck. After shuck split, they become more exposed to damage from insects like plum curculio. With the warm weather coming up, plum curculio may become active. Photo by Mike Reinke, MSU Extension.

Peach and nectarine are at petal fall in central Berrien County. Plum curculio, tarnished plant bug and oriental fruit moth are the targets for petal fall sprays. The need for bacterial spot management generally becomes more important after bloom to protect leaves from becoming a source of infection for fruit after shuck split. Shift from copper to oxytetracycline for bacterial spot treatment generally should start when fruit come out of the shuck to reduce potential phytotoxic effects of copper.

Cherries are at petal fall for tart and sweet cherry in Berrien County. Fungicide coverage for brown rot and cherry leaf spot are the primary concerns. Plum curculio will become a concern starting at petal fall.

In plum, Japanese plum fruit are in the shuck and European plum are in petal fall in central Berrien County. Disease coverage concerns are both black knot and brown rot. Like other stone fruit, managing plum curculio starts at petal fall.

Apples range from king bloom to full bloom (e.g., Zestar), depending on the variety and location. The Cornell apple carbohydrate model is available in the apple section on the MSU Enviroweather website to help timing thinning sprays. Using caustic sprays during bloom is an option for reducing crop load. This week is the first scab infection of the season for the lower part of the southwest region—very unusual. Disease management concerns now are scab, powdery mildew and rust. Fire blight management has not been needed to date because of cool temperatures.

Apples are starting to bloom. Early varieties such as Ruby Macintosh are in king to early bloom. During this time, be careful of spray programs to protect pollinators. Photo by Bill Shane, MSU Extension.

Pear (Bartlett) is in petal fall in the south end of the region. Scab and pear psylla management are the major concerns. Fire blight management is usually needed when rain and temperatures above 60 F occur during bloom.

Small fruit

Grapes: Widespread freezing temperatures the first half of the past week caused sporadic damage in low areas. The worst damage appears to be due to Thursday morning. Wine grape prospects still look good. Juice grapes with good air drainage also appear in good shape. Bigger differences between varieties can be seen compared to a couple weeks ago. Shoot lengthening has begun on concord juice grapes and early hybrids like Marquette. Other hybrids and early vinifera varieties have had no movement with buds between full bud swell and budbreak.

The disease focus at this time is on phomopsis, black rot, anthracnose and powdery mildew. With the mild winter, expect high levels of surviving inoculum on shoots, dried clusters and canes. Generally, wet conditions are necessary for disease development. Powdery mildew is the exception. It prefers humid conditions with no rain and average temperatures in the 60s F and 70s F. The next week will be cool and dry enough that significant disease development is not expected.

Blueberry leaf buds have opened. One to two leaves are visible. Fruit buds are separating. More advanced locations are at late pink bud to early bloom. The window for application of copper, Sulforix or lime sulfur products to suppress early season diseases is closing. Be prepared to start scouting for mummy berry soon. As leaves expand, mummy berry and phomopsis shoot strikes are the main disease.

Strawberries have greened up and new leaves continue to emerge from the crown. Early sites where strawberries are being grown on plastic mulch are more advanced. Some blooms have been seen in those situations. Open fields are not as advanced with flower trusses still protected in the ground or just starting to emerge. With the cool weather expected this next week, floating row covers or other protection may be needed if frost conditions develop. Growers are looking at early season herbicides to control overwintering weeds. When selecting an herbicide, make sure and check the pre-harvest interval (PHI). We are getting to the part of spring where some herbicide PHIs are cutting it close to predicted harvest dates.

Bramble buds have separated from the cane and are starting to open. Some early varieties have expanded leaves.

Currants and gooseberries are blooming.

Hops are being strung now. Early bines are being mowed or chemically removed. This prepares the plants to focus on later-growing bines that will be more productive.

Hop yards are now being strung for the spring. Burndown or mowing of early bines is also being performed. Photo by Mike Reinke, MSU Extension.


Our regular southwest Monday fruit IPM updates are once again a hybrid format. The meetings are held in-person with virtual attending also available online. Our first meeting was Monday, April 10, at 5:30 p.m. and will continue through the rest of the season. You need to register to receive the Zoom link and password for these meetings. The webinars are free and one pesticide applicator credit is available for each meeting. The same Zoom link will be used with all the Monday meetings—you only need to register once. 

Derek Plotkowski, the fruit educator in southeast Michigan, is organizing an Orchard and Fruit Production Classifieds & Exchanges service. Looking for something that you can’t get ahold of in time? Maybe one of your neighbors has some on hand. Have extra of something you’d like to offer? Fill out this form and we’ll add your needed or extra items to the Orchard Classifieds/Exchanges list. The items currently on the exchange can be found here: Orchard Classifieds and Exchanges.

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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