West central Michigan tree fruit update – May 5, 2026
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EmailCool temperatures have slowed bud development in the region. Stone fruit bloom is continuing.
Weather update
Changes in bud development have slowed with cooler temperatures over the past week across west central Michigan (Figure 1). Cool air masses continue to move down from northern regions in North America over the Midwest and Northeast. Based on the Hart MSU Enviroweather station for May 4, current degree-day (DD) accumulation is 386 DD42 and 181 DD50. At the Sparta MSU Enviroweather station, current DD accumulation is 488 DD42 and 255 DD50. Across the region, DD accumulation is above the five-year average for the Hart and Sparta Enviroweather stations. Last week, daytime highs were in the 50s and 60s and nighttime temperatures were in the 30s and 40s, with below freezing temperatures overnight on May 2.
This week started out warmer on Monday, May 4, with high temperatures in the 70s on Monday and lows in the 40s. Rain was in the forecast for May 4, but no precipitation was recorded at the Hart or Sparta Enviroweather stations. Temperatures will be cooler for the rest of this week with highs in the 50s to low 60s in Hart and Sparta. Low temperatures will be in the 30s and 40s. Across the region, dry conditions are forecasted for the rest of the week with slight chances of rain as we go into the weekend.
Listen to the weather update from Jeff Andresen, MSU climatologist, at the Fruit & Nuts Weather page from MSU Extension.
Weather data was gathered from MSU Enviroweather.
More information and reports on normal weather conditions and departures from normal can be found on the NOAA Climate Prediction Center website, NOAA U.S. Climate Normals website, NOAA Climate Normals Quick Access Page.
Crop update
Similar to last week, field conditions are drying out, and it has been easier to get crew members and machinery in the fields to trim trees, chop brush, plant trees and install trellis. Timing for bloom thinning is here for peaches and apples if needed for your orchard blocks.
Cool temperatures are extending bloom across the region. Honey bees and bumble bees have been actively working in blossoms this week. Honey bees will forage at temperatures at 65 degrees Fahrenheit or warmer. Bumble bees and solitary bees will forage at temperatures 5-10 degrees cooler than honey bees. During bloom, use practices that minimize pesticide exposure to bees. Find tips and guidelines to minimize bee pesticide exposure in the articles below, provided by Michigan State University Extension bee educator Ana Heck.
- Pollinator stewardship during fruit crop bloom
- Protecting Pollinators – a guide to understand pollinator language on pesticide labels
- Michigan Pollinator Protection Plan Resources
- Pollinator supportive trees and shrubs for farm and orchard windbreaks
- Pollinator planting guide
Apple varieties in Oceana County range from pink to early bloom. Early varieties such as Zestar and Idared are at about 20% bloom, and later varieties such as Gala and Honeycrisp are at pink. In Sparta, early varieties are at full bloom, and later varieties like Gala and Honeycrisp are at king bloom to full bloom.
Growers are continuing to assess potential damage from cold temperatures on April 19-20 and May 2. As a reminder, damage will depend on the stage of development and the environmental variability across orchard blocks at the time of the cold event. Scout block by block to determine the damage in apple and other tree fruit crops. Damage can occur at a range of temperatures depending on stage of development. It’s important to look at the center of the flower to see if the pistil is damaged. See this article on evaluating frost or freeze damage and assessing the impact of cold temperatures on early fruit development.
Apple thinning programs should be considered as we get closer to bloom and return bloom can be evaluated. Thinning of apple can start with pruning by removing excess fruit buds. Earlier thinning will improve fruit size and quality. Carbohydrate and nutrient resources available early in the season are divided between the number of fruit buds on the tree. By removing excess buds, more resources are available to remaining buds. While it is still early and freeze damage is still being evaluated in some apple blocks, begin thinking about thinning strategies for this season. See this article on general apple thinning recommendations and decision-making tools.
Some trees may be stressed from last season due to the drought conditions experienced in 2025. Consider tree stress, return bloom and freeze damage when determining thinning programs for this season.
Apple scab risk is predicted to be little to none this week in Hart according to the RimPro model due to dry conditions. For the Hart Enviroweather station, risk for apple scab infection was low during the rain event on April 29. Only three spores per rod were counted in Hart.
For Sparta, the RimPro model also shows little to no risk this week due to dry conditions in the forecast. However, this is always subject to change depending on weather patterns and lake effect conditions.
Early copper application in apple and pear will knock down bacterial populations of the fire blight pathogen, Erwinia amylovora. The MSU Enviroweather fire blight model for Hart and Sparta is predicting little to no risk of fire blight infection over the next few days due to cool temperatures and dry conditions. EIP values are predicted to be zero from May 7–11, well below the recommended 70 EIP threshold for treatment. As flowers continue to open over the next few weeks, monitor infection risk through the Enviroweather model if rain and high temperatures occur during bloom.
Pink sprays will be needed to manage early season pests like obliquebanded leafroller, European red mite, aphids and tarnish plant bug if needed. Scout block by block to determine management needs. Now is a good time to put up mating disruption for oriental fruit moth and codling moth before first flight begins.
Tart and sweet cherry buds are in full bloom. Cool, dry conditions are leading to lower risk for European and American brown rot during bloom. European brown rot (blossom blight) infection occurs under cool, wet conditions. Infection can begin in the popcorn stage before bloom. Treatment should include two applications, one at white bud and the other at full bloom. See more information on managing European brown rot. American brown rot infection occurs in warmer temperatures above 65 F.
The risk for cherry leaf spot in tart cherry is currently low but will start to increase as bract leaves emerge and temperatures warm up. Cherry leaf spot is caused by the fungus Blumeriella jaapii. This fungus overwinters on the ground in diseased leaves. Fungal ascospores are released in spring during prolonged wetting events. According to George Sundin, MSU tree fruit pathologist, spores can infect as soon as bract leaves emerge. Spores infect through open stomata, and stomates on bract leaves were shown to be open when they emerged from buds.
Peaches are at full bloom and early petal fall in some varieties. During bloom, fungicide applications for brown rot may be needed; however, with cool, dry conditions, brown rot infection risk is low. Rusty spot (powdery mildew) management may be needed in peaches, particularly if disease pressure was high in 2025. Now is a good time to put up mating disruption if you have not done so yet. Oriental fruit moth traps should be placed in peach blocks to monitor for first catch and set the biofix date.
Plum varieties are at full bloom or early petal fall in west central Michigan.
Pear varieties are at full bloom. Similar to last week, applications to manage pear scab may be needed to cover new green tissue before the next rain event.
Additional pest and disease information
Only one green fruitworm adult was trapped this week out of five traps. One redbanded leafroller was also trapped.
At the Trevor Nichols Research Center, an average of 19 oriental fruit moth adults per trap were caught. No plum curculio were trapped this week, likely due to cooler temperatures over the weekend. The first catch of lesser apple worm was reported with 0.3 adults per trap.
For more information about regional reports, please visit the Michigan State University Extension website.
This work is supported by the Crop Protection and Pest Management Program [grant no 2024-70006-43569] 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.
