West central Michigan tree fruit update – April 30, 2024
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EmailCherry trees are in full bloom. King bloom is beginning in early apple varieties.
Weather update
Over the past week, we’ve had a mix of warm and cold temperatures with rainy and windy conditions. Bud development has progressed with cherry orchards going into full bloom over the weekend (Figure 1). Below-freezing overnight temperatures were observed across the region last week on April 25 and 26. In some areas, overnight temperatures ranged from 24-28 degrees Fahrenheit on April 25, and as low as 31 F on April 26. Based on the Hart Enviroweather station for April 30, current growing degree day (GDD) accumulation is 336 GDD42 and 130 GDD50. Over 1.5 inches of rain were recorded for the Hart Enviroweather station from April 27 –29.
Warm weather, with highs in the 60s and lows in the 40s and low 50s, are forecasted this week. Rain is also in the forecast for the next few days. With the warmer weather this week, bud phenology is changing daily (Figure 2). Apples are expected to be in full bloom by the weekend. Over the weekend, highs will be in the 60s and 70s with lows in the 40s and 50s.
Weather data was gathered from 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 (which may be searched by region) and Midwest Regional Climate Center website.
View a full weather outlook from Michigan State University meteorologist, Jeff Andresen.
Crop update
Apple varieties in the west central region range from pink to king bloom. Early varieties such as Empire, Zestar and Idared have king blossoms open. Later varieties such as Gala and Honeycrisp are at pink. With bloom rapidly approaching, consider an early thinning program early this year. For general information on thinning strategies for Honeycrisp, check out this article from Michigan State University Extension, “Honeycrisp crop management for 2022.”
Tart cherry is at full bloom and bract leaves have emerged. Sweet cherry varieties are at full bloom. To increase fruit set in sweet cherries, growers can use ReTain, a plant growth regulator that has been shown to increase fruit set and yield. Based on experiments at the Northwest Michigan Horticulture Research Center, Michigan State University Extension recommends making ReTain applications early: popcorn to first bloom. Slow, drying conditions are preferred. See more information on ReTain experiments in sweet cherry.
Peaches are at full bloom to petal fall for early varieties. Thinning blossoms can help enhance fruit size and quality in peaches. Potential blossom thinning options include dragging large diameter ropes across canopies, rubbing buds with a gloved hand or brush, and spraying canopies with high pressure water systems. Chemical methods using caustic blossom thinners such as ammonium thiosulfate (ATS) are effective, and they damage flower parts and prevent pollination. Use of ACC as a bloom thinner may also be a viable option in the future. Formulations of ACC are not widely available for growers at this time and are under evaluation, but preliminary results suggest that ACC could be an effective chemical thinner for peaches. See more information on peach thinning strategies.
Pear is in full bloom, and Bartless was in full bloom over the weekend at the West Central Michigan Research and Extension Center.
Damage from freeze events last week is being assessed. Early observations suggest some damage in peaches, tart cherries and pears at the West Central Michigan Research and Extension Center. Early apple varieties such as Empire or Idared may also show damage to king blooms and laterals; however, a full crop is still expected this season in the west central region.
Pest and disease update
In the west central region, pear psylla eggs and adults have been observed on Bartlett pear at the West Central Michigan Research and Extension Center. Green fruitworm, redbanded leafrollers and variegated leafrollers were trapped in Oceana County this week. Oriental fruit moth was also trapped for the first time in Oceana County. If trapped again next week, a biofix date will be set based on sustained catch for two consecutive weeks.
Apple scab
Emerging tissue in apple remains at risk for apple scab infection. Generally, temperatures have been so cool that wetting periods have only led to low infection risks; however, warmer temperatures over the next week will result in high infection periods. Once new green tissue is present, protective sprays should be applied with adequate fungicide coverage.
Cherry leaf spot
It's time to start managing for cherry leaf spot. 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. In 2020, George Sundin reported that 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. Bract leaves are unfolding, so providing coverage of new tissue is critical moving forward this season.
Fire blight
Some growers have applied copper in apple and pear to knock down bacterial populations of the fire blight pathogen, Erwinia amylovora. Dormant and delayed dormant sprays help management fire blight primarily if fire blight was present the previous season. Early apple varieties are at pink and may be in bloom this weekend or early next week. Once flowers open, protecting blossoms is key to managing blossom blight. Streptomycin is an excellent material to manage blossom blight. If orchards have streptomycin resistance fire blight bacteria, Kasumin is another option for excellent control. See more information about blossom blight management. As trees advance to fruit set, an active fire blight management program is needed to target shoot blight with the Apogee and Actigard in combination.
Powdery mildew
Warm temperatures and high humidity this week may result in powdery mildew infection. Powdery mildew has already been observed in some orchards where disease pressure was high in 2023. Powdery mildew is caused by the fungus Podosphaera leucotricha. It affects cherries, apples and pears and causes infections on the underside of the leaf that lead to chlorotic patches or spots on the upper side of the leaf. Infected blossoms can cause poor fruit set or stunted and russetted fruit. Note that sterol inhibitors, strobilurins,and succinate dehydrogenase inhibitors control powdery mildew. Captan, Scala, Vangard and EBDC fungicides will not control powdery mildew. Manage powdery mildew from tight cluster or bloom through midsummer.
For pest and disease management recommendations, please refer to the Michigan Fruit Management Guide (E-154) for product guidelines.
For more information about regional reports, please visit the Michigan State University Extension website.
