West central Michigan tree fruit update – June 19, 2024
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EmailTart cherries are turning from straw colored to red, and sweet cherry harvest may begin at the end of the week for early varieties.
Weather update
Temperatures have been hot over the past week with highs in the 70s and 80s and lows in the 50s and 60s according to the Hart Enviroweather station. Temperatures will remain high through the end of the week with high temperatures reaching the upper 80s by the beginning of next week. Over the past few days, weather conditions have been mixed with rainy and dry days. Windy conditions continue to be prevalent across the region. Relative humidity ranged from the 60s up to 100% this week, and evapotranspiration has been high. More rain is forecasted through the rest of this week.
Fruitlets are growing steadily (Photo 1). Based on the Hart Enviroweather station for June 18, current growing degree-day (GDD) accumulation is 1,297 GDD42 and 715 GDD50. Over the next few days, high temperatures will remain high and in the 80s through early next week.
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.
Crop update
For early apple varieties, most advanced fruitlets range from 43 – 49 millimeters (mm) for Zestar, Honeycrisp fruitlets ranged from 37 – 43 mm and Gala were 32 – 37 mm. Minnieska fruitlets were 44 – 46 mm in Hart.
More apple scab (Venturia inaequalis) lesions were observed this week on leaves. Continue scouting orchards to determine if some blocks have apple scab symptoms showing from primary scab infections. With rapid tree growth in our region, adequate fungicide coverage is key to minimizing apple scab infection as primary scab season continues. Coverage is also important for pear blocks in the region for pear scab (Venturia pirina).
Tart and sweet cherry are growing rapidly. Fruit size for early sweet cherry varieties are 26 – 29 mm. Tart cherry fruitlets are about 16 – 17 mm in size. Cherry leaf spot pressure has been consistent with warm and wet weather conditions. Lesions on leaves, stems and fruit have been observed across the region. Continue protecting leaves from rapid cherry leaf spot infection. As a reminder, chlorothalonil, copper products and Captan are effective materials against cherry leaf spot. Note that chlorothalonil has a 10-day retreatment interval, and application of captan or copper products may be needed sooner than 10 days to protect leaf and fruit tissue. Note that captan and copper application at high temperatures (80s) may lead to phytotoxicity. Apply these products at cooler temperatures or at nighttime.
Powdery mildew has been observed in apple and cherry orchards in the region. Powdery mildew is caused by the fungus Podosphaera leucotricha. As a reminder, sterol inhibitors, strobilurins and succinate dehydrogenase inhibitors control powdery mildew. Captan, Scala, Vangard and EBDC fungicides will not control powdery mildew.
American brown rot was observed this week in a mature sweet cherry block. Cracking from rain or wounding due to bird damage or bacterial canker infection in sweet cherries leads to higher likelihood of brown rot infection. As fruit gets closer to harvest, susceptibility to brown rot increases. Consider if brown rot management is needed. Using Indar may not be effective, even at the highest labeled rate of 12 ounces per acre. Previous research and resistance screening of American brown rot isolates in west central and northwest regions found that most screened fungal isolates had functional resistance to Indar. Find more information about this study. Effective materials for managing American brown rot include Merivon, Miravis and Cevya. Full coverage of all rows will be important to manage this disease.
Peach fruitlets are growing steadily with many fruit setting this year across varieties. Venture peach fruitlets are 34 – 39 mm in size at the West Central Michigan Research and Extension Center. Some growers are hand thinning peaches this week in the region.
Pear fruitlets are growing rapidly and fruit set is moderate for varieties such as Bartlett, Gem and Cold Snap. The largest fruitlets were 27 – 31 mm in diameter for Bartlett pear trees at West Central Michigan Research and Extension Center.
Plums are growing rapidly with high fruit set for many varieties. Growers have been hand thinning plums as needed this week.
Pest update
Consider scouting reports and block history to target hot spots for orchard pests according to fruitlet stage. Spotted wing drosophila (SWD) was trapped this week in Oceana County at four locations. Spotted wing drosophila has been observed in other fruit grower regions across the state.
On June 17, the Trevor Nichols Research Center in Fennville, Michigan, trapped pests such as codling moth, oriental fruit moth, adult obliquebanded leafroller and greater peachtree borer. Dogwood borer was trapped at Trevor Nichols Research Center and was also trapped at two locations in Oceana County this week.
Dogwood borer was observed this week in Oceana County. Adult emergence is typically in mid-June, and egglaying occurs over a four- to six-week period. Trees with burr knots (adventitious roots) are highly susceptible to dogwood borer infestation. Burr knots typically develop on the above ground portion of the clonal rootstocks. Dogwood borer larvae feed inside the burr knots, and if larvae continue to feed below the bark, damage can eventually girdle the tree. For more information about the borer pest complex and control alternatives, read this article by John Wise and Julianna Wilson, Michigan State University Department of Entomology.
Greater peachtree borer (peachtree borer) has not yet been trapped in the region.
Green apple aphid nymphs and adults were observed feeding on the underside of leaves this week. Scout to determine if management is needed. Many aphid predators such as lady beetles and lacewings can help keep aphid populations in check. In general, established orchards can sustain thresholds of an average of three to four infested leaves on terminals before fruit damage occurs from honeydew.
Green peach aphid was observed this week. Adults and nymphs were present and caused leaf curling and yellowing from feeding on the undersides of leaves. Monitor orchard blocks to determine if a treatment is needed.
Lesser apple worm was observed in low numbers this week. Only 0.7 adults per trap were found in Oceana County. Lesser apple worm larvae feed on small fruit or can borer into succulent shoot terminal this time of year. Growers should apply sprays that target adults before egg lay occurs.
Lesser peachtree borer has been observed in the region. An average of 1.3 borers per trap were counted at the West Central Michigan Research and Extension Center. Similar to greater peach tree borer, mating disruption is recommended for lesser peach tree borer in orchard blocks with at least 5 acres and trees that are at least 3 years old.
Rosy apple aphid and woolly apple aphid are common pests in our region. Scout for colonies of rosy apple aphid nymphs in fruit clusters. Woolly apple aphids were found in pruning scars and nodes of interior and upper branches. They are starting to become more prevalent in orchards and are often more dense in the center of the orchard compared to the orchard edge.
Obliquebanded leafroller adults were trapped this week in Oceana County in tart cherry and apple orchards. An average of 15.5 adults per trap were found in tart cherry, and 1.3 adults per trap were found in apple.
Oriental fruit moth was trapped at one location in Oceana County with an average of two oriental fruit moths per trap. Adult moth catches have declined. For the West Central Michigan Research and Extension Center, oriental fruit moth was first observed in peaches this season, and a biofix date of April 29, but the second generation should be starting soon.
Spotted wing drosophila was trapped this week in Oceana County. On average, 56 females and seven males were trapped. As the fruit are turning red and softening, they are susceptible to SWD infestation. Read more information on SWD and management recommendations.
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.
