A few days ago, Michigan State University Extension released a new report containing relevant information for the local cherry industry, delving into the main aspects to consider just weeks before a new season: weather, pests, and crop conditions are some of the topics addressed.
The low temperatures, especially in the spring months, have caught the attention of experts. According to Jeff Andersen, a climatologist at Michigan State University, medium to long-term forecasts indicate warmer-than-normal temperatures for the growing season, although so far, low temperatures have dominated the landscape in the state.
So far, the season has accumulated 218 growing degree days (GDD) base 42 and 148 GDD base 50. Still ahead of the long-term average of 72.7 GDD base 42 and 58.7 GDD base 50. With warmer weather, Michigan is catching up to the average with base 50 accumulations.
Crop Report
The following growth stages were assessed at the Northwest Michigan Horticultural Research Center on the afternoon of April 22nd:
Balaton – tight cluster
Bartlett Pear – green cluster
Montmorency – bud break
Potomac Pear – late green cluster
Emperor Francis – early white bud
Gold – tight cluster
Ulster – early white bud
Riesling – early bud swell
Gala – tight cluster
Honeycrisp – tight cluster
To run frost fans or not? That’s precisely one of the doubts that has arisen among producers due to the predictions for these days. According to Andersen, the forecasted low temperatures could be a mix of frost events, both advective and radiative. Advective frost events occur when cold, dry air blows into a region from elsewhere, while radiative frosts occur when clear and calm conditions allow heat to escape from the Earth’s surface and lower the local temperature.
Radiative frosts often have a warmer layer of air above the surface called inversion: inversions create a situation where frost fans are useful to mix warm and cold air and reduce potential frost damage. However, advective frost events do not have a warm and cold layer and are often associated with wind; therefore, frost fans are not effective against this type of frost event.
Pests
With warmer temperatures, there has been a lot of pollinator activity in recent days. Commercial honeybee colonies and bumblebees have been coming to northwest Michigan orchards for cherry and apple pollination. Honeybees will forage at temperatures of 65ยฐF or warmer. Bumblebees and solitary bees will forage at temperatures five to ten degrees cooler than honeybees.
As we approach flowering, it is necessary to implement practices that minimize pollinator exposure to pesticides by using reduced-risk pesticides and spraying at times when pollinators are not active.
Brown rot: Concerns arise when brown rot infects sweet cherry at the white bud stage and peaches at the pink bud stage. Optimal conditions for its growth involve warmth and moisture.
Dormant oil use: It’s advised to refrain from using dormant oils due to the anticipated low temperatures in the forecast. Optimal temperatures for application range from 40 to 70 degrees Fahrenheit to prevent any phytotoxicity concerns. It’s crucial to avoid applying oils within 48 hours before or after a frost event, and refrain from using sulfur or Captan within five days of applying oil. Once the risk of low temperatures diminishes this week, dormant oils can be safely applied: on apricot until first bloom, on cherry until the white bud stage.
Source: Michigan State University
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