Northwest Michigan fruit update – May 14, 2024

Apples are in full bloom and fire blight EIPs are low with the cooler weather. Sweet cherries are coming out of the shuck and tart cherries are at late petal fall.

For decorative purposes.
Honey bee on Gala flower. Photo by Erin Lauwers, MSU Extension.

Weather report 

Following some cool and wet weather on Saturday, May 11, the weather has been sunny and clear. Daytime temperature highs have varied across the region, but for the most part the days have started off cool and warmed into the low to mid-60s. Mother’s Day was a beautiful day, and we hope everyone had a great one: conditions were sunny and slightly breezy with daytime highs topping out at almost 76 degrees Fahrenheit. Even with the warmer conditions, the cold north wind is still present this spring. With all the outside work at the Northwest Michigan Horticulture Research Center so far this season, we have commented on how warm it feels when we are out there, and we are caught off guard when temperatures are only reading 58 F; we need to toughen up before summer hits.  

According to Jeff Andresen, we will have variable clouds today, May 14, and some areas to the south may see isolated thunderstorms and scattered showers. Here in the north, it will mostly be sunny and cool. Similar conditions will be present tomorrow in the north with rain moving in Thursday, May 16, into Friday. The forecast is also predicting a lower chance for rain to continue into the weekend.  

Daytime temperatures will remain in the 60s with overnight lows in the 40s to low 50s by the weekend. Andresen also predicts that the northern part of the state will have above normal potential evapotranspiration (PET) rates (weekly totals of 0.90-1.20 inches) this week. The medium range forecast is calling for near to above normal precipitation for the rest of May. Temperatures will fall from normal to above normal next week to below normal levels for the end of the month.  

We have accumulated 464.9 growing degree days (GDD) base 42 and 189.8 GDD base 50 so far this season. These accumulations are still well ahead of our long-term average: 351.2 GDD base 50 and 159.2 GDD base 42. At the Northwest Michigan Horticulture Research Center, we received 0.19 inches of rain on May 11 and 0.06 inches of rain on May 12. 

Crop report 

The following growth stages were evaluated at the Northwest Michigan Horticulture Research Center yesterday afternoon (May 13): 

  • Balaton – petal fall 
  • Bartlett Pear – petal fall 
  • Montmorency – petal fall 
  • Potomac Pear – petal fall 
  • Emperor Francis – early shuck split 
  • Gold – petal fall/in the shuck 
  • Ulster – early shuck split 
  • Riesling – bud burst 
  • Gala – full bloom, early petal fall 
  • Honeycrisp – full bloom 

Most growers are wrapping up pruning. There is still some planting going on in the region. We planted 2,000 trees this spring at the Northwest Michigan Horticulture Research Center. Bees can move into the orchards with their tractors. Honey bee hives are more common in orchards this week as growers prepare for bloom. Honey bees are being moved out of blocks as growers prepare to make applications for insect control appropriate for the growth stages of the crops.  

We planted new sweet cherries at the Northwest Michigan Horticulture Research Center, and we removed many buds during the planting process. To address the lack of lower branches, we painted on latex paint with Promalin added for improved bud break and future lower branching; Promalin works best at warmer temperatures. In addition to Promalin, we also notched to better ensure future branching. It is still early for Pro-Gibb applications in cherry. 

Pest report 

Honey bees will forage at temperatures at 65 F or warmer. Bumble bees and solitary bees will forage at temperatures 5-10 degrees cooler than honey bees. During bloom, growers are encouraged to implement practices that minimize pesticide exposure to bees by using reduced risk pesticides and spraying at times when pollinators are not active. Find tips and guidelines to minimize bee pesticide exposure in the Michigan State University Extension article “Pollinator stewardship during fruit crop bloom.” 

Apple scab: Leaf tissue will continue to expand and need to be covered before the next rain to protect against primary scab infection. There is a noticeable warming trend later this week and widespread precipitation expected on Thursday evening into Friday, which will provide good conditions for apple scab to infect. 

RIMpro links:   

Cherry leaf spot: The wet weather and warm temperatures in the forecast will be optimum for cherry leaf spot infection. Rapidly expanding leaf tissue will need to be protected.  

Fire blight:  Blossom blight infection of fire blight should be kept in mind during bloom. The Enviroweather fire blight model can be used to assess infection risk potential by choosing your closest weather station and entering date of full bloom. Epiphytic infection potentials (EIPs) are currently low but should be monitored as temperatures increase with the coming warming trend. Disease management is recommended if the EIP exceeds 70.  

Powdery mildew: Powdery mildew is reportedly showing up in southeast Michigan on apples. Powdery mildew was severe in many apple and cherry orchards in 2023 and inoculum levels are expected to be high this year. Managing this disease will become critical if dry conditions return now through petal fall. Emerging leaves from buds infected last season will begin to produce conidia and result in an early secondary infection period. 

American plum borer: An average of 17 American plum borer were caught this week at the Northwest Michigan Horticulture Research Center.  

Black stem borer: Numbers were lower this week with an average of four per trap.  

Codling moth:  The first codling moth were trapped this week at the Northwest Michigan Horticulture Research Center. If we have sustained catch next week, that will determine our biofix for this year.  

Green fruitworm: An average of six green fruitworm were caught at the Northwest Michigan Horticulture Research Center.  

Oriental fruit moth: No oriental fruit moth were caught this week at the Northwest Michigan Horticulture Research Center. 

Plum curculio: Damage is showing up on apples and other fruits in southwest Michigan. The warmer evening temperatures as the week goes on could increase plum curculio activity and cherries are coming out of the shuck. A prompt petal fall spray for apples is advised if temperatures are around the 70s.  

Spotted tentiform leafminer: An average of 56 spotted tentiform leafminer were trapped in apple orchards monitored at the Northwest Michigan Horticulture Research Center.  


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