Northwest Michigan fruit update – May 9, 2017

Fruit damage assessments are underway following two nights of freezing temperatures in the region.

Weather report

Unfortunately, northwest Michigan recorded some low overnight temperatures for the past two nights, May 7-9. During the early morning of May 8, the Bear Lake Enviroweather station recorded temperatures in the mid-25 degree Fahrenheit range for five hours. Benzonia, East Leland, Eastport and Elk Rapids Enviroweather stations also fell below freezing. Kewadin, Northport, Old Mission and the Northwest Michigan Horticulture Research Center Enviroweather stations did not record temperatures below freezing on that evening. The next evening and into this morning, May 9, all northwest Michigan Enviroweather stations recorded temperatures below freezing. The East Leland Enviroweather station recorded the lowest temperatures in the region, and temperatures hit a 23.2 F low at 6 a.m. this morning.

Overall temperatures have been cool over the past week. The weekend also brought very cold winds from the north; these winds continued into Monday but then the wind died down on Monday into Tuesday morning when the region became calm overnight. We have accumulated 284 growing degree-days (GDD) base 42 and 113 GDD base 50. With the recent cool temperatures, we have fallen behind on our GDD accumulations compared with our long-term average.

GDD accumulations as of May 8, 2017, at Northwest Michigan Horticulture Research Center

Year

2017

2016

2015

2014

2013

2012

27 Yr. Avg.

GDD42

284

279

309

146

274

528

303.1

GDD50

113

109

145

41

147

260

135.1

2017 growth stages as of May 8, 2017

  • Bartlett pear – white bud
  • Potomac pear – early white bud
  • Mac – early pink
  • Gala – pink
  • Red Delicious – pink
  • Honey Crisp – pink
  • Montmorency – early white bud
  • Balaton – early white bud
  • Hedelfingen – Full bloom
  • Gold – 10 percent bloom
  • Napoleon – Full bloom
  • Riesling – Early bud swell

Crop report

Plant development has been extremely slow with the recent cool temperatures over the past week—development seems to be at a standstill. However, temperatures are expected to warm this week into the 60s, and plant development will move along quickly under these conditions.

In the wine grape research vineyard, all varieties are showing bud swell to some degree. Some of the earliest hybrids, such as LaCrescent, have pushed to the point that the edges of the first leaves are showing. There was no injury from the Monday or Tuesday morning frosts, but there may have been injury at other sites in northwest Michigan where temperatures in the low 20s were recorded. No pest insect activity has been seen. The window for dormant or delayed dormant applications for powdery mildew will be over soon.

Very little change in saskatoons has occurred since last week; most sites I’ve seen are just beginning to show the white tip stage of bud development. No pest insect activity has been seen. We are not certain of the prime infection periods for Entomosporium leafspot or saskatoon-juniper rust, but these fungal diseases may now be releasing spores if rainy weather occurs.

Currently, we are at various stages of bloom in sweet cherries depending on variety and location across the region. We are just starting to see the first white in tart cherries, and apples are just approaching the pink stage. Hopefully, we will see less damage from the frost/freeze events since we are not as far along in development.

In tart cherry early white bud, we typically see damage at 24-28 F, and 25-28 degrees F at first bloom in sweet cherries (see critical spring temperatures for tree fruit bud development stages). Apples at pink will have damage at 24-28 degrees F. Due to cool temperature, some growers are considering ReTain applications to extend blossom life and encourage pollination. Apple growers in frosted areas are weighing their options for Promalin (Valent)/Perlan (Fine Americas) applications in hopes to set parthenocarpic (e.g., seedless) fruit. For more information, see the Michigan State University Extension article, “Setting apples with plant growth regulators.”

Pest report

The weather has been dry since last week’s report and, as a result, these conditions have not been favorable for disease development. The coming forecast looks mostly dry with a slight possibility for rain toward the end of the week. Hence, the coming week is, for the most part, a positive outlook for low chances of infections of most tree fruit diseases.

Bacterial canker is a concern in areas with freezing temperatures that killed blossoms and in some cases cherry foliage. Although copper is phytotoxic on sweet cherry foliage, growers that had blossom and foliage damage in sweet cherries are considering a copper application to reduce bacterial canker populations. As frozen tissues thaw, the bacteria can move into woody tissue; hence, minimizing the surface populations with a copper spray could help to lessen infections.

The last apple scab infection period occurred during the first few days of May and growers should continue to monitor the forecast to determine when to put on their next scab spray. Warmer conditions are predicted, which should accelerate growth, and as the season progresses, we can expect higher numbers of spore discharge and increased risk of infection in future rains when they come.

At this time, the forecast of dry weather with moderate temperature is not looking particularly favorable for European or American brown rot. Additionally, the inoculum load in most orchards is low coming into this season. However, if Balaton or Montmorency orchards had European brown rot last season and the forecast changes to cool wet conditions, growers may want to consider a European brown rot spray. Similarly, growers may want to consider management in orchards if they had American brown rot-infected fruit last season and warm wet conditions arise during bloom. Again, conditions do not look particularly favorable for either brown rots.

Bract leaves are present and these small leaves are susceptible to cherry leaf spot when conditions favor cherry leaf spot infection periods. Fortunately, leaf spot infections were low last season in the region and recent conditions have been cool and dry, which does not favor cherry leaf spot development. Temperatures above 46 Fahrenheit are needed for this pathogen to develop and sufficient rains are required for spore release.

As temperatures are predicted to warm up this week, we are anticipating apple blossoms could open quickly. If this is the case, growers should be ready to start fire blight sprays. Last season was highly favorable for fire blight and infections were widespread in the region. We encourage growers to monitor the epiphytic infection potentials (EIP) values on Enviroweather’s MaryBlight model if we do move into bloom quickly.

Cooler temperatures have slowed insect activity in the last week. We found an average of six green fruitworm moths at the Northwest Michigan Horticulture Research Center in our American plum borer traps in cherries. In apples, oriental fruit moth and spotted tentiform leafminer traps are up with no catches thus far, and we will begin monitoring for San Jose scale and codling moth later this week.

Related Articles

Related Resources