Northwest Michigan fruit update – May 5, 2020

The region is two weeks behind normal due to cold temperatures and freezing temperatures are forecasted for this week.

Weather report

Happy Cinco de Mayo! With a persistent chilly spring, it doesn’t seem there is anything new to report with the weather. However, we did have 1.5 warm days over the weekend, which felt great and moved things along surprisingly quickly. On Saturday, May 2, the daytime temperature hit 68.8 degrees Fahrenheit at the Northwest Michigan Horticulture Research Center Enviroweather station. Those springtime temperatures disappeared quickly on Sunday, May 3, and we were back to cold winds and temperatures in the 40s.

Cold conditions have continued so far this week, and Michigan State University’s state climatologist Jeff Andresen says we can expect cold weather to dominate for the next two to three weeks. He predicts we will see some moderations about the third week of May.

Thus far, we have accumulated 130 growing degree days (GDD) base 42 and 32 GDD base 50. These accumulations are well behind our averages: 245 GDD base 42 and 105 GDD base 50. Currently, we are similar to degree day accumulations last season (2019).

Growing degree days (GDDs) through May 4, 2020

Year

2020

2019

2018

2017

2016

2015

30 Yr. Avg.

GDD42

130

134

140

271

239

224

245.7

GDD50

32

49

61

111

93

90

105.1

More of a concern with weather is the coming cold conditions later in the week. At this point, potential freezing conditions could occur overnight Thursday into Friday and Friday into to Saturday, and Andresen thinks that Friday into Saturday could be the most challenging. However, weather may change, but the MSU fruit team has written an article on how to best prepare for a frost/freeze event, if it happens. Additionally, anecdotal evidence suggests that cold and dry conditions prior to a frost/freeze event may be helpful in reducing damage.

We received rain last week, and the Northwest Michigan Horticulture Research Center Enviroweather station recorded 0.38 inch on Monday, April 27, and 1.65 inches on May 29. There is little rainfall in the forecast for the remainder of the week, but we may see snow on Monday. Andresen thinks that some areas will have snow accumulation. You can view Andresen’s weather report for May 5, 202.

Crop report

Cool conditions have slowed tree development. At the Northwest Michigan Horticulture Research Center, we are currently at bud burst in sweet cherries and green tip in Montmorency. We are slightly ahead in Balaton, and we have observed bud burst in this variety. Honeycrisp and Gala are at half-inch to early tight cluster, respectively, and apples have moved particularly fast with the weekend’s warm temperatures. Growers were active over the weekend covering green tissue, but the cold conditions will slow tree growth as well as pathogen development. Growers are also still planting trees, but the wet conditions made for muddy work in many sites.

Pest report

Rainy weather last week resulted in moderate to heavy apple scab infection periods throughout much of the region. If infection occurred, symptoms could be visible in the second week of June. Some areas received a brief rain that brought a few hundredths of an inch and lasted just a few hours over the weekend. RIMpro models are reporting that spores were released during both the long infection period over the April 29 to May 1 and during the short rain on May 2 that did not result in an infection. Last week’s moisture and warm weather over the weekend pushed new growth on apples. Growth will continue albeit potentially slowly in the cooler weather ahead. Currently, this week is looking mostly dry, but keep an eye on the forecast and the RIMpro models as forecasts can change quickly.

Sweet cherry varieties and Balaton pushed over the weekend and are at budburst. Again, development will be slower in cooler weather, but growers should start thinking about popcorn and bloom management strategies for diseases.

With regard to insects, we have been slow to accumulate degree days. Despite cool conditions, we set pheromone traps for oriental fruit moth, spotted tentiform leafminer and American plum borer at the station. It is still pretty early for these pests to be active, but we will be ready for them when they emerge.

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