Northwest Michigan fruit update – April 18, 2017

Tree fruits are developing and primary apple scab season is underway in northwest Michigan.

Weather report

We had warm, summer-like temperatures over the weekend, and we hit daytime highs of 73 degrees Fahrenheit at the Northwest Michigan Horticulture Research Center on Saturday, April 15, and 66 F on Sunday, April 16. Growers have been concerned about the recent cold, overnight temperatures, and we had some growers use frost fans last night, April 17-18. Cold, overnight temperatures are also predicted to drop to or just below freezing April 20. 

Our growing degree-day (GDD) accumulations are similar to our long-time average. So far this year we have accumulated 153.9 GDD base 42 and 55.5 GDD base 50. Our averages are 120.5 GDD base 42 and 47.1 GDD base 50. Using forecast data, we anticipate to be at bud burst in tart cherry by April 30.

We also had rainfall over the weekend, and the Northwest Michigan Horticulture Research Center received about 0.75 inch of rain. Most growers were covered prior to the rain and likely will need to cover up again for the next predicted rain. The forecast is predicting rain on Thursday and Friday this week, April 20 and 21.

GDD accumulations as of April 18, 2017, at the Northwest Michigan Horticulture Research Center








27-year average

42 F








50 F








Crop report

Tree fruit continues to move slowly, but we are seeing green tip or side green in all apple and cherry varieties. Growers have been watching forecasts to predict when to cover up prior to rain. Growers are also watching temperatures and rainfall/snow for pruning sweet cherries with the threat of bacterial canker.

We had an excellent high-density sweet cherry pruning demonstration at Lutz Farms and King Orchards on April 17.  We had over 40 growers in attendance at King’s. Thank you to all that came out to this event.

Pest report

Primary apple scab is underway in northwest Michigan and growers that had green tissue present last week covered susceptible tissue prior to rainfall. Depending on when green tip occurred, there could have been either one or two apple scab infection periods. The Northwest Michigan Horticulture Research Center is monitoring for primary apple scab spore discharge this season and following rainfall over the weekend, spores were discharging. Most areas received enough rainfall to wash off residue and growers are planning to recover prior to the coming rain.

Furthermore, although temperatures have been cooler and development has slowed, there has been new growth since last week and this new growth should also be protected from possible scab infections. Dry weather last season was a blessing, and most of the area had low scab incidence; however, maintaining good protection during primary scab season is key for effective season-long scab management.

Green fruitworm have been flying on warmer days and we have received several calls regarding scale insects in apples and sweet cherries. Last season’s weather had favorable conditions for scale development and we had a few reports of San Jose scale on apples late in the season. We have also found San Jose scale in sweet cherries, particularly in Golds and other light varieties in previous years, so Michigan State University Extension encourages growers and consultants to keep a look out for this insect. We also visited an orchard last week with lecanium scale on sweet cherries adjacent to a woodlot.

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