Northwest Michigan fruit update – July 30, 2019

Sweet and tart cherry harvest is underway in northwest Michigan.

Weather report

The weather has been cooler and drier for the past week, but we did have some storms blow through on Friday evening into Saturday morning, July 26 and 27. This weather front brought various amounts of rainfall; East Leland Enviroweather station received just under an inch of rain while Bear Lake Enviroweather station reported almost no rain. Unfortunately, there was some hail reported in the weekend storms, but the orchards that were hit were fairly isolated. There were reports of some damage in apples and tart cherries, and there were also orchards that had high winds that resulted in wind whip. We have also heard reports of trees and limbs down in the highest hit areas.

Crop and pest report

In cherries, harvest season is ongoing and growers have been balancing harvest with pest and disease protection. Sweet cherry harvest is still underway, and growers have been challenged by spotted wing Drosophila (SWD), American brown rot and isolated incidences of sap beetles. All stages of SWD—eggs, larvae, pupae and adults—are not difficult to find at the Northwest Michigan Horticulture Research Center, especially in dark sweet cherries. Brine fruit are less infested and SWD do not appear to prefer the sweet cherry variety Gold in our choice tests.

Tart cherry harvest has also begun. Tart cherries seem to have less SWD infestation, but our previous experience suggests tart cherries are highly susceptible to SWD, and growers should continue to be diligent with management programs through harvest. Most reports of tart cherry quality have been good; there is some really ripe fruit in some blocks. This cooler weather will help with fruit quality at harvest.

Cherry fruit fly was detected on a trap on Old Mission Peninsula on July 27. We have not yet detected cherry fruit fly at the research station. After emergence, there is a seven-to-10-day preoviposition window to manage this pest. Many, but not all, of the products that are effective against SWD will also have efficacy against cherry fruit fly.

Cherry leaf spot post-harvest management is encouraged to help the trees keep leaves for as long as possible. Keeping leaves on through September should improve winter hardiness and prevent overall decline of tree health.

In apples, the hail that was received in some areas over the weekend was a fire blight trauma event and growers with blocks impacted by hail took action to prevent the potential for infection due to trauma. There is a greater risk for infection due to trauma blight until trees reach terminal bud set.

For obliquebanded leafroller, we have accumulated 886 growing degree days (GDD) base 42 since biofix (June 30), which indicates that more than 50% of eggs have hatched. Egg hatch is predicted to end at 1,000 GDD base 42.

Codling moth flight was down this week at the station with just one moth in each of the three traps. Since biofix (June 8), we have accumulated about 941 GDD base 50 and most eggs have hatched at this time. The first flight is expected to end at about 1,000 GDD base 50 after biofix, which could be by the weekend. However, we don’t often observe distinct generations for this pest in northern Michigan.

Apple maggot and brown marmorated stink bug have not been detected at the station at this time.

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