East Michigan fruit update – Aug. 1, 2017

Brown marmorated stink bugs are being caught in traps in apple blocks, with spotted wing Drosophila and apple maggot populations remaining high.


While the average July rainfall for the eight Michigan State University Enviroweather stations that I regularly report on was 2.42 inches, as I move about the region I see signs of extreme variability for the month. Many fruit farms have soils that are very dry, with wilting of newly planted tree and small fruits. You can travel less than five miles from farms that are very dry to find farms that have too much soil moisture, with lush green grass in the orchard. Most farms have been dry for the last two weeks.

Our season remains ahead of normal in terms of growing degree-day (GDD) totals and the beginning of harvest of our summer fruit crops, however with some cooler temperatures, our season has dropped back a bit to being about two to five days ahead of normal.

East Michigan GGD totals for March 1 to July 31, 2017





Commerce (Oakland County)




Deerfield (Monroe County)




Emmett (St Clair County)




Flint (Genesee County)




Freeland (Saginaw County)




Lapeer (Lapeer County)




Pigeon (Huron County)




Romeo (Macomb County)




Tree fruits

Apples have continued to size well for this time of the season, surprisingly even on some sites that have been on the dry side. Apples are mostly 2.75 to 3.25 inches in size for the largest fruit, like Honeycrisp, however there is a wide range of fruit size this season. Apples continue to color well. Some varieties have set most of their terminal buds, and summer pruning has begun on these varieties.

A number of summer apples are being harvested, including Jersey Mac. For more information see the MSU Extension article “Predicted 2017 apple harvest dates.”

Brown marmorated stink bugs are being caught in traps at several orchards. If you had brown marmorated stink bug fruit damage in 2016 or are finding them feeding on apples in the last few days, now is the time to begin to control them. They seem to prefer to feed on green varieties at this time of the season, but not always. As was discussed at the brown marmorated stink bug clinic in June, the timing for brown marmorated stink bug control is generally the same as for the second-generation codling moth larvae, which is this week. Many growers biofixed for second generation codling moth in mid-July, so adding 250 GDD base 50 from that biofix this week is also good timing to control codling moth.

Apple maggot trap catch started on red sticky traps last week, and numbers have continued to climb this week. This is occurring even on farms where soils are dry, which is unusual.

Twospotted spider mites were found last week and this week apple rust mites are being found in isolated hotspots in apples. Woolly apple aphids continue to move from pruning cuts to terminal branches. Japanese beetle numbers seem to be leveling off or even starting to decline in several fruit crops. Where it has been controlled, numbers are generally low this week. Assassin bugs, a beneficial insect, are being seen this week in apples and other tree fruit crops.

Sooty blotch, flyspeck and black rot were first reported as new pests last week. This week, their symptoms are becoming more common. A few new fire blight strikes continue to show up, mostly in bearing apple blocks.  

Pears are close to 2 inches in size, with much of the fruit having frost marks. All stages of pear psylla are being found, with close to a third of the fruit on some varieties having sooty mold from this pest.

Peach harvest of pre-Red Haven varieties continues at most farms. Red Haven harvest is expected to begin later this week. Most varieties have sized and colored well in the last week, with most being 2.4 to 2.6 inches in size. Leaves and fruit in a few blocks have a touch of bacterial spot.

Sweet cherry harvest has wrapped up.

Tart cherry harvest has wrapped up. Cherry leaf spot continues being found in most tart cherry blocks, causing leaf yellowing and premature leaf drop. Leaf drop is extensive in some blocks.

Plums have taken on a nice swell and are starting to color for European types, which are mostly 1.35 inches in size. Some Japanese varieties continue to be harvested, like Shiro. Overall, this season’s plum crop is extremely variable, with some varieties having little to no fruit this season. Twospotted spider mites are being found in isolated hotspots in plums.

Small fruits

Strawberries are starting to regrow from renovation where soil moisture has been adequate. New plantings continue to runner well.

Potato leafhopper populations continue to build in new plantings where they have not been controlled. Keep an eye on the new foliage in newly planted fields for signs of continued leaf curling from this insect feeding.

Raspberry harvest continues for summer red raspberry varieties, although we are past the peak of harvest. Fall raspberry varieties continue having good growth, with most canes 40 to 44 inches in length. The bud berries on shorter canes continue to ready to harvest, with the main crop starting to size well and even some early color development.

Spotted wing Drosophila (SWD) are continuing to be caught in traps in summer raspberries in very high numbers. In the last week, I have heard even more reports of SWD-infested fruit.  

Blueberry harvest continues for many varieties this week, including Jersey. Berry size on Jersey has been on the small side this season. Overall, we have a very nice blueberry crop this season at most farms.

SWD trap catch continues at very high levels for this time of the season. I have had several reports of SWD infested fruit in the past week, causing a halt in harvest operations. Control measures should be underway in blueberries. As I shared last week, I have not caught any blueberry maggot yet, but am expecting to see catch any day now.

Phomopsis canker was first reported in blueberries last week, and this week I am finding isolated strikes to be more widespread. It causes sudden wilting and death (flagging) of canes.

Grapes continue to size well for Concord and Vinifera types.

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