Southwest Michigan fruit update – Aug. 13, 2019

Spotted wing Drosophila numbers continue to climb.

Bumble bees pollinating fall red raspberry.
Bumble bees pollinating fall red raspberry. The bloom is at the shoot tips of the primocanes, the shoots that emerged this year. Photo by Mark Longstroth, MSU Extension.


Last week began warm with highs in the upper 80s. Temperatures dropped into the lower 80s later in the week. Scattered showers fell Tuesday and Thursday. Rainfall totals for the week varied from 0.5 to 1.3 inches. Rainfall totals for the season remain at about 14.6 to 20.6 inches across the region since April 1.

The forecast for this week is rain Monday night into Tuesday and then cooler with highs in the 70s and lows in the upper 50s. Soil are moderately dry and irrigators should be applying about an inch or more of water every five to seven days. Plants are using about 0.15 to 0.2 inches of water per day.

With the cooler temperatures last week, we accumulated heat units more slowly than the week before, about 198 growing degree days (GDD) base 42 and 195 GDD base 50.

Southwest Michigan GDD summary from March 1 – Aug. 11, 2019


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMREC)




Lawton (Lawton)




Fennville (TNRC)




Average for the SW region




Accumulation last week




Check out the animated weather forecasts from Jeff Andresen at the Weather tab in the Michigan State University Extension Fruit & Nuts Page. Articles and other regional reports can be found at the Fruit News page. There is no weather forecast for this week.

Tree fruit

Stone fruit trees not receiving their normal full nitrogen program are starting to show light green leaves due to deficiency and earlier dry conditions. August is the time to take leaf samples for nutritional analysis and soil samples for nematode analysis. First catch and biofix for first generation oriental fruit moth was May 6 (165 GGD base 45) at the Trevor Nichols Research Center. We are past the second generation. The third generation should be emerging now for the next two or three weeks. Oriental fruit moth trap catches are continuing to decline slightly but still are relatively steady for the past six weeks.

First trap catch and biofix of obliquebanded leafroller was June 14. The Trevor Nichols Research Center trap catch shows the start of summer generation flight and numbers are up in many commercial traps. Brown marmorated stink bug juveniles are being caught in traps. Summer adults should show up soon. Japanese beetle numbers are declining but are still causing feeding injury in fruit crops. Potato leafhopper are feeding and causing hopper burn on sensitive plants. The trap catch of male San Jose scale is still increasing at the Trevor Nichols Research Center. Twospotted spider mites have been building in some young fruit tree plantings, causing leaf browning and stunted growth.

In peaches the post-Redhaven group of varieties (Starfire, PF15A, John Boy and PF Lucky 13) are due to start harvesting this week, about one week later than normal. Estimated peach harvest dates are available on Enviroweather. Oriental fruit moth and San Jose scale are the primary insect concerns at this time.

Cherry post-harvest chlorothalonil applications help reduce late-season cherry leaf spot buildup without risk of resistance buildup. Cherry leaves are always susceptible to leaf spot, so management is needed to maintain a healthy leaf canopy during the entire season.

In plums, the start of Castleton harvest is about eight days away. This variety showed better fruit bud hardiness this year than most European plum types. Potential insect pests now are obliquebanded leafroller, codling moth and cherry and apple maggot. SWD can be a problem of ripe plums.

Golden 8_12_19
Golden Delicious apples near Paw Paw, Michigan. These apples will be harvested around the beginning of October. Photo by Mark Longstroth, MSU Extension.

Apple harvest of Paulared is about 10 days away. Foliar testing of Honeycrisp is recommended if bitter pit has been a problem. Excessive potassium in leaves and fruit can promote bitter pit problems. Estimated harvest dates for apples are approximately six to eight days later than normal and about eight days later than last year. ReTain applications for harvest management (stop drop) are generally recommended at 30 and 14 days before harvest.

The Enviroweather sooty blotch and flyspeck model indicates that fungicides to reduce these diseases may be necessary. The flight of the second generation of codling moth is declining. Codling moth, oriental fruit moth and obliquebanded leaf roller are threats to developing fruit. All three of these pests will be flying and laying eggs in the next few weeks. Apple maggot flies catches are continuing in the Trevor Nichols Research Center trap line. Yellow sticky traps are used to track emergence of this fly and red sticky sphere traps plus attractive scent lures are used to monitor egglaying. This is a pest of sandy soils.

Normal and predicted 2019 peak harvest dates for apple varieties in central Berrien County in southwest Michigan based on weather data at the Southwest Michigan Research and Extension Center, Benton Harbor, Michigan.


Normal date

2018 Predicted peak harvest date

2019 Predicted peak harvest date

Paula Red

Aug. 22

 Aug. 20

Aug. 28


Aug. 22

 Aug. 20

Aug. 28


Aug. 20

 Aug 18

Aug. 26


Sept. 10

 Sept 8

Sept. 16


Sept. 8

 Sept 6.

Sept. 14

Early Fuji

Sept. 3

 Sept. 1

Sept. 10


Sept. 13

 Sept. 13

Sept. 20


Sept. 19

 Sept. 23

Sept. 26


Sept. 22

 Sept. 24

Sept. 30


Sept. 22

 Sept. 24

Sept. 30

Golden Delicious

Sept. 25

 Sept. 27

Oct. 1

Red Delicious

Sept. 28

 Oct. 1

Oct. 7

Ida Red

Oct. 5

 Oct. 8

Oct. 15


Oct. 5

 Oct. 8

Oct. 15


Oct. 20

 Oct. 22

Oct. 28


Oct. 20

 Oct. 22

Oct. 28


Oct. 26

 Oct. 28

Nov. 3

Small fruit

Spotted wing Drosophila (SWD) trap catches are high. This pest’s population increases rapidly in August and builds to very high numbers. It breeds on wild and commercial berries. It only takes 10 to 14 days for the fly to go from egg to egglaying adult. Monitor for this pest in the field and field edges and protect ripening fruit. Potato leafhoppers are common and sensitive crops should be protected.

Grapes are at or nearing veraison when the berries become resistant to black rot infection. We have entered the summer season when we have heavy dews every morning and downy mildew becomes a real problem. In juice grapes, the canopy has closed and the fruit is hidden behind several layers of leaves. Slow down and increase gallonages to get good control. Scouting has found most diseases established in grapes, both downy mildew and powdery mildew on leaves and fruit, and phomopsis can be found in vineyards now. Grape berry moth third generation egglaying began last week. See the “MSU vineyard IPM scouting report – July 31, 2019” for more information.

Blueberry harvest continues. Growers are finishing early mid-season varieties. Harvest of Jersey, Nelson, Liberty and other late mid-season varieties is underway. Hand harvest crews and machine harvesters are a common sight. The primary pest concern is controlling SWD. Almost all SWD traps are catching lots of flies. Protect your fruit from SWD. Sprays should be applied as soon as fruit starts to turn blue in the field. Spray coverage needs to be maintained until harvest is finished. You should also be sampling the fruit. We still see some shoot collapse due to phomopsis canker.

Blueberries are using about 0.2 inches of water a day and growers are irrigating. Balancing harvest and irrigation with the need to maintain good coverage with insecticides to reduce SWD can create a real scheduling problem.

Strawberries are growing well after renovation. The fields should be irrigated to good plant growth. After the leaves emerge, treat with a material to control potato leafhopper to prevent this pest from stunting the plants. Include fungicides to protect the leaves from foliar diseases. See “Protect strawberries from foliar diseases after renovation” from MSU Extension for more information.

Raspberry harvest continues. Summer raspberries are finished but the fall raspberry season is just beginning with bloom on the primocanes. Raspberries and blackberries are very attractive to SWD and fruit needs to be protected from this pest. One effective way to reduce SWD is to shorten the harvest interval to two days and pick all ripe fruit, sorting out the soft berries and harvesting and destroying them away from the field.

Japanese beetles are feeding on raspberry leaves. Potato leafhopper also feed on raspberries, distorting the leaves. Both of these pests should be controlled by SWD sprays. Old floricanes are declining and should be removed after harvest to increase sunlight and air flow in the planting reducing disease.

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