Southwest Michigan fruit update – Aug. 6, 2019

Harvest is underway for blueberries, raspberries, peaches, plums and early varieties of apples.

Marquette wine grapes
Marquette wine grapes are in veraison now. Other varieties are not far behind. Photo by Mike Reinke, MSU Extension.


Last week began cool with highs around 80 degrees Fahrenheit. Last week was dry with no significant rainfall. The passage of a cold front on Monday dropped temperatures and brought a few scattered showers across the region. Rainfall totals for the season remain at about 14 to 20 inches across the region since April 1.

The forecast for this week is a mirror of last week. The week will mainly consist of cooler and drier air with highs near 80 and lows around 60. Light showers are expected Tuesday morning, Aug. 6, and again Thursday morning, Aug. 8. Soils are dry and irrigators should be applying about an inch or more of water every five days. Plants are using about 0.2 inches of water per day.

We accumulated heat units a little quicker than the week before, about 250 growing degree days (GDD) base 42 and 180 GDD base 50. This is about 40 GDD more than the previous week.

Southwest Michigan GDD summary from March 1 – Aug 5, 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.

Tree fruit

Recent warm and dry weather has dried soils in sandy sites, putting stress on young trees with shallow root systems. 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 peak for the second generation. The third generation should be emerging now after 1,900 GDD base 45 and peak at about 2,200 to 2,400 GDD, during the next two or three weeks. The second and third generations are hard to distinguish with trap catches. The third generation is often a problem in early September.

First trap catch and biofix of obliquebanded leafroller was June 14, and large, late instar larvae are feeding on leaves. The Trevor Nichols Research Center trap catch does not show the start of summer generation flight yet, but it is expected soon. Brown marmorated stink bug activity has been increasing and more juveniles are being caught in traps, but no summer adults have been found. Expect the adults to start showing up in a few weeks. Japanese beetle numbers continue to be significant in the area. Potato leafhopper are feeding and causing hopper burn on sensitive plants. The summer flight of male San Jose scale is in the third week of significant trap catches. Red spots due to new scales are showing up now.

In peaches, the Redhaven group of varieties (PF9A-007, Redstar, Blazingstar) have started harvest in some sites, 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. Phomopsis twig dieback is becoming obvious on some trees. Bacterial spot infected leaves are dropping.

Cherry post-harvest chlorothalonil applications are a good resistance management option to help reduce late-season cherry leaf spot buildup. Cherry leaves are always susceptible to leaf spot, so management is needed to maintain a healthy leaf canopy during the entire season.

Castleton plum
Harvest of Castleton, a European-type plum, will start in about 10 days in southwest Michigan. Photo by Bill Shane, MSU Extension.

In plums, Santa Rosa and Ozark Premier harvests will start soon. Potential insect pests now are obliquebanded leafroller, codling moth and cherry and apple maggot. Spotted wing Drosophila is generally a problem of ripe plums.

Apple harvest of Pristine, a scab-resistant yellow summer apple, has started in some sites. 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 second generation codling moth is ongoing, with the peak flight expected this week at about 1,600 GDD base 50. Peak egglaying is expected next week at 1,700 GDD. Larvae of codling moth, oriental fruit moth and obliquebanded leafroller are threats to developing fruit. All three of these pests will be flying and laying eggs in the next few weeks.

Apple maggot fly catches have continued to be significant 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 trap catches have risen sharply in the last two weeks. This pest has sharp population increases in late July and August and builds to very high numbers. It breeds on wild fruits as well as commercial berry crops. 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. Protect ripening fruit. Potato leafhoppers are common; protect sensitive crops.

Grapes are at berry touch and cluster tightening. Take this opportunity to get a fungicide active on botrytis into the interior of the fruit cluster to reduce the disease later in the season. Scouting has found most diseases established in grapes; black rot on berries, downy mildew and powdery mildew on leaves and fruit, and phomopsis on leaves and stems can be found in vineyards now. Grapes are nearing veraison and the berries are becoming 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.

Grape berry moth sprays to control the third generation of this pest should be applied this week. See the MSU vineyard IPM scouting report from July 31, 2019 for more information.

Blueberry harvest continues. Growers are finishing Bluecrop and other early mid-season varieties. Jersey harvest is underway. Hand harvest crews and machine harvesters are a common sight. The primary concern is controlling spotted wing Drosophila (SWD). Almost all our 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 get the plants off to a good start. 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” for more information.

Raspberry harvest continues. 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. Sort out the soft berries and destroy them away from the field. Japanese beetles are feeding on raspberry leaves. Potato leafhopper are feeding on raspberries. Both of these pests should be controlled by SWD sprays.

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