Southwest Michigan fruit update – July 30, 2019

Spotted wing Drosophila numbers climbed sharply again the last week. The summer tsunami of the “spotted weapon of destruction” is here, and growers need to protect their berries now.

Honeysuckle berries
An abundant crop of wild bush honeysuckle berries has provided a good breeding population of spotted wing Drosophila in the woods. This shrub serves as a hotspot, producing many flies in late July and August. Photo by Mark Longstroth, MSU Extension.


Last week began cool with highs in the 70s and then warmed up in the 80s into the weekend. 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. Monday’s showers dropped about 0.2 inches across the region, with totals ranging from a trace to 0.4 inches. 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. It starts with cooler and drier air with highs in the 70s and lows around 60. There is no significant rain in the forecast. Soils are becoming 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.

With the cooler temperatures last week, we accumulated heat units more slowly than the week before, about 200 growing degree days (GDD) base 42 and 140 GDD base 50. This is about 50 GDD less than the previous week.

Southwest Michigan GDD summary from March 1 – July 28, 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 on the Michigan State University Extension Fruit & Nuts Page. There is no weather report this week. Articles and other regional reports can be found at the Fruit News page.

Tree fruit

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. Trap catch for oriental fruit moth declined in most orchards last week. 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.

First trap catch and biofix of obliquebanded leafroller was June 14, and larvae are feeding on the leaves. The summer generation flight should begin soon. Obliquebanded leafroller catches numbers rose in a few orchards. Brown marmorated stink bug activity has been increasing, but summer adults are not expected until mid-August. 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 second week of significant trap catches. Crawlers should be showing up soon.

Local peach harvest of Garnet Beauty, Sentry and Risingstar has begun, about one week later than normal. Estimated peach harvest dates are available on Enviroweather. Oriental fruit moth and perhaps 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 trees look pretty good. Defoliation has stopped and most of the yellow leaves have fallen. This leaf loss was due to multiple factors, including cherry leaf spot, bacterial canker and preharvest ethephon sprays. 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.

Plum harvest of Shiro and Vibrant varieties is underway. The plum crop varies considerably from variety to variety and site to site. Potential insect pests now are obliquebanded leafroller, codling moth, cherry maggot and apple maggot. Spotted wing Drosophila (SWD) is generally a problem of ripe plums.

Apple Estimated harvest dates are approximately six to eight days later than normal and about six to eight days later than last year. ReTain application 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. Codling moth flight of the second generation is underway now, with the peak flight expected last week at about 1,600 GDD base 50 and peak egglaying 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 flies catches have increased the last week, but we expect many more after Monday’s rains. 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. Potato leafhopper injury is fairly common on actively growing shoots. Apple aphid colonies are building on these shoots as well.

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

Pear terminal growth is slowing, reducing the attractiveness of foliage to pear psylla. The second generation codling moth adults should be emerging now and this generation does attack pears as they soften before harvest.

Small fruit

Spotted wing Drosophila (SWD) trap catches are up sharply. This pest has started the sharp population increase we see in late July and August. There are abundant wild fruits as well as commercial berry crops. Under these conditions, it only takes 10 to 14 days for the fly to go from egg to egglaying adult. Growers and scouts should be monitoring this pest both in the field and along the edges of the field. Protect ripening fruit. Last week’s hot, humid weather did not seem to slow this pest down and the heat could have made insecticides degrade quickly. Potato leafhoppers are common and sensitive crops should be protected.

In the next two weeks we will see veraison in grapes when the berries start to color and ripen. Photo by Mark Longstroth, MSU Extension.

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 should have been applied now to control the larvae attacking the fruit. See the MSU vineyard IPM scouting report – July 17, 2019 for more information.

Bluecrop harvest (4)1
Many Michigan blueberries are harvested by machines. Most machine harvested berries are destined to be frozen, but more and more are sold as fresh blueberries. Photo by Mark Longstroth, MSU Extension.

Blueberry harvest continues. Growers are still harvesting Bluecrop and other early midseason varieties. Harvest of Jersey has begun. Hand-harvest crews and machine harvesters are a common sight. Many fields have pockets of poor growth and discolored leaves from winter damage from the polar vortex in January.

The primary concern is controlling SWD. SWD numbers are now increasing rapidly. Almost all our SWD traps are catching lots of flies. Protect your fruit from SWD and apply sprays as soon as fruit starts to turn blue in the field. You should also be sampling your fruit. Unless you are using a microscope, you will only be able to see the larger larvae from eggs which were laid three or four days ago.

We still see some shoot collapse due to phomopsis canker. Blueberries are using about 0.2 inches of water a day and many 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 putting out new leaves after renovation. 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. An effective way to reduce SWD is to shorten the harvest interval to two days, pick all ripe fruit, sort out the soft berries, and harvest and destroy them away from the field.

Japanese beetles are feeding on raspberry leaves. Potato leafhopper are also feeding on raspberries. Both of these pests should be controlled by SWD sprays.

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