Southwest Michigan fruit update – Aug. 29, 2017

Peach harvest is winding down. Apple harvest picking up with Gala harvest.

Gala apple harvest has started. All photos by Mark Longstroth, MSU Extension.

Gala apple harvest has started. All photos by Mark Longstroth, MSU Extension.


Last week was cool. High temperatures were in the 70s with lows falling into the 40s and 30s. Scattered showers brought rain showers several times during the week, but significant rain fell only on Tuesday, Aug. 22, and Thursday, Aug. 24. Rainfall totals for the week ranged from a trace to half an inch.

Rainfall has been very variable this year. Total rainfall in southwest Michigan for August ranged from 0.75 to 3 inches of rain. Last week’s potential evapotranspiration was about 1 inch of water. The season’s total demand since April 1 has been about 24.5 inches and the season’s rain across southwest Michigan averages almost 14 inches. Some areas are very dry and drought symptoms in unirrigated woods and fields are common.

This week will be cool with highs in the upper 70s. There is little chance of rain after Tuesday, Aug. 29, until next week. We continue to be about a week ahead of normal.

Southwest Michigan GDD summary from Jan. 1 – Aug. 27, 2017


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMRC)




Lawton (Lawton)




Fennville (TNRC)




Average for the SW region




Ave from March 1




Accumulation last week




Tree fruit

Japanese beetles are scarce. Brown marmorated stink bug trap catch numbers have been low except in the few sites where catches have been ongoing since mid-July. We expect an upsurge in brown marmorated stink bug feeding damage in late August. Cover susceptible fruit if you suspect brown marmorated stink bugs. Review the insect trap catches at Trevor Nichols Research Center. San Jose scale are causing red spots on fruit.

Peach harvest is winding down with many wholesale growers finishing up with PF23, Glowingstar, PF28-007 and Encore. Other late varieties coming up include Autumnstar, PF-35, PF Legendary and Victoria. Fruit color and quality continues to be good.

In general, bacterial spot problems were relatively light this year in southwest Michigan. Oriental fruit moth trap catch numbers are still significant in some orchards. We are in the third generation oriental fruit moth flight.

Bacterial spots on peach

Spots from bacterial spot. These cosmetic spots do not affect the flavor of the peach.

Suspected spotted wing Drosophila (SWD) larvae were found in mature, apparently sound peach fruit. Growers may need insecticides close to harvest, especially where SWD populations are high due to nearby brambles or other hosts. This would be a bigger problem for peaches picked more mature for direct sales.

Stink bugs and tarnished plant bug damage increases fruit susceptibility to brown rot. As fruit colors, the need for brown rot protection increases. Rotate fungicide classes used for brown rot control to avoid fungicide resistance problems.

In cherries, defoliation from cherry leaf spot is a serious problem in some orchards. This reduces reserves from next season and winter hardiness.

Plum harvest continues with Stanley, Simka, NY9 and Luisa. Flavor is generally good this year. Thicker-skinned European plums may be a less favorable host for SWD than thin-skinned Japanese plums, but still protect them from SWD, especially where fruit is picked relatively soft for direct sales. Ripening plums should be protected from brown rot. Apple maggot also attacks plums. SWD sprays should control apple maggot.

Apple fruit size is down in some sites due to the dry conditions. The effects of the May 8 freeze have been apparent for a while with a light crop in the bottoms of the trees and a good volume of large fruit in the tops of the trees. Harvest is quite low in these orchards due to spring freeze losses.

McIntosh and Gala harvests are underway in the area. Growers are harvesting smaller Jonathan apples for taffy apples. We are testing apple maturity using starch conversion on the Cornell University scale. Skin color and starch conversion seem advanced this year. See Michigan State University Extension’s predicted apple harvest dates. We will begin our regular apple maturity reports on Wednesday, Aug. 30. Look for them on the MSU Extension Apples page.

We are seeing necrotic leaf blotch in some orchards. Oriental fruit moth and codling moth trap catches are relatively low but still significant in some orchards in southwest Michigan. It is unlikely there will be a third codling moth generation in 2017. Obliquebanded leafroller larvae are feeding on foliage and fruit. Apple maggot catch numbers are falling off. Be sure the insecticides you are using will control all the insects attacking your fruit. Woolly apple aphid aerial colonies are easier to find.

Bartlett pear harvest is finishing up and Harrow Sweet will start soon. Fruit quality and size is generally good. A minimal spray program will help to hold sooty blotch and fly speck in check. Codling moth and oriental fruit moth entries in fruit are rare.

Pears ripen off the tree

Pears are picked mature before they ripen and are ripened off the tree after harvest.

Small fruit

Grape veraison is ending. Berries are showing color, softening and beginning the process of sugar accumulation. Flight of third generation of grape berry moth continues and numbers are up sharply in many vineyards. We are expecting a partial fourth generation this year. SWD catch is higher this year than previous years. SWD may be a problem in wine grapes—hang traps, monitor for SWD and be prepared to treat if necessary.

Symptoms of powdery mildew and downy mildew are present. Scout for these diseases and treat when necessary. Grape leafhopper and potato leafhopper are not a problem in most vineyards this year. Japanese beetle numbers are high in a few vineyards.

Blueberry harvest is ending in Van Buren County. Growers near Lake Michigan are finishing their late varieties. Harvest continues in the northern growing areas for a few more weeks. SWD and anthracnose fruit rot were significant problems this year. SWD numbers are still high. Tight spray schedules are needed to control SWD.

Flower buds are forming at the shoot tips. Maintain irrigation if you have finished harvest. If the bushes dry up and shut down for the season, flower bud set and next year’s crop will suffer.


Blueberry flower buds have begun forming at the shoot tips.

Bramble harvest continues. Fall red raspberry harvest is picking up and more fruit is ripening. Blackberry harvest is continues. We received a report from Cass County of significant damage to brambles by stink bugs.

SWD continues to be a real problem in raspberries and blackberries—two of their favorite hosts. SWD are attracted to the fruit as it changes color and begins to ripen. Protect fruit from SWD—see the MSU recommendations for SWD control in brambles. One of the best defenses is to pick as often as you can, removing ripe fruit as quickly as possible. After harvest, cool the fruit as quickly as possible.

Strawberries show good growth with runners. Protect plantings from leaf diseases and potato leafhoppers. Maintain irrigation on strawberry fields to get good growth and flower bud formation for next year. A fall application of fertilizer in September will set the fields up for good growth in the spring.

Upcoming meetings

A research field day at the Trevor Nichols Research Center is Tuesday, Sept. 26, from 1 – 4 p.m. The field day will focus on insect and disease research and efficacy trials.

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