Southwest Michigan fruit update – Aug. 22, 2017

Growers are harvesting peaches, plums, pears and early apples.

Zestar is a new early apple being harvested now. All photos by Mark Longstroth, MSU Extension.

Zestar is a new early apple being harvested now. All photos by Mark Longstroth, MSU Extension.


Last week was warm. High temperatures were in the 80s and lows near 60. Scattered showers brought rain last Tuesday morning, Aug. 15, and this Tuesday, Aug. 22. Rainfall totals have been very variable this year, with intense rain in some areas and much less in others. Total rainfall for the week was about a half-inch, but amounts varied from 0.3 to 1.3 inches of rain. Last week’s showers temporarily reduced the drought stress in some areas.

Last week’s potential evapotranspiration was about 1 inch of water, where it was available. The season’s total demand since April 1 has been almost 23.5 inches and the season’s rain across Southwest Michigan averages of almost 13.5 inches. Some areas are very dry and drought symptoms in unirrigated woods and fields are common. Leaves coloring and falling is common.

This week began hot with highs near 90. It will be cooler with highs in the low 70s. There is little chance of showers after Tuesday until next week. We continue to be about a week ahead of normal, but with the actual crop harvests, about two weeks ahead of normal.

Southwest Michigan GDD summary from Jan. 1 – Aug. 20, 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 beetle numbers are low. Brown marmorated stink bug trap catch numbers have been low except in a few sites where catches have been ongoing since mid-July. We expect an upsurge in brown marmorated stink bug feeding damage soon in mid- to late August. Growers can review insect trap catches at Trevor Nichols Research Center. San Jose scale red marks on fruit are showing up from the third generation of crawlers.

Peach harvest continues to move rapidly. Growers are harvesting the Cresthaven group, including PF24C, Messina, Glowingstar and Gloria. Fruit color and quality are good. Fruit size is good where thinning was done early.

Brown rot is the primary problem in some orchards. Fruit speckles due to bacterial spot can be seen where infected leaves are nearby. Peaches continue to shed older leaves. Some of these are the basal leaves with no discernable disease symptoms. To increase fruit color, lightly summer prune one to two weeks before harvest on varieties needing more color.

Oriental fruit moth trap catch numbers are generally up and are significant in some orchards. We are in the third generation oriental fruit moth flight. Stink bug 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. Other stresses such as drought can cause leaf drop as the stressed trees shut down. This reduces reserves from next season and reduces winter hardiness.

Plum harvest continues with NY6, Early Italian and some early picking of Stanley. Thicker-skinned European plums may be a less favorable host for SWD than thin-skinned Japanese plums, but protect all fruit from spotted wing Drosophila (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 also control apple maggot.

In apple, Zestar, Ginger Gold and Paula Red harvest continues. We are testing apple maturity using starch conversion on the Cornell University scale. Zestar fruit is testing at 4 to 6 (a 5 on the starch is considered mature). Ruby Mac is testing 3 to 4. Gala is testing 2.6, with good skin color this week. Honeycrisp tests an average of 2.1 on the starch scale, still relatively immature. See Michigan State University Extension’s predicted apple harvest dates. We will begin our regular apple maturity reports next week, which will be available on MSU Extension’s Apple Maturity page.

Necrotic leaf blotch is visible in some orchards. Oriental fruit moth and codling moth trap catches are still significant in some orchards in southwest Michigan. Day length determines if codling moth larvae enter diapause and overwinter or continue on to adulthood this season. 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 relatively high in some sites. Be sure the insecticides you are using will control all the insects attacking fruit. Woolly apple aphid aerial colonies are easier to find.

nectroic leaf blotch

Necrotic leaf blotch affects mainly Golden Delicious and related apples. It seems to worsen after a rain that was preceded by a long, dry period. Sections of the leaf die and the rest of the leaf yellows and falls off the tree.

Bartlett pear harvest continues with Harrow Sweet harvest starting in a week or two. Fruit quality and size is generally good. A minimal spray program will help hold sooty blotch and fly speck in check. Codling moth and oriental fruit moth entries in fruit are rare.

Small fruit

Grape veraison is under way. Berries are showing color, softening and beginning the process of sugar accumulation. Third generation grape berry moth flight continues. We are expecting a fourth generation to occur in September. SWD catches are 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.

Powdery mildew and downy mildew symptoms 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 are picking Liberty, Elliott and other 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. Growers who have finished harvest should maintain irrigation. If the bushes dry up and shut down for the season, flower bud set and next year’s crop will suffer.

Two-year-old ‘Last Call’ blueberry bushes.

Two-year-old ‘Last Call’ blueberry bushes.

Bramble harvest continues. Fall red raspberry harvest is picking up and more fruit is ripening. Blackberry harvest is underway. 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.

To help protect your 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 are showing good growth and most fields are producing runners. Protect renovated plantings from leaf diseases and potato leafhoppers, which stunt plant growth. Maintain irrigation on strawberry fields to get good growth and flower bud formation for next year. A fall fertilizer application in September will set the fields up for good growth in the spring.

Upcoming meetings

There is a research field day at the Trevor Nichols Research Center 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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