Southwest Michigan fruit regional report – August 26, 2014

Summer fruit harvest continues and grapes are in veraison.

‘Concord’ grapes at veraison. The color changes when the berries begin their final stage of growth and ripening. Grapes become soft and accumulate sugar. Photo by Mark Longstroth, MSU Extension
‘Concord’ grapes at veraison. The color changes when the berries begin their final stage of growth and ripening. Grapes become soft and accumulate sugar. Photo by Mark Longstroth, MSU Extension


Last week was warm and humid. Storms crossed the region Tuesday, Aug. 19, and brought rain to most sites. Rainfall totals for most sites was about a half-inch. Storms were severe in northern Van Buren County and caused damage to property and blew ripe blueberries off the bushes. High temperatures last week were in the 80s with lows in the 60s. The rain did ease drought stress caused by dry soils. Evapotranspiration (ET) for the last week was low due to the humid cloudy weather. ET for the next week should be around 0.15 inches a day or about an inch of water for the week. Irrigation now will maintain plant vigor and help size fruit for harvest.

Last week we picked up about 216 growing degree days (GDD) base 42, about 30 per day, and 160 GDD base 50, about 23 a day. Despite the warm weather, we continue to lag about two weeks behind normal in GDD accumulations. This does not mean harvest timing is delayed by two weeks, but many insect populations are running late and there is no chance of extra pest generations this cool year. The upcoming week is forecast to continue warm with highs in the 80s and lows in the 60s and a chance of showers most days.

Southwest Michigan GDD summary from Jan. 1 through Aug. 24, 2014


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMREC)




Fennville (TNRC)




Average for the region




Tree fruit

We should be seeing the third generation of oriental fruit moth. Trap catches for oriental fruit moth continue to be low, but a few sites report catching up to 180 per trap per week. The Trevor Nichols Research Center (TNRC) catch of San Jose scale males remains high for the fourth week. With a July 21 biofix for the second generation, San Jose scale crawlers should be emerging and active. This generation is the one that typically leaves red marks on light-colored fruit.

Codling moth trap catch has dropped to near zero for the TNRC trapping site, but still continues for many sites. Japanese beetle adults are still active and potato leafhopper damage can be found in many sites.

Peach varieties being harvested in the region include Loring, Coralstar, PF23, Glowingstar and PF24C Cold Hardy. Oriental fruit moth and obliquebanded leafrollers are the typical insect concerns in August. Specks from bacterial spot infections are common on peach fruit.

In cherries, most tart cherry orchards have lost a significant portion of their leaves. Michigan State University Extension recommends growers continue protection against cherry leaf spot to maintain good, healthy foliage into the fall. Chlorothalonil (Bravo, Chloronil) can be used post-harvest with a maximum of 15.4 pounds of active ingredient per acre per year.

Plum harvest of Fortune, NY9 and Stanley is underway in some local orchards. Apple maggots, obliquebanded leafrollers, codling moths and brown rot can be problems in plums in August.

Apple maturing tests in central Berrien County shows McIntosh internal starch conversion has begun, ahead of Gala. See “Checking apple maturity: What to look for” for more information. Growers should check the dates for applying Retain for stop drop control for the apple varieties they grow. Apples seem to be developing and maturing faster than we expected. The actual harvest dates may be before the predicted apple harvest dates issued earlier and closer to the average harvest dates in your region. Make sure you do not miss the application window – 30 days or less.

Sooty blotch and fly speck can be found on unprotected fruit. Obliquebanded leafroller trap catches have been climbing over the past two weeks, but are still low. Apple maggot adult trap catch still continues at the TNRC. Flight usually tapers off by late August. Codling moth trap catch has dropped to near zero for the TNRC trapping site, but still continues for some sites. We are past peak egglaying for the second generation of codling moth. Bronzing caused by European red mites is very apparent in some orchards. See “Managing mites in apples” for more information.

Bartlett pear harvest is underway. Codling moth larvae are showing up in fruit and obliquebanded leafroller larvae are also active. Fabraea leaf and fruit spot is becoming easier to find.

Small fruit

Spotted wing Drosophila (SWD) numbers remain at moderate levels. These traps located in fence rows near fruit plantings give an idea of the pest population outside sprayed fields. SWD numbers are dependent on the amount of small fruit near the trap and most sites appear to have less wild fruit than last year. SWD were caught in all our traps and the numbers were higher than last week. SWD usually increases rapidly in early August and we are seeing a more gradual rise this year. If you are not trapping for SWD, you should be spraying for this pest. More information is available on the MSU Spotted wing drosophila website.

Grapes veraison in Concord juice grapes is well underway, indicating the beginning of the final stage of fruit growth and ripening. Egglaying for the third generation of grape berry is underway and we are in the spray window for this pest. There is little chance of a fourth generation of grape berry moth in southwest Michigan this year.

Growers should protect against downy mildew and powdery mildew, which are common this year. Weather conditions for the rest of the growing season with heavy dews every morning are ideal for the spread of downy mildew and growers should make every effort to get in front of this disease. See “Weather is ideal for downy mildew on grapes at this time” for background on the disease and controls recommended by MSU Extension. Additional fungicide sprays may be warranted as veraison approaches.

Southwest Michigan GDD summary for grapes from April 1 to Aug. 24, 2014


GDD 50 F

Benton Harbor (SWMREC)




Fennville (TNRC)


Average for the region


Blueberry Jersey harvest is ending, and Elliott harvest and other late-season varieties continues. Next year’s flower buds are appearing near the shoot tips in many fields. Many growers are irrigating blueberry fields. Discolored leaves that are appearing in many fields may be due to winter injury to the canes. These weakened canes should be removed at pruning time. SWD trap catch numbers in blueberries have been low this year. See “SWD Management Recommendations for Michigan Blueberry.” Growers are reminded that MSU Extension recommends that the fruit should be chilled quickly after harvest to reduce post-harvest problems. Powdery mildew is common in many plantings.

Strawberry plants are runnering well in new and renovated fields. Some fields are getting very dry and need irrigation. Growers need to protect against potato leafhoppers, which stunt plant growth. Day-neutral plantings are producing fruit. Growers need to protect this fruit from SWD.

In Brambles, fall red raspberry and fall-bearing variety harvest is underway. Brambles seem to be the favorite host for SWD. Growers need to apply controls as soon as there is ripening fruit in the field. Generally, control of this pest has been much better than in previous years. See “Spotted Wing Drosophila Management Recommendations for Michigan Raspberry and Blackberry Growers.”

Black raspberry
Fall blackberries bear their fruit on the primocanes in late summer and early fall. Photo by Mark Longstroth, MSU Extension

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