Southwest Michigan fruit regional report – July 22, 2014

Apricot, blueberry and raspberry harvest are in full swing across the region, while peach and plum harvest are beginning. Spotted wing Drosophila numbers continue to climb.

These three ripe apricots indicate that harvest is well underway. Photo credit: Mark Longstroth, MSU Extension
These three ripe apricots indicate that harvest is well underway. Photo credit: Mark Longstroth, MSU Extension


Last week was pleasant. High temperatures fell from the 80s at the beginning of the week to around 70 mid-week, and then rose back to the 80s. Low temperatures were generally in the 40s. Frequent showers brought little rain to many sites. Rainfall totals were generally less than 0.1 inches and sandy soils are beginning to dry. Evapotranspiration (ET) has been a little less than 0.2 inches of water a day and shallow-rooted crops should be irrigated.

This coming week will start with high temperatures into the 80s and cooler with a chance of rain mid-week. All the rain early in the month has resulted in a lot of shoot growth in many crops. Last week we picked up about 156 growing degree days (GDD) base 42 – about 22 per day – and 95 GDD base 50 – about 13.5 a day. We continue to lag about a week behind normal in GDDs.

Southwest Michigan GDD summary from Jan. 1 through July 20, 2014


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMREC)




Fennville (TNRC)




Average for the region




Tree fruit

Trap catches for oriental fruit moth have been very high in some orchards. The Trevor Nichols Research Center (TNRC) reports the start of male flight of San Jose scale this week. This should be the biofix for the second generation with crawlers expected about 500 GDD base 51 F after this biofix. First generation biofix for codling moth was May 26, with the start of the next flight predicted to begin 1,060 GDD base 50 F later, approximately the week of July 20.

There have been no reports of brown marmorated stink bugs in local fields and orchards. Japanese beetle adults are still active and potato leafhopper damage can be found in many sites.

Apricot harvest is still underway in the area.

Peach varieties ripening this week in central Berrien County include Harrow Diamond, Early Star and PF-5D Big. Glenglo and Rising Star harvest should start soon. Fruit shapes of some varieties are irregular with prominent tips and more than usual numbers of split pits. Brown rot is showing up on damaged fruit. Stink bugs can be found feeding on fruit causing small holes with gummy droplets. Oriental fruit moth trap catches are generally high with numbers over 200 per trap per week in some locations. Bacterial spot symptoms continue to increase on leaves and fruit of susceptible varieties, with some leaf drop.

Cherry growers need to continue protection against cherry leaf spot.

Sweet cherry trees that have filled their space can be trimmed modestly after harvest into early August with less risk of bacterial canker than the traditional delayed dormant pruning time. Pruning in the post-harvest window is less invigorating than spring pruning.

In tart cherries, cherry leaf spot is becoming more apparent in area orchards. Growers should continue to apply sprays to control cherry leaf spot. Chlorothalonil (Bravo, Chloronil) can be used post-harvest with a maximum of 15.4 pounds per active ingredient per acre per year.

Japanese plum harvest has begun. European plums are 0.875 to 1 inch. Apple maggots, oblique banded leafrollers, codling moths and brown rot can be problems in plums in July.

Shiro plum
Shiro is the first plum of the season and harvest has begun in southwest Michigan. Photo credit: Mark Longstroth, MSU Extension

Apple fruit range from 1.75 to 2 inches in diameter with some summer apple varieties at 3 inches. New fire blight symptoms have been seen in tops of trees due to the severe weather of June 30. Young trees infected with fire blight may develop rootstock blight. For more information, see the following Michigan State University Extension articles: “Field symptoms of rootstock blight in apples” and “New video resources in tree fruit pathology from MSU.”

The frequent rains have been conducive to sooty blotch and fly speck disease infections and symptoms can be found on unprotected fruit. Codling moth and oriental fruit moth larvae from the first generation have been found in apple fruit. Spotted tentiform leafminer leaf mines are hard to find. Obliquebanded leafroller trap catch has declined as the first generation flight comes to an end. Apple maggot adults continue to be trapped in low numbers starting on June 30 at the TNRC near Fennville, Michigan. Sandy sites with early summer varieties tend to be most prone to apple maggot problems. Unsprayed apples and crabapples have been losing their leaves to apple scab for the last few weeks.

Pear fruit are 1.5 inches or more in diameter. The next generation of codling moths and obliquebanded leafrollers will target developing fruit. Pear rust mite bronzing of leaves is becoming easier to find.

Small fruit

Raspberries and blueberries are harvesting. Japanese beetles and spotted wing Drosophila (SWD) are the pests of major concern. Wet weather has been good for disease development.

Grape berries are sizing rapidly. Clusters are tight for tight-clustered varieties. Winter-damaged canes and trunk are collapsing as the damaged woody tissue is unable to supply enough water to the developed leaf canopy. While some vineyards suffered significant injury from the winter, other vineyards have a good crop and several French hybrid varieties have needed to be thinned and many Concord and Niagara vineyards have a full crop. We should begin to see veraison in early varieties by the end of the month.

Concord grapes
This Concord grape shoot has three large clusters of berries, indicating a full crop in this vineyard. Photo credit: Mark Longstroth, MSU Extension

Southwest Michigan GDD summary for grapes from April 1 to July 20, 2014


GDD 50 F

Benton Harbor (SWMREC)




Fennville (TNRC)


Average for the region


Grape growers are applying sprays for grape diseases and grape berry moth. Downy mildew has been reported in many wine and table grape vineyards due to the rains earlier this month. See “Weather is ideal for downy mildew on grapes at this time” for background on the disease and controls recommended by MSU Extension.

Egglaying for the second generation of grape berry moth began the week of July 7. A wide variety of materials are available to control grape berry moth. See the “2014 Michigan Grape Management Guide” for a list of recommendations. Many grape varieties become less susceptible to black rot a month after bloom. As this season has been especially wet, additional fungicide sprays may also be warranted as veraison approaches (see “Controlling Botrytis bunch rot in grapes”).

Blueberry harvest of Bluecrop and other early mid-season varieties is well underway. Hand-harvest for the fresh market is common. Fruit size is generally large and quality is generally good. With all the rain early in the month, a new flush of growth is apparent in most fields.

Spotted wing Drosophila numbers have been rising as more wild berries, especially black raspberries, ripen. Many growers have applied sprays to control this pest. Trap catch numbers are high in field edges where wild berries are ripening. As the wild berries decline, large numbers of flies will be looking for new ripening fruit. Border sprays may be an effective way to slow the spread of SWD into commercial berry fields. Growers only need to protect fruit that has begun to ripen. SWD is not a pest of green fruit.

Strawberry renovation has been finished in most fields that renovate. Many growers no longer mow back their plants. Having healthy leaves out restricts the number of herbicides that are safe to use.

Bramble harvest of black raspberries (black caps) and red raspberries continues. Bloom of fall-bearing raspberries is underway. Japanese beetles are out. SWD numbers are building in southwest Michigan. Raspberries seem to be the favorite fruit for SWD. Many growers have been applying controls since harvest began. Growers should be trapping to determine if controls are needed. MSU Extension has posted SWD recommendations for raspberry growers. More information is available on the MSU Spotted Wing Drosophila website. 

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