Southwest Michigan fruit regional report – September 3, 2013

Apple harvest is ramping up as the harvest of summer fruits is winding down.


Last week was hot and humid, with highs in the upper 80s and lows in the 60s with heavy dews. A cold front passing Sunday night (Sept. 1) dropped highs to near 70. The forecast for the upcoming week has highs in the 70s and lows in the 50s. No rain fell last week and there is little chance of showers most of this week. Soils are drying out. We are starting to see fall color change in the leaves of some wild plants, indicating that the growing season is ending. We are about one week behind the five-year average. Check your local weather station and conditions at Enviro-weather.

Southwest Michigan GDD summary from March 1 to September 1


GDD 42 F

GDD 45 F

GDD 50 F

Benton Harbor (SWMREC)




Fennville (TNRC)




Average for the region




GDD increase last week




Five year average




Tree fruit

Spotted winged Drosophila (SWD) trap numbers are high with traps catching hundreds of flies in the woods edges where wild fruits are supporting the flies. Growers should assume that SWD is available to attack their fruit. Brown marmorated stink bug catches have been very low in southwest Michigan, but more nymphs are being found. Scout for this insect on field borders close to woods, especially close to water. The red spots due to the latest generation of San Jose scale crawlers should be showing up on fruit. Growers should check trees planted this year for evidence of water stress.
Obliquebanded leafroller, codling moth and oriental fruit moth catches increased significantly last week compared to the previous three weeks.

Peach harvest is over for most growers growing for the chain stores, but a few late varieties such as PF28-007, Autumn Star, PF Big George, Flameprince, Fayette and Encore are finishing up the season for direct marketers. The recent hot weather induced inking on the sun-exposed sides of some highly colored varieties. A few varieties have noticeably bitter skin this year.

Brown rot control programs and possibly insect control of SWD will need to be ramped up as we approach harvest. Oriental fruit moth trap catches have climbed for several farms in the area, but is only of concern to growers with very late season peach varieties.

Most cherry trees have lost half or more of their leaves to cherry leaf spot. Post-harvest pruning should be finished by early September to allow the wounds to harden off for winter. Significant American plum borer damage has occurred in several area tart cherry plantings. Affected trees are showing general tree stress due to the larvae damage to cambium tissue.

In plums, Stanley, Italian, Vision and Empress harvest is continuing in some sites. Fruit size is suffering on sandy sites, especially where leaves are heavily tattered from earlier bacterial spot infections. Increase brown rot controls as fruits color and ripen. Spotted wing Drosophila can be a problem, especially for fruit being picked relatively ripe for direct sales.

Apples are being harvested for processing and Gala varieties are being harvested for the fresh market. U-pick orchards had good business over the Labor Day weekend and early apple varieties taste good. Gala peak harvest for mid-Berrien County is estimated for Sept. 6. Macintosh and Honeycrisp are next in line.

Growers should double-check timing for stop drop control (Retain and Maxcel) for the apple varieties they grow. Sooty blotch and fly speck symptoms are present, but new infections are inhibited by current dry conditions. Average trap catches for oriental fruit moth, codling moth and obliquebanded leafrollers are climbing significantly for southwest Michigan over the past week.

In pears, Bartlett harvest began two weeks ago with the fire blight-resistant variety Harrow Sweet ready now for some sites.

Small fruit

In grapes, berry ripening is continuing slowly due to high crop loads and cool temperatures. Long-term weather predictions are for a warmer and wetter than normal fall. Warmer temperatures may help get the heavy crop ripened, but expectations of wetter weather may mean more issues with bunch rots. The tentative date for the beginning of ‘Niagara’ harvest by National Grape is Sept. 13. Some early wine grape varieties such as ‘Marechal Foch’ are being harvested.

Trap catches for adult grape berry moth last week in monitored vineyards ranged from 2.5 to 27 adult berry moths per trap. The percent of grape berry moth-infested berries last week was 2 to 13 percent. Some growers have reported not getting good control of grape berry moths this year, which may be due in part to dense canopies of foliage, making it difficult to achieve good insecticide coverage of the fruiting zone. We are not expecting a fourth generation this year – expected beginning of egglaying = 2,430 GDD base 47 from biofix. As of Monday, Sept. 2, we were at 2,208 GDD base 47 at Berrien Springs and 2,166 GDD base 47 at Lawton for a biofix date of May 27.

Bunch rots are showing up in wine grapes with tight clusters, such as ‘Pinot gris,’ but dry weather is expected for the next week or so, which should help slow down disease development. Powdery mildew is appearing on fruit of ‘Concord’ with dense canopies of foliage. There is considerable downy mildew in the unsprayed sentinel plots we monitor.

Blueberry growers are picking ‘Elliott’ and ‘Aurora.’ Growers still need to protect against SWD. Some growers have had to walk away from late pickings due to control failures. Some of these can be traced to holes in coverage due to rain or long spray intervals. Our trap catches in sprayed blueberry fields have been generally low in comparison to trap catches at the field edges, which are much, much higher. See entomologist Rufus Isaacs’ article “What are we learning about spotted wing Drosophila management in berries this season?” for more information.

Strawberry growers should protect plants against potato leafhoppers to prevent stunted growth. Everbearing strawberries are producing berries and should be protected from SWD. Infested fruit tends to have a soft spot on one side and very small, white maggots may be present. Most of the emphasis on insect pest management now is on SWD, but sap beetles can also cause damage to ripe fruit.

In brambles, blackberry and fall raspberry harvest continues. Michigan State University Extension’s recommendations for spotted wing Drosophila management in raspberries and blackberries is posted at the MSU Spotted Wing Drosophila website. Growers should be monitoring their plantings for SWD and applying insecticides. Some operations have stopped picking due to SWD.

Sanitation is very important for managing SWD. Our trap catches in and around brambles is very high with hundreds of flies. Frequent picking of ripe fruit and removal of overripe fruit is important to help reduce SWD populations. One sign of SWD infestation in raspberry is a red staining on the receptacle when the raspberry is picked.

High-tunnel fruit are also at risk. Trap catches and SWD activity in the high tunnels at the Southwest Michigan Research and Extension Center (SWMREC) more than doubled over the last week. One result of the increased infestation of raspberry fruit is a marked decline in the shelf life of the berries.

The dry weather has brought an increase in two-spotted spider mite activity. Multiple applications of insecticides to control SWD can also lead to mite population explosions. Where possible, choose products that will not flare mites. Insecticides to control SWD in brambles and other insect problems should not be applied while bees are actively foraging.

Did you find this article useful?