Southwest Michigan fruit update – Sept. 5, 2017

Gala apple harvest continues. Grape harvest has begun. Growers need to be mindful of late season pests, which appear just before harvest.

Bins of picked apples are waiting in the shade to keep them cool for their trip to storage of the packing line. All photos by Mark Longstroth, MSU Extension.

Bins of picked apples are waiting in the shade to keep them cool for their trip to storage of the packing line. All photos by Mark Longstroth, MSU Extension.


Last week was cooler. Several cold fronts moved across the region dropping highs into the low 70s. Temperatures rose back to around 80 degree Fahrenheit over the next few days and then another cold front would drop the temperatures again. There were scattered showers with the passage of these cold fronts, but no widespread significant rain fell during the week.

Regional rainfall totals for the last two weeks averaged about 0.40 inches. Rainfall has been highly variable this year. Total rainfall in Southwest Michigan so far has averaged about 14 inches. Rainfall for the entire month of August ranged from 0.75 to about 3 inches of rain. The potential evapotranspiration for August was about 1 inch of water a week or 4 inches for the month. The season’s total demand since April 1 has been about 25.5 inches and the rainfall has been about 14 inches. Some areas are very dry and drought symptoms in unirrigated fields are common. Deep-rooted perennials do not seem to be suffering as much, but fall color change can be seen in stressed plants. This week will be cooler with highs dropping below 70 F into the 60s for most of the week. There is a chance of rain on Tuesday and Wednesday.

Southwest Michigan GDD Summary from Jan. 1 through Sept. 3, 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

Brown marmorated stink bug adults can be found in many locations around the region, but trap catch numbers remain low except where catches have been ongoing since mid-July. We expect an upsurge in brown marmorated stinkbug feeding damage. Growers who suspect problems with stinkbugs should protect susceptible fruit such as late harvesting apples. Growers can review insect trap catches at Trevor Nichols Research Center. San Jose scale are causing red spots on fruit. Late September is typically the time that bucks will start rubbing their antlers on young fruit trees, especially trees close to woods. Growers depending on pheromone disruption for control of codling moth and oriental fruit moth, consider adding sprayable pheromones to keep protection strong up to harvest. Apply white latex paint to trunks of young trees to help prevent southwest damage caused by direct sunlight on trunks in winter.

Peach harvest continues primarily for direct market sales. Growers are harvesting with late varieties such as Autumnstar, PF-35, PF Legendary and Victoria. Fruit color and quality is good with dry weather enhancing sweetness. Oriental fruit moth trap catch numbers continue to be significant for some orchards. We should be at the end of the third generation oriental fruit moth flight. Suspected spotted wing Drosophila (SWD) larvae have been found in mature, apparently sound peach fruit. SWD could be a problem for peaches picked late for direct sales. Peaches with their fuzzy skin present a problem for SWD egg laying. Growers may want protection close to harvest, when they are late harvesting ripe peaches for direct sales of ripe fruit. SWD populations may be high due to nearby wild berry hosts. Stink bugs and tarnished plant bug damage increases fruit susceptibility to brown rot. As fruit colors, the need for brown rot protection increases. Growers should rotate fungicide classes used for brown rot control to avoid fungicide resistance problems. Borer sprays can be applied to trunks post-harvest and provide protection for the following several years.

In cherries, fall application of foliar nitrogen can help fruit size for next year. Defoliation from cherry leaf spot is the primary problem in some orchards, but many trees have at least half or more of their leaves remaining. Early defoliation reduces reserves for next season and reduces winter hardiness. Check trees showing water stress symptoms for American plum borer damage to the trunk at or slightly below the soil line.

Plum harvest continues with Damson, Italian, Simka, NY9 and Luisa. Flavor is generally good this year. Thicker-skinned European plums may be less favorable host for SWD than thin-skinned Japanese plums, but growers should still protect their fruit from SWD, especially when fruit is picked soft for direct sales. Ripening plums need to be protected from brown rot. Apple maggots also attackplums. SWD sprays should also control apple maggots.

In apples, 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 bottom of the trees and larger fruit in the top of the trees. Harvests are quite low in these orchards due to spring freeze losses. McIntosh harvest has ended. Honeycrisp and Gala harvests are underway. Growers are harvesting smaller Empire and Jonathan apples for taffy apples. We are testing apple maturity using starch conversion on the Cornell University scale. Skin color and starch conversion seems advanced this year. See predicted apple harvest dates. We have begun our regular apple maturity summaries posted online on Wednesdays. Oriental fruit moth and codling moth trap catches were up in some orchards in Southwest Michigan. This flight probably occurred when we had warm nights. Flight of both these pest should be ending for 2017. Obliquebanded leafroller trap catches are up indicating the second flight. Larvae from this generation will feed on foliage and fruit and then over winter in the orchard to emerge next spring.

Brown marmorated stinkbug was a problem is several small orchards last year especially in late harvested apples. We can see brown marmorated stink bugs about as we travel but have not seen a migration into orchards. We expect an upsurge in brown marmorated stink bug feeding damage. Growers who suspect problems with stink bugs should maintain protection on their fruit.

Apple maggot numbers in sprayed orchards have been low. Growers need to be sure that the insecticides they are using will control all the insects attacking their fruit. Wooly apple aphid aerial colonies are common is some areas.

Harrow Sweet pear harvest is finishing up. Fruit quality and size is generally good. A minimal spray program will help to hold sooty blotch and fly speck in check. Codling moth continues to be a threat in September, but so far, fruit entries are rare.

Small fruit

Grape berries are showing color, softening and accumulating sugar. Harvest of the early hybrid wine grapes has begun. Niagara harvest is scheduled to begin on Sept. 18. Flight of third generation of grape berry moth is ending and numbers are generally down in many vineyards. Only a few vineyards had increases last week. We are expecting a partial fourth generation this year, but not for another week or more. Catch of  SWD is higher this year than previous years. SWD may be a problem in wine grapes but we also have native Drosophila, which go to grapes. Testing the fruit with the salt test for drosophila larvae will not identify SWD from the other drosophila larvae. Symptoms of powdery mildew and downy mildew are present. Growers should scout for these diseases and treat when necessary.

concord grapes

Ripening Concord berries.

Blueberry harvest has ended in Allegan and Van Buren counties. Harvest continues in the northern growing areas. 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.

Bramble harvest continues. Fall red raspberry harvest is underway. Blackberry harvest is continues. We have a report from Cass County of significant damage to brambles by stinkbugs. 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. Growers need to protect their 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. Weeds are a problem in some fields. Directed herbicide sprays between the rows can control some weeds. Growers need to protect plantings from leaf diseases and potato leafhoppers. Be sure to 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.

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