Southwest Michigan fruit update – August 20, 2024

Mike Reinke<reinkem3@msu.edu>, Bill Shane and Cheyenne Sloan<sloanche@msu.edu>, Michigan State University Extension - August 21, 2024

Sunny days and cool nights ahead will help fruit to build sugar and develop skin color.

blueberry bush with viral infection — Blueberry bush exhibiting mosaic virus symptoms. Photo by Cheyenne Sloan, MSU Extension.

Weather

Cool and dry conditions are expected this week.

Southwest Michigan GDD Summary from March 1 through August 19, 2024
Station	GDD 42 F	GDD 45 F	GDD 50 F
Benton Harbor (SWMREC)	3415	2978	2296
Lawton (Lawton)	3396	2957	2269
Fennville (TNRC)	3195	2765	2099
Grand Junction	3362	2928	2255

The weather report from Jeff Andresen is posted online.

Oblique banded leafroller damage to plum. The surface feeding insect webs a leaf to the fruit surface for protection against predators and insecticide. Photo by Bill Shane, MSU Extension.

Tree fruit

Pome fruit harvests are about 2 weeks earlier than normal this year. San Jose scale male trap catches for the second generation at Trevor Nichols Research Center in Fennville have been decreasing the last two weeks with the peak in the first week of August. Crawlers from this generation began emerging at the end of July, earlier than usual.

San Jose Scale Control Survey for Tree Fruit Growers

If you are a tree fruit grower, please take this simple survey to help MSU Extension gauge grower interest in using mating disruption to manage San Jose Scale.

Peach and nectarine harvests are wrapping up earlier than normal. Customer demand and quality have been good. Regrowth has greened up some peach orchards with temporary slow growth due to low nitrogen. Second generation Oriental fruit moth trap catches have decreased in the last month at the Trevor Nichols Research Center. The third generation is usually too late to cause problems in peaches, except for very late varieties.

Cherries. Post harvest hedging of tart cherries, especially tops, helps to keep interior of trees accessible to insect and disease management sprays.

Apples. Apple harvest date predictions are available online. Premier Honeycrisp, Paulared, and Wildfire Gala have been harvested over the past two weeks. Current disease concerns are sooty blotch and flyspeck, and bitter rot. Captan, Flint, and Sovran are commonly used to manage these diseases. Insect concerns are codling moth and oriental fruit. Apple maggot flies are a concern for sandy sites. Oblique banded leafroller and marmorated stink bugs are occasional pests that should be monitored by scouting, especially orchard borders.

Pears are also ripening early this year. Bartlett in Berrien County tested at 16 to 18 lbs firmness this week. Insect concerns now are codling moth, oriental fruit moth and possibly oblique banded leafroller. Sooty blotch and flyspeck are common problems on pears (see the apple section). Captan is not labeled for in season use on pears.

Small fruit

Grapes. Most varieties are going through veraison now or have completed veraison. Concord juice grapes have been developing color for just over a week and are around 8 Brix. Many hybrids are between 16-20 Brix. For those varieties near harvest, acidity levels are still particularly high this year. Harvest of early hybrid varieties has begun.

Grape berry moth populations have been near average this year. With the early third generation this year, we are watching for a fourth generation. According to the grape berry moth model (using May 19 as biofix, and SWMREC as the site), if the fourth generation develops, it will be the first week of September.

Significant powdery mildew and downy mildew infections are being reported in wine and juice grapes. These diseases can be challenging to eradicate once they are established, so maintain spray programs to protect foliage. With sugar developing, bunch rot sprays should be incorporated into the program. Botrytis and sour rots can be an issue in warm, humid years. Sour rot is spread by flies and other insects, so management of both the disease and the insect vectors are necessary to maintain control.

Blueberry. Blueberry harvest is nearly over up through Van Buren County with late season varieties finishing up. Disease focus should continue to be on early fruit rot management. Spotted wing drosophila populations continue to increase, both in traps and in fruit.

Upcoming meetings

Blueberry Field Day will be held September 4 at the Trevor Nichols Research Center in Fennville, Michigan. Registration begins at 9 a.m. The program begins at 10 a.m.

This work is supported by the Crop Protection and Pest Management Program [grant no 2021-70006-35450] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).