Wisconsin Fruit Crop Scouting Report: September 10, 2025
Hello fruit growers, we are excited to share apple and grape scouting updates with you this year through the Wisconsin Fruit Newsletter. Weather has continued to be cool and dry, shifting to warmer weather over the weekend. Table grape variety trials are now fully harvested at WMARS, along with Brianna and Marquette.. As a reminder, this newsletter will cover apple and grape phenology, general scouting observations, and includes an overview of degree day accumulation. Growers can reference the Midwest Fruit Pest Management guide for further information on pest management best practices, including recommended chemical best practices.
Grapes
Phenology
At the West Madison Agricultural Research Station (WMARS) in Madison, WI, Marquette and Brianna have been picked. Remaining fruit will be picked in the coming week or two.
*E-L stands for Eichhorn-Lorenz growth stages scale to describe grapevine development.
Growing Degree Day (GDD) Accumulations
Below displays the GDD accumulations from April 1 through September 10 for the current and last two seasons. This data is collected using the NEWA website. You can visit their “About degree days” page to learn more about the concept of degree days as well as the formulas utilized for calculations.
Growing degree day (GDD) accumulation as of September 10 (April 1 start date; base 50°F BE*) at the WMARS and PARS.
Note: The Sturgeon Bay NEWA weatherstation is out of service and not included in this report.
| Location | 2025 | 2024 | 2023 |
| Verona WMARS | 2375 | 2447 | 2574 |
*BE = Baskerville-Emin calculation method
Maturity Testing – Titratable Acidity and Brix
Below displays brix and acidity testing results for both table and wine grapes at WMARS between August 6 and September 9. Harvest dates include:
- August 27: Reliance, Somerset Seedless, and MN1369
- September 2: Mars and MN1325
- September 4: Brianna
- September 8: Marquette
Pests and other considerations
- Grape phomopsis and black rot continues to be observed in West Madison. Black rot fruit infections have been reported across much of Wisconsin. Black rot fruit infections will eventually shrivel into a blue/black hardened fruit “mummy”.
- Continue monitoring Spotted wing drosophila traps through harvest.
- Sap beetles have been observed feeding on over-ripe and damaged fruit. Review best management practices here.
- Wasps are becoming more active. Review this Wisconsin Fruit News article from 2020 for more information on wasp monitoring and management: September 3, 2020 Scouting Report.
- Overview of Cornell grape insect/mite monitoring and management recommendations: Grape Insects and Mite Pests, 2024 Field Season (Cornell, 2024).
- Wisconsin grape growers can reference the Midwest Fruit Pest Management Guide (MFPMG) for a list of registered products and recommended best practices. View the MFPMG Online or order a hard copy here: MFPMG Hard Copy.
Apples
Phenology
In southern Wisconsin, common varieties like Honeycrisp, Cortland, Gala and Crimson Crisp are currently being picked. This has been a heavy fruiting season for many apple growers in Wisconsin.
Growing Degree Day (GDD) Accumulations
We are tracking growing degree days (DD 43 °F BE) from January 1 to monitor bud development in apples. This data is collected using the NEWA website. You can visit their “About degree days” page to learn more about the concept of degree days as well as the formulas utilized for calculations. Growing degree day (GDD) accumulation in 2023, 2024 and 2025 as of September 10 (January 1 start date; base 43°F BE*).
Note: The Sturgeon Bay NEWA weatherstation is out of service and is not included in this report.
| Location | 2025 | 2024 | 2023 |
| Verona WMARS | 3483 | 3615 | 3590 |
| Gays Mills | 3486 | 3572 | 3606 |
| Eau Claire | 3224 | 3251 | 3406 |
| Fond Du Lac | 3207 | 3527 | 3534 |
| Racine | 3372 | 3761 | 3473 |
*BE = Baskerville-Emin calculation method
Other considerations:
- Continue to keep an eye on degree-day accumulation for codling moth based on trap biofix in your area.
- Apple maggot will emerge through September. Growers should continue using red sphere traps to monitor fall population levels.
- Check out the WI DATCP Orchard Insect Pest Bulletin for more information on current insect trap captures across the state.
- Sooty blotch and flyspeck continues to be observed in Southern WI. Continue monitoring NEWA models and scout susceptible varieties.
- Sun scald and southwest injury to trunks and branches has been observed across many orchards and vineyards this summer, likely due to wide variations in winter temperatures that can cause trunk and branch damage.
- Fruit sunburn and bird injury has been observed across many fruit crops in southern WI. Consider removing this fruit while out picking to prevent other pests attracted to the volatiles released from impacting fruit.
- Brown marmorated stink bug has been observed at West Madison.
That’s all for this week – good luck to all WI Fruit Growers!
This article was posted in Apples, Disease, Grapes, Insects and tagged Amaya Atucha, Apples, Courtney Meeks, disease, gdd, Grape Acidity, Grape Brix, Grapes, growing degree day accumulations, Growing Degree Days, insects, Josie Dillon, Leslie Holland, pests, phenology, Wisconsin Fruit Crop Scouting Report.