Vineyard Scouting Report: July 17, 2024
A cool front has made its way into Wisconsin. I think we are all sighing with relief and soaking up the cooler temperatures for however long they might last.
Phenology
At the West Madison Agricultural Research Station (WMARS) in Madison, WI, vines average around E-L* stage 32 (Beginning of bunch closure, berries touching) in Frontenac and E-L* stage 33 (Berries still hard and green) for Brianna.
The minimum air temperature recorded at NEWA weather station at WMARS for the early morning of July 17th was 61.1°F.
E-L 32
“Beginning of bunch closure, berries touching”
E-L 33
“Berries still hard and green”
E-L 33
“Berries still hard and green”
E-L 33
“Berries still hard and green”
E-L 33
“Berries still hard and green”
*E-L stands for Eichhorn-Lorenz growth stages scale to describe grapevine development.
Pests
While some previously reported foliar diseases have persisted in the vineyard, the major one to report is downy mildew. The wet conditions have made the environment ideal for the pathogen. The downy mildew infections were only observed in La Crescent vines. Other commercial vineyards have reported the disease in their St. Pepin vines, so be sure to scout your vineyard! We have combed and skirted our vines at WMARS as of this week. This opened up our canopy to aid in air flow and ensure better penetration of future pesticide applications. Air flow will make the environment less hospitable for downy mildew infections. We are anticipating an additional fungicide application in the near future.
On the insect side, phylloxera galling has decreased since my last scouting report. After my first sighting of Japanese Beetles only two weeks ago, they have grown in number. Damage is averaging around 5 – 10% of a panel’s canopy. Just a reminder, cold-climate grapes are hardy – just like Midwesterns. The action threshold is 30% damage. You can read more about phylloxera and Japanese beetle management by reading the articles linked.
Growing Degree Day (GDD) Accumulations
Below displays the GDD accumulations from April 1 through July 17 for the past three 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 accumulation as of July 17, 2024 (April 1 start date; base 50°F BE*) at the WMARS.
| Location | 2024 | 2023 | 2022 |
| WMARS | 1417 | 1425 | 1341 |
| PARS | 999 | 1062 | 931 |
*BE = Baskerville-Emin calculation method
Accumulation of growing degree days (GDD) as of July 17 (Starting April 1) at WMARS and PARS for 2022, 2023, and 2024.
This article was posted in Grapes and tagged Courtney C Meeks, Downy mildew, gdd, grape phenology, Grapes, grapevine downy mildew, growing degree day accumulations, Growing Degree Days, PARS, phenology, vineyard, vineyard scouting, WMARS.