Phenology

At the West Madison Agricultural Research Station (WMARS) in Madison, WI, shoots from primary buds average around E-L* stage 31 (Berries pea-size) in Marquette and Frontenac to 32 (Beginning of bunch closure, berries touching) in Brianna and Petite Pearl. The minimum air temperature recorded at NEWA weather station at WMARS for the early morning of June 26 was 63.9°F.

At the Penisular Agricultural Research Station (PARS) in Sturgeon Bay, WI, shoots from primary buds average around E-L* stage 25 (80% caps off) in Marquette. The minimum air temperature recorded at NEW weather station at Sturgeon Bay for the early morning of June 26 was 60°F.

*E-L stands for Eichhorn-Lorenz growth stages scale to describe grapevine development.

Insect Pests and Diseases

Minor black rot and Phomopsis were observed in Marquette and La Crescent, respectively. With the berries gaining in size, we will administer sprays to protect the rachis of the fruit. After the rains and overcast weather, we are keeping an eye out for potential powdery mildew and downy mildew infections. You can always stay up-to-date on potential infection events by finding your local NEWA station and using the Grape Disease Model tool. To read more about protecting flowers and developing fruit from these pathogens, click here.

Grape phylloxera has only been observed in irrigated vineyards. Some leaf curling was noticed. Non-irrigated vineyards did not show galling. However, with the rain this past weekend (0.65 inches total), we are keeping an eye out for any changes. To read more about phylloxera and management recommendations, click here. We are also expecting to see the first Japanese beetle feeding on grape leaves anytime now as they usually start emerging right after Father’s day. For more information about Japanese beetle management, please click here.

Growing Degree Day (GDD) Accumulations

Below displays the GDD accumulations from April 1 through June 26 for the past three seasons. This data is collected using the NEWA degree day calculator. 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 June 26, 2023 (April 1 start date; base 50°F BE*) at the WMARS and PARS.

Location	2023	2022	2021
WMARS	973	898	1011
PARS	704	616	718

*BE = Baskerville-Emin calculation method

Accumulation of growing degree days (GDD) as of June 26 (Starting April 1) at WMARS and PARS for 2021, 2022, and 2023.

This article was posted in Grapes and tagged Amaya Atucha, Christelle Guédot, cold climate grapes, Courtney Cameron, Grapes, Leslie Holland, vineyard scouting.