Phenology

At the West Madison Agricultural Research Station (WMARS) in Madison, WI, shoots from primary buds average around E-L* stage 32 (Beginning of bunch closure, berries touching) in Marquette and Frontenac and 33 (Berries still hard and green) in Brianna and Petite Pearl, and we anticipate veraison in about 10 to 15 days for the most advanced cultivars. The minimum air temperature recorded at NEWA weather station at WMARS for the early morning of July 10 was 62.1°F. 

At the Penisular Agricultural Research Station (PARS) in Sturgeon Bay, WI, shoots from primary buds average around E-L* stage 31 (Berries pea size) in Marquette. The minimum air temperature recorded at NEW weather station at Sturgeon Bay for the early morning of July 10 was 63.2°F. 

Insect Pests and Diseases

Minor black rot was observed in Petite Pearl and Brianna at WMARS. Phomopsis foliar lesions were observed on the Marquette vines at PARS. With the much-needed rainfall last week, we are keeping an eye out for pathogens as the wet and humid conditions are conducive for pathogen spread. You can always stay up-to-date on potential infection events by finding your local NEWA station and using the Grape Disease Model tool. 

Phylloxera is still a minor problem in the WMARS vineyards. The incidence is random and clustered with damage primarily on younger leaves on the outer parts of the canopy. To read more about phylloxera and management recommendations, click here. We have started to see minor Japanese beetle presence in the WMARS vineyard. For more information about Japanese beetle management, please click here.

Growing Degree Day (GDD) Accumulations

Below displays the GDD accumulations from April 1 through July 10 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 July 10, 2023 (April 1 start date; base 50°F BE*) at the WMARS and PARS. 

Location	2023	2022	2021
WMARS	1292	1196	1300
PARS	982	853	949

*BE = Baskerville-Emin calculation method

Accumulation of growing degree days (GDD) as of July 10 (Starting April 1) at WMARS and PARS for 2021, 2022, and 2023. 

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