Grape variety developmental stages and fruit maturity evaluation: August 16, 2019
At the West Madison Agricultural Research Station (WMARS) in Madison, WI, grapevine development has reached E-L* stage 35 (“Berries begin to color and enlarge”). At this point vines are still behind in development compared to 2017 and 2018 seasons due to the cooler spring. Similarly, at the Peninsular Agricultural Research Station (PARS), all varieties are at E-L stage 33 (“Berries still hard and green”).
The following photos were taken on August 13 at West Madison Agricultural Research Station.
Brianna E-L stage 35 
Crimson Pearl E-L stage 35 
Frontenac E-L stage 35 
Itasca E-L stage 35 
LaCrescent E-L stage 35 
Marquette E-L stage 35 
Petite Pearl E-L stage 35
The following photos were taken on August 13 at Peninsular Agricultural Research Station.
Brianna E-L stage 33 
Frontenac E-L stage 33 
Marquette E-L stage 33 
LaCrescent E-L stage 33 
LaCrosse E-L stage 33 
St. Croix E-L stage 33
*E-L stands for Eichhorn-Lorenz Phenological stages to describe grapevine development
Growing degree-day accumulation from April 1 to August 16 for the past three seasons. Currently, the 2019 season is running behind in GDD accumulation compared to 2017 and 2018 seasons. Degree-days were calculated using a base 50°F, starting on April 1 as a biofix. We calculated degree days using the NEWA website, and you can visit their “About degree days” page to learn more about the degree days and the formulas used for their respective calculations (http://newa.cornell.edu/index.php?page=about-degree-days).
At WMARS most grape cultivars have reached veraison and we have started our fruit maturity evaluation to track berry ripening, which will continue until harvest. Sugar (Brix) and TA (titratable acidity) concentrations as of August 12th are shown in the table below.
| Cultivar | Brix (%) | TA (g/L) | pH |
| BR | 8.9 | 31.5 | 2.7 |
| FR | 12.7 | 31.5 | 2.7 |
| IT | 13.7 | 28.4 | 2.8 |
| LC | 12.1 | 33.9 | 2.7 |
| MQ | 12.7 | 31.6 | 2.7 |
| PP | 8.6 | 28.6 | 2.7 |