At the West Madison Agricultural Research Station (WMARS) in Madison, WI, grapevine development has reached E-L* stage 36 (“Berries with intermediate sugar values”). Currently, 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 35 (“Berries begin to color and enlarge”).

The following photos were taken on August 26 at West Madison Agricultural Research Station.

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The following photos were taken on August 28 at Peninsular Agricultural Research Station.

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^*E-L stands for Eichhorn-Lorenz Phenological stages to describe grapevine development

Growing degree-day accumulation from April 1 to August 30 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). 

The charts below present fruit quality data Brix and TA from berries sampled from WMARS as of August 26^th.

Grape Brix (%)

Cultivar	Aug 19	Aug 26
Brianna	11.9	14.6
Frontenac	12.7	15.9
Itasca	16.3	17.5
La Crescent	13.2	15.5
Marquette	13.8	17
Petite Pearl	9.9	12.6

Grape TA (g/L)

Cultivar	Aug 19	Aug 26
Brianna	21.6	13.4
Frontenac	33	24
Itasca	21.6	19.1
La Crescent	25.6	21.8
Marquette	24.1	21.4
Petite Pearl	24.8	18.5

This article was posted in Grapes and tagged Grapes, grapes developmental stages.