Phenology

At the West Madison Agricultural Research Station (WMARS) in Madison, WI, shoots from primary buds average around E-L* stage 7 (First leaf separated from shoot tip) on Marquette and Petite Pearl, and stage 9 (2 to 3 leaves separated; shoots 1-2 inches long) in Frontenac. In general, vines are somewhat irregular in terms of development with buds that have just broken to shoots that are over 2 inches long with inflorescences exposed. There is also a mix of primary and secondary shoots, as well as axillary shoots developing for the base of spurs (for more information see the article “Shoots management in grapevine for this season”) .

The minimum air temperature recorded at NEWA weather station at WMARS for the early morning of May 15 was 41.9°F.

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

Insect Pests and Diseases

There were no signs of insect pests or diseases at WMARS. As temperatures continue to warm up, we will be on the lookout.

Growing Degree Day (GDD) Accumulations

Below displays the GDD accumulations from April 1 through May 15 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 May 15, 2023 (April 1 start date; base 50°F BE*) at the WMARS and PARS.

Location	2023	2022	2021
WMARS	273	243	209
PARS	183	142	95

*BE = Baskerville-Emin calculation method

Accumulation of growing degree days (GDD) as of May 15 (Starting April 1) at WMARS and PARS for 2021, 2022, and 2023.

This article was posted in Grapes and tagged Amaya Atucha, Courtney Cameron, gdd, grape phenology, Grapes, grapes developmental stages, growing degree day accumulations, Leslie Holland, vineyard scouting.