Phenology

At the West Madison Agricultural Research Station (WMARS) in Madison, WI, shoots from primary buds average around E-L* stage 23 (17-20 leaves separated; 50% caps off) in Petite Pearl to E-L 27 (Setting; young berries enlarging (>2 mm diam.), bunch at right angles to stem) in Brianna. By the end of the week, we predict bloom to be complete. 

The minimum air temperature recorded at NEWA weather station at WMARS for the early morning of June 12 was 43°F. 

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

Insect Pests and Diseases

Foliar black rot and Phomopsis were observed in Petite Pearl, Brianna, and Frontenac. The dry and hot weather conditions have not been favorable for pathogen dispersal. 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 started to form galls on new emerging leaves and was observed on some Petite Pearl vines. At this time, it is important to scout for galls on emerging leaves to prevent the build up of the second generation which can form 40-50 galls per leaf on the 5th-6th open leaves, possibly resulting in leaves curling and being less efficient at photosynthesis. To read more about phylloxera and management recommendations, click here.

Growing Degree Day (GDD) Accumulations

Below displays the GDD accumulations from April 1 through June 12 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 12, 2023 (April 1 start date; base 50°F BE*) at the WMARS and PARS. 

Location	2023	2022	2021
WMARS	703	581	726
PARS	492	353	515

*BE = Baskerville-Emin calculation method

Accumulation of growing degree days (GDD) as of June 12 (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, vineyards.