2019 Late bunch stem necrosis status and survey

Late bunch stem necrosis (LBSN) is a complex physiological disorder found in grapevines.
Symptoms of this disorder typically become apparent shortly after veraison when the cluster’s
stem, or rachis, becomes necrotic and decays. As the disorder progresses, the flow of water and
photosynthates is cut off and the berries lose turgor pressure and cease to ripen further (Figure
1). The disorder often renders symptomatic clusters unusable. LBSN is found in many parts of
the world and has been observed in several different cultivars including popular vinifera such as
‘Riesling’ and ‘Cabernet Sauvignon’. Here in Nova Scotia the disorder has been observed in
many cultivars, including ‘Marechal Foch’, ‘Marquette’ and ‘La Crescent’, to name a few.
Outbreaks of this disorder can be minor, with only the odd cluster here or there, to severe, with
50% of clusters exhibiting the disorder in some vineyards and up to 80 to 90% in particularly
bad pockets within a vineyard.