2017 ASHS Annual Conference

Elderberry rust (Puccinia bolleyana) commonly occurs in elderberry plantings when the alternate host, sedge (Carex sp.) is present. Two studies were conducted to determine the effect of rust on vegetative growth, fruit yield, and chemistry of berry puree of American elderberry plants. When sedge plants were placed within elderberry plant blocks (11 Mar. to 19 May), there were 30 potential infection periods with ≥ 3 h of continuous leaf wetness and mean maximum hourly temperatures ranging from 9° to 17° C. The first rust pustules were observed on 5 Apr. at the Horticulture and Agroforestry Research Center (HARC) near New Franklin, MO. In the first study with potted ‘Bob Gordon’ elderberry grown at HARC, rust-infected plants averaged 6 pustules/plant on 19 May. Although not statistically significant, berry yield was 84 g/plant for rust-infected plants and 121 g/plant for uninfected plants. Shoot dry weights were similar among plants. In a second study, canes of 3-year-old ‘Wyldewood’ elderberry plants were tagged in a commercial planting near New Bloomfield, MO. Rust-infected canes averaged 137 pustules/cane on 31 May. First date of fruit harvest for rust-infected canes was 5 days earlier than that of uninfected canes. Number of berries and berry yield for rust-infected canes was reduced by ≈ 50% as compared to uninfected canes. Shoot dry weight of rust-infected canes was generally lower than that of uninfected canes and titratable acidity of berry puree from rust-infected canes was lower than that from uninfected canes.