PT  - JOURNAL ARTICLE
AU  - Warneke, Brent W.
AU  - Nackley, Lloyd L.
AU  - Pscheidt, Jay W.
TI  - Phenology-Based Applications of Biofungicides and Sulfur with an Intelligent Sprayer for Management of Grape Powdery Mildew
AID  - 10.5344/ajev.2026.26008
DP  - 2026 Jul 01
TA  - American Journal of Enology and Viticulture
PG  - 0770017
VI  - 77
IP  - 2
4099  - http://www.ajevonline.org/content/77/2/0770017.short
4100  - http://www.ajevonline.org/content/77/2/0770017.full
SO  - Am J Enol Vitic.2026 Jul 01; 77
AB  - Background and goals Though biological fungicides are often organic compliant, they can be expensive and have variable efficacy against grape diseases. In research fields, these products have not adequately managed grape powdery mildew (Erysiphe necator; GPM) alone. Phenology-based applications of biological fungicides were hypothesized to provide a more effective evaluation strategy for biological fungicide efficacy than traditional season-long regimes, due to their mode of action.Methods and key findings In a 2021 experiment, biological fungicides were applied only during bloom and ~4 wk after, with sulfur applied before and after that period (S/B/S treatments). In 2021 to 2023, sulfur was applied only during bloom and 4 wk after, while biological fungicides were applied before and after bloom (B/S/B treatments). Additionally, regimes were applied using a variable-rate intelligent sprayer to determine the effect of variable-rate applications on GPM control efficacy. In the B/S/B regime, the largest applied quantity of Life-Gard resulted in the lowest cluster severity in 2022 and 2023, which was significantly lower than phenological sulfur applied alone in 2023. In the B/S/B regime, Theia applied in standard or intelligent modes showed no differences in cluster severity in 2022 and 2023.Conclusions and significance When using variable rate sprayers and biological fungicides, some products (such as Theia) may be more robust to application across a wider range of rates for GPM management than others (such as LifeGard). Biological fungicides and phenology-based application regimes could provide a more effective evaluation regime for biological fungicide efficacy research, as well as alternatives to calendar applications or synthetic fungicides for GPM management.