Controlling downy mildew (Plasmopara viticola) in field-grown grapevine with beta-aminobutyric acid (BABA)

Two foliar sprays of BABA (DL-3-amino-n-butanoic acid, DL-beta -aminobutyri c acid), or a mixture of BABA and different fungicides at reduced rates, ef fectively controlled (>90%) downy mildew, caused by Plasmopara viticola, in the foliage of field-grown grapevines. In live field trials BABA sprays re sulted in a significant reduction of infectious leaf area and fungal sporul ation, and of necrosis of oilspots. The level of disease control for BABA i n four trials was similar to that achieved by metalaxyl-Cu or 'Acrobat Plus ' (dimethomorph + mancozeb), Two-way tank-mixtures of BABA + fosetyl-Al, BA BA + folpet, or BABA + Bion (benzothiadiazole), each at half the recommende d rate, provided an additive effect against P. viticola, performing as well as the full rate of each fungicide alone. BABA was not phytotoxic and did not affect pH, total titratable acids, or (o) Brix of the juice, as determi ned by commercial fungicidal standards. The results indicate that foliar ap plications of BABA can efficiently be integrated into a downy mildew contro l program in vineyards.