INFLUENCE OF FORMULATION ON EFFICACY OF THREE SYSTEMIC FUNGICIDES FOR CONTROL OF OAT LEAF RUST

Abstract

Three systemic fungicides, oxycarboxin (5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilido-4,4-dioxide), benodanil (2-iodobenzanilide), and pyracarbolid (2-mefhyl-5,6-dihydro-4,4-pyran-3-carboxylic acid anilide) appear promising for control of rust diseases. The ability of different formulations of these three fungicides to control oat leaf rust (Puccinia coronata f. sp. avenue) was compared by an eradicant test and a systemic test in a controlled environment. Large differences between dosage response (DR) curves were observed. In general, liquid formulations, i.e. emulsifiable concentrates (EC) and oil dispersible (OD) concentrates, had lower ED50 values than wettable powder (WP) formulations. The slope of DR curves for WP formulations was less steep. In field tests, an EC formulation of oxycarboxin and an OD formulation of benodanil gave, per unit of active ingredient, better disease control, less lodging and greater yield than their respective WP formulations. Pyracarbolid at low rates gave inadequate rust control and yield response in field tests. None of the ultralow volume formulations was effective in small plots.