Evaluation of Organisms Antagonistic to the Sclerotioid Organs of Drechslera teres, the Causal Agent of Barley Net Blotch. D. -E. Ali-Haimoud, Laboratoire d’Ingénierie Agronomique, Ecole Nationale Supérieure Agronomique de Toulouse, 145, Avenue de Muret, F-31076 Toulouse Cédex, France. M. Mostafa, G. Barrault, and L. Albertini. Laboratoire d’Ingénierie Agronomique, Ecole Nationale Supérieure Agronomique de Toulouse, 145, Avenue de Muret, F-31076 Toulouse Cédex, France. Plant Dis. 77:1251-1255. Accepted for publication 24 June 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-1251.

Twenty-seven microorganisms were evaluated for their ability to reduce sclerotioid organ formation and myceliogenesis in barley straw when applied prior to and following colonization by Drechslera teres. Ten of them were able to partly or totally inhibit the formation of sclerotioid organs on barley straw when applied as a precolonization treatment. All antagonists inhibited sclerotioid organ morphogenesis, whether through direct application or via the crude culture filtrates. Form maculata was more sensitive than form teres to culture filtrates of the antagonists. Treated barley straw did not display new sclerotioid organs in the postcolonization treatment, irrespective of the pathogen form. The postcolonization treatment of straw with certain antagonists also had a strong inhibitory effect on myceliogenesis of D. teres sclerotioid organs. The mycelium application also appeared to more effectively inhibit myceliogenesis than did crude culture filtrates of the antagonists. All antagonists employed reduced the aggressiveness of the mycelium from germinating sclerotioid organs previously treated with antagonists in the maculata form.