Development of Septoria Nodorum Blotch on Wheat from Infected and Treated Seed

Abstract

Effects of seed infection on development of Septoria nodorum blotch on the upper leaves and heads of wheat was assessed at two locations over 3 yr. As the incidence of seed infection at planting increased from 1 to 40%, the intensity of subsequent disease increased but the relationship of seed infection to disease was nonlinear. About 10% seed infection supplied sufficient inoculum to cause a severe epidemic. In 1983, disease severity on the head was similar at two widely separated locations but percentages of seed infection at harvest were greatly different. Thus, percent seed infection at harvest seems to be infleunced by environmental conditions in the heading phase of crop development. Seed treatments (benomyl or triadimenol) resulted in reduced disease severity on the upper leaves and heads at both locations in all 3 yr.