Abstract:
The severity of speckled leaf blotch (Mycosphaerella graminicola (Fuckel) Schroeter, Septoria tritici Rob. ex Desm.) in wheat crops was surveyed in the Wimmera during the 1974-77 seasons and in all the major wheat growing areas of Victoria in 1978. Speckled leaf blotch was found in all crops and the severity varied greatly within and between seasons. The average percentage of affected area on the penultimate leaf of main tillers was 24%, 28%, 1.5%, 0% and 9.4%, respectively, for the successive seasons. The corresponding grain yield losses were estimated at 19, 21, 5, 0 and 12% by using an experimentally derived relation between yield loss and disease severity. In 1978, glume blotch (Leptosphaeria nodorum (Miiller, Septoria nodorum (Berk.) Berk.), stem rust (Puccinia graminis Pers. f sp. tritici Erikss and Henn.), leaf rust (Puccinia recondita Rob. ex Desm. f sp, tritici Erikss) and powdery mildew (Erysiphe graminis DC. f sp. tritici E. Marchal) occurred in 8%, 3%, 1% and 0.5%, respectively, of the crops sampled. These surveys have shown speckled leaf blotch to be the most important foliar disease of wheat in Victoria.