Plot Size Effects on Disease Progress and Yield of Wheat Infected byMycosphaerella graminicolaand Barley Infected byPyrenophora teres

Abstract

Areas under disease progress curves (ADPC) for 2 cereal pathogens of different spore dispersal mechanisms (P. teres on barley and M. graminicola on wheat) and grain weights obtained from field plots were subjected to pertinent orthogonal comparisons to determine if ADPC and crop loss estimates are functions of plot size. The study was made in Morocco. ADPC from plots 40 .times. 40 m and infected with P. teres were statistically greater than ADPC from plots 20 .times. 20 and 10 .times. 10 m, yet grain weights were not significantly different. Initial severities were similar in all plots, but final severities at hard dough to ripeness were 23-36% greater in plots 40 .times. 40 than in plots 20 .times. 20 and 10 .times. 10. ADPC from plots 40 .times. 40 and infected with M. graminicola also were statistically greater than ADPC from plots 20 .times. 20 and 10 .times. 10, but final severities were only 2-10% greater in plots 40 .times. 40 than in plots 20 .times. 20 and 10 .times. 10. As with P. teres, grain weights were not significantly different. ADPC from plots 20 .times. 20 and 10 .times. 10 were not significantly different for P. teres or M. graminicola. The proportion of P. teres conidia escaping from plots was inversely proportional to plot size at Ellouzia and Jamaa Shaim.