Effect of ascochyta blight (Mycosphaerella pinodes) on yield components of single pea (Pisum sativum) plants under field conditions

Field studies were made in 1992 and 1993 to examine the yield components of pea inoculated with Mycosphaerella pinodes and those of healthy pea (sprayed with a mixture of flutriafol + chlorothalonil), in a split-plot design with the cv. Solara sown at different plant densities. Ascochyta blight was severe on leaves and on internodes of the basal part of the plants; pods had few lesions. The number and length of stems per plant were the same for diseased and healthy plants. The number of reproductive nodes and pods per stem were affected by disease only in 1993. In 1992 and 1993 respectively, disease caused reductions in the number of seeds per stem of 18% and 25%, and in seed size of 13.5% and 16.7%, compared with healthy plants. The harvest index and total biomass were lower in diseased than in healthy plants and seed yield was reduced by 40% in diseased plots. These results show a high relationship between the disease parameters (disease mean on stipules/nodes 8–18/ and on internodes/nodes 5–15/, percentages of stipules or internodes with a disease score 4, and percentage of stems encircled by lesions), plant density and yield reduction.