Alternaria leaf spot is one of the most important diseases of green onion in organic farming. The objective of this study was to evaluate the effect of weekly sprays of silicate clay (Rocksil®) and extract of Ulva fasciata in disease control and yield of the green onion in organic farming. Final disease severity and area under the disease progress curve were evaluated on central leaves (Yl and AUDPCl) as well as the whole plant (Yp and AACPDp). Length and fresh weight of leaves was determined at harvest. The experiment was repeated in four crop cycles. Data on disease severity and yield were subjected to analysis of variance and Duncan test (P < 0.05). In most of the experimental cycles, significant differences were observed in the sanity and yield of the treatments compared to the control (plants treated with water). Overall, both preparations reduced the final disease severity (Yf and Yp (by 41-62% ) and the AUDPCs by 28-58%. Treatments of plants with silicate clay and seaweed extract increased the fresh weight of leaves by 46% and 32%, respectively. Although this study indicates that silicate clay and seaweed extract have the potential for disease control, further studies are needed to elucidate the control levels of these treatments in different edaphoclimatic conditions.
Alternaria porri; organic system; silicate clay; seaweed extract
