Efficacy of sar elicitors and fungicides against late blight of potato and downy mildew of muskmelon

A study was conducted to induce systemic acquired resistance (SAR) in potato against Phytophthora infestans and in muskmelon against Pseudoperonospora cubensis by incorporating SAR elicitors viz. jasmonic acid (JA), salicylic acid (SA), benzothiadiazole (BTH) each @ 500μM and β amino butyric acid (BABA, 50 mM) in the five week spray schedule of fungicides. The four elicitors were used at weekly interval starting with first application on three-week-old plants. Sporangial inoculation was done after one week of elicitor/fungicide spray and disease severity was recorded at weekly intervals. Late blight control varied from 75 per cent in BTH treated plots to 94% in standard recommended fungicide treatment. The second best treatment was three sprays BABA followed by two sprays of mancozeb with 92.8% disease control. SA singly gave 82.6 per cent disease control whereas in combination with mancozeb and Ridomil Gold, it gave 87.7 per cent and 92.8 per cent disease control, respectively. In case of muskmelon, SA singly gave 76.2 per cent downy mildew control whereas in combination with mancozeb and Ridomil gold, it gave 81.7 per cent and 85.1 per cent disease control, respectively. Hence, SA treatment can be combined in five week spray schedule with half dose of contact or systemic fungicide for late blight control in potato and downy mildew control in muskmelon by initiating spray application before disease onset.