| The toxicities of seven fungicides including 68% Metalaxyl mancozeb WG, 64% Oxadixyl mancozeb WP,72% Cymoxanil mancozeb WP, 50% Acrobat WP, 25% Azoxystrobin SC, 18.7% Cabrio-team WG, and 70% Mancozebon WP on phytophthora infestans were determined by using in vitro radial growth assay, respectively. Nine combinations from these seven fungicides were used to control potato late blight in the field trial. The results indicated that, except for 70% Mancozeb WP and 64% Oxadixyl mancozeb WP, the other five fungicides showed good inhibition on the growth of hypha of phytophthora infestans, and the values of EC50 were between 0.017 mg/L and 0.243 mg/L. All the combinations based on the seven fungicides showed good control efficiency and yield-increasing effect in the field trial. The control effects on potato late blight from five combinations including 70% Mancozeb WP+72% Cymoxanil mancozeb WP+50% Acrobat WP+72% Cymoxanil mancozeb WP, 70% Mancozeb WP +72% Cymoxanil mancozeb WP +18.7% Cabrio -team WG +72% Cymoxanil mancozeb WP, 70% Mancozeb WP +72% Cymoxanil mancozeb WP +68% Metalaxyl mancozeb WG +72% Cymoxanil mancozeb WP, 70% Mancozeb WP+72% Cymoxanil mancozeb WP+68% Metalaxyl mancozeb WG+50% Acrobat WP and 70% Mancozeb WP+72% Cymoxanil mancozeb WP+18.7% Cabrio-team WG+50% Acrobat WP were more than 90%, and the yield-increasing production rates were from 13.92% to 18.54%, which could increase the net income of 660~905 Yuan per 666.7 m2. According to the above results, the following method was provided to control potato late blight in winter of Guangdong Province: using 70% Mancozeb WP as protective agent in the early stage of infection, then using 72% Cymoxanil mancozeb WP+68% Metalaxyl mancozeb WG+72% Cymoxanil mancozeb WP or 72% Cymoxanil mancozeb WP +68% Metalaxyl mancozeb WG +50% Acrobat WP or 72% Cymoxanil mancozeb WP +18.7% Cabrio-team WG+50% Acrobat WP during the period of disease. |
