The comparison of the efficacy of some fungicides and non-chemical compounds in control of potato early blight disease

Early blight disease on potato is caused by Alternaria solani and A. alternata. The damage rate of this disease is variable and has been reported between 5-78%. In this study, the effect of Propamocarb+fenamidone SC45%, Chlorothalonil WP75%, Azoxystrobin+difenoconazole SC32.5%, Boscalid+pyraclostrobin WG33.4%, Cymoxanil+copper hydroxide, Sodium bicarbonate, Calcium chloride, Cang Mei and Pars Basil in the laboratory and greenhouse was investigated. Generally, all of these treatments inhibited mycelial growth of A. solani and A. alternata. Azoxystrobin+difenoconazole and Boscalid+pyraclostrobin with concentration of 30 ppm and 100 ppm, respectively with 99% had the highest of percentage inhibition on the growth of A. alternata mycelium. The lowest effective treatment in mycelial growth inhibition of this species was Cymoxanil+copper hydroxide with concentration of 150 and 200 ppm. In greenhouse, Azoxystrobin+difenoconazole with concentration 1/1000 and Pars Basil with concentration 1/100 were the most and the least effective treatment in disease severity index of A. alternata, respectively. Azoxystrobin+difenoconazole, Sodium bicarbonate and Boscalid+pyraclostrobin with concentration 30, 20000 and 100 ppm, respectively decreased the growth of A. solani mycelium by 99%. Cymoxanil+copper hydroxide with concentration 150 and 200 ppm as the lowest effective treatment, inhibited the A. solani mycelium by 26%. In greenhouse, Azoxystrobin+difenoconazole and Boscalid+pyraclostrobin with concentration of 1/1000 and 0.5/1000, respectively decreased the disease severity index of A. solani by 100%. Cang Mei with concentration 1/100 decreased the disease severity index of this species by 5% with no difference with the control.