Sensitivity of Alternaria Species to Different Treatments on Disease Severity in Potato

Potatoes are the third most important food for human consumption, with high production potential. Early blight ( Alternaria sp.) can generate significant economic losses, and the difficulty in managing this disease lies in the lack of cultivar resistance to the pathogen, use of products with low efficacy, and the decreased sensitivity of the pathogen to some fungicides available. Thus, the present study aimed to determine the efficacy of different treatments in controlling potato pathogens, A. alternata , A. grandis , and A. solani , as well as the influence of climatic conditions on the development of the disease. The treatments were: T1- Control (water); T2 - Pidiflumetofen + Difenoconazole; T3 - Pidiflumetofen; T4 - Fluxapyroxad + Pyraclostrobin; T5 - Acibenzolar-S-methyl (ASM); T6 - T. harzianum ; T7 - ​​Pidiflumetofen +  T. harzianum ; T8 - Pidiflumetofen + Difenoconazole +  T. harzianum ; T9 - Pidiflumetofen + ASM; T10 - Pidiflumetofen + Difenoconazole + ASM. Results demonstrate that Pidiflumetofen and Difenoconazole, alone or in combination, presented superior efficacy in vitro tests. Their field performance, however, did not differ statistically from that of Fluxapyroxad + Pyraclostrobin. These fungicides still showed greater efficiency in controlling different species of Alternaria when compared to isolated treatments with ASM and T. harzianum . Furthermore, all treatments evaluated were superior to the control, evidencing the effectiveness of chemical and biological control in relation to the absence of treatment. These findings highlight the importance of the integrated evaluation of products in different experimental conditions for the recommendation of more effective strategies in phytosanitary management.