Optimizing the application of acibenzolar-S-methyl and copper to control bacterial spot on fresh-market tomato

Abstract

This study aimed to adjust the number of applications of acibenzolar-S-methyl (ASM) and copper in an integrated program for the control of bacterial spot on fresh-market tomato. Two field trials were carried out during 2018 and 2019. Four sets of number of weekly applications of ASM were evaluated (7, 9, 11, and 13 applications). In addition to these, four other treatments were included: two as a tank mixture compound [13 weekly applications of ASM + biostimulant and nine applications of ASM + copper oxychloride]. Copper oxychloride was applied after ASM treatments in order to complete 13 applications per growing season. Copper oxychloride and untreated plots were used as a control. The variables evaluated were bacterial spot severity, total yield, and yield per classes of fruit according to the Brazilian market standards. Benefit-cost ratio (B/C) was calculated considering the income increase of a given treatment in relation to the untreated control. The disease ratings and yield data were subjected to ANOVA and the means tested for significance by Fisher, Dunnett, and orthogonal contrasts comparison tests. Regression analysis were carried out with the disease ratings to evaluate the ASM number of applications. As the number of ASM applications increased, disease severity decreased, although, the best B/C was obtained with seven applications of ASM, followed by copper applications until the end of the cycle. The tank mixture compound treatments did not result in economic gain increase. Moreover, disease severity was significantly high when ASM was applied in tank mixture with copper.