Evaluating the effect of greenforces and greenforce cuca products on the severity of bacterial spot and wilt, and powdery mildew diseases on tomato

Abstract

Tomato, the second most consumed vegetable in Brazil, is highly limited in production due to a variety of diseases. Among the most important diseases are bacterial spot (BS, Xanthomonas perforans), bacterial wilt (BW, Ralstonia solanacearum), and powdery mildew (PM, Oidium lycopersici). Management of these diseases is very challenging, costly, and has not provided long-term control. Thus, there is a need for identifying cheaper, less toxic, and longer lasting control methods. To this end, the goal of this work was to evaluate the effect of two formulations prepared from coffee residues (plant extracts), GreenForce S (GF-S) and GreenForce CuCa (GF-CuCa), on the severity of those three tomato diseases. The tomato cultivar ‘Santa Clara’, which is susceptible to BS, BW, and PM, was used in all experiments. The concentrations tested for GF-S and GF-CuCa were: 5, 10, and 15 ml/L for GF-S and 2.5, 5, and 10 ml/L for GF-CuCa. For the BS experiments, the controls used were: inoculated control (no product applied), Kocide (copper hydroxide; 3 g/L), and Kasumin (antibiotic; 3 ml/L). For the BW and PM experiments, the controls used were: inoculated control (no product applied) and Kocide (copper hydroxide; 3 g/L). All the experiments had three biological replicates. The direct toxic effect of GF-S and GF-CuCa on BS, BW, and PM was also evaluated. GF-S and GF-CuCa were effective in reducing the severity of BS to the same levels observed for Kocide and Kasumin, and there was not a dose effect. However, GF-S and GF-CuCa were not effective in reducing the severity of BW. The severity of PM was also reduced by GF-S and GF-CuCa. We also observed that both products, GF-S and GF-CuCa, had direct toxic effects on the pathogens tested. Overall, GF-S and GF-CuCa could be recommended for controlling BS and PM diseases in tomato.