Nanopartículas metálicas no controle da ferrugem do cafeeiro

Abstract

The objective of this work was to evaluate the efficiency of low concentrations (≤ 500 mg.L-1) of silver (NPAg) and copper (NPCu) nanoparticles in the control of coffee rust (Hemileia vastatrix Berk. & Br). Therefore, five experiments were conducted: one in vitro, three in a greenhouse and one in the field. In the in vitro experiment, the effect of treatments on the germination of H. vastatrix uredospores was evaluated. This was performed in DIC in a factorial design 2 x 5 + 1 and four repetitions. The nanoparticles of Ag and Cu constituted Factor A and the concentrations (0, 50, 100, 200 and 400 mg.L-1) Factor B, the fungicide (epoxiconazole + pyraclostrobin) was also used as an additional treatment. In greenhouse two experiments were carried out in DBC to determine the efficiency of the nanoparticles, one with NPAg and the other with NPCu, both at doses of 0, 50, 100, 200 and 400 mg.L-1. In the third experiment, the effect of NPCu 250 mg.L-1 was compared to other sources of copper (cuprous oxide, copper hydroxide and copper chelate with EDTA (Cu EDTA)). The field experiment was carried out in DBC, with four replications and seven treatments (T1: control without application; T2: fungicide; T3: NPs Cu + Zn + B + Mn; T4: NPs Cu + Zn + B + Mn + B. subtilis; T5: NPs Cu + B + Fungicide; T6: NPs Cu + B + Fungicide + B. subtilis; T7: Fungicide + boric acid + Cu EDTA), the variables incidence of rust and plant leafing were evaluated monthly, between December 2019 and May 2020. Data were subjected to analysis of variance (p≤0.05) and when significant, qualitative variables were compared using the Scott-Knott test (p <0.05) or by orthogonal contrast with the additional treatment. For the quantitative, the adjustment of linear and non-linear models was carried out by regression analysis. In the in vitro experiment, the dose of 400 mg.L-1 of NPAg completely inhibited the germination of H. vastatrix spores. For NPCu the maximum inhibition was 85% at a dose of 400 mg.L-1. In the greenhouse in the experiment with five doses of NPCu, the greatest reduction in AACPS was observed in the dose of 400 mg.L-1 (97.5%). For the experiment with NPAg, the behavior was similar and the greatest reduction in AACPS occurred in the dose of 400 mg.L-1, about 92%. In the third greenhouse experiment, NPCu 250 mg.L-1 and cuprous oxide were the same (p <0.05), which promoted 84.2% and 83.1% reduction in AACPS, respectively. In the field experiment, Fungicide reduced approximately 60% of AACPI. The Cu and B nanoparticles when applied mixed with the Fungicide were efficient and did not differ from the treatment where the Fungicide (T2) was applied alone. Therefore, nanoparticles appear as an alternative to be included in integrated disease management strategies.