Uso de óleos essenciais no controle da antracnose em bastão do imperador (Etlingera elatior (Jack) R. M. Smith)

Abstract

ABSTRACT

Torch ginger is susceptible to several diseases, among which anthracnose stands out, which causes losses in the crop, generating losses for producers. The control of the disease is carried out mainly by the use of chemical products, being necessary the association with other methods of control. The objectives of this work were to evaluate the in vitro and in vivo effect of mint, citronella and lemongrass essential oils, and the fungicides Thiophanate methyl and Mancozeb in the control of anthracnose in inflorescences of torch ginger. For this, a pathogenicity test of an isolate of Colletotrichum tropicale (collection of microorganisms from CECA-UFAL) was carried out, followed by the determination of the Percentage of Inhibition of Mycelial Growth (PIC) of C. tropicale in Petri dishes containing PDA medium supplemented with the following products: mancozeb 240g p.c./100L); methyl thiophanate (45 g p.c./100L) and essential oils, at concentrations of 0.75; 1.5; 2.25 and 3% and ADE (sterilized distilled water) for all controls. Subsequently, the fungicidal or fungistatic activity test of the essential oils was carried out in Petri dishes with Agar-Water culture medium. Healthy stems of torch ginger were sprayed (10mL/plant) with the selected in vitro treatments, applied 72 and 48 hours after pathogen inoculation. For all solutions, ADE was used as solvent and Tween 20 spreader adhesive, 0.1 mL for each 100 mL of solution, was added before spraying. The stems were placed in plastic containers with a calcium sulfate solution (50 mM) to prolong post-harvest durability. After 4 days, the severity and incidence of the disease were determined using a grade scale. The experimental design was completely randomized with 15 treatments and 5 replications. The data obtained were subjected to analysis of variance and the averages compared using the Scott- Knott test at 5% probability. Peppermint, citronella and lemongrass oils inhibited the mycelial growth of C. tropicale; lemongrass oil in all concentrations and citronella oil (0.75 and 1.5%) showed a fungicidal effect. In post-harvest conditions, fungicides reduced the incidence and severity; mint (2.25 and 3%) and citronella (0.75%) oils were effective in reducing disease severity. Lemongrass oil (0.75 and 1.5%) and citronella oil (0.75%) have the ability to inhibit, respectively, the incidence and severity of anthracnose in torch ginger. It is concluded that essential oils are able to control anthracnose in torch ginger. Keywords: Fungus. Plant disease. Alternative control.