Métodos alternativos no controle de podridões de morango e maçã

Abstract

The present work was divided into three articles. For the first article, essential oils (EO) of Aloysia citriodora, Aloysia hatschbachii, Lippia alba, Cymbopogon winterianus, Cymbopogon martinii, Corymbia citriodora and Eucalyptus grandis were tested at concentrations of 0.0; 0.5; 1.0; 1.5; 2.0 and 2.5 μL. mlˉ¹ of EO in PDA medium, in petri dishes inoculated in the centre with mycelial disc of the pathogen Rhizopus oryzae, causing soft rot in strawberries. The chemical composition of the oils was identified. Fungal growth evaluations were carried out during a period of 10 days. The essential oils of A. citriodora, C. martinii, L. alba and E. grandis, showed inhibitory effect on fungal development in vitro at concentrations of 1.5; 2.0; 2.0 and 2.5 μl.mLˉ¹. When the essential oils were applied in the in vivo test on strawberries, the same synchrony of the results obtained in the in vitro test was not observed. In the second article, essential oils of Aloysia citriodora, Aloysia hatschbachii, Cymbopogon citratus, Cymbopogon martinii and Cymbopogon winterianus were tested in vitro and in vivo against the pathogen Penicillium expansum, the cause of blue mold rot in apples. Concentrations of 0.0; 0.2; 0.4; 0.6; 0.8 and 1.0 μl.mLˉ¹ of EO in PDA medium were tested on petri dishes inoculated in the centre with mycelial disc of the pathogen P. expansum. The essential oils of A. citriodora, C. citratus, C. martinii showed inhibitory effect at the concentration of 0.8 μl.mLˉ¹, while C. winterianus and A. hadtsibachii at the concentrations of 1.0 and > 1.0 μl.mLˉ¹. When evaluated the action of EOs on apple fruits, the essential oil of C. martinii presented the lowest Area Below Disease Progress Curve (ABDPC), differing statistically from the control treatment and not differing from the treatment with fungicide Cercobin®, thus presenting control efficiency rate approximately at 30%. In the third article, organically grown Topaz apples were heat treated with hot water alone or with calcium chloride at 8 and 12% concentration or sodium bicarbonate at 4% concentration; three essential oils and Pyrimethanil fungicide and stored in regular air (RA) and controlled atmosphere (CA) for 4 and 6 months, respectively. The hot water treatment plus addition of calcium chloride at 8 and 12% maintained the firmness of the pulp of fruits stored in RA and showed a positive correlation among themselves (r=0.92), however physiological disorders were observed. The thermal treatment plus sodium bicarbonate presented the lowest rot indexes, however undesirable characteristics such as reduction of pulp firmness and fruits with wilted aspects was the main negative effect observed, followed by fruits with necroses. Treatments with essential oils presented phytotoxicity, which led to intense fruit rot, mainly in RA. The treatments with hot water and fungicide reduced the incidence of rotting and maintained the quality of the fruits during storage.