Controle de Alternaria solani em tomateiro (Lycopersicon esculentum) com óleos essenciais

Abstract

O tomateiro (Lycopersicon esculentum Mill.) e uma das principais hortalicas de valor economico no mundo e e a segunda solanacea mais cultivada, sendo superada apenas pela batata. Essa especie esta sujeita a varias doencas que comprometem seu desenvolvimento, e dentre ela esta a pinta preta, provocada pela acao do fungo Alternaria solani (ELL. & Martin) Jones & Grout. E a doenca mais frequente nos cultivos de tomate oque resulta no uso indiscriminado de defensivos agricolas com alta toxicidade, comprometendo a qualidade do alimento. Neste contexto, estudou-se a acao inibitoria dos oleos essenciais de diversas especies de plantas no desenvolvimento fungo Alternaria solani, in vitro, e no controle da pinta preta em tomateiro cultivado. Na avaliacao in vitro, os oleos essenciais das especies Cinnamomum zeylanicum, Cymbopogon citratus e Syzygium aromaticum inibiram totalmente o crescimento micelial e a germinacao dos conidios a partir da concentracao 750 æL/L-1; Eucalyptus citriodora e Melaleuca alternifolia a partir da concentracao de 2000 æL/L-1, e Mentha piperita na concentracao de 5000 æL/L-1. No tomate cultivado em ambiente protegido, os oleos essenciais de Cinnamomum zeylanicum, Cymbopogon martini, Cymbopogon citratus e Syzygium aromaticum, aplicados de forma preventiva, em intervalos de 3 dias, inibiram a doenca na planta a partir de 750 æL/L-1, e Eucalyptus citriodora a 5000 æL/L-1. No cultivo a campo, os oleos essenciais de Eucalyptus citriodora, Cinnamomum zeylanicum e Cymbopogon citratus inibiram a doenca, mas nao foram tao eficientes quanto o fungicida tiofanato metilico + chlorothalonil. Os frutos do tomateiro cultivado a campo submetido a pulverizacoes com oleos essenciais e o fungicida para controle de A. solani apresentaram maior vida util pos-colheita, em ambiente natural.

Lycopersicon esculentum Mill is one of the main vegetable crop with economic value in the world and is the second solanacea cultivated, being surpassed only for the potato. This species is vulnerable to some diseases that compromise its development, and among them here is the black dot, caused by Alternaria solani fungi (ELL. & Martin) Jones & Grout. This disease is the most usual in tomato crop, and as a consequence, results in the abusive use of agricultural defensives with high toxicity. In this context, it was studied inibitory action of essential oils of several species of plants in the development of Alternaria solani, in vitro, and in the control of the black dot in cultivated tomato. In the evaluation in vitro, the essential oil of species Cinnamomum zeylanicum, Cymbopogon martini, Cymbopogon citratus and Syzygium aromaticum totally inhibited the micelial growth and the germination of the conidia at concentration 750 æL/L-1; Eucaliptus citriodora and Melaleuca alternifolia at the concentration of 2000 æL/L-1, and Mentha piperita at 5000 æL/L-1. In the tomato cultivated protection, the essential oil of Cinnamomum zeylanicum, Cymbopogon martini, Cymbopogon citratus and Syzygium aromaticum, applied in a preventive form, in intervals of 3 days, inhibited the symptom in the plant at 750 æL/L-1, and the Eucaliptus citriodora 5000 æL/L-1. In field condictions the essential oils of Eucaliptus citriodora, Cinnamomum zeylanicum and Cymbopogon citratus inhibited the symptons, but werenit so efficient as fungicide methylic tiofanate + chlorothalonil. The fruits harvested in field experiment which sumitted to sprayings with essential oil and the fungicide control, presented greater post-harvest, shelft life in the natural storage.