In vitro and in vivo activity of essential oils extracted from Eucalyptus staigeriana, Eucalyptus globulus and Cinnamomum camphora against Alternaria solani Sorauer causing early blight in tomato

Use of plant compounds has been reported to reduce severity of diseases in many crops. In an attempt to establish new control practices against plant pathogens with low mammalian toxicity and low persistence in the environment, the objective of this work was to study the activity of essential oils extracted from Eucalyptus staigeriana F. Muell. ex Bailey, Eucalyptus globulus L. and Cinnamomum camphora Ness and Eberm var. linaloolifera Fujita against Alternaria solani, causing early blight on tomato, under in vitro and in vivo conditions. In order to test in vitro antifungal activity, potato dextrose agar (PDA) medium was used with essential oils diluted at 0.1-10.0 μL mL−1 concentrations. Inhibition of disease severity on tomato was evaluated under greenhouse conditions and essential oils concentrations used were 2.0 and 10.0 μL mL−1. Results showed that all essential oils were capable to control early blight disease, for both in vitro and in vivo assays. Tomato plants treated with essential oils presented an area under the disease progress curve (AUDPC) ranging from 126.71 to 166.43 and fungicide azoxystrobin ranging from 154.97 to 160.89, differing from control condition which demonstrated an AUDPC of 279.14. Therefore, essential oils could be an effective alternative to control tomato early blight disease.