Occurrence, Virulence and Evaluation of Essential Oils against Fusarium oxysporum f. sp. niveum causing Wilt of Watermelon

Roving surveys were conducted to assess the prevalence of Fusarium wilt of watermelon from major watermelon growing areas of Tamil Nadu, India during 2013-2014. The results revealed that sample collected from Veppur chekkadi village have registered the maximum disease incidence (40.21%) and least disease incidence was recorded in Lalapetti (8.0%) village. The pathogen was isolated from the infected roots and 15 Fusarium isolates were maintained and studied their cultural characteristics. Pathogenicity test were conducted to assess the pathogenic variation among the isolates under greenhouse condition. Among the 15 isolates, isolate FW11 recorded the maximum disease incidence of 81.66% and the isolate FW8 recorded the least incidence of Fusarium wilt recording 43.33%. Six different plant essential oils were tested against the test pathogen under in vitro condition. The results revealed that Pelargonium graveolens, Cymbopogan citratus and Cymbopogan martinii recorded the complete mycelial growth inhibition of F. oxysporum f.sp. niveum even at minimum concentration (0.02%). Whereas, Cymbopogan nardus and Eucalyptus globulus oils required complete mycelial growth inhibition of 0.04 and 0.06%, respectively.