Essential Oils and Trichoderma Harzianum as an Integrated Control Measure Against Faba Bean Root Rot Pathogens

Abstract

Essential Oils andTrichoderma Harzianumas an Integrated Control Measure Against Faba Bean Root Rot PathogensCarnation, caraway, thyme, peppermint and geranium essential oils have been found to have inhibitory effects against the mycelial growth ofFusarium solani,Rhizoctonia solani,Sclerotium rolfsiiandMacrophomina phaseolinaunderin vitroconditions. Complete inhibition of fungal growth was observed with the use of 4% carnation and geranium oils. Mycelial growth of the tested fungi showed more sensitivity to high concentrations of thyme than to caraway and peppermint oils. Moreover, essential oils used to coat seeds resulted in a significant reduction of root rot incidence of bean, at both pre- and post-emergence stages under greenhouse conditions. Under field conditions seeds coated with essential oils at a concentration of 4% sown in soil treated with the bio-agentTrihoderma harzianum, gave pronounced protection to emerged bean seeds against the invasion of root rot pathogenic fungi. Compared to the control, the above treatment resulted in a reduction of disease incidence at the pre-emergence stage. This reduction was calculated to be between 47.3 and 55.4% compared with a 16.1% reduction with the use of the Rizolex-T treatment. At the post-emergence stage, all applied treatments were able to reduce the percentage of root-rot incidence. Reduction ranged between 41.4 and 47.1% over the untreated control. Reduction in disease incidence was reflected in a yield increase of 15.1-28.8% and 40.1-50%, in seeds coated with one of the different essential oils, or combined withT. harzianumsoil treatments, in the respective order. Seeds coated with the fungicide Rhizolex-T caused a yield increase estimated as 11.3% over the check treatment. These results show that application of essential oils in integration with the bio-agentT. harzianummay be considered as an applicable, safe and cost-effective method for controlling such soilborne diseases.