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.

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Abstract:The fungicidal effect of some essential oils against Alternaria solani one of the species that cause early blight of potato was evaluated under in vitro and field conditions. Effect of carnation, caraway, thyme oils and the chemical fungicide Ridomil MZ 72 at various concentrations on mycelial growth of A. solani was tested. Carnation oil had the strongest and most extensive inhibitory effect on fungal growth. Slightly less effective were caraway and thyme oils followed by the chemical fungicide. Extended field trails for two cultivation seasons proved that the application of essential oils twice as foliar spray had a superior effect to the fungicide treatment for reducing the early blight incidence comparing with untreated control. An opposite relationship between the disease incidence and concentrations of applied essential oils was observed. The increase in potato yield also followed the same trend. The highest reduction in disease incidence and yield increase was recorded in treatments with 1% of carnation, caraway and thyme oils in descending order. Ridomil MZ 72 applied at the dose recommended by manufactories had a low effect in this regard. Essential oils treatments might be used as easily applied, safe and cost effective control methods against such plant diseases.

Abstract:The suppressive effect of sodium and calcium salts applied individually or combined with the yeast Saccharomyces cerevisiae against Alternaria solani the causal agent of early blight disease of potato was evaluated under laboratory, greenhouse and field conditions. In vitro test a complete inhibition in fungal growth was observed at concentration of 30 mg/ml of both sodium bicarbonate and calcium chloride. The commercial backing yeast S. cerevisiae (CBY) enhanced the inhibitory effect of tested salts reflected in increasing mycelial fungal growth reduction when combined at the rate of 1:1 at each concentration tested. In pot experiment, under artificial infestation with pathogenic fungus, application of sodium bicarbonate or calcium chloride significantly reduced the early blight incidence and severity by increasing their concentrations. Their most effective concentration were 30 mg/ml that reduced the disease incidence by 50 and 62.4%, respectively. Superior effect of sodium bicarbonate or calcium chloride in disease reduction was observed when they combined with CBY. Field trails for evaluating the most promising greenhouse treatments were preformed under natural infestations during two successive summer seasons. Calcium chloride proved higher efficacy for reducing both disease incidence and severity than that of sodium bicarbonate when applied either alone or combined with CBY. Also, it is observed that increasing concentrations of both sodium bicarbonate or calcium chloride showed parallel decrease in disease incidence and severity. Application of (CBY) enhanced the efficacy of salts spraying against early blight disease. Similar trend was also observed with the increase of potato tubers yield. On the light of the present study it could be suggested that the usage of combined application of the yeast S. cerevisiae with sodium bicarbonate or calcium chloride might be used as easily applied, safely and cost effective control methods against such plant diseases.