Impact of Vermicompost Tea and Tagetes erecta Extract to Control Onion Purple Blotch Disease

Vermicompost tea (VCT) and extract of Tagetes erecta L. (TE) were used to study their effect on onion purple blotch caused by Alternaria porri (Ellis) Cif, under laboratory and field conditions in comparison with the recommended fungicide Luna Experience. In vitro, efficacy of TE extract at 0.25, 0.50, 1.0, 2.0 and 3.0 ml/L PDA medium on linear growth of A. porri was estimated. The inhibitory effect of TE on A. porri was increased by increasing the TE concentrations, as the 3 ml/L caused 51.3% growth reduction. Under field conditions, at Etay El-Baroud Agricultural Research Station, Beheira governorate, Egypt, seven sprays with VCT at 12.5 and 25 ml/L and TE at 2 and 3 ml/L were used on Italy red and Giza 20 cvs. onion plants during 2015/2016 and 2016/2017 growing seasons to evaluate their effect on disease severity, no. of leaves, plant height, onion bulb yield, chlorophyll a and b content and activity of peroxidase and polyphenoloxidase enzymes. TE extract at 3 ml/L was the most effective comparing with VCT and Luna Experience to reduce purple blotch severity with efficacy of 66.2 and 72.5% on Italy red and Giza 20 plants, respectively. Leaves number, plant height and onion bulb yield were increased positively with treatment concentrations. VCT at the rate of 25 ml/L gave 49.6, 50.4 kg/plot for cv. Italy red and 47.9, 47.3 kg/plot for cv. Giza 20 as the best tested treatment to increase onion bulb yield in the two successive seasons. All treatments increased contents of chlorophyll a and b and activity of peroxidase and polyphenoloxidase in onion plant leaves.