Effects of plant extracts and chitosan against alternaria leaf spot of chinese kale

Abstract

Ethanol extracts of Alpinia galanga (L.)Willd. (rhizome), Coscinium fenestratum (Goetgh.) Colebr. (stem), Piper betle Linn. (leave), Piper longum L. (fruit), Zingiber cassumunar Roxb.(rhizome) and chitosan were evaluated for their fungicidal activities in controlling Alternaria leaf spot of Chinese kale, caused by Alternaria brassicicola, under field conditions. The results showed that the application of these plant extracts resulted in reduction of disease severity in a concentration-dependent manner. Among the five plant extracts tested, the extracts of P. betle and C. fenestratum at a concentration of 10,000 ppm displayed potent fungicidal activity in the suppression of disease severity, causing 43% and 41% disease reduction, respectively. The extracts of Z. cassumunar and A. galanga at 10,000 ppm showed moderate effectiveness in controlling the disease, causing 28% and 25% disease reduction, respectively, whereas the extract of P. longum at the same concentration possessed the lowest antifungal activity, reducing the disease severity by less than 20% at the highest dosed tested. The application of chitosan at 2% had a moderate effect; it reduced the disease severity by 30%. However, the application of the systemic fungicide, iprodione, displayed the greatest fungicidal activity in suppression disease severity, causing 65% disease reduction. The results in this study indicated that the P. betle and C. fenestratum may be promising eco-friendly candidates for controlling Alternaria leaf spot disease in Chinese kale production.