Aqueous extracts from Acalypha gaumeri and Bonellia flammea for leaf blight control in chrysanthemum (Chrysanthemum morifolium)

Abstract

The chrysanthemum is the second most important cut flower in the world, however, its quality and commercial value is affected by the leaf blight produced by Alternaria spp. The objective of this work was to evaluate the causal agent of leaf blight in Chrysanthemum, and its control with aqueous extracts of Acalypha gaumeri and Bonellia flammea. The fungus was collected and identified from leaves and stems of chrysanthemum plants. Subsequently, molecular identification and pathogenicity tests were performed on chrysanthemum plants. In the field, treatments were evaluated with weekly applications of: T1: B. flammea bark extract, T2: A. gaumeri root extract, T3: negative control (water) and T4: Captan® fungicide. Prior to the application of the treatments, plants were inoculated with the isolated fungus (2.5 × 106 spores mL-1) and severity was evaluated. Alternaria chrysanthemi was identified as the causal agent. Based on the severity percentage, the lowest averages of the area under the disease progress curve, the lowest rates of apparent infection, the lowest intensity of the disease and the greater effectiveness in controlling the disease were observed for T2 (165, 0.017, 8 and 67%, respectively) followed by T1 (186, 0.022, 13 y 50 %, respectively) and T4 (179, 0.023, 14 y 45%, respectively), observing a significantly different than negative control T3 (369, 0.025, 25 and 0%, respectively). Plant extracts have potential to be used as an alternative in the management of Alternaria leaf blight in chrysanthemum.