IDENTIFICATION OF THE CAUSAL AGENT OF LEAF BLIGHT DISEASE ON Ochna integerrima AND EVALUATION OF NANO-MATERIALS FOR SPORE GERMINATION INHIBITION

Abstract

Leaf blight is one of the most severe diseases affecting yellow apricot trees (Ochna integerrima) in the main cultivation areas of Ho Chi Minh city. The disease is also a significant factor leading to the overuse of chemical pesticides by farmers for prevention and treatment, posing a major threat to the ecological environment and public health. This study was conducted to identify the causal agent of leaf blight disease on Ochna integerrima in Ho Chi Minh city. To evaluate the effectiveness of Ag-Cu nanoparticles and copper nanoparticles in inhibiting the pathogen under laboratory conditions. Field surveys determined that leaf blight causing on 36% of the leaves on branches. Morphological identification combined with molecular biology techniques and pathogenicity confirmation via Koch's postulates identified Neopestalotiopsis sp. as the causal agent of the disease. Typical symptoms include circular, dark brown lesions with raised, irregular margins and a faint yellow halo. The infected tissue dries out but does not tear. Black fruiting bodies form and are scattered on the underside of the lesions. Under laboratory conditions, both Ag-Cu and Cu nanoparticles at concentrations of 250 ppm and 200 ppm respectively, completely inhibited the germination of Neopestalotiopsis sp. spores for up to 15 hours after incubation.