EFFECT OF AQUEOUS LEAF AND BARK EXTRACTS OF AZADIRACHTA INDICA A. JUSS, EUCALYPTUS CITRIODORA HOOK AND PINUS ROXBURGHII SARG. ON LATE BLIGHT OF POTATO

Abstract

Aqueous extracts of sundried powder of leaves and bark of three test plants Eucalyptus citriodora Hook., Azadirachta indica A. Juss and Pinus roxburghii Sarg. were evaluated for their efficacy on epidemiological components (disease severity, lesion size and area under disease progress curve) of late blight of potato caused by Phytophthora infestans (Mont.) de Bary in pot culture during 2008. Among the tested plants, aqueous extracts of A. indica and P. roxburghii significantly contributed in reduction of disease severity, lesion size and area under disease progress curve (AUDPC) after potato leaves were inoculated with P. infestans. Extracts of E. citriodora had no effect on the studied epidemiological parameters of late blight disease comparative to control. Results demonstrated that extracts of A. indica were more effective than P. roxburghii in controlling late blight disease. Similarly, leaf extracts were found to be more effective in minimizing disease severity, lesion size and AUDPC than bark extracts. Further research is needed as to whether these extracts can be used as commercial formulations for management of late blight disease.