Efficacy of plant extracts against Alternaria leaf blight (Alternaria helianthi) of sunflower.

Abstract

Alternaria leaf blight caused by Alternaria helianthi (Hansf.) Tubaki and Nishihara is one of the major diseases of Sunflower. In the present study different plant extracts i.e., Allium sativum (garlic), Azadirachta indica (neem), Pongamia pinata, Eucalyptus globules, Catheranthus roseus, Jatropha multifida, Polyalthia longifolia, Tridax procumbense, Calotropis jelodona and Prosopis julifera were evaluated against Alternaria leaf blight under in vitro and in vivo conditions. Plant extracts were prepared with sterile water at concentrations of 0.5, 1.0, 2.0 and 5.0 %. These were tested by spore germination method in in vitro and whole plant assay method under pot culture conditions. Among different concentrations tested, reduction in spore germination of A. helianthi was recorded with 0.5 % of all plant extracts. Garlic extract was found to be effective with 85.1% reduction in spore germination over control followed by neem (83.3%) and P. pinata (75.9 %.). In pot culture studies, these extracts were sprayed three times at different intervals on sunflower plants artificially inoculated with A. helianthi. Garlic showed disease reduction of 52.0% over pathogen check followed by neem. Thus from the above studies it is clearly evident that concentration of 0.5% is effective dose and among plant extracts, garlic showed highest disease reduction against Alternaria leaf blight in sunflower both under in vitro and in vivo conditions.