Leaf spot of Aloe barbadensis (Miller) and its management

Aloe barbadensis (Miller), also known as Aloe vera is cultivated for its thick fleshy leaves which have great medicinal value. In May 2006, leaf spot disease on aloe leaves was observed in the herbal garden, Department of Agronomy, Punjab Agricultural University, Ludhiana. These spots were small, circular to oval and dark brown in colour. These spots were sunken with grey centres and brown margin. In later stages of infection the spots increased in size and the affected leaves dried from the tip downward. The causal agent was isolated on PDA and identified as Alternaria alternata (Kamalakannan et al, 2008). The pathogenicity was proved by spraying the spore suspension (1x10⁶ spores per ml) on the pin-pricked leaves of the potted plants. Four fungicides viz. Indofil M-45, Score, Tilt and Amistar were tested for their efficacy against the pathogen under in vitro as well as in vivo conditions. Amistar and Score were found to be highly effective in inhibiting the spore germination of the pathogen at as low as 25 µg ml⁻¹. These fungicides also reduced the disease intensity as compared to control under field conditions during 2008.