Optimization of epidemiological conditions to enhance the mycoherbicidal efficacy of Alternaria alternata against Chenopodium album

Abstract

A new foliage disease was found on Chenopodium album L. (family chenopodiaceae) in Punjab, Pakistan. Alternaria alternata (Fr.) Keissler was identified and confirmed as the causal agent. The present study aimed to optimize environmental condition that could enhance mycoherbicidal potential of A. alternata against C. album. In growth room trials, the effects of various inoculum concentrations of A. alternata (10⁵, 10⁷ and 10⁹ conidia ml^-1) on disease development was studied at different growth stages of the host plant (5 - 10, 10 - 15 and 20 - 25 leaf/flowering stage) at various dew period (100% humidity for 12, 18 and 24 h) and temperature (20, 25 and 30°C) regimes. To enhance the mycoherbicidal potential of the pathogens, different formulations; 1 and 2% gelatin, 1 and 2% carboxymethylcellulose (CMC), 1:1 gelatin and CMC, 10 and 20% canola oil emulsion were used. The pathogenicity of A. alternata increased with increasing spore concentration and length of dew period. A spore concentration of 10⁹ conidia ml^-1 in 20% canola oil emulsion with 24 h dew period and at temperature 25 and 30°C caused 100% mortality of C. album plants at 5 - 10 and 10 - 15 leaf stages and resulted in maximum reduction in biomass of the target weed. The present study concludes that under a certain set of conditions, A. alternata can completely control C. album.

Key words: Alternaria alternata, Chenopodium album, conidial concentration, dew period, formulations, mycoherbicide, plant growth stage, temperature.