Effect of environmental factors on disease development caused by the fungal pathogen Plectosporium alismatis on the floating-leaf stage of starfruit (Damasonium minus), a weed of rice

Starfruit, Damasonium minus (R. Br.) Buch, is a herbicide-resistant, aquatic-weed occurring in Australian rice fields. The fungal pathogen Plectosporium alismatis (Oudem) W.M. Pitt, W. Gams & U. Braun is a potential mycoherbicide for the control of this weed. Previous work showed that the fungus can suppress the growth of starfruit juvenile plants. This paper reports the effect of environmental factors on the disease development on starfruit at the floating-leaf stage. Fungal inoculation of plants in advanced phases of floating leaf stage reduced significantly (P<0.05) the green leaf area, but only when the percentages of diseased areas were deducted. However, inoculation when the first floating leaf was emerging reduced significantly (P<0.001) both, plant dry above-ground biomass and leaf area.