Dispersal of Spores of Fusarium culmorum in Aquatic Systems.

ABSTRACT The dispersal of spores of Fusarium culmorum, a biological control agent for the aquatic weed Hydrilla verticillata, was investigated in aquatic systems. Macroconidia and chlamydospores that were applied to the surface of the liquid settled rapidly in deionized water, tap water, 5% Hoagland's solution, natural spring water, or river water held in glass containers. The rate of fall, as measured for 50% of the spores, was determined to be 9 cm h(-1). Rapid lateral dispersal of spores from a point source occurred in still water. This initial spore movement occurred at a rate of >9 m h(-1) (15 cm min(-1)), approximately 100 times faster than the rate of settlement. The spores attained an even lateral distribution in a still, closed system. Spores dispersed rapidly in moving water and were transported with the water current. Spores were determined to carry positive electrostatic charges as they migrated towards the negative pole during electrophoresis. The physical components of dispersal of F. culmorum spores were defined in a still aquatic system to consist of rapid lateral dispersal and sinking due to gravity. In moving water, the dynamics of water movement was superimposed over the other two factors.