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- Influence of Herbicides on Sclerotium Damping-Off in Tomato.
Influence of Herbicides on Sclerotium Damping-Off in Tomato.
Thesis Abstract:
Laboratoty and greenhouse experiments were conducted to determine the effect of herbicides on damping-off in tomato.
Treatments with napropamide (2.0 kg/ha), butralin (1.5 kg/ha) and napromide plus butralin combination (1 + 1 kg/ha) on direct-seeded tomatoes previously inoculated with Sclerotium rolfill Sacc., significantly reduced damping-off incidence. Among the treatments, butralin produced the highest reduction in percentage of diseased plants.
Tomato plants predisposed to the herbicides for 7 and 14 days before transplating to herbicide-free inoculated soil did not change their response to S. rolfill. The magnitude of the manifestedherbicide injury was insufficient to alter the susceptibility of tomatoes to the pathogen.
Increasing concentration of the herbicides correspondingly inhibited mycelial growth. Butralin proved to be inhibitory at lower concentrations and napropamide at higher concentrations. Significant inhibitation of mycelial growth even at a concetration as low as 5ppm strongly indicated the fungicidal action of the herbicides.
Exposure to the herbicide solution prior to inoculation also significantly reduced the virulence of the pathogen, as evidenced by the increasing inhibitation action o fthe herbicides.
Furthermore, the herbicide treatments suppressed the production of sclerotial bodies and consequently decreased the greatest reduction in the formation of sclerotial bodies.
The influence of Butralin and Napropamide on the reduced incidence of Sclerotium damping-off in tomato was due to their direct toxic effect on the pathogen itself. The herbicidal effects were expressed as inihibition of the mycelial growth, virulence and propagule production of the pathogen in the soil.
