Indoor Screening and Field Trial of Fungicides against Tobacco Brown Spot

The aims of this investigation were to screen for effective fungicides to control tobacco brown spot. The indoor toxicities of ten fungicides against A. alternata were tested by the method of colonial growth-rate and spore germination. The field trial was conducted with four selected fungicides. The results of the indoor experiment showed that the fungicides with strong activities against both mycelia growth and spore germination of A. alternata were difenoconazole 10% WG, polyoxin 10% WP, prochloraz-manganese chloride complex 50% WP, difenoconazole·azoxystrobin 32.5% SE, difenoconazole·propicondzole 30% SE and trifloxystrobin·tebuconazole 30% SE. In addition, tebuconazole 430 g/L SC had strong activities against spore germination but not mycelia growth of A. alternate. The fungicides with weak inhibitory activities were myclobutanil 40% WP, dimetachlone 40% WP and cytosinpeptidemycin 6% AS. The results of the field experiment indicated that the control effect of difenoconazole 10% WG, trifloxystrobin·tebuconazole 30% SE, difenoconazole·propicondzole 30% SE and difenoconazole·azoxystrobin 32.5% SE were 90.60%, 88.21%, 87.21% and 83.84%, respectively. These four fungicides could be used in control of tobacco brown spot.