Plant Disease Research

Relative performance with respect to bio-efficacy, phytotoxicity and impact on vigour of four seed treatment fungicides belonging to different groups was assessed against Pythium aphanidermatum, Rhizoctonia solani and Fusarium oxysporum f.sp. lycopersici, responsible for damping-off disease in tomato nurseries. The combination of carboxin+thiram and carbendazim were found effective in inhibiting R. solani (IC₅₀=47.01 and 57.47 μg/ml, respectively) and F. oxysporum f.sp. lycopersici (IC₅₀=48.14 and 24.63 μg/ml, respectively), but provided comparatively lesser inhibition of P. aphanidermatum (IC₅₀ > 500 μg/ml) under in-vitro conditions. Captaf was adjudged inferior to carboxin+thiram and carbendazim in inhibiting R. solani (IC₅₀=167.8μg/ml), F. oxysporum f.sp. lycopersici (IC₅₀=129.08μg/ml) but comparatively better against P. aphanidermatum (IC₅₀ > 500 μg/ml). Tebuconazole provided excellent broad-spectrum efficacy against all the three fungi in vitro but showed phytotoxicity to seedlings. Seed dressing with carboxin+thiram was adjudged superior in controlling pre-emergence seed rot followed by carbendazim and captaf but at post-emergence stage, all the four treatments were found at par but significantly better than the untreated seeds. Seedling vigour studies revealed that seedling length was significantly affected with seed treatments. Carboxin+thiram increased the shoot length significantly and germination of seeds compared to untreated control. Though tebuconazole exhibited promising activity against all three test fungi and also reduced the disease significantly, but severely reduced shoot length of seedlings. Seed treatment with all the test fungicides increased germination but best being carboxin+thiram as it caused 8.40 per cent increase over the untreated seed.