This work was carried out at the International Institute of Tropical Agriculture (IITA), Yaoundé Nkol bisson. Ten improved and four local cultivars of taro were used to carry out a pathogenicity test of Phytophthora colocasiae isolates from which one virulent isolate from both improved cultivar BL/SM123, and BL/SM120, were selected and subsequently used in determining the effect of Original Research Article media, temperature, pH, and light on growth parameters-mycelia growth and spores density. There was a significant difference (P ≤ 0.05) on the growth media for the optimal fungal growth parameters. The most appropriate media for mycelia growth and spores production were V6 and V8 juice agar. The optimum temperature for mycelia growth and spore density was 24°C and also optimum pH value for spores production was 6. The selection of the best growth medium was important to screen the fungal pathogen for virulence and potential field pathogenicity testing. Incubation in both light and dark was best for mycelia growth and sporulation.

all the research farms. Ninety corms of the each cultivar were treated before planting with fungiforce at 0.33% concentration while others were not treated. Fungiforce is a contact and systemic fungicide containing high levels of copper oxide (600 grams) and mild levels of metalaxyl (120 grams), various concentrations of 0.4%, 0.33%, 0.27%, at the onset of the first symptom of leaf blight on the leaves using knapsack sprayer of 15 litres at two weeks interval, while the control experiment consisted of unsprayed taro leaves. Data for the disease incidence of taro leaf blight was recorded from the onset of disease in fields and continued at two weeks interval for 6 weeks. The results of planting taro in four seasons in three experimental field sites revealed that there was a decrease in disease incidence in fields sprayed with fungiforce than in the control field. Plots sprayed with fungicide at different concentrations showed no variation on the 4 cultivars in the different field sites. The disease incidence ranged from 10% to 100% in the 4 seasons, at the three experimental field sites. The variation in disease incidence in the three planting sites is an indication of possible genotypes by environment (GXE) interaction that may have significant influence on the taro leaf blight resistance potential.

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