Pathogenic diversity of Puccinia kuehnii strains, causal agent of sugarcane leaf rust and biological control approach using biopesticides under semi-controlled conditions

Context: In Côte d'Ivoire, sugarcane plays an important role in the economy. However, its production is constrained by biotic factors, particularly orange rust caused by Puccinia kuehnii. Pathogenic diversity of strains is not widely understood. Existing control methods are ineffective and limited. The aim of this study was to determine the pathogenicity of Puccinia kuehnii strains, and to evaluate anti-fungal activity of essential oil-based formulations against this disease. Materials and methods: Strains 51bB and 381Z were evaluated for infectivity by foliar spraying plants of variety SP711406 under semi-controlled conditions at the Université Félix Houphouët-Boigny in Abidjan (Côte d'Ivoire). Curative control was carried out by foliar spraying plants with formulations based on natural substances of Ocimum gratissimum L, Zingiber officinale and Cymbopogon citratus, at 1000 and 2000ppm. The synthetic product copper oxide was used at a single dose of 5000 ppm. Results: Strains 51bB and 381Z showed infection rates of 62.26 and 67.36% respectively after a four-month incubation period. Severities of 30.64% (51bB) and 30.23% (381Z) were observed. ZinC1 and ZinC2 treatments had an estimated incidence reduction rate of 64.28%. Treatments based on natural substances achieved a reduction in severity of over 50%. The CymC2 treatment was the most effective, with a reduction rate of 86.04% followed by ZinC1 with rates of over than 50% reduction rate of incidence and severity due to the synthetic product was 50 and 48.83% respectively. Conclusion: Puccinia kuehnii strains induced orange rust disease in sugarcane. The effect of essential oil-based formulations has been proven on the disease under semi-controlled conditions.