Evaluation of Systemic Acquired Resistance Inducers for Management of Groundnut Early Leaf Spot in Kaduna State, North West Nigeria

Early leaf spot of groundnut, caused by Cercospora arachidicola, is a yield-limiting disease in northern Nigeria that is predominantly managed through fungicide applications, raising concerns about resistance development and input costs. Systemic acquired resistance inducers represent an alternative management strategy that has not been empirically evaluated under North West Nigerian field conditions. This study assessed the efficacy of four systemic acquired resistance inducers, including acibenzolar-S-methyl, jasmonic acid, potassium phosphite, and a commercial harpin protein formulation, for management of Cercospora early leaf spot on groundnut in two experimental sites in Kaduna State over two growing seasons. A randomised complete block design with seven treatments, including fungicide standard, four inducers, combination of the best-performing inducer and fungicide, and untreated control, was applied. Leaf spot severity, area under disease progress curve, photosynthetic efficiency by chlorophyll fluorescence, and pod yield were measured. Acibenzolar-S-methyl at 50 mg per litre applied three times reduced area under disease progress curve by 59 percent and produced pod yield statistically equivalent to the fungicide standard at one of two sites. Jasmonic acid treatment showed significant variability between sites. The inducer plus fungicide combination produced the highest consistent suppression across both sites and seasons, suggesting additive effects. The study concludes that acibenzolar-S-methyl is a viable resistance management component for groundnut leaf spot and recommends its integration into a reduced-fungicide programme suited to Kaduna State production conditions. Keywords: groundnut, Cercospora early leaf spot, systemic acquired resistance, acibenzolar-S-methyl, Kaduna State.