Prevalence of Powdery Mildew on Cucumber (Cucumis sativus) under Greenhouse Conditions in Abuja, North Central Nigeria

Greenhouse cucumber (Cucumis sativus) production has expanded rapidly in Abuja and its surrounding areas as urban agricultural enterprises seek to supply fresh vegetables to high-demand residential and commercial markets. Powdery mildew, caused by Podosphaera xanthii, is a major fungal disease in enclosed and semi-enclosed growing environments, often spreading rapidly due to reduced air circulation. This study assessed the prevalence, distribution, and management of powdery mildew on cucumber in 20 commercial greenhouse facilities across the Abuja Municipal Area Council and neighbouring Nasarawa State. Disease prevalence was evaluated through fortnightly foliage ratings using a percentage leaf area infected scale. P. xanthii was identified as the predominant causal agent based on conidial morphology and molecular confirmation. Prevalence reached 85 percent across sampled facilities by mid-cropping period, with full powdery mildew colonisation of leaf surfaces observed in unventilated structures. Low relative humidity and elevated daytime temperatures were identified as contrary to published epidemiological reports favouring P. xanthii, suggesting that high-inoculum loads within closed structures overrode climatic suppression. Most growers applied potassium bicarbonate and sulfur-based fungicides but without strict adherence to resistance management protocols. The study recommends mandatory integration of ventilation management, resistant hybrid cultivars, and anti-resistance fungicide rotation programmes in commercial cucumber greenhouse operations. Keywords: cucumber, powdery mildew, Podosphaera xanthii, greenhouse, Abuja.