Efficacy of fungicide alternatives against late wilt disease of maize and their influence on plant morphogenesis and yield characters

Summary Efficiency of various organic acids, organic salts, essential oils, algae (an extract of Chlorella vulgaris and a commercial product), and bioagents against Magnaporthiopsis maydis, causing maize late wilt disease, was evaluated in laboratory and field conditions. For the in vitro tests, isolated M. maydis field strains from Egypt were used. Additionally, in field experiments different application methods were tested for their efficacy throughout two successive growing seasons. Results showed maximum growth inhibition of M. maydis at different concentrations of salicylic acid, ascorbic acid, benzoic acid and humic acid as well as sodium benzoate, potassium sorbate, di-potassim phosphate and calcium choloride, in descending order. The essential oils of carnation, lemongrass and black seed followed a similar trend. The minimum pathogenic fungal growth was achieved when the pathogen was exposed to the antagonistic Trichoderma viride followed by Trichoderma harzianum, Bacillus subtilis and Pseudomonas fluorescens treatments. Under field conditions, the highest disease reduction was recorded after treatment with salicylic acid (all application methods), humic acid (all application methods), sodium benzoate (seed dressing), carnation oil (seed dressing or seed dressing +foliar spray) and the bioagents B. subtilis and P. fluorescens (soil drench). Overall, all treatments and all application methods led to significant lower disease incidence compared to the untreated control in both growing seasons. Additionally, all treatments achieved an enhancement of plant morpho-genesis and yield characters. The most effective combinations of compounds/bioagents and application methods can be considered for future use in IPM management of late wilt disease of maize.