Evaluation of natural products and chemical compounds to improve the control strategy against cucumber powdery mildew

Powdery mildew, caused by Podosphaera xanthii, is a devastating disease that can wipe out a cucumber crop in optimal weather conditions. Disease control management depends mainly on fungicides to inhibit the pathogen. However, they have fatal side effects on most organisms. This study evaluated the use of natural products as safe alternatives to fungicides for controlling cucumber powdery mildew. The effectiveness and phytotoxicity of the studied products, as well as their effects on leaf anatomy and pollen fertility, were evaluated. Although the fungicide tested (Score 25% EC) was the most effective treatment, it caused the highest phytotoxicity, leaf morphological changes, and pollen sterility. All the treatments used significantly reduced disease severity under greenhouse and field conditions, except for Spirulina, which recorded the lowest efficacy rate. Lemon oil, garlic oil, and Blight stop achieved the desired goal of controlling the disease and improving the plant's physiological state. Therefore, we recommend using any of them to control cucumber powdery mildew, except for Spirulina, which we recommend as a biofertilizer.