From my leaves' point of view, the first sign is a subtle change. A faint, white, dusty film begins to appear on my surface, often on my upper side. This is not morning dew or dust; it is the beginning of an invasion by the fungal pathogen *Podosphaera xanthii*. This mildew blocks my stomata, the tiny pores I use to breathe and transpire. It feels like a suffocating blanket, hindering my ability to photosynthesize and convert sunlight into the energy I need to grow and produce my beautiful flower spikes. My affected leaves may start to curl, twist, and yellow as my vitality is sapped.
If your keen eyes notice this white powder on me, your first action must be to prevent its spread. Please carefully remove and destroy my most severely infected leaves. Do not compost them, as the fungal spores will survive. This is a triage to stop the disease from moving to my stems and nearby plant friends. Next, assess my living conditions. This fungus thrives in humid, still air. If my foliage is constantly damp from overhead watering or we are crowded together, the environment is perfect for the mildew. Please water me at my base in the morning so my leaves can dry fully under the sun. If possible, gently thin the plants around me to improve air circulation.
Several gentle, topical remedies can be applied directly to my leaves to combat the mildew without harsh chemicals. A weekly spray of a solution made from one part milk to nine parts water can be very effective. The compounds in the milk create an antiseptic effect when exposed to sunlight, helping my surface fight the fungus. Alternatively, a solution of one tablespoon of baking soda, half a teaspoon of liquid soap (not detergent), and one gallon of water can alter the pH on my leaf surface, making it less hospitable for the mildew. Always test any spray on a few leaves first to ensure I do not have an adverse reaction, and apply it in the cooler hours of the day.
If the infection is widespread and threatens my overall health, stronger measures may be necessary to save me. You may need to use a registered horticultural or plant-based oil, such as neem oil. These oils work by coating the fungal spores and preventing them from germinating and breathing. It is crucial to follow the dilution instructions meticulously, as oil can damage my foliage if applied too strongly or during the heat of the day. Apply these treatments in the early evening. Furthermore, as a perennial, I would greatly benefit from a preventative fungicidal treatment next spring before the disease has a chance to take hold, giving me a healthy start to the new growing season.
