Powdery mildew is a common problem on susceptible varieties of plants, and when overhead watering is continually used, paired with shady locations or when cool night temperatures are present. It’s a fungus that spreads by spores when in the right phase of the lifecycle and when moisture hits the mildew. It appears white and powdery on leaves and stems, can look fuzzy and transfer from one plant to another quickly. A plant can live and produce fruit while it is present while another can be overtaken, not be able to photosynthesize well and weaken too much to grow flowers or fruit. It’s best to catch it as early is possible to avoid problems like poor fruit development later.

Prevention includes planting varieties that are resistant, planting with good air circulation between plants, in proper sun exposure, and limiting overhead watering to when it can evaporate off of the leaves quickly at the beginning of the day or in full sun.

Removing infected leaves and stems and disposing of powdery mildew plant matter in the trash can help. Don’t compost the infected plant material unless your compost gets above 140 degrees Fahrenheit for a couple of days.

Neem oil is a know organic oil that can help suppress the mildew from spreading but it needs to be applied exactly in line with the label instruction for highest efficacy and it can get expensive in a large garden setting.