Diplocarpon rosae, or black spot fungus does not just affect roses. This fungus can affect any plant in your garden that has fleshy leaves or stems. Identifying this fungus should be easy enough, since the name accurately describes the first stage of infection. Plants with this disease have black spots, and when it progresses, the leaf around the spot starts to turn yellow, until eventually the entire leaf is yellow and falls off. On the plus side black spot fungus does not kill plants, but it is very unsightly. This fungus grows in the spring when temperatures start to climb into the sixties, and does not stop until temperatures reach the mid eighties. This fungus also thrives when plants are wet for 6 to 9 hours in the day.
To treat black spot fungus, there are organic fungicides that will not harm your plants that you could use to treat the disease. Neem oil is a more natural remedy that you could also use when diluted with water in a plant sprayer, neem is an oil that is pressed from the evergreen tree. A third remedy is a gallon of water, a large tablespoon of baking soda, and a splash of neem oil; the baking soda will create an inhospitable ph level on the leaf while the neem oil helps the solution to stick to leaves.
Inspect your plants regularly in the spring to help prevent fungus from gaining a foothold in your garden. While it is not going to kill your plants, black spot fungus is unsightly and will take much diligence to remove from your garden. If you do have black spot fungus, make sure to cut plants back and remove all debris from the affected area in the fall. This fungus can survive through the winter months and reappear next year. Some preventative measures you can take is to start spraying plants before temperatures reach the sixties. Fungicides should have directions on how to apply for preventative measures, and the other solutions suggested above should just need a light weekly application. Also, try to avoid watering plants on cloudy days, watering will keep the plant moist longer and give the mold optimal conditions to grow. Bright, sunny days are best so the water dissipates quicker. Prevention starts with being vigilant, so make sure you are inspecting your plants in the spring time for the first indications of black spot fungus.