Powdery Mildew is a fungus that occurs on many plants. Its name comes from the powdery, flour-like spots that it causes to appear on leaves. There is not one, singular fungus that causes this; rather, it refers to a variety of fungi that affect plants in a similar manner. The good news is that all powdery mildew can be treated the same way.
Luckily, powdery mildew is an aesthetic fungus meaning it will not hurt the plant unless there is a huge explosion of the fungi. In that case, it can hurt the growth of the plant and weaken it going into winter. In severe cases year after year the plant could end up dying. As long as you tackle the problem early on and incorporate the correct practices into your plant care, your plants should be fine.
above: Some rose leaves afflicted with powdery mildew.
The main cause is poor circulation leading to extended time of moisture on the leaf which causes the fungus to thrive. It can be an issue any time of the season if the conditions are right, but you will see it more often in the fall when the days become shorter.
The best way to prevent it to make sure your plants have good air circulation. Some plants are more susceptible to powdery mildew than others, so don’t place highly susceptible plants in poor air circulation areas. A general fungicide can also be used every 10-14 days as a preventative if this has been an issue in the past. The best way to manage any plant disease is to research plants before putting them into the ground. This will help you make informed decisions on where to place your plants in order to reduce the risk of them getting diseases they are prone to get.
Make sure to clean tools between each cut on infected plants.
Powdery mildew if fairly easy to treat. All you need to do is to cut off and throw away infected leaves, clean your tools between every plant with bleach water, and spray the plants with a fungicide (which you can get at most garden centers). In general, it is good practice to always clean tools between plants to help prevent the spread of diseases.
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