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Powdery Mildew is a very common and easily recognizable fungal disease. It is important to treat it before it gets out of hand as it can be fatal to weaker plants.
Powdery Mildew is the collective name of several different species of fungi. They all have their own narrow range of host plants but present the same signs and symptoms. For example, Rose powdery mildew spreads only to other roses and Begonia powdery mildew only spreads to other begonias.
Powdery mildew infects the surfaces of the leaves, stems, flowers and sometimes fruits of the plant. A powdery mildew infection can be fatal to stressed and weak plants if left untreated. More established plants that are grown in good conditions are better able to handle a light infection without any major damage.
The spores of powdery mildew are air-borne and spread most quickly in humid environments. Unlike most other types of fungi, however, these have a high water content which enables them to continue spreading even during dry conditions.
Weakened plants are more susceptible to infection from fungi and other pests and plant diseases. For example, a plant that is exposed to drought will be more at risk of being infected with powdery mildew, especially if it's fluctuating between being heavily watered and being allowed to dry out too much.
Signs to look out for are:
Dust-like, light-colored, white or gray spots or patches. - Often on leaves, stems and/or new growth. This may be confused for dust or dirt at first, but if you wipe it away, it'll come back. This is the most common and distinctive symptom, but your plant may also show:
Withering and drying leaves
Disfigured leaves and new growth
WHAT TO DO NOW
Check all the nearby plants within the same genus or family as the infected plant.
If the damage is only moderate, remove and prune off badly affected leaves and parts of the plant.
If the damage is more severe, it may be difficult to treat the plant - try to remove all infected material and dispose of it to help stop the spread.
Consider using a fungicide. There are several good ones on the market, and some are even organic.
If you're looking for a DIY method, spray the plant with a baking soda mixture: 1 tbsp of baking soda, 1/2 tsp of liquid soap, 1 gallon of water (try spraying on a small area of the plant first).
Follow the instructions on the product you're using. If you aren't using a specific product you should repeat the treatment once a week for at least 4 weeks and then continue if necessary.
- Note that some plants, especially their flowers, can react badly to fungicides, oils or soaps, so test it on a smaller area of the plant first and treat your plant carefully. Always avoid direct sunlight after application as it can otherwise burn the plant.
HOW CAN I PREVENT THIS FROM HAPPENING AGAIN?
Avoid growing plants indoors if they aren't suitable to the indoor environment.
Always check any plant before bringing them home so they are healthy and not infected with any fungi or pests.
Avoid exposing your plants to excessive drought or to imbalanced watering.
Repot your plants before they get pot bound.
Try to choose plants that are specifically bred to be resistant to powdery mildew. For example, cucumbers are particularly susceptible to powdery mildew, but you can buy varieties that are more resistant than others.
During hot, dry seasons it can be beneficial to avoid watering your plants during the evenings as it will increase the humidity which can benefit the powdery mildew.
Supply your plants with good air flow.
WHEN IS POWDERY MILDEW MOST PREVALENT? Powdery mildew goes into dormancy during colder seasons and then starts to spread and grow during spring to early summer, when the days are beginning to get warmer. Because of this, it’s a good idea to keep an eye on your plants during this time - check them regularly for early signs to try and stop it from spreading.
WHICH PLANTS ARE MORE PRONE TO POWDERY MILDEW INFECTION? There are several different species of powdery mildew that has become specialized for different types of plants. Some are more prone to infection than others. Here's a few examples of plants that are more known to get powdery mildew
All types of Cucumbers, Melons and Squash plants
Jade plants and Echeverias
Herbs such as Parsley, Mint and Rosemary