Are your houseplants covered in white mold spots? Then you probably have to deal with mildew. Unfortunately, mildew is more common than we would like and besides being an annoying sight it can be harmful to your plants. Don't panic! This pest is super easy to prevent and, should it be too late, also easy to control. Read here what mildew exactly is and how you can prevent and fight this nasty pest.
What is mildew?
Mildew is a collective name for a group of fungi that grow on green parts of plants. You can recognize mildew by the white spots on the leaves of the plant. It is a fungal disease and looks like a white, powdery deposit. You can easily wipe it off the plant. Because of its white color, powdery mildew is sometimes called white disease. The fungus is a parasitic white mold that invades the leaves of your plant. It draws moisture from the leaves, causing the leaves to dry and eventually die. Plants with powdery mildew grow slower because the fungus prevents photosynthesis. Powdery mildew is caused by several different types of powdery mildew fungus and distinguishes between "powdery" and "downy" mildew. Both varieties are fungi and have the same attack pattern, but they belong to a different family and have a different lifestyle.
Powdery mildew is often seen on the top and bottom of the leaf. As soon as you have spotted the white deposit on the top of the leaves, it is important to start treating immediately. The sooner, the better! Fortunately, a little mold will not kill your plant, but if you wait too long, it can!
Besides powdery mildew, there is also downy mildew. The difference between powdery and downy mildew is the place they affect. Downy mildew grows in the leaf, but the visible fungal threads are generally on the underside of the leaf. This is also where most of the plant's stomata are located. Because downy mildew is on the underside of the leaves it is less easy to see. So always check all sides of the leaves! Mildew can give white and brown spots. Most mildew fungi only form visible fungal threads on the outside of your plant's leaves. Yet there are also a few variants where the fungi invade the plant's cells. Mildew occurs mainly in warm temperatures, after it has been damp from rain or watering. Mildew spreads on and between plants via the spores that are spread by the wind, animals or people.
How do I recognise mildew?
Mildew is one of the best known and most common fungi on plants. There are two types of mildew: powdery mildew and downy mildew. Powdery mildew can often be recognised by pale yellow spots on the leaf, followed by white, powdery patches of mold on the top of the leaf. The fungus lives on in moist conditions and warm temperatures. The degree of infestation is super dependent on the susceptibility of your plant.
Downy mildew also starts with yellow or brown spots on the leaf, but here the fungus is hidden on the underside of the leaf. The fungus can also live in fallen leaves and scraps on the potting soil. If you water the plant too much, the fungus can spread quickly. The leaves of the plant will become brown and dry and will eventually shrivel up. So also check the underside of your plant's leaves from time to time to prevent your plant from being sick without you even realizing it!
How does mildew damage my plants?
Mildew or white disease: the white fungal fluff on your plant's leaves. It starts as a small dot, but soon entire leaves are covered. Mildew is therefore a fungus, and fungi belong to a lower plant species that do not have leaves, stems and roots to get the nutrients they need to grow on their own. That's why they choose your plant as their host! They penetrate the leaf cells of your plant to get the nutrients they need. The affected parts of your houseplant will grow poorly and deform. The leaves will wither and curl. In small plants and cuttings, an attack of powdery mildew can even end very badly!
How can I prevent mildew?
The mildew fungus spreads super fast. Fortunately, this fungus is easy to prevent. Mildew grows from spores in the air. It grows in moist, warm conditions without much air flow. In the summer, when it is warm in the house with high humidity, the mildew can most easily infect the plant. The fungus thrives in a wet plant, for example after watering. A strong and healthy plant can withstand quite a bit. A little mildew on the leaves will not matter, but do you want to prevent the mildew from spreading to the whole plant and other plants? Then check carefully whether you can apply these tips!
The position of your plant is super important. Besides taking into account the needs of your plant you will also have to take into account the distance between two or more plants. A big urban jungle is of course fun, but make sure they get enough air and can dry properly after watering. A moist plant is a paradise for mildew!
Like other types of mold, mildew is caused by poor air circulation, among other things. Nowadays our (newly built) houses are super well isolated. To prevent the white mold on your plant, it is important to increase the air circulation in your home. Regularly open a window to let fresh air in, install a humidifier or place a few air-purifying plants! A great excuse to get even more plants in the house, right! Then again, make sure you don't place the plants too close together so they get enough air.
Another tip that helps prevent mildew is to water your plants in the morning instead of in the evening before you go to bed! That way they have all day to drink the water and the soil will be dry again. A damp place attracts mildew!
How can I control mildew?
Spotted mildew in your houseplant? Then it is important to take action as soon as possible. Of course there is no reason to panic. Your green plant will not die from mildew overnight. However, your plant may be weakened by the fungus. With young plants and cuttings it can go wrong faster: they are not as strong yet and will find it harder to survive an attack of mildew. So it is very important to act immediately. If one of your plants is suffering from mildew, your other plants can also become infected. It is important to remove the brown, infected leaves immediately. Mildew spreads easily through clothing and air currents throughout your home. Therefore, keep the plant separate from other houseplants and wash your hands well after touching it to prevent cross-contamination.
Fight mildew with milk
The easiest and cheapest way to tackle mildew is one for which you probably already have everything in the house. Mildew can be effectively combated with... milk! Milk contains proteins that mildew does not like. Mix about 40% milk with 60% water and spray this with a plant sprayer on the mildew-infested leaves of your plant. Keep repeating this until the leaves of your plant have recovered and the mildew has disappeared. You got this!
Fight mildew with neem oil
The wonder product called neem oil is available in our shop and also found in our super handy PLNTSdoctor Kit. Neem oil helps against almost every kind of pest. Mix the oil with water and dish soap and spray it on the plant. Repeat until you don't see the mildew anymore. This may take a few days. Stubborn spots can also be treated by going over them with a cotton pad with neem oil.
PLNTS hacks against mildew
If you search online for the best way to fight powdery mildew you will come across a huge number of options. It is good to know that there is not one specific method that works for everyone. For some plants one way works better than the other. It's a matter of trying!
Below are a number of alternative hacks to help you fight mildew.
Fight mildew with vinegar
Fight mildew with vinegar by mixing one part vinegar with two parts water and spray it on the plants. Be careful! Vinegar is a strong remedy that can cause the plant and other plants or animals in the area of the affected plant to suffer as well.
Fight mildew with garlic
Mildew control with garlic is super simple. Chop about five cloves of garlic and mix it with one liter of water. The idea is that you let this stand for a day and then dilute with another three liters of water. Drain this mixture well and spray it over the affected plants. Repeat this a few times and check well if the mildew disappears!