The Pro Farmer

How to Identify and Treat Powdery Mildew on Plants: Chemical and Organic Solutions

What is that white powder on plants?

It’s a white colored fungus. 

Its name is powdery mildew. 


Powdery mildew appears as a white or grayish powdery coating on the leaves, stems, flowers, and fruit of plants.

The powdery substance is actually made up of fungal spores.

Powdery mildew is a common disease that can affect both indoor and outdoor plants, especially in areas with high humidity and moderate temperatures.

Some of the most commonly affected plants include roses, zinnias, cucumbers, squash, and grapevines.

Powdery mildew on tomato leaves
Powdery mildew on cucumber leaf

 It attacks many crops’ leaves.

It doesn’t need high humidity.                 

The fungus can cover all of the plant’s leaves.

Powdery mildew totally covering cucumber leaves
Infestation of pumpkin leaves with powdery mildew
high infestation of tomato plants with powdery mildew
Watermelon leaves infested with powdery mildew
Pumpkin leaves infested with powdery mildew
Tomato leaf covered with powdery mildew
Melon leaves with an inoculum of powdery mildew
Pepper leaves infested with powdery mildew

When the leaves are infected, they turn brown and shrivel.

Leaf covered with powdery mildew, and dries

affected plants may experience stunted growth, distorted leaves, premature leaf drop, and reduced fruit yield.

In severe cases, powdery mildew can cause the death of the plant.

It is recommended to use at least 3 kinds of different pesticides,

and alternate between them every 4 days,

in order to overcome pest’s resistance, and completely exterminate them.

For further information about this, read this post , and this post also.

There are 2 ways to eliminate Powdery mildew: Chemical, and organic.


Best pesticides for Powdery mildew,

Active ingredients:



Sulfur –

Sulfur is the best organic solution to powdery mildew. It kills the spreading spores by disrupting respiration within their cells.

It does this either by residual action or, at higher temperatures, by volatilization.

Residual action requires direct contact with the spores.

Mineral oil

Covers the egg, larvae, nymph and adult stages, causing suffocation.

It leaves no toxic residue on plants.

Bacillus Subtilis

A biological fungicide containing a strain of the bacterium Bacillus subtilis.

The bacterial spores occupy space on the plant surface, and compete with the pathogens; then active compounds called lipopeptides, produced by the bacterium, disrupt the germination, and growth of invading pathogens.

Due to this action, resistance is not likely to develop.

Neem oil

A naturally occurring pesticide, found in seeds from the neem tree.               

Azadirachtin is the most active component here.                                                         

It reduces insect feeding and acts as a repellent.

It also interferes with insect hormone systems, making it harder for insects to grow and lay eggs.

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