Plant Diseases: 7 Common Ailments and How to Identify them

Translated by Nick R

Have you noticed uneven spots on the leaves of your plants? Or, have your flowers been changing color and turning dark? They are probably under attack from disease.

That’s right, plants are also susceptible, not only to pests but also to diseases that weaken them and take away all their vitality.

Don’t you worry! In this blog, we’ll teach you to identify 7 of the most common diseases that can attack your plants. You’ll also learn the causes and what to do to prevent their spread.

Why do plant diseases occur?

In general, a plant gets sick when it’s continually disturbed by some external agent that disrupts its structure, growth, function or other normal plant activities.

Infectious plant diseases are caused by pathogenic organisms such as bacteria, fungi and viruses. These agents have the ability to reproduce in one plant and spread to others.

However, plants are usually relatively resistant to the presence of these diseases. Especially because for a plant to get diseased, 3 factors must happen.

  • The plant should be weak, which makes it more sensitive.
  • The disease-causing pathogen must be present to attack.
  • Environmental conditions must be conducive to disease adaptability and development.

What causes weakness in plants?

A pesar de esto, no estás exento de que tu jardín sufra una enfermedad y como pudiste observar, el primer paso es que las plantas estén débiles. Por esto, ahora te mencionaremos cuáles son las causas que dejan vulnerables a las plantas.

Presence of pests  

If your plants are being attacked by garden pests or you just got rid of them, they may be more damaged than they seem.

It turns out that when those insects feed on plants they debilitate them and leave behind a sticky substance known as honeydew. Such a substance is a welcome letter for diseases such as fungus.

Lack of nutrients

All plants have different preferences and care, so you must be aware of your garden plants’ needs regarding soil.

This way, they’ll grow stronger and more comfortably without being exposed to pathogens due to a lack of nutrients. In addition, enriching the soil with compost also helps plants resist disease.

Wrong watering

Once you know the type of soil your plants need, you’ll know how to water them. This will especially avoid excess moisture produced by improper watering.

A tip, in this case, is to touch the soil in order to feel if it’s dry, and also lift the pot to sense its weight. Clearly, if it’s difficult to move it, it’s because the water hasn’t drained yet.

How to prevent plant diseases

We’ll give you some tips to avoid the arrival of garden diseases and prevent their spread. You’ll see that prevention will save you later from dealing with those, difficult to combat, nuisances.

  • Rigorously check new plants that are going to enter your garden or orchard. If you can inspect them before buying, look for strange spots or leaves infected by a fungus. You must cut off the damaged parts of the plant if you want to incorporate them.
  • Inspect your plants constantly. This is important to early detect the presence of pests or diseases and eradicate them before they do more damage. Not only you’ll avoid further damage to your plants, but it will also be easier to get rid of them.
  • Let your plants breathe properly. At the moment of planting leave good space between each plant, allowing good aeration. When they are crowded together, humidity increases and promotes disease development.
  • Avoid overwatering. A common mistake is to water plants more than they need, especially houseplants that are not so fond of humidity, for fear of lack of water. The problem is that overwatering decreases oxygen and increases carbon dioxide levels in the soil, which makes roots more susceptible to root rot organisms.
  • Remove infected plants. If you are already suffering from a disease in your garden, you’ll need to properly maintain infected plants in isolation for a while.

7 most common plant diseases

Now, let’s go to the top 7 of the most common diseases that you could have in your garden. Thanks to this, you’ll know how to identify them by their symptoms and you’ll be able to take action in time.

Powdery mildew

enfermedad de moho polvoriento en plantas

It’s a fungal disease that is quite common but also easy to recognize. Cucumbers, pumpkins, tomatoes, melons and roses are particularly susceptible to getting it.

The microscopic spores of this mold are usually carried into gardens by the wind. This also facilitates it to spread to other plants more quickly. Additionally, it flourishes in warm climates and on plants with surrounding moisture.

Symptoms of powdery mildew

You’ll be able to tell when a plant has powdery mildew by the following symptoms:

  • Powdery white spots. It will look as if the plant has been dusted with flour. First, as small white spots but will spread throughout the leaves, stems and fruit.
  • Yellow and wilted leaves. The appearance of this mold will cause leaves to stunt, flowers to alter, and fruit quality to suffer. This is especially true for new shoots, which are more prone to severe disease development.

How to fight powdery mildew 

To control and eradicate powdery mildew you can implement the following recommendations:

Prepare a home remedy  

In 1 liter of water or more, mix 1 tablespoon of baking soda or potassium bicarbonate with 1 tablespoon of some vegetable oil and 1 teaspoon of dish soap.

Using a diffuser, apply this liquid to plants making sure they are well-covered. You don’t need to remove it, but let the plant dry in the shade. You can apply it daily until you see results, usually in a short time.

Spray the plants with organic fungicides

We recommend sulfur-based fungicides, which are also effective in prevention. It is preferable to use it when the infection is just beginning for better results.

Try to spray the plants either early in the morning or late at night. Let the product dry and check the next day to see if the mildew continues; if so, reapplying it should be effective.

Remove the damaged leaves

In case the disease is more developed, the ideal is to quarantine the affected plants and remove the most damaged leaves. However, we recommend using any of the above steps to ensure that the mildew has been eradicated.

Mosaic virus

enfermedad virus mosaico en una planta

Mosaic virus is usually transmitted by pests such as aphids, whiteflies and beetles; likewise, soil, seeds, pots and containers can become infected with the virus and transmit it to the plant.

Several crops are vulnerable to this virus, such as cassava, potatoes, beets, cucumbers, beans and tomatoes.

Symptoms of mosaic virus 

It’s said that identifying this virus is difficult since its attack varies according to the type of plant. However, you can be guided by these symptoms:

  • Leaves with yellow, white or green spots or stripes. This is precisely why it is called the “mosaic” virus.
  • Leaves with deformities. The virus causes the leaves to wrinkle or have ripples in the above-mentioned spots. They will also look like small blisters.

Unfortunately, there is no way to eliminate this virus. However, we advise you to perform the following actions to control its spread.

How to control mosaic virus 

Destroy infected foliage

You’ll have to remove all affected plants and dispose of them, preferably by burning them. Keep in mind that you cannot use them in compost because the virus may still be present.

Sanitize your gardening tools

After removing diseased plants, it’s vital that you clean and disinfect your entire gardening kit to prevent the virus from spreading. Finally, wash your hands thoroughly; the disease may be transmitted this way as well.


enfermedad óxido en una planta

Also known as stem rust, this is a fungal disease that needs living plants to survive. It’s transmitted by spores that travel by air or water from infected plants to healthy ones.

It’s easy to spot because its presence resembles rust spots. It tends to attack roses, lilies, beans and tomatoes.

Symptoms of rust

You’ll identify the presence of rust on your plants by the following symptoms:

  • Orange or reddish spots. At first, they may appear as white spots that soon turn deep orange or reddish. Ultimately, they may even turn black.
  • Blisters underneath the leaves. These spots will look like pustules on the underside of the leaves, although they can also appear on the upper side.

How to control rust 

Now, although it’s not an easy task, we’ll show you how to control rust on your plants.

Use insecticides with sulfur or copper

Separate the affected plants first and spray them with this product to mitigate the fungus from spreading and causing further damage. However, it’s worth mentioning that insecticides are more effective for prevention than cure.

Collect and dispose of the affected leaves

At the first sign of this fungus remove only the infected leaves, leaving the stem or branch as long as they are free of rust. Then discard or burn them and wash your hands before handling other plants.

Fumagine or sooty mold

enfermedad fumagina en una planta

Sooty mold grows as a result of honeydew produced by sap-sucking insects. Its presence not only lowers the leaves’ vitality but also impedes photosynthesis and slows plant growth.

Over time, the leaves affected by the fungus also fall off, so it’s important to recognize it in time to prevent it from becoming a serious disease.

Symptoms of sooty mold 

You’ll identify the presence of this fungus in your plants by these symptoms:

  • Leaves, stems, and fruits with a thin black layer. In fact, the plants will look as if charcoal has fallen on them.
  • Leaves with a black crust. In case the disease hasn’t been controlled in time, it’ll spread all over the leaf and become thicker, thus generating a scab that affects the plants much more.

How to fight sooty mold 

The ways to control and eradicate fumagine are the following:

Remove the pests

As we mentioned earlier, the presence of this and other diseases is caused by pests, so eradicating them quickly will be a method of prevention.

We also advise you that after eliminating the insects, you should clean the plant to wipe off the traces of the sticky substance they excrete.

Wash the plants carefully

When the presence of fumagine is detected on time, the solution will be very simple as you’ll only have to clean the affected leaves. You can use a strong jet of water or a cloth.

If you prefer, you can use a home remedy for pests and with this, you remove the fungus while creating an insect protection bar.

Perform sanitation pruning

This is in case the disease is advanced to the point that a crust has been generated. It’s best to remove the affected parts to prevent the fungus from infecting another plant.


enfermedad antracnosis en una planta

It’s a fungal disease that affects fruits and vegetables, both developing shoots and trees. It can survive on the remains of affected plants and thrive in warm, moist conditions.

Additionally, it’s transmitted through wind, water, pests and gardening tools.

Symptoms of anthracnose

If you want to identify the presence of this fungus, you should pay attention to the symptoms mentioned below:

  • Irregular yellow and brown spots. Over time, these spots or patches become darker and expand on the leaves or fruits. Certain types of wrinkles may also appear on the leaves.
  • Rotten fruit. At first, the fruits or vegetables will have small, dark, almost black spots and will show sinking. Clearly, this will later cause them to rot and become inconsumable.

How to control anthracnose

We’ll show you how to control anthracnose through the following means:

Use copper-based fungicides

Spray diseased plants especially to prevent the spread of the fungus. If you treat it early, the fungicide can be more effective at fighting it.

Generally, this product is applied daily until you see improvements, but we recommend following the instructions on the package.

Cut the affected vegetative part

As we have seen in other cases, a very effective solution is to perform sanitation pruning to eliminate the “root” of the diseases. Although it may seem painful, this will give the plant a breathing space to grow strongly.

Do not compost the cut parts 

Least of all in this case as the fungus survives on the dead plant. It’s always preferable to burn those remains to prevent other plants from getting infected.

Fire blight

enfermedad tizón de fuego en un árbol

Fire blight is a bacterium that affects cherry, apple, almond, plum, raspberry and rose plants. This disease enters through the branches and travels up the stems, attacking the leaves as well.

It’s a severe disease that can kill the infected plant in little time.

Symptoms of fire blight 

You’ll notice the attack of this bacterium by these symptoms:

  • Brown or black branches and leaves. They will look as if they have been directly burned by fire. They don’t fall off, in fact, they remain on the plant; however, they will be very wrinkled and brown or black depending on the plant.
  • Bent or withered branches. They will look like canes hanging from the plant and will also have that distinctive reddish-brown color.

How to control fire blight

To control fire blight, we have the following options:

Cut off the damaged parts

The best way to control the spread of this bacterium is to remove all areas of the plant that contain the disease. Remember the importance of disinfecting your tools and washing your hands thoroughly after pruning.

Use liquid copper fungicide

There have been reports of effective cases where liquid copper has eradicated the bacteria, especially when used early in the infestation. You’ll need to mix it with a good amount of water and spray it all over the plant.

As something to consider, the use of this product can also cause fruit loss and leaf drop.

Gray mold

enfermedad moho gris en fresas

This disease easily infects plants that are already damaged, weak and dying. Once established, it spreads rapidly and can cause extensive damage to healthy plants.

It’s also a moisture-loving fungus and primarily affects flowers and buds, although infections can occur on fruit, leaves and stems. Among the most prone plants are roses, peonies and strawberries.

Symptoms of gray mold 

You’ll know your plants are being attacked by gray mold from these symptoms:

  • Brown spots covered by a powdery white mold. This sign occurs mostly on the fruit, where there is also sinking as the fruit rots.
  • Grayish or whitish spots. Present on petals, stems and shoots.

How to fight gray mold

To control gray mold, you can follow these tips:

Use fungicides with potassium bicarbonate

It’s ideal to use this type of product when the infestation is just emerging, to prevent the fungus from developing further and to protect the rest of the plants.

Potassium bicarbonate will protect healthy plants better than sodium bicarbonate and is a more eco-friendly option.

Remove and dispose of the affected parts

Perform sanitation pruning to the vegetative parts that are most affected, remember to burn any residue, including cuttings and dead leaves.

With a cloth soaked in fungicide, you can wipe those parts of the plant that were close to the affected parts and where the white mold spores were beginning to spread. This may save them on time.


As a reminder, you should first test the homemade remedies or organic fungicides on a small part of the plant. This is because the plants may have bad reactions to some of the components and the aim is to eliminate the diseases without causing further damage.

Also, for all diseases, there are chemical fungicides available on the market. These can be quite effective, but it’s up to you to decide whether to use them in your garden. I remind you that they should be used with caution to avoid any harm to your health, animals and the environment.

Finally, I hope this blog has helped you to know how to prevent the occurrence of garden diseases and, if the time comes, to be able to identify them and act quickly.