Most Common Fungal Pathogens and how to Identify them
18 Feb 2020

Most Common Fungal Pathogens and how to Identify them

Jessica Rosslee

Table of Contents

Fungal Pathogens

After pouring your time and energy into your plants, it can be pretty disheartening to wake up one morning, take a look at your in vitro children, and find that they are looking a little under the weather.

Sometimes, all they need is a bit of TLC, water or sun. Other times, you need something more. If you have exhausted all your care options and you’re still left with struggling plants, this article can help you identify the larger problem at hand and understand how you can use PPM™ to address them.

Before you know how to treat your sick plants, you are going to have to be able to diagnose your plants. In this article, we’ve compiled a list of some of the most commonly occurring fungal diseases. So next time you wake up and see something odd on your leaves or roots, you know what issue you are dealing with and whether your premium PPM™ plant preservative can come to the rescue.

Most diseases, especially fungi, get their strength from their hosts, the plants they are living on. You may notice wilting, blotches, mold, scabs, or even plant matter that begins to rot. There are many different fungi or diseases that could be causing this, and they can be challenging to identify, never mind treat.

Identifying Signs and Symptoms

Before you can address a plant problem, you need to identify whether it is a bacterial, fungal, or viral problem. Knowing the physical appearance of the different diseases can go a long way towards helping you to diagnose your plant diseases.

It may come as no surprise to you, but the majority of plant diseases are fungal. Fungal related organisms cause around 85% of plant diseases. However, there are many other diseases that can affect your plants that are not fungal related. These could be viruses, bacteria, or even related to nematodes.

Diseases arising from airborne microbial pollution, airborne microbial hazards, toxins, or nutritional deficiencies are known as abiotic diseases. And that’s as far as we will go about airborne microbial diseases. We’ll address those in a separate article; for now, we will discuss diseases caused by fungi related organisms.

The main giveaway clue about what disease or pathogen is affecting your plant is the physical appearance. There are two main things to pay attention to:

The Signs

Physical evidence of disease is referred to as a ‘sign’ of disease. For fungal diseases, this can often appear as a mildew powder. Powdery mildew is the main sign but not the only sign to look out for (more below), so be sure to note any physical changes.

The Symptoms

The second thing to look out for is symptoms. A symptom is also something physical that you can see, but instead of being the pathogen itself, the symptom is a result of the pathogen. A symptom means a change to the plant itself, such as a change in color or shape. These symptoms could vary depending on what reaction the plant has to the pathogen. Symptoms could be wilting, brown lesions with yellow halos, or other changes that make the plant look unhealthy.

Fungal Diseases: Signs and Symptoms


  • Powdery mildew
  • Leaf rust (common leaf rust in corn)
  • Sclerotinia (white mold)
  • Stem rust (wheat stem rust)


  • Chlorosis (yellowing of leaves)
  • Birds-eye spot on berries (anthracnose)
  • Damping-off of seedlings (phytophthora)
  • Leaf spot (Septoria brown spot)

Common Fungal Diseases:

Bacterial Spot: Caused by warm and wet environments, this disease is often found in humid climates. It is identified by dark, raised spots on the leaves of the affected plant.

Black Root Rot: This fungal infection, also known as Thielaviopsis, is caused by damp soil that has temperatures in the range of 55 to 65 F. It is physically identified by a blackening of the roots and stunted foliage.

Botrytis: Otherwise known as Gray Mold, this infection is caused by leaves and petals that are either dead or dying. You can notice this by light to dark rot that forms around the plant tissue that is wounded.

Rhizoctonia: This infection is also caused by soil that is too moist and warm. A rotting stem identifies Rhizoctonia, along with ruddy red-colored lesions.

In an effort to treat infections in plant tissue culture, antibiotics are often used. However, antibiotics can encourage the growth of low-level contamination, and most plant strains will develop a resistance to antibiotics, making it an unsustainable option for many tissue culture cultivators. Furthermore, fungal infections are often unaffected by antibiotics.

Alternatively, Plant Preservative Mixture is a useful option for not only treating fungal infections but preventing contamination in the first place. Since it is unlikely for plants to develop resistance towards PPM™, it is a more sustainable option as well. Curious to learn more about PPM™? We have a wealth of information on just what PPM™ is and how to use it to both prevent and treat airborne and waterborne infections.

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