Difference Between Signs and Symptoms in Plant Pathology

Difference Between Signs and Symptoms in Plant Disease Diagnosis

Plant pathology, also known as phytopathology, is the scientific study of plant diseases caused by various pathogens and environmental factors.

Here, understanding the distinction between signs and symptoms is crucial for diagnosing plant diseases. These two describe different aspects of plant disease but are often confusing. Let us break down the key differences between them.

Key Differences Between Signs and Symptoms in Plant Pathology

Here are the differences between signs and symptoms in plant pathology:

Features	Signs	Symptoms
Visibility	It is visible directly on the plant	Requires observation over time
Cause	Caused by the pathogen itself	Caused by the plant’s response to the pathogen
Type of Evidence	Direct evidence of infection	Indirect evidence showcasing symptoms of damage
Role in Diagnosis	Helps to identify the pathogen	Helps to confirm the presence of a disease

What are the Symptoms in Plant Pathology?

Symptoms in plant pathology are the measurable and visible responses of a plant to a disease. They reflect the reactions of a plant to a pathogen.

The pathogens can be fungi, bacteria, nematodes, or viruses. Symptoms can vary depending on the type of pathogen, species of plant, and environmental conditions. Here is a list of some common symptoms in plant pathology:

Wilting – Leaves droop because of water loss.
Yellowing– It is also known as chlorosis and refers to the loss of green colour in leaves.
Leaf Spots– Necrosis or discolouration in leaves.
Canker – Dead or lesions on stems and branches of a plant.
Mosaic Pattern– Irregular dark and light green patterns on leaves caused by viral infections.

What are the Signs in Plant Pathology?

Signs refer to the actual physical evidence of the presence of a pathogen in or on the plant. It can be fungal fruiting bodies, the presence of nematodes, or a bacterial ooze. The signs are a direct indicator of the pathogen’s activity. Here is a list of some other common signs in plant pathology:

Spores – Reproductive bodies of fungi, often found on stems or leaf surfaces.
Mould or Mycelium – Fungal growth that is visible on the plant tissue.
Insect Vectors – Insects carrying pathogens can sometimes feed on plants.
Egg Masses– Egg masses are a protective structure around insect eggs. They come in different varieties to protect eggs from predation or the weather.
Larvae – This is the juvenile stage of certain insects like maggots, caterpillars and grubs. They cause a lot of damage to the plants.

Why Does a Distinction Matter?

In plant pathology, it becomes important to recognise both the signs and symptoms to get an accurate diagnosis of a disease. Symptoms provide clues to the presence of any disease. However, they are often nonspecific and can be confused with other conditions. Signs, on the other hand, are direct evidence of the pathogen. It provides a more accurate identification.

For example, wilting can happen due to a variety of issues like pest damage, water stress, and fungal infection. However, if fungal spores are visible on the plant, it is very likely a fungal disease. Therefore, both the signs and symptoms need to be considered together to confirm the cause of a disease.

Signs and symptoms in plant pathology serve different purposes but work together in diagnosing plant diseases. By understanding these differences, plant pathologists and gardeners can take appropriate action for the management of plant diseases.