Symptoms of Disease in Crop Plants

Our Objective

To collect and study symptoms of diseases in locally available crop plants.  


The Theory

Plant disease is defined as the state of abnormal physiological functioning of a plant, as a result of the pathogenic organisms. Microbes like fungi, bacteria and virus are capable of causing serious diseases in plants. All species of plants such as wild and cultivated are subject to disease. The occurrence of plant diseases vary from season to season, depending on the presence of the pathogen, environmental conditions, and the crops and varieties grown. Plant diseases can be broadly classified according to the nature of their primary causal agent, both infectious and non-infectious.

Infectious plant diseases are as a result of a pathogenic organism together with a fungus, bacterium, virus, nematode, or parasitic flowering plant. An infectious agent is able to reproduce inside or on its host and spread from one inclined host to another.  

Non-infectious plant diseases are caused by unfavourable growing conditions, including extremes of temperature, moisture etc. Because Non-infectious causal agents are not organisms capable of reproducing within a host, they are not transmissible.

The parasitic microbes affect many of our commercial crops like cereals, pulses, vegetables, fruits etc. Some microbes are capable of infecting plant species belonging to a particular group. Parasitic microbes require a living host for completing their life cycle. They absorb nutrients from the host plants and may even kill the host. If the disease is not checked, it is capable of spreading rapidly to other plants causing severe loss. Bacterial blights, smuts, white rust, black rust, tobacco mosaic are a few common diseases of crop plants.

Common Diseases in Crop Plants

Bacterial Blights

Bacterial blights diseases shows the dark spots on leaf which is due to bacterial infection and it is caused from bacteria known as bacterium psuedomonas.

Symptoms of bacterial blight first appear on leaves as small, light green spots. As these spots enlarge, the tissue in the center dies and turns brown. These irregularly shaped spots are bordered by a lemon yellow ring. Bacterial blights are commonly found in plant such as, Potato, Tomato, Chilly plant etc.

White Rust

It is a type of fungal infection and is caused by several fungus like oomycetes in the genus Albugo, which attacks many herbaceous plants.

Symptoms of infection include light yellow areas develop on leaves, with chalky-white spots and then forms into a powdery pustules that finally darken on the under leaf surface and other above ground parts of plant. White rust occurs on a wide range of crops including Cabbage, Cauliflower, Collard, etc. 

Tobacco Mosaic

Tobacco mosaic infection in plants is caused from tobacco mosaic virus (TMV). It is a plant virus that belongs to the genus Tobamovirus group.

Symptoms of tobacco mosaic infection appear on leaves as small, light green mosaic pattern, continue its infection by molting or malformation of leaves and finally leads to yellow to brown spotting on leaves. Tobacco mosaic occurs mostly on tobacco plants.

Black Rust

Black rust is a type of fungal infection which is caused by the fungus puccinia graminis, which causes significant diseases in cereal crops. It mostly infects the wheat plants.

Symptoms of this infection are, it causes small brown pustules on leaf blades, if this infection is severely affected it develops brown patches throughout the leaf.


Learning Outcomes

  • Student will learn about plant diseases and their causes.
  • Students will understand the infectious and non- infectious diseases in plants.
  • Students will understand the common types of diseases in plants and their symptoms.