[6][7] Foliar diseases such as leaf spots are commonly caused by ascomycetes and so-called deuteromycetes (mitosporic fungi).

Distinctive dark green and black spore producing bodies edged by white hyphae occurs in lesions.

[7] Whilst other pathogenic causes such as fungi and bacteria induce leaf spot disease by way of enzymes, toxins and spores, virus infections affect the host by means of synthesising new proteins that are biologically active substances such as enzymes which may sabotage the metabolism of the host.

Viral leaf spot diseases include the Apple chlorotic leaf-spot virus from the genus Trichovirus, Tospoviruses, and Coconut cadang-cadang viroid.

[3] Accurate identification of leaf spot disease is needed as to distinguish signs of illness from damage done by herbicides.

[7] Fungal leaf spots often have a brown, black, tan or reddish centre with a darker margin and vary in size.

This is because in leaf spots, the plant cuticle, epidermis, and cell tissues, including the xylem may be destroyed in the infected areas.

The cuticle protects the leaf and the destruction of these cell tissues results in an uncontrollable loss of water from the affected areas.

[7] Leaf spots reduce the surface area available on leaves for photosynthesis and so can result in smaller growth and yield of plants.

[1] Leaf spot disease occurs when the following factors are all present: favourable environmental conditions, a pathogenic agent, and susceptible host.

[2] Different types of pathogens, including fungal, bacterial and viral agents have unique ways to suppress and attack the host plant's immune system, thereby resulting in the progression of leaf spot disease.

[2] Fungal leaf spot pathogens follow the path of attaching to the plant surface, germinating via spores and entering into the host tissue.

[16] Horizontal transmission of viral pathogens include dispersal through touching of nearby infected leaves and through root systems or through vectors for more distant hosts.

[8] Infection occurs when the bacteria enter into wounds, or by natural entry (cell adhesion), under favourable warm and moist conditions.

[8] Pathogens can be dispersed by the wind that can lift nematode eggs, insects, and many tiny fungal spores as well as bacterial cells by air currents.

[2] Animal and insect vectors are another way in which fungal, bacterial and viral leaf spot diseases are spread.

[2] Tools used by humans and worker's hands during transplants, watering, and market practices can contribute to the dispersal of leaf spot pathogens.

[7] Strains of plant pathogenic bacteria becoming resistant to chemicals contributes to the difficulty of managing bacterial leaf spot disease.

[18] Prevention of leaf spot disease includes variety selection, crop rotations, plant hygiene and fungicide use for seeds and foliage.

[11] Collecting and removing fallen leaves is important in reducing the amount of pathogenic agents on the ground to prevent dispersal of disease.