Common Diseases

Interior plants are occasionally affected by diseases.

The effects of an infection may vary from a cosmetic disfigurement to a life-threatening condition that might spread to other plants. Fortunately, the occurrence of plant diseases is rare in most interior landscape situations.

Definition of disease

A plant may be said to be diseased when there is a harmful deviation from normal functioning of physiological processes. (Federation of British Plant Pathologists, 1973). This definition is very wide ranging and includes conditions such as those caused by environmental factors or nutritional disorders. For the purposes of this Information Leaflet, disease relates only to those conditions caused by pathogens infecting plants.

A pathogen is defined as a parasite that causes a disease. A parasite is defined as an organism or virus living in or on another living organism (the host) from which it takes materials it requires for growth without conferring any benefit in return. Infection is defined as the establishment of a parasitic relationship. All the important diseases infecting interior landscape plants are usually caused by infection by species of fungi, bacteria or viruses, although other organisms can also be said to be disease causing.

Identifying plant diseases

Plant diseases can be identified by examining the symptoms of the plant. However, many diseases show similar symptoms, but it is usually possible to narrow down the possibilities to a small number. Laboratory cultures may be necessary to confirm the correct identity of the disease. The following table describes some of the commonest symptoms of plant diseases.