Pests and diseases of house plants

Abstract

By a "disease" of a plant we mean any condition that interferes with its typical normal development. The growth of the stem, branches and roots, the unfolding of the leaves of a certain shape and size, the formation of characteristic flowers - all these are phases of the normal development of a plant. If the stem is stunted or spindly , the plant wiIts, if the leaves are curled or mottIed - if the plant manifests such abnormalities in its development, it is said to be diseased. The causes for plant diseases fall into two main groups: the parasitic and non-parasitic . Included in the former are viruses , bacteria and fungi . The term 'pest' is usually reserved for animal organisms and in these cases we speak of 'infestation' rather than ' disease' . The distinction is not very clear-cut , however , and for our present purpose we may include everything under the generic heading of 'disease ' . Among the non-parasitic causes are such widely different agents as lack or surplus of nutrients, unfavourable water relationships including lack or excess of moisture, sudden changes in temperature, the action of toxic chemicals and many others . In these brief notes , the author has included only the diseases caused by living agents as he feels that the control of the environmental conditions influencing the plant's health should be treated as a separate subject in its own right. One may find a large number of such publications although, unfortunately, not many of them are quite relevant to Maltese conditions. These notes are addressed to the homeowner who would Iike to know what sort of pathological damage might assail his plants but who has no time or inclination to go into the labyrinths of mycology, entomology, acarology or any of the other -ologies gravitating around what is, after all, a scientific hobby: indoor plant cultivation.