PESTS ON PLANTS

Gardeners sometimes confuse the terms ‘pests’ and ‘disease’. Pests belong to the animal kingdom and are represented by insects like aphids (greenfly, black fly, etc.), thrips, caterpillars, leaf hoppers, weevils and so on, as well as creatures such as millepedes, slugs, snails and red spider mites which are not really insects at all. Note that insect and other pests may attack any part of a plant and not merely the portions above ground. Thus millepedes and wireworms injure roots, tubers, bulbs etc. Pests in the garden or greenhouse are tackled by spraying or dusting with insecticides such as Pyrethrin, gamma-BHC, aldrin, dicldrin, nicotine and malathion. Always spray or dust at the first signs of damage, repeating treatment where attacks are persistent or severe. Diseases are disorders of one kind or another in the normal functioning of plants and may be caused by fungi or bacteria. Disorders arising from malnutrition, unsuitable soil conditions, weather upset etc. are also termed diseases. These are corrected by cultural methods but most fungus diseases are dealt with by preventive spraying with fungicides such as sulphur, Karathanc, captan or thiram.

Pests which attack particular crops are treated under the flower, fruit or vegetable concerned, e.g. apple sawfly is discussed under APPLE and turnip flea beetle under TURNIP. A few pests which attack a very wide range of plants, notably APHIDS, MILLEPEDES, WIREWORM are covered alphabetically. Diseases are treated similarly. Thus rose black spot will be found under ROSE and MILDEW alphabetically.

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