Although these all too common pests are known as greenfly, they can be coloured black, reddish-brown, pink or yellow rather than green. Aphids usually congregate near to the growing points of the plants where they are easy to spot. Some species, however, feed on the undersides of the leaves where they are hidden from view. They feed by puncturing the plant tissues and sucking up the sap. This not only weakens the plant but also can cause the growth to become distorted. Furthermore, they excrete large quantities of a sweet fluid known as honeydew which is deposited on the foliage making it sticky and shiny. This is an ideal growth medium for black sooty moulds which flirther disfigure the plant. Apart from the harm done to the plants as a direct result of their feeding, aphids can be responsible for the plant becoming infected with diseases which enter through the pinpoint feeding punctures. Many aphids also act as carriers of plant viruses which they transmit from one plant to another. Female aphids produce six to eight live young daily for two to three weeks. These offspring start producing young within eight days so infestations build up at an alarming rate if the pests are not controlled.
Most types of houseplants are liable to attack but flowering pot plants are especially susceptible.
Aphids are readily controlled by general insecticides or by special greenfly killers.