Aphids or greenfly are the most common and widespread of all the pests which attack house plants.
Usually green in colour they may also be black, grey or orange. Included in this group of related insects are blackfly and woolly aphids. Individual insects are very small, and may not at first be noticed. However as they thrive in colonies, a severe attack of aphids will be obvious.
These insects have a complicated life-cycle and all stages — egg, wingless nymph and adult aphid — may be present on the plant. They multiply at an alarming rate so it is important to control them.
Attack on buds
They attack plants with soft tissues in preference to those with woodier tissues. They live by sucking the sap of the plants from which they obtain amino acids. Particularly favoured are the growing tips and buds.
As a result of aphid activity the plant growth will be distorted and the whole plant weakened. Aphids need to consume vast amounts of sap because the concentration of amino acids is not as great as that of sugar in the sap. They are unable to use the sugars and deposit them as a sticky secretion on theand of plants, as well as all over your furniture and woodwork.
Ants are attracted to the sticky honeydew and you may find an infestation of ants close to an aphid colony. In some cases ants will actually transport aphids from plant to plant to start up new sources of honeydew.
If there is a large amount of honeydew on thesooty mould will develop. This black fungus thrives on the droplets of honeydew and clogs the breathing pores (stomata) of the plant. This inhibits the plant’s ability to make its own nutrients.
They may also carry disease to your other healthy house plants.
Using chemicals safely
- Always read the instructions on the label carefully before you use the , product. Note in particular, if spraying edible plants, that there must be a time lapse between spraying and harvesting the plants.
- Avoid breathing the spray yourself. Spray house plants outdoors, if possible.
- Make sure that the spray you use doesn’t harm any insects which might be beneficial to the plant’s welfare.
Getting rid of aphids
There are many methods of dealing vith aphids. If there are only a few and you have seen them before too much damage is done simply remove them.
Spray them with water from a hand sprayer or hold the affected part of the plant under a gentle flow of water from a shower and rinse them away. If you add a small amount of liquid soap to the water in the hand sprayer the treatment will be doubly effective. You should repeat the treatment after a week to catch any aphids that might have hatched.
You can also wipe them off with a damp sponge or a moistened cotton swab.
Aphids have many natural enemies which keep their population in check, when they occur outdoors. Ladybirds and lacewings in particular will help to control an infestation.
Strong measures are needed to combat a severe attack. The safest way is to cut out the aphid-infested parts. However, this may not be successful, as aphids may return to parts so far not affected.
In this case use insecticides which are derived from organic products. Pyrethrum is a mildavailable as a dust or powder which is applied in solution with water.
It is a natural product with no known harmful side effects. It is especially useful as a spray on edible plants as it is non-toxic.
It works more effectively if a second application is made a week after the first.
Other insecticides. There are many products available which are effective in combatting aphids. Some are contact sprays which kill the insect on contact. Others are systemic — they poison the insect as it draws up the sap.
Plants to watch
Not only will an attack by aphids damage single plants, but they can carry other diseases and infect healthy plants.
Plants prone to aphid attack include kalanchoe, the Persian violet and busy lizzie. On the Cape primrose, aphids rarely attack the leaves but are often found on flower buds and stalks. On, Fatsia, Schefflera they are found on young growth only; on the asparagus fern on the stems. On cyclamen plants look on the undersides of leaves and on flower petals. Outdoors, aphids attack fuchsias, nasturtiums, pansies, roses, lilies and pot marigolds.