APHIDS

These insects are usually called greenfly or plant lice (sometimes simply blight) by gardeners. They occur both in the open and in the greenhouse and may be green, black, red, grey, reddish-brown etc., depending on the species. Aphids pierce the leaf and stem tissues and suck the sap from the young shoots, undersides of the leaves, also flower stems and buds. Their action causes premature leaf fall, distortion and curling of the leaves, bud drop, discoloration of blooms and a general reduction in vigour. The type of damage varies according to the species and plant attacked. Aphids also transmit virus diseases infecting chrysanthemums, lilies, strawberries, potatoes, sugar beet, and so on. Foliage of roses etc. can be disfigured by the sticky ‘honeydew’ excreted by the insects, encouraging the growth of sooty mould.

Overfeeding with nitrogen, whether in the form of farmyard manure or ‘artificial’ fertilisers, causes soft, sappy growth which is often more prone to attacks by aphids and other sucking insects. Warm, humid weather encourages attacks; during wet, cold spells aphids are less abundant. On rose trees attacks are usually more serious in late spring and early summer.

A very wide range of plants is attacked, including roses, carnations, pinks, petunias, tulips, aquilegias, asters, sweet peas, nasturtiums, Cotoneaster horizontalis, eunonymus, pyracantha, lettuces, broad beans, runner beans, carrots, all fruit trees and bushes.

Control Measures:

Aphids are not difficult to control provided spraying or dusting is undertaken directly they appear. Their rate of reproduction is exceptionally high, notably during late spring and summer. Fresh attacks after a really thorough spraying do not necessary mean that the insecticide has failed. Ants carry aphids from one plant to another and successive migrants arrive from other untreated plants and weeds, the aphids moving their quarters after exhausting the food supply of a particular leaf or shoot.

Gamma-BHG (lindane) derris, nicotine, malathion, etc., are used to control aphids, sprays being usually more efficient than dusts. Always spray both sides of the leaves, using a high pressure as aphids in common with thrips, leaf hoppers, etc., tend to infest the undersides. Systemic insecticides are also used against aphids.

Many species of aphids migrate to various weeds such as plantains, docks, shepherd’s purse, thistles, fat hen or goosefoot, which should, of course, be kept under control.

Sorry, comments are closed for this post.