APHIDS Order; Hemiptera Family; Aphididae Symptoms The presence of the 500 species of aphid is indicated by large amounts of sticky honeydew and sooty moulds on the upper surfaces of leaves. Aphids are extremely well-known to gardeners under the guise of greenfly, blackfly and various local names. As well as the above symptoms, the effects of aphids feeding on plant material weakens and distorts new growth, and these pests will also spread viruses from diseased plants to healthy plants through their saliva. Aphids are clearly visible on the stems and leaves of infested plants, and the mosaic patterns of the various viruses they transmit can also be seen on the leaves. Many of the hundreds of species of aphids are common pests of fruits, vegetables and outdoor ornamental plants as well as greenhouse and house plants. Some species will feed exclusively on one plant species but others will attack hundreds of different plant hosts. Description and Life Cycle All species of aphids can be found on plant stems and leaves of the host plant. These small soft-bodied insects range in size from 0.5mm to 6.5mm in length, and colours can vary from shades of green to black, yellow, brown, pink, grey and white. Unfortunately for the gardener, aphids have the ability to produce live young from unimpregnated females although the reproduction of this pest is complicated by seasonal alternation of sexual and asexual periods of development and the differences between the hundreds of species. Some aphids are winged and although they cannot fly as such, they can be carried hundreds of miles on thermal breezes, leading to further infestations. Generally, eggs are laid in the autumn on the winter host plant which hatch in the spring; this is followed by migration to the summer host plant (hence the species peach-potato aphid). Another generation is produced in the autumn which returns to the winter host for egg production. Biological Pest Control Treatment The coccinellidae family (more commonly known as ladybird beetles) are well known as beneficial garden predators. There are various species of ladybird but most will feed on aphids, and some species will also attack scale insects, mites, mealybugs and whitefly. It is good horticultural practice to encourage ladybirds into the garden and greenhouse environment as they will attack any aphids in the margins and will also move into an adjacent area when infestations of aphids appear. Generally the eggs of the various ladybird species are laid on the underside of leaves in spring. The adults overwinter in buildings or under bark so the provision of a ladybird nest or bug box will help to keep numbers of overwintering adults high. The larvae which eventually hatch from the eggs are mobile and benefit from having the same biting jaws as adults, and are in fact, more voracious feeders than the adults when almost fully grown. The larvae pupate either in close proximity to their main food source or in a simple pupal case on the ground.Occasionally, ants may be seen swarming over aphid populations on the stems of plants; these ants are actually feeding on the honeydew secreted by the aphids and are not consuming the pests
