Aphids in the Garden

Our Pest Control Expert, Julian Ives, has spent many years advising commercial growers and gardeners on the subject of safe and efficient natural pest control treatments.

Here he shares his experience on the problems Aphids can cause in the garden...

Appearance and Lifecycle
The aphid family is a large one with about 4000 species. Some of these species have common names like greenfly and black fly. Aphids are small in size and range from 0.5mm to about 7.0mm. Their colour varies between different species. They can appear in many different colours including; green, black, pink, grey and waxy white. There are about 250 species, which are harmful to plants and crops. They have a very rapid reproductive capacity and cause significant damage to plants and spread plant viruses.
Aphid population development is influenced by many factors including; temperature, the type of host plants and the amount of natural enemies present. Aphids can reproduce asexually and produce huge numbers of already formed young aphids daily.

Symptoms and Damage
The damage aphid causes is as a result of the sap that they extract from plants. This weakens plants causing stunted growth. Leaves can be deformed and young plants can be killed. For larger plants defoliation can occur and yield is reduced for fruit and vegetables. As aphids feed on the plants they also produce honeydew, which they deposit on leaves and plant stems, black sooty moulds then grow on the honeydew.  Aphids are also capable of spreading damaging plant viruses.
The first sign of aphid activity is often the appearance of individual winged aphids, which then go on to form colonies of aphids. If this is not observed, other signs of aphid activity can be the appearance of aphid skins on leaves, which can be mistaken for whitefly. Other symptoms will include sticky honeydew deposits appearing on leaves and the general stunting of plant growth. Aphids will attack many different types of plants indoors and outdoors. Greenhouse grown plants will generally suffer damage more quickly as the higher temperatures increase the reproductive capacity of the aphid.

Natural Choice Treatments
Aphids have a number of natural enemies that can be used to combat their development and reduce their harmful effects these include; parasitic wasps, ladybirds and lacewings. There are also safe spray treatments available to use when it is not practical to use beneficial insects. These options are brought together in the Harrod Horticultural Natural Choice pest control range.