Family: Aphididae
Common examples affecting South African crops:
Green peach aphid (Myzus persicae), cotton/melon aphid (Aphis gossypii), black bean aphid (Aphis fabae), among many other species.
Aphids are small, typically 1–3 mm long, pear-shaped insects that may be green, black, yellow, pink, or grey depending on species. A pair of tail-like structures called cornicles projecting from the rear of the abdomen is a reliable identifying feature of the group. Aphid biology is unusual: for much of the year, females reproduce asexually and give birth to live young without needing to mate, allowing populations to expand extremely quickly under favourable warm conditions. Winged forms develop when colonies become crowded or host plant quality declines, allowing aphids to disperse to new plants or fields. In cooler climates, a sexual generation may occur that produces overwintering eggs, though in warmer regions asexual reproduction can continue almost year-round.
Aphids are not a single species but a very large family of small, soft-bodied sap-feeding insects found virtually worldwide. Many of the species that trouble South African growers, such as the green peach aphid and cotton aphid, are cosmopolitan pests that have spread to almost every region where suitable host crops are grown, rather than being confined to one origin point. Their presence is essentially universal wherever susceptible crops are cultivated, and local populations build up seasonally rather than through discrete invasion events.
Collectively, aphid species attack an enormous range of crops, including vegetables, cereals, fruit trees, and ornamentals; most individual aphid species have a narrower, though still often broad, host range within this group.
Aphids feed by inserting piercing mouthparts into plant tissue and withdrawing sap, which can cause leaf curling, distortion, and stunted growth, especially on young, actively growing tissue. As they feed, aphids excrete a sugary substance called honeydew, which coats leaves and fruit and promotes the growth of black sooty mould, reducing photosynthesis and fruit marketability. Beyond this direct feeding damage, aphids are highly efficient vectors of plant viruses, and in many crops virus transmission, rather than the feeding damage itself, is the more economically significant threat, since even low aphid numbers can spread disease through a field or orchard.
Aphids have a rich natural enemy complex, including ladybird beetles and their larvae, lacewings, hoverfly larvae, and small parasitic wasps that lay their eggs inside aphids, eventually killing the host and leaving behind a characteristic swollen, papery "mummy." Conserving these natural enemies by avoiding unnecessary broad-spectrum insecticide use is a key part of managing aphids sustainably, since populations can rebound very quickly once natural predators are removed.
Aphids have a rich natural enemy complex, including ladybird beetles and their larvae, lacewings, hoverfly larvae, and small parasitic wasps that lay their eggs inside aphids, eventually killing the host and leaving behind a characteristic swollen, papery "mummy." Conserving these natural enemies by avoiding unnecessary broad-spectrum insecticide use is a key part of managing aphids sustainably, since populations can rebound very quickly once natural predators are removed.
Insect Science Yellow and Blue Sticky Cards make use of aphids' natural attraction to specific colours, helping growers and gardeners monitor aphid activity alongside other small sap-feeding and flying pests such as leafhoppers, leafminers, and whiteflies.
