Nymphs and adults feed by extracting plant sap, which disrupts the balance of growth hormones and can lead to distorted leaf development or, in severe early infestations, even the death of young plants. This feeding damage often results in poor plant growth and defoliation, ultimately reducing yield.

Because plant sap is high in sugars but low in protein, aphids must consume large volumes to meet their nutritional needs. The surplus sugar is excreted as honeydew, which coats leaves and fruit, making them sticky. This sticky residue supports the growth of black sooty moulds (Cladosporium spp.), which further contaminates crops and diminishes their market value. Additionally, the mould and honeydew can block sunlight from reaching the leaves, thereby impairing photosynthesis and further reducing plant health and productivity.

Aphids have a complex life cycle that includes both winged and wingless adult forms and can display a wide range of colours. In greenhouses and under favourable conditions, they often reproduce through parthenogenesis—where unfertilized females continuously give birth to live young (nymphs) without mating. These nymphs begin feeding immediately on plant sap and pass through four moults before reaching adulthood. Each moult leaves behind a white, cast-off skin that can be seen on the crop, signaling aphid presence. When reproduction occurs sexually—usually outdoors—eggs are laid that can overwinter and hatch the following season.

The potato aphid (Macrosiphum euphorbiae) is one of the larger aphid species. Adults are slender and can be green, pink, or even reddish, with long legs, a prominent cauda (tail-like appendage), and distinctly long green cornicles (siphunculi). The wingless adults measure between 1.7 and 3.6 mm in length and are elongated in shape. Immature stages have a light coating of whitish-grey wax. When disturbed, potato aphids often drop quickly from the plant as a defensive behaviour.

A dark longitudinal stripe runs along the top side of the body, appearing green in green morphs and dark red in pink morphs—this stripe is a key feature for identifying the species, especially in nymphs.

Preventing potato aphid (Macrosiphum euphorbiae) infestations involves a combination of cultural and environmental practices that reduce the likelihood of outbreaks and support overall plant health. Start by maintaining strict hygiene in and around the growing area—remove weeds, crop debris, and volunteer plants that may host aphids. Monitor new plant material carefully before introducing it into your growing space, and isolate or inspect transplants for early signs of aphid presence.

Regular crop scouting is essential—check the undersides of leaves and growing points, where aphids tend to cluster. Early detection allows for timely interventions before populations build up.

Managing environmental conditions can also help deter aphids. Avoid overly warm and humid conditions if possible, and optimize airflow and plant spacing to reduce plant stress. For greenhouse crops, using insect-proof screens on vents and doors helps limit entry by winged aphids. Combined, these practices can significantly reduce the risk of infestation and the damage that follows.

To control potato aphid (Macrosiphum euphorbiae) infestations in greenhouse and protected crop environments, several biological control agents can be used effectively. These beneficial insects and parasitoids target the aphid at various life stages, helping to naturally reduce populations and limit damage to crops.

Chrysopa (green lacewings) are generalist predators known for their voracious larvae, which actively hunt down aphids and consume large numbers during their development. Lacewing larvae are especially useful in hotspots or early infestations, as they provide quick suppression.

Aphidalia, which contains Adalia bipunctata (the two-spot ladybird), is a powerful predatory beetle. Both larvae and adults feed on aphids and are highly mobile, making them effective even in dense plant canopies where aphids hide. Ladybirds are long-lived predators and continue feeding throughout their lifecycle.

Aphided is based on Aphidoletes aphidimyza, a predatory midge whose larvae are highly specialized aphid hunters. Adult midges lay eggs near aphid colonies; once the larvae hatch, they seek out and paralyze aphids, feeding directly on their body fluids. Under favorable conditions, Aphidoletes can collapse large infestations in a matter of weeks.

Ervipar contains Aphidius ervi, a parasitic wasp particularly well-suited for targeting larger aphid species like the potato aphid. This parasitoid lays its eggs inside live aphids. As the wasp larva develops, it consumes the host from the inside, leaving behind a hardened shell known as a “mummy.” This method provides ongoing suppression as new generations of wasps emerge.

Aphilin, containing Aphelinus abdominalis, is another specialist parasitoid effective against Macrosiphum euphorbiae that can be used for treatment.

Combining these biocontrol agents based on crop type, climate, and infestation level provides a well-rounded strategy. Preventative or early curative releases, paired with routine monitoring, help maintain a balanced ecosystem and reduce the need for chemical inputs.