Sow thistle aphid

Taxonomic position. The sow thistle aphid (Uroleucon sonchi) belongs to the order Hemiptera and the family Aphididae. It is a specialized pest primarily associated with the Asteraceae plant family, often found in both wild and cultivated habitats.

Host plants and damage. While its primary host is the sow thistle (Sonchus), this aphid species frequently attacks lettuce, chicory, and ornamental plants. Feeding on phloem sap causes leaf curling, yellowing, and significant stunting, which negatively affects the overall vigor of the host plant.

Biology and life cycle. The life cycle involves both apterous (wingless) and alate (winged) morphs, allowing for rapid colonization of host plants through parthenogenetic reproduction. They typically overwinter as eggs on the basal parts of perennial weeds, with rapid population growth occurring as temperatures rise in spring.

Nature of injury. Aphids congregate in large numbers on the underside of leaves and stems. Their persistent feeding extracts essential nutrients, leading to reduced photosynthetic capacity and market value of the crop. Additionally, they serve as vectors for various plant viruses that cause systemic diseases.

Control measures. Integrated pest management should prioritize the removal of host weeds like sow thistle from field margins to reduce reservoir populations. If infestation levels are high, systemic insecticides are recommended for control. Encouraging natural enemies such as lady beetles and lacewings is also highly effective.