Salivary-effector
Guides
Therioaphis trifolii
yellow clover aphid, spotted alfalfa aphid
Therioaphis trifolii is a phloem-feeding aphid and major agricultural pest of alfalfa (Medicago sativa) and clover species (Trifolium spp.). The species exhibits significant intraspecific variation, with distinct biotypes showing host-specific adaptations: the spotted alfalfa aphid (SAA) primarily colonizes Medicago species, while the spotted clover aphid (SCA) specializes on Trifolium. Native to the western Palaearctic, it has established globally including Australia, North America, and parts of Asia. The species manipulates host plant defense pathways through salivary secretions, activating salicylic acid signaling while suppressing jasmonic acid responses to improve host suitability.