Flowering plants in the genus Cuscuta (dodders) are vine-like obligate parasites that obtain nutrients by attaching to above-ground shoots of other plants. Host plant defense responses to attack by Cuscuta haustoria include phytoalexin production and a hypersensitive response, two mechanisms that also characterize plant responses to pathogens. Anti-pathogen responses are mediated by the phytohormone salicylic acid (SA), which is known to often inhibit production of jasmonic acid (JA), a major signaling component of the anti-herbivore defense pathway. Preliminary data indicate that host plant defenses against Cuscuta attack are regulated by SA, raising the possibility that defense responses to herbivory may be negatively affected. Host plant resistance to herbivores may be further compromised by the ability of Cuscuta to act as a powerful ‘sink’, translocating nutrients, valuable secondary metabolites, and phytohormones essential for plant defense. Furthermore, because Cuscuta creates a phloem connection to its host, host plant defenses may concievably be induced by parasite-feeding herbivores, or by herbivory on a neighboring plant via a shared Cuscuta connection, since signaling components of plant defenses can be transported throughout the plant (e.g., systemin in tomato). The chemical ecology of these interactions is investigated utilizing tomato as the host plant, and determining in planta levels of phytohormones and plant volatile responses to insect herbivory.