Dodder parasitising tomato plants. Dodder (Cuscuta sp.) tendrils (yellow) wrapping themselves around tomato (Solanum lycopersicum) plants. The dodders, which are parasitic on tomato plants, are showing a preference for the healthy plants. Research has shown that the dodder uses the unique odours given off by the tomato to recognise and grow towards the plant. Stressed (unhealthy) and healthy plants give off different odours.