Cuscuta europaea (European dodder)

Holm et al. (1979) list C. europaea as a 'serious' weed in Afghanistan and Poland, and a 'principal' weed in Czechoslovakia and the former USSR. It is rarely a major weed over large areas, perhaps because of the lack of attack on Gramineae [Poaceae], and the cleaning effect of cereal crops in rotation. But once contact is established with the host phloem, Cuscuta becomes a powerful sink for metabolites, causing a severe drain on host resources and often completely preventing normal fruit development, as shown by Wolswinkel (1979) for C. europaea on faba bean (Vicia faba). Owing to this powerful metabolic sink effect, studied and described in detail by Wolswinkel and Ammerlaan (1983), the damage to infected hosts can be severe, to the extent of total crop loss. Less dry matter and ash were found in the leaves of parasitized Urtica dioica and Aegopodium podagraria than in those of healthy plants. Leaves of parasitized U. dioica plants contained 8.5% less chlorophyll than uninfested ones (Gal'vidis, 1993). Perhaps the crop most seriously affected is sugarbeet in Italy, the former Yugoslavia and eastern Europe. There is also further economic loss when crop produce, such as clover or lucerne seed, intended for export, is rejected or has to be expensively cleaned.There are occasional reports of toxicity to livestock from Cuscuta species, including toxicity to horses from C. europaea (Pergat and Stolyarova, 1961).