The first of these is Cuscuta, which attacks the stems and leaves of other plants - having no roots of its own, this plant entwines itself around other species and sucks nourishment out of their vascular tissues. Its appearance is that of reddish threads interrupted by dense groups of very small white flowers. There are three species of Cuscuta in Malta.
The other relevant genus is Orobanche. In contrast to Cuscuta, these parasites attack the roots of other plants. In Malta, one of the commonest species is Orobanche crenata Forsskål, which is very well-known to farmers since it generally attacks legumes (such as broad beans, as in the picture below) and diminishes crop yield.
It may also adapt to parasitism on other plants like Nasturtium, as can be seen in the following picture, taken in St. George's Square at Valletta.
Orobanche crenata Forsskål - Valletta, 2010. Host - Tropaeolum sp.
I would like to thank Dr. S. Lanfranco for confirming the identity of the second Orobanche specimen.