Cuscuta is a genus of about 150 species of parasitic plants, commonly known as Dodder. They are twining climbing plants with herbaceous, thread-like, highly branched, and delicate stems, lacking chlorophyll and, depending on the species, can be yellow, pink, cream, red, or orange in color. Their leaves are reduced to small scales and are imperceptible. The inflorescences appear in the summer, in racemes, panicles, or cymes, and feature waxy, small flowers that can be pink, white, or cream. Dodder produces thousands of tiny seeds, which can remain viable for up to 15 years in the environment.
As soon as they germinate, the seedlings are green and have roots, remaining alive for up to 10 days without relying on a host. Once it finds its victim, the small seedling coils around and emits haustoria, which are suction and anchoring organs that penetrate the tissue of the affected plant, stealing its elaborated sap. The original roots then die as they are no longer needed. Its growth is rapid, and some species can grow about 3 inches (7 cm) per day.
Various species of plants, from herbs to shrubs and even trees, can be affected by Dodder. The speed of its growth depends on the species of Cuscuta, the host, and environmental conditions. They spread easily through seeds that are mainly carried by people and birds and by stem segments that birds use for nest building. In general, Dodder prefers full sun conditions.
Besides parasitizing other plants, weakening and suffocating them, Dodder is capable of transmitting viral diseases from one plant to another. These parasites are problematic in agricultural crops, reserves, and urban gardens. Serious damage is reported in crops of alfalfa, flax, petunias, chrysanthemums, clovers, dahlias, crown-of-thorns, tibouchinas, camellias, thymes, orange trees, ivies, potatoes, among others. Many countries have strict laws regarding the entry of seeds that may be contaminated with Dodder.
There is no specific herbicide to eliminate this parasite. Control measures include manually pulling out the entire infestation and burning the infested remains, preferably before flowering and fruiting. If you are willing to sacrifice the host plant to contain the spread of Dodder, pre-emergent herbicides like Dacthal, combined with the application of 2,4-D, will kill both the host and the parasite.
