P&PDL Picture of the Week for
October 6, 2008

Dodder-A Parasitic Seed Plant

Gail Ruhl, Sr. Plant Disease Diagnostician, Department of Botany & Plant Pathology, Purdue University

Dodder (Cuscuta spp.) is a twining plant that obtains its moisture and nourishment by parasitizing various kinds of wild and cultivated plants. The seedlings must attach to a suitable host within a few days of germinating or they die. Once the Dodder seedling finds a plant, it quickly twines itself around the plant's stem and the basal part of the parasite soon shrivels away so that no soil connection exists. Its water, minerals and carbohydrates are absorbed from the host plant through haustoria, specialized absorbant organs that press up against the stem of the host plant , penetrate the tissue and act as “straws”. Dodder rarely kills its host plant, although it may stunt its growth.

Dodder flowers are numerous and are borne in tight balls or in a loose cluster (depending on species). The fruit is about 1/8 th inch in diameter, with thin papery walls and contain 1 to 4 seeds. These seeds drop to the ground and germinate the next growing season if a suitable host is present. If no suitable host is present, the seed may remain dormant for five years.

Its wide host range and the long life of its dormant seeds make dodder hard to control and nearly impossible to eradicate. There is no herbicide that can be applied to garden and/or landscape plants once the dodder is up and growing on plants. Hand-pulling and pruning is the only method of control once the dodder is established. Pulling and destroying dodder infected plants before it produces seeds is recommended. Prior to germination, dodder can be prevented reasonably well with the application of a pre-emergence herbicide. Be sure to read and follow all label directions before using any pesticide.

Reference:
Dodder”, Colorado State University Cooperative Extension

Click image to enlarge

Dodder on pepper

Dodder on a pepper plant
Photo courtesy of Lorraine Lee

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service