Dodder is a weed not commonly found in landscape and garden situations. When present, usually it is because this weed has been introduced from some outside source such as contaminated soil, tools or clothing. Once dodder is on a plant, there is no way to get rid of it and save the plant.
Dodder is easily recognized since it has no leaves and is simply strand-like pale yellow stems that form a mat over the desirable plants if allowed to grow. Its unusual color is due to a lack of chlorophyll. Thus it is a parasitic plant, meaning it must get its nutrition from another plant instead of from the soil. Although the seeds germinate in the soil, when the seedling comes in contact with a host plant, the young dodder inserts root-like haustoria into the host. The dodder then breaks contact with the soil and continues to use the host as a means of nutrition and support.
Dodder forms tiny flowers which may produce up to 3000 seeds on a single plant. These seeds have a very hard seed coat which allows them to survive several years. So the results of one year's infestation can have long term effects as these seeds germinate year after year.
Once dodder has been introduced it is difficult to control. The best control is to remove all infested plants and dodder before the weed goes to seed. Be sure to dispose of all traces of dodder including cleaning your tools and clothes. It only takes a very small portion to begin a new plant. Repeated cultivation is also helpful as it allows more of the seed to germinate and be killed before going to seed. This decreases the number of seeds remaining in the soil. A pre-emergent herbicide used after the desirable plants are established will have some effectiveness. It should prevent the dodder seeds from germinating without harming the plants they would latch on to.
Without a host, dodder seedlings will live for only a few weeks before they die. By planting species that are not susceptible to attack by dodder such as grasses and other plants in the grass family, the weeds will eventually die. Any of the ornamental grasses would be a good choice to put into infested areas for a year or two.
Generally it is best to make every attempt to not introduce dodder into your growing situation. Use only clean soil taken from locations where there has been no dodder infestation. Remove infested plants immediately upon discovery. Although it is possible to introduce the dodder on purchased bedding plants, careful sanitation procedures can prevent the problem from becoming widespread.