Understanding and Controlling the Parasitic Weed

“Last year, dodder infested my fodder beets. This summer, it’s taken over the alfalfa. Is it toxic? How does it spread, and how can I fight it?”

Among the most tenacious weeds, few are as challenging to eradicate as field dodder. This vine-like parasite, with its long, yellowish-orange tendrils, ensnares cultivated plants, stifling their growth. To combat it effectively, gardeners must first understand the peculiarities of its life cycle.

Dodder seeds remain viable even after passing through an animal’s digestive tract. They germinate at temperatures of 64–68°F, requiring high soil and air humidity. Upon sprouting, the young shoot “senses” the scent of nearby host plants and slithers across the soil toward them. Once it encounters a stem, the dodder coils around it, anchoring itself with suckers that eventually penetrate the host plant’s tissues. If it fails to find a host within 7–10 days, the shoot perishes, as this parasitic vine cannot survive independently.

Lacking roots or leaves, dodder relies entirely on its host for sustenance. Wrapping around its “victim,” it grows, blooms around June or July, and produces seeds within two to three weeks. A single dodder plant can yield 25,000 to 30,000 seeds—sometimes as many as 140,000.

Dodder’s Spread and Control Measures

Dodder also propagates through fragments, making manual removal futile. Once its suckers infiltrate a host plant, the parasite becomes deeply entwined, rendering separation impossible.

To protect garden and field crops, the first step is to eliminate dodder’s seed reserves in the soil. In heavily infested areas, all plants must be mowed down before the dodder flowers. Unfortunately, this means sacrificing the host crops as well. Once the mowed plants dry out, they should be burned. Applying a herbicide like Roundup or its equivalent can be effective, though it will destroy all treated plants, not just the dodder. Afterward, the area should be plowed to a depth of 12 inches, turning the soil to bury any remaining seeds.

Moving forward, avoid using fresh manure, as it may contain viable dodder seeds. Opt for well-composted manure instead.

Dodder contains toxic alkaloids, posing a danger to livestock. Cases of poisoning have been reported in horses and cattle, whether the weed is consumed in fresh forage or hay, with equally harmful consequences.