How dangerous is invasive dodder to Kaua‘i?

KILAUEA — An inconvenience to some and a nightmare to others, the invasive dodder plant poses a threat to some native flora and fauna but has rarely received any attention.

Kilauea resident Neal Beissert said that for the past year dodder has been eating up the vegetation on his vacation rental property on Kolo Road, directly above the Kilauea River adjoining the Kilauea Point National Wildlife Refuge.

He considers his property threatened by the plant, which is spreading to neighboring land.

“It is spreading uncontrolled along the hillside and throughout the valley,” Beissert said. “It literally kills everything in its path and is advancing toward the wildlife reserve. I am concerned it will destroy numerous native plants necessary to support the wildlife population.”

Dodder is a nickname for cuscuta, a parasitic plant with more than 100 varieties that are present in temperate and tropical climates. Some varieties live out their cycle through photosynthesis, while most, including the variety found on Beissert’s property, live by feeding off of host plants.

Dodder seeds can survive for years before being carried by wind, animals or man and taking root in disturbed ground. Once the plant germinates it must find a host quickly by wrapping vine-like stems around plants — taking its water, nutrients and dropping seeds in its dead shell before moving on to the next plant.

Keren Gundersen, project manager of Kaua‘i Invasive Species Committee, said there appear to be two known dodder species in Hawai‘i. The western field dodder, a non-native plant, is common to western North America and known to be on O‘ahu and the Big Island.

The species, Cuscuta sandwichiana, which is known to Kaua‘i with six names including Kauna‘oa, are a twining, yellow to yellow-orange variety that are unique for preferring lagoon environments.

“That is here on Kaua‘i,” said Gunderson. “That is a parasitic plant like mistletoe.”

Gunderson said that this variety is invasive but other plants on Kaua‘i are “horribly invasive,” such as strawberry guava, clidemia, melastoma, Australian tree feren, miconia and Kahili ginger. She said these species deserve more attention and funding for eradication efforts as they threaten the watershed.

She encouraged more awareness on lower level risk invasive plants and on what not to plant and how to get rid of them.

A botanist at the National Tropical Botanical Gardens identified Beissert’s plant as dodder. He noticed it on his land two years ago. It didn’t become a threat until recently and is spreading across the hillside.

Beissert contacted Dr. James Leary, an invasive-weed specialist with the University of Hawai‘i at Manoa Agricultural Research Center, for help. Without a meaningful solution for immediate results, he suggested “aggressive manual removal over several iterations” and acknowledged that Beissert has difficult terrain to accomplish this goal.

Beissert said his initial attempts to dig up the plants failed and they keep returning.

“We have been trying for the past year to find a means to eradicate this growing problem, to no avail,” Beissert said. “Our property is one of the few places on island where we have seen its damage.”

The long-term natural defense against dodder is to surround it with non-host plants that it cannot feed off. These includes many flower plants, grains, pasture grass, banana, ginger, onion, garlic, sugar and bamboo. Man-made removal comes from herbicides or controlled burning followed by planting non-host vegetation.

Now that he recognizes the plant, the avid hiker has noticed it only in one other spot just about a mile south of his property near the Kilauea Lighthouse and Kilauea Point National Wildlife Refuge.

“This is kind of an east coast problem,” he said.

Trae Menard, Kaua‘i director of The Nature Conservatory, said he has not dealt with dodder too much, mostly because it doesn’t come into play with his work with other invasive species considered to be more serious threats.

“This (dodder) plant can be a problem in some areas, but it does not threaten the watershed,” he said.

The Kaua‘i Watershed Alliance, which Menard also directs, lists the current threats to forests and waterways stemming from non-native animals and invasive plants. It also states that pigs, goats, cattle and deer do damage to the vegetative structure and introduce diseases, which help invasive plants take root.

Another contributor are the hurricanes, which disturb the vegetation and spread weeds around the island. The presence of man with recreational vehicles, hiking trails, domestic cultivation and burning also contribute to the growth of invasive species.

Online:

www.hawaiiinvasivespecies.org/iscs/kisc/

www.kauaiwatershed.org/www.nature.org/

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