CHENNAI: An invasive weed, native to North America, is slowly choking the Chengalpet forests and Vedanthangal Bird Sanctuary, threatening the local vegetation, ecology and habitat of migratory birds.
Cuscuta dodder, a parasitic vine without roots, has already infested acres of trees in the reserve forests and has begun to spread inside India’s oldest bird sanctuary. When TNIE visited Vedanthangal recently, it found the plant covering the canopy of Barringtonia trees, which are preferred by migratory water birds for nesting.
Botanists say this holoparasitic plant builds a canopy on the host plant and casts thousands of tendrils to form a dense spectacle before it strangles and eventually kills it.
“In the Vedanthangal landscape, Cuscuta spread can’t be allowed and the problem must be addressed immediately,” they said.
A forest staff at the sanctuary said Cuscuta started to invade the area in the last couple of years and the department was manually removing it during the summer months when water level in the lake recedes and migratory birds fly away.
Chief Wildlife Warden Srinivas R Reddy also confirmed it saying the department can only take action after the migratory bird season.
However, the invasiveness is serious outside the sanctuary area. TNIE has found Cuscuta spread in tens of acres in the reserve forests of Thiruporur in Chengalpet district.
Naturalist Yuvan Aves, who conducted a biodiversity study and documented wildflowers in Thiruporur forest last year, said, “A large area of the forest is highly infested and during our survey, we found several native trees already dead. The forest department must take necessary steps to control the species’ growth.”
D Narasimhan, the leading taxonomist in India, told TNIE, “Cuscuta infestation is observed in a few locations in Tamil Nadu. The forest department must collect the seed samples and identify the exact plant species because, in the Cuscuta genus, there are few identical species, which are difficult to differentiate.”
As per a technical paper published by the National Research Centre for Weed Science, in India, Cuscuta poses a serious problem in oilseeds, pulses and fodder crops in the states of Andhra Pradesh, Chhattisgarh, Gujarat, Orissa, West Bengal and parts of Madhya Pradesh under rain fed as well as irrigated conditions.
Legislation in 25 countries has listed the dodder as a ‘declared noxious weed’ with seeds and plant material denied entrance. In United States, it is the only weed seed whose movement is prohibited in every state.
The seeds of Cuscuta are spheroid and have a hard, coat, which aids them to survive up to 50 years in dry storage and at least 10 years in the field. Unlike root parasites, Cuscuta seeds do not require a specific stimulant to induce germination.