This leafless, stringy, bright-yellow parasitic vine on willows, blue elderberry, and wild plums on Cerrito Creek, on the Albany-Contra Costa border, is Japanese dodder (Cuscuta japonica), a new California invader that can form dense mats on a wide variety of hosts in wild lands, gardens, and orchards.

There is a Department of Agriculture quarantine against importing plants or viable seed. But the rules are weak. Vince Guise of the Alameda/Contra Costa Weed Management Authority reports that seed from a recent, supposedly sterile shipment were found to sprout readily.

This parasite can infest many broad-leaved hosts, from Pittosporum to plum, willow to elderberry and blackberry. Plants spread both by seed and vegetatively, by bits and pieces. Once a seed or growing tip finds a host, it sends root-like hausatoria into this host's limbs, sucking out water and nutrients. The host becomes heavily weighed down and weakened and may die.

Plants should be handled and disposed of with extreme caution. The Weed Management Area recommends that you contact them for removal rather than doing it yourself. If you do work on the parasite, their recommendation is removal of the entire tree or shrub down to the ground, careful double bagging of all debris, and disposal where nothing could possibly take root (buried in landfill with good soil cover, not composted).

In Alameda or Contra Costa Counties, contact Vince Guise, vguis@ag.cccounty.us. Elsewhere, contact your county agriculture department.

(Learn about more invasive species.)