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Originally Posted by joe_b  I wonder just how toxic this substance is to invertebrates for example? Presumably rotting laburnum leaves don't poison the worms that feed on them, or else bioaccumulation would cause laburnum tree gardens to be full of dead birds and all sorts? And is the poison soluble in water?
I'm trying the Pond Conservation Society next, out of interest really. Maybe I should do a PhD on the subject?  |
Certainly looks like there's enough to this issue to support a PhD thesis !
The main research (as with most ornamental species) looks pretty much targetted at human poisoning (suprisingly once source says 3,000 cases a year in the UK - what are all those people doing ?) Anyway it looks as though for a human sized mammal toxicity is rarely lethal, for other animals though the effects of cytisine look to be more serious
Cytisine: Facts, Discussion Forum, and Encyclopedia Article Toxic Plants Quit smoking, Cytisine substance
The problem of course for a UK habitat is that laburnum is an exotic introduction and none of the native species have any history of adaptation. Cytisine is a close formulation to nicotine -a poison which has been widely used as an insecticide. However it does seem that cytisine is not so readily soluble in water as nicotine, nevertheless long suspension of plant material in a closed pond will presumably yield increasing levels of the toxin. As far as effects on worms and amphibians (in addition to insects) there's this web page on nicotine which would suggest there is a problem - see Aquatic Toxicity low down the page:
Nicotine - toxicity, ecological toxicity and regulatory information
I think it is quite possible that incidental ingestion of laburnum is killing quite large numbers of creature in localised population - birds and mamals may be immune because the seeds, flowers and leaves are unappatising but water and soil borne poison could well be killing invertebrates and amphibians and no one would notice.
CM