Webworm is New Zealand's lord-of-the-parsnip

Webworms are having a field day in New Zealand. Colleague Brian Patrick reported in 2004 that "surveys convinced authorities that the species had entered New Zealand through the port [Port Chalmers] and had been resident in New Zealand for at least one summer prior to the 2003-2004 summer".  So numerous were webworms that year that "complete destruction of individual plants above ground" was commonly seen.

Although wild parsnips had made their way to New Zealand over a 150 years earlier (brought along by colonists for its delectable culinary properties, of course), the appearance of its arch nemesis must be quite a shock, and indeed it is! Never in our 25 years of experience in America or Europe have we seen such devastation as is being meted out by the webworms in New Zealand.  In some of the populations at the center of the distribution, we found close to 3/4 of the plants entirely stripped of flowers and seeds.  Stems of these plants were chock full of webworm pupae.  Moreover, as soon to be reported in the Proceedings of the National Academy of Sciences (see press release), webworms are substantially altering the selection pressures on plant chemistry, and not just furanocoumarins.  In fact, we suspect that a massive reshuffling of chemical characters, including furanocoumarins, terpenes, fatty acid esters and others, will result and will be occur rather quickly.  How fast is anyone's guess, but with a short generation time and a limited seed bank, probably not long--recall that parsnips appear to have responded to webworms within 20 years of reassociation in North America.

A New Zealand parsnip denuded by webworms
A New Zealand
webworm moth