February 2011. One of the strengths of the scientific method is the way it encourages opposing views and debate. So it is in discussions on non-native species. Under a rather provocative title, Welcome weeds: How alien invasion could save the Earth (in the Australian edition it is worse: Aliens to the rescue), an article appeared in the New Scientist. The author makes a case that in some instances ecosystems can benefit from non-native species, especially in rebuilding them after they have been altered by human activity.

It’s not saying do away with quarantines; it is saying that informed decisions on fighting some non-native weed species may be misguided, and a waste of resources.

This topic is not unknown to PestNet. In March 2002, under the heading of “What makes a pest invasive”, there was discussion on the merits of Spathodea – the tulip tree – in Fiji, and its importance in protecting the native forest community from fires, and creating conditions for native forest regeneration. The same tree is mentioned in the NS article, and it seems it has played a similar role in forest regeneration in Puerto Rico.

Another controversial weed is Mikania micrantha.

Mikania is a weed that, like Spathodea, is a friend to some and a foe to others. In the past, farmers in American Samoa have said that it was easy to roll up and plant behind. It also kept the ground most, and built up a fair amount of humus between crops. Not as good as a legume cover, but better than grasses, perhaps. See, Pests/PestsEntities/Weeds/Mikaniacordatamileaminute.aspx.

Others see it quite differently and wish to control it. Queensland, which does not have the weed, is assisting PNG and Fiji with the introduction of two biocontrol agents: Actinote anteas and A. pyrrha thalia) from Indonesia and the mikania rust (Puccinia spegazzinii). Rusts of course do not always stay put.

One PestNet member said that he had oppsed the introduction of the rust. Mikania was one weed that he liked to see on his land in Samoa, rather than Mint weed, grasses and African tulip. It did not seem to be an invasive weed to him; infact, it was disappearing in some parts of the country. Also, it is easily controlled by hand weeding, with the help of a bush knife.

On the Queensland Primary Industry and Fisheries (now DEEDI) website, the ACIAR-funded project:http://www.dpi.qld.gov.au/4790_13776.htm, reports impact assessments of the weed in both countries. Mikania vine was considered a serious weed by 65% of respondents, causing yield losses of over 30% by smothering crops and trees.