The number of invasive species is growing by leaps and bounds. This is likely as we - the Greatest Invasive Species from which all others floweth - expand global trade. Ah Columbus, what hath thou wrought?
We also are always looking for an invader's natural predator from its homeland to import in a attempt to control them. Unfortunately it takes years of research to predict likely side effects of the "controlling" species and some times the cure is is worse than the disease. An example is the Kudzu bug*, Megacopta cribraria, which showed up unexpectedly in the US in 2009. The good news is that it eats Kudzu, significantly slowing its growth. Unfortunately, it likes our soybeans for dessert and has become a significant pest which spreading rapidly in the south.
The Kudzu bug has an interesting digestive system. Like most of us it carries bacteria in its intestine. These symbiotic bacteria help it digest food and without them it grows slower and smaller and dies earlier. The bugs apparently "know" this as the females deposit these symbionts with their eggs and the newly hatch nymphs eat them upon hatching, colonizing their gut with the right bacteria from birth.
On a personal level, we have debates on which invasive species to attack first, or even at all. Certainly identifying early invasives such as Gypsy Moth can prevent or delay their spread. Paulownia and Callary Pear (a.k.a Bradford Pear) have not yet taken over and may be controllable.
Harder decisions lie with pervasive species such as Sericea lespedeza and Johnson Grass. It is unlikely that we will ever eliminate them and we must decide which field of battle to fight on and which to ignore. Johnson grass as biofuel would make that decision easier.
Barb found an interview at Invasive.org which is extremely interesting. Bob Flasher trained in cultural anthropology before working on vegetation management and weed control in regional and national parks for twenty years. His thoughts on attacking or relaxing and embracing unwanted plants are both controversial and enlightening. The interview is available in the September 27th posting at invasiveplantnews.com.