It’s true– for four summers, I was a bug rancher. I worked at the Western Agricultural Research Center doing various manual sort of tasks for the Biocontrol of Weeds lab. Mostly, I helped raise insects in cultivated plots of Spotted Knapweed (Centaurea maculosa). Later in the summer, we collected the insects and shipped them off to various land management agencies around the state, and the west. We concentrated on raising two sorts of insects: a yellow moth called Agapeta zoegana, and a large, flightless weevil known as Cyphocleonus achates. Because the weevils were flightless, we raised them in a little fenced pen, and picked them off the plants like berries. The moths were cultivated on small plots inside of tents, and we caught them using a carefully modified dust-buster. It was a pretty fun and kind of ridiculous way to spend the summer, really– deliberately raising noxious weeds, vacuuming up moths, and shipping insects around the state is a little unusual in terms of summer jobs.
I haven’t kept up on the literature about the efficacy of biocontrol since 2003, but I think they’re doing some good. Most people I talk to seem to expect that the bugs will simply eradicate the knapweed to extinction, but they don’t– natural systems usually don’t work that way. What they do is inhibit the spread and growth of the plant, allowing native vegetation to compete more effectively with the invasive knapweed. Basically, they’re part of a multi-faceted management approach, not a magic solution.
I see the wikipedia page indicates that there’s some question about the efficacy of biocontrol insects in knapweed, but I also noticed the referenced study is nearly 20 years old, which is ancient in terms of scientific literature regarding insects that were only introduced in the early 1980s. I’m curious as to what their efficacy is now, some 25 or 30 years from when they were first introduced. It’s much less of a problem on our family ranch these days, I know that much.