But there is a tastier alternative to using pesticides. And that is to eat the invasive species!
One of the nastiest (as far as ecological impact) invasive species in the Pacific Northwest is Garlic Mustard (Allilaria petiolata). It is a biennial plant that can take over forest understories, forming monocultures and excluding many important native species. Garlic mustard releases a chemical from its roots that inhibits the growth of surrounding plants (this is known as allelopathy; walnut trees use a similar mechanism).
It is a big problem, but it is also edible. As you may have gathered from the common name, it is in the mustard family and has a taste resembling garlic. The leaves are used as a salad or cooking green. We got permission to harvest some leaves from a patch that Kristy found at Reed College. The plant has a fairly shallow root system and it is easy to just pull it out and bag it.
At home we cleaned the leaves like we would any other vegetable. We decided to add it to a Irish yellow broth soup that we enjoy in place of spinach.
Terrible. Just terrible. The leaves were so bitter that they made the rest of the soup inedible. I think our problem was that we waited too long to harvest and by the time we did many of the leaves were too large and the plants were preparing to bolt. When we try using garlic mustard again (it will probably have to be next year) we will get out earlier and just harvest the tender new leaves.
Don't let our experience scare you off. Experimentation is a good thing, and we will try again next year. One word of warning: only harvest from populations that you know have not been sprayed with pesticides. Many government agencies in our region spray garlic mustard found along roads, in parks, and in natural areas. I would not eat any garlic mustard you find in these areas. At Reed, Kristy talked to the grounds manager and found out that they do not spray the garlic mustard)
Here are two websites where you can find out more information about garlic mustard, find recipes, and find out more about the movement to eat invasive species.
Eat Invasive Species