Thugs in the garden come in many varieties.
One that is especially bothering me these days is the dog or cat that insists on traveling through the Siberian Irises. Ordinarily, the foliage of the iris stands until mid winter. This year, I am tying them up in odd looking haystacks to keep them from smothering the plants at their feet. Grrr.
Another common thug is this little monster:
Japanese beetles love to munch just about anything. They have a particular fondness in my garden for my shasta daisies and my ostrich ferns. I don't have chickens, and I don't like to use poisons, so I use a by-hand method to get rid of some of them. I recycle a margarine or cottage cheese container, filling it about 2/3 with water. Add about two tablespoons of vegetable oil. Approach the pants with the sun facing you and position the container under the place where the bug is. Touch the bug - their flight mechanism starts with a straight drop - if you position the bucket just right - in they go. The oil clogs their pores and drowns them very quickly. This is not for the squeamish but is very effective.
The third type of thug is a plant thug.
Kathy mentions one of these in my comments. She's having problems with a self-introduced thug, Campanula rapunculoides, and asks me how to tell them apart from Adenophora (Ladybells, shown above). The best I can come up with is a few minor differences. The campanula seems to have a hairy stalk. It's leaves are not as lanceolate as the Adenophora. In other words, boy are these plants similar. (Kathy, if you send a photo of your thug I will post it here to compare)
And sometimes we are our own worst enemies. I have introduced many plants that I have later attempted to eradicate. Euphorbias, perennial sweatpea, species toadflax, Queen's Anne Lace, Tansy, Violets... all are plants that are entirely too successful under cultivation. For the toadflax and the euphorbia I have turned over the entire bed and let it lie fallow for a year, pulling up any and all sprouts as I saw them (daily at best, or at least weekly). The tansy I have yet to begin removing, as it has encroached upon plants that I want to try and save... and July might not be the best time to pull them out of the ground.
The violets and queen anne's lace I pull when they get out of hand, and I try to catch the lace before it goes to seed - these are easy enough to deadhead when the flower is spent.
And I will forever be pulling the sweatpeas out... the birds have carried the seed everywhere and they crop up in the oddest and most unexpected places.