These capsules produce hundreds of seeds. Squirrels, deer, and humans walking through garlic mustard infested areas easily carry seeds. Garlic mustard spreads very rapidly. Controlling garlic mustard requires more than a one-year effort. It may take two to five years of control efforts to reduce the seed bank.
Hand pulling is probably the most effective method.
Try to do this before the plant flowers and sets seeds. Garlic mustard starts very early in spring and also remains green into late fall, so learning what it looks like and where it has developed is helpful in planning future control efforts. Right now it is very visible while two-year plants are blooming. Herbicides may be used for control. Consider late fall or very early spring application in the future when other plants may be dormant but the garlic mustard will be green.