Verb (type 1): To avoid, eschew, shun, stay away from, steer clear of.
Karttaa appears in our example in its 3rd person plural form, karttavat. (See karttaa fully conjugated here.)
Translating the whole phrase, punkit is the nominative plural of punkki, which means ”mite” or ”tick.”
Valkosipulia is the partitive singular of valkosipuli, which means ”garlic.”
So our phrase means ”ticks stay away from garlic.”