Whitefly eggs are nearly microscopic! If you are sure that's what they are, spray with a weak solution of organic dish soap, or commercial insecticidal soap, every day for three days, then every three days after, until the problem is over. In the meantime, you might want to put up yellow cards smeared with petroleum jelly to catch the adults before they lay eggs.

If you're not sure, re-post the question with further particulars, and a picture, if possible.

Are you sure they are not cabbage white butterfly eggs? Though it is late in the year for them.

Cabbage aphids can also look like eggs, and their shed skins are sometimes mistaken for whiteflies.