22 year old evades on foot and is caught. he has a prior conviction for evading as a juvenile. Can the evading as an adult be enhances using juvenile conviction on the on site arrest.

No. Your misdemeanor cannot be enhanced with the juvenile adjudication. The provision that allows a juvenile adjudication to be used as an enhancement is in the Penal Code Sec. 12.42(f) - TO BE USED AS AN ENHANCEMENT A JUVENILE ADJUDICATION MUST BE FOR A FELONY OFFENSE AND MUST RESULT IN COMMITMENT TO TYC - and, in addition the adult offense to be enhanced must also be a felony - and there are some limitations on that set out in the statute.