Mo. R. Civ. P. 90.04
The service of the writ of garnishment and summons attaches the property subject to garnishment in the garnishee's possession or charge or under the garnishee's control at the time the writ of garnishment and summons is served and continuing through the return date of the writ or, in the case of a continuous wage garnishment, until the judgment is paid in full or until the employment relationship is terminated, whichever occurs first. Writs of garnishment that would otherwise have equal priority shall have priority according to the date of service on the garnishee. If the employee's wages have been attached by more than one writ of garnishment, the employer shall inform the inferior garnishor of the existence and case number of all senior garnishments.
Mo. R. Civ. P. 90.04