Dim filename As String = "ftp://caminhocompleto/arquivo_a_remover.txt"
Dim ftpReq As FtpWebRequest = WebRequest.Create(filename)
ftpReq.Method = WebRequestMethods.Ftp.DeleteFile
ftpReq.Credentials = New NetworkCredential("usuario", "senha")
Dim ftpResp As FtpWebResponse = ftpReq.GetResponse
MsgBox(ftpResp.StatusDescription)