trigger Trigger_Task_Send_Email on Task (after insert)
{
  
    Set<Id> ownerIds = new Set<Id>();
 
    for(Task ta: Trigger.New)
    ownerIds.add(ta.ownerId);
 
    // --------------------Build a map of all users who are assigned the tasks.-----------------------------------
  
Map<Id, User> userMap = new Map<Id,User>([select Name, Email from User where Id in :ownerIds ]);
    for(Task ta : Trigger.New)
    {
        User theUser = userMap.get(ta.ownerId);
//-------------------------Mail Messenging-------------------------------------------------------

        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        String[] toAddresses = new String[] {theUser.Email};

        if(ta.Email_Bcc__c!=null)
        {
        string[] BccAddresses =String.valueOf(ta.Email_Bcc__c).Split(',');
         mail.setBccAddresses(BccAddresses);
         }
       
         if(ta.Email_To__c!=null)
        {
         string[] toaddress =String.valueOf(ta.Email_To__c).Split(',');
         mail.setToAddresses(toaddress);
         }
         if(ta.Email_CC__c!=null)
         {
         string[] ccAddresses =String.valueOf(ta.Email_CC__c).Split(',');
         mail.setCcAddresses(ccAddresses);
       
       
         mail.setSubject('New Task Created by  '+ Userinfo.getName()  +'');
         }  
        //---------------------------------------- Creating Template----------------------------------
String template =  'New Task \n\nTo: '+theUser.Name+',\n\n '+ Userinfo.getName()  +' has assigned you the following task: \n\n';
      
        template+= 'Subject - {1}\n';
        template+= 'Due Date - {2}\n';
        template+= 'Priority - {3}\n';
        String duedate = '';
        if (ta.ActivityDate==null)
            duedate = '';
        else
            duedate = ta.ActivityDate.format();

     if(ta.Description!=null)
        {
            template+='Description - '+ta.Description+'\n';
          
        }

        List<String> args = new List<String>();
        args.add(theUser.Name);
        args.add(ta.Subject);
        args.add(duedate);
        args.add(ta.Priority);
// -----------------------For Creating Task Link--------------------------
        template+= '\n\nFor more details, click the following link: \n\n';
        template+= URL.getSalesforceBaseUrl().toExternalForm() + '/' + ta.Id; 
          
        mail.setSaveAsActivity(false);
        mail.setPlainTextBody(template);
     
        // Here's the String.format() call.
        String formattedHtml = String.format(template, args);
     
        mail.setPlainTextBody(formattedHtml);
        Messaging.SendEmail(new Messaging.SingleEmailMessage[] {mail});
    }
}



Test class
---------------
@isTest
public class Test_Trigger_Task_Send_Email{
static testmethod void createTask(){
    task t = new task();
    t.priority = 'low';
    t.status = 'In Progress';
    //t.ActivityDate='Due date';
    t.description = 'testing description';
    t.Email_To__c = 'a@b.com';
    t.Email_Bcc__c = 'a@b.com';
    t.Email_CC__c = 'a@b.com';
   
    test.startTest();
   
    insert t;
   
    test.stopTest();
}
}


when i am deploy to server its throwing error like Invalid field Email_Bcc__c for SObject Task


i tried but i can't able to find out the error.how to solve it