1.Logging into Plesk
2.Click on the Websites & Domains
3.Click on Show Advanced Operations(a small gray link in the middle of the page), if the advanced options are not already shown.
4.Click on Scheduled Tasks.
5.Select the appropriate system user.
6.Check the box next to the Scheduled Task you want to remove.
7.Click on the Remove
8.It will load a new page and ask if you really want to delete it. Check the Confirm Removal box and click on the OK
9.You will be taken back to the Scheduled Tasks screen and it should say: “Information: Scheduled tasks were removed.”