A common herbicide for controlling invasive aquatic plants is being used in Lake Zoar in Newtown, Monroe and Oxford this week.   Notices have been posted in the areas where the applications are planned for tomorrow, with a rain date of Thursday.  Adjacent lake users and residents were notified that Diquat herbicide and Copper Sulfate will be used to control Eurasian watermilfoil and curlyleaf pondweed.  The DEEP restrictions on water use in those areas include for drinking purposes and irrigation for three days, and for livestock consumption for one day.  There are no restrictions on swimming, boating, and fishing.