Mosquito Control Spray. FYI Pending weather conditions, Chatham County Mosquito Control’s aircraft will treat areas east of the Wilmington River, including Isle of Armstrong, Oatland Island, Whitemarsh Island, Talahi Island, Wilmington Island, and Tybee Island before sunset on Wednesday, August 11. Residents can expect to see low-flying yellow aircraft. If you have any questions, please call 912-790-2540.