David A. Lawson, director of the Norfolk County Mosquito Control Program, will hold an informational meeting on the changes to the ultra-low-volume aerosol spraying program Tuesday at 7 p.m. at the Chenery Meeting Room in the Medfield Town House . This meeting will be hosted by the Medfield Board of Health. Lawson will explain why the state is changing its schedule to spray in the evenings rather than in the mornings. Each year, beginning around Memorial Day, the mosquito control district sprays in Medfield on Tuesdays throughout the mosquito season. Residents can call 781-762-3681 or fill out an online service request format www.norfolkcountymosquito.org to be sure their streets are sprayed. Last year, mosquitoes in several towns west of Boston were confirmed to carry EEE and West Nile virus. As a result, many area towns canceled outdoor activities. For more information, contact the Medfield Board of Health at 508-906-3006.