Residents having a problem with mosquitoes can call the Norfolk County Mosquito Control District and request that their property be sprayed. Spraying is done only upon request, according to Elizabeth Donnell, administrative assistant at the regional agency. Donnell said the district has scheduled spraying in Dover on Mondays throughout the summer, and that a separate request must be made each time spraying is needed. Spraying is done between 2 and 6 a.m., and requires dry conditions with a temperature above 55 degrees, according to Donnell. A variety of products are used to kill adult mosquitoes and larvae to control the spread of diseases such as West Nile virus and Eastern equine encephalitis, according to the control district’s website, www.norfolkcountymosquito.org, which gives detailed descriptions and label information about the materials used. Spraying can be requested online at the website, or by calling 781-762-3681.