Mid summer the Via de la Plata is bone dry so there should be no problem with moquitos.
Mid summer on the VdlP is blazing hot and I would say that unless you have to go at that time it is not wise. We had a number of very uncomfortable days and the heat after about 13.00 in the South can make it difficult to cover much distance. It is not so bad as you get towards the north, by Zamora you are not far off the same latitude as the Camino Frances.
well, thank you for your kind advice and wishes. of course, as in anything, we are often unable due to constraints of work, schools, etc to do things at the the time we would prefer. thus, i am leaving seville on june 14 accompanied by an overweight 21 year old daughter and a delinquent but fit 17 year old daughter: talk about brat school. we shall see who prevails. or, as my wife says, who somes home in a box first.
well, writing this from valladolid bus station waiting for ryanair kite home. there were a lot of mosquitoes. the route is a long series of dams, huge rivers, canals, irrigation systems...a lot of stagnant water lying around even in summer. take repellent. otherwise it was a fairly easy hike. my 17 year old got a chronic dose of diarrhea around salamanca and called it a day. my elder girl was doing great but took a tumble near rio negro and broke her foot, so was similarly casevaced home. which just left yours truly to complete the galician phase. great fun.