There are mozzies on Tenerife but I haven't seen any at this time of year. Even when they're about, there's not enough to be a problem. Like trasjohno says, nothing like Greece. Well I get bitten every year and have 4 bites on my face at the moment despite a plug in in the bedroom.
Will I get bitten in Tenerife?
In fact, the risk of contracting a mosquito-borne disease in Tenerife or the other Canary Islands is generally low.