The warm April climate provided a continuation of the year to dates ideal environment for wasp populations. The low numbers of wasps last year means there will be less competition for good nesting spots and for food and building materials, so there is a distinct likelihood of a very waspy year in 2009.
To repeat last months warning about nests under construction, if you see regular wasp activity involving a large wasp please be aware that this is probably a Queen looking for, or just having found, a suitable location for a nest.
Be especially vigilant if you have seen a large wasp indoors, check your attic, roof void, or loft space to see if there is a nest being built hidden away in the nooks and crannies. Wasps like older houses best as there are more ways to enter and exit, and more sites where they can hide themselves away, but we do hear of nests built in wall cavities and roof voids of modern homes too.
Check your garages and sheds also. If you do find a nest be very careful indeed even at this early stage. We would always advise employing a professional pest controller.