A dozen angry wasps swarming at you when you remove the dead front cover of an outdoor electrical panel can ruin a home inspector’s day. They might also attack a homeowner that gets too close to the box. Wasps prefer exterior electrical panels to build their nests because they are warm, due the small amount of heat generated by some of the breakers, and the enclosure provides protection against predators. Any small opening will allow them access, but it is most often an open knockout hole at the bottom of the box, like the example shown at right, that gives them easy entry.

     Any wasp species in a panel is bad, but the mud dauber wasp also creates a second problem when they occupy the box over several years and gradually fill it with their mud nests. This may cause a short circuit in the panel, but the nests are more likely to interfere with the required dispersal of the heat generated by the breakers and wiring into the surrounding air.

     We have seen instructions online for spraying insecticide in the panel or setting cotton balls soaked with insecticide in the bottom of the box. But the simplest, permanent solution is to simply close up any access holes to the panel.

    If your panel has mud dauber nests inside, and you are not familiar with the risks of poking around inside a panel and how to do it safely to avoid electrocution, we recommend that you have an electrician both clean out the nests and plug any entry holes. 

• • • • • • • • • • • • • • • • • • • • • • • •     Also see What does a termite mud tube look like? and What's causing those holes in the fascia? and Do carpenter ants cause structural damage to houses in Florida? and What does roach poop (fecal pellets) look like? and Does a homebuyer’s pest inspection include rats, mice, bedbugs, roaches, and ants?

    Visit our TERMITES, WOOD ROT AND PESTS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.