For past several years, leaf eating bees have drilled in and nested in exterior porch beam ends of my house. Any appropriate method to discourage them from visiting next year?
If you are concerned that the leaf cutter bees are damaging your house, there isn't much evidence (that I can find) that the burrows will be expanded from year to year. Rather, they seem to prefer burrows of a certain size and return to them because they're located close to a reliable food and pollen source. Some species are particularly fond of roses. Do you grow these? Like mason bees, leaf cutter bees are excellent pollinators, particularly for early flowering crops. Now that honey bee populations have been seriously reduced by varroa mite, those of us who grow fruits and vegetables need all of the pollinators we can get. And like mason bees, leaf cutters can sting, but they rarely do unless harassed. My recommendation is to plug the existing holes, then provide them with an alternative nesting area. As far as I can ascertain from a cursory search for information, leafcutters prefer slightly smaller entrance holes than mason bees (i.e., less than the mason's optimal 5/16" diameter). Nesting boards or blocks (which are available commercially) can be hung from fences or trees in the sun away from the house. For a really cool picture of a leaf cutter bee with a bit of leaf in tow, see the following link posted by David Jones, from Hampshire, UK.
