Many a home and garden owner is concerned about the constantly appearing sand mounds in the joints between the paving stones. The active phenomenon, which occurs again and again, points to animal activities. If flying insects swarm out of the spots, it is most likely digger wasps.
The spinning top wasp stays true to its location
Wasps nesting under the pavement
Anyone who continuously observes sand joint accumulations at one point in the pavement of their driveway or courtyard is often dealing with ants. But these are easy to identify by their busy crawling in and out. If this clear indication of the culprit is missing, they may be less conspicuous subterranean inhabitants. If you look closely, you may be able to spot flying insects flying in and out - then the burrow under the pavement most likely belongs to a digger wasp colony.
Digger wasps belong to the group of wasps commonly known as earth wasps - because they build their nests underground. If you're unlucky, they will also choose the sandy bottom under your pavement and dig numerous entrances to their breeding grounds. The digger wasps include, for example, the common sand wasp, the spinning top wasp or the beewolf.
Nesting under the pavement can, of course, cause damage. Because the sand bed underneath is undermined and can sag in places.
interim balance:
- Constant accumulations of sand in the joints between paving stones can indicate digger wasps
- Digger wasps include common sand wasp, spinning top wasp and beewolf
- Undercutting of the pavement can lead to sagging
Long-term measures needed
The problem with gyroscope wasps (which look very similar to bees) is their location loyalty. This means they like to nest in the same spot year after year, unlike other ground wasp species like the hornet, common wasp, or German wasp. That's why it's not enough to just open the pavement in autumn when the digger wasp nest is empty and level the sand base again. It should also be consolidated and compacted with a slightly damp substrate, because digger wasps only like dry, sandy soil for nesting.
If you can somehow live with the digger wasps and a pavement that might be a bit crooked in one place, you should do so. Because even if digger wasps are not protected, fighting them is not advisable given their beneficial properties and their contribution to the ecological balance in the garden.