What do wasps do?

In early spring and summer wasps munch a huge amount of garden pests. From caterpillars to aphids the Queen wasp and her early brood are voracious and important garden predators.

I admit I’m not a huge fan of wasps, especially in late summer when they can become a right pest around summer drinks, ripening fruit and the compost heap. But since I’ve learned a bit more about their life cycle I’m a bit more tolerant. I have been stung by the rascals and that’s not nice, but like all creatures, they have an important role to play in the ecosystem and you might not realise, but wasps are also important pollinators.

The wasps that bother us in the garden have a similar life-cycle to the bumblebees, these are the social wasps, so called because they live in a community. But there are about seven thousand different species of wasps in the UK, many of these are regarded as solitary wasps, including the parasitic wasps we use to control greenhouse whitefly, digger wasps and cuckoo wasps.

The Queen wasps of the social species hatch out in mid to late summer, mate and then hibernate until spring, when they build a fascinating, intricate papery nest. You might see or hear them gnawing at garden fences, timber furniture or other timber. They harvest the fibres and process it into a light paper mache with which to make a nest.

Wasps rarely return to a former nest and a nest usually dies out in autumn or winter when the workers and males die off and the Queens vacate the nest to overwinter somewhere safe, warm and dry.

Almost every spring I find one or more Queen wasps in my greenhouse. Early in the season they work as aphid munchers, working on the sappy green stems that are host to the greenfly that have also overwintered in the glasshouse. They rarely nest inside, but once they get outside they find a suitable place to build their papery castle and start laying eggs.

The Queen wasp has to work very very hard in her first few weeks after emerging and that’s when she does the most good in the garden. She needs protein to feed her young grubs. When fed, the larvae produce a sweet substance that the Queen and any worker wasps feeding the grubs get as a sort of bonus. This is really key to what happens in mid-summer, all through spring and early summer this exchange goes on as more and more new wasps are reared to raise the next batch of babies. The foraging workers bring back protein in the form of garden pests. They feed on the  nectar from nectar bearing plants to sustain their frenetic activity.

But when the brood rearing slows, the exchange all but stops. The workers still crave sweetness and go in search of anything that can replace the sweet treats they are missing. This is when they become a nuisance to you and me and can become aggressive. At this point I would say that they could be considered to be a foe, but unless you have a nest close to your home or where children play, they will be gone by the autumn and rarely use the same nest site twice. So live and let live if you possibly can.

Wasps are territorial so if a new Queen visits where an old empty nest still exists it can be enough to force her to look elsewhere for a nest site. So it can be a good idea to leave an old papery nest where it is.

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