Why Wasps Are Good for Gardeners

, written by gb flag

Wasp on raspberry fruit

My brother once had a wasp's nest in the unlikely location of the extractor unit in his bathroom. 'I don't mind bees,' he complained. 'They pollinate crops; they've got a use. But wasps are just pests. What's the point of wasps?'

It's a common sentiment; usually uttered just after being stung, discovering a nest in an inconvenient place, or while competing with them for jam sandwiches and sweet drinks! I can't deny that wasps have their downsides, but fortunately for us gardeners they have important benefits too.

Wasps as Pollinators

My brother was not entirely correct when he assumed that wasps don't pollinate crops. Their smooth bodies don't collect pollen for transferring between flowers as well as those of hairy bees, but they are attracted to nectar and do carry out a useful amount of pollination in the garden.

“Wasps
Wasps carry out a useful amount of pollination in the garden

One type of wasp is incredibly specialised at pollination. Fig wasps, as you can probably guess from their name, pollinate fig trees. They are in fact the only pollinator of fig trees. One cannot exist without the other, so their importance to the fig growing industry and lovers of figs cannot be overstated!

The tiny female fig wasp pushes into the figs through a tiny hole - so small that her wings are torn off in the process. If the fig is male, she'll lay her eggs and the larvae will then make their way out when they're ready. If, however, the fig (which is actually an inverted flower, not a true fruit) is female, there isn't enough space for her to lay eggs. She is trapped inside, dies there and is digested by the fig - but not before pollinating it. Nature is cruel but ingenious!

Free Pest Control

The presence of social wasps such as paper wasps at barbecues and picnics, and their habit of building nests in sheds, house eaves and other inconvenient places is undoubtedly annoying (and occasionally painful). Yet there is a very compelling reason why it's worth tolerating them if at all possible: the prodigious appetites of their carnivorous offspring.

Wasps spend their summers seeking out aphids, flies, caterpillars and other bugs - many of them pests - to feed to their larvae. Hundreds or even thousands of larvae can be produced each year in a paper wasp hive, so they get through a lot of bugs!

“Braconid
Braconid wasps lay their eggs on tomato hornworms and other caterpillars

As well as the familiar black-and-yellow social wasps, there are other kinds of wasp that provide essential pest control. Many kinds of solitary wasp will also hunt and kill insects for their larvae to feed on. Others are parasitic, such as the minuscule wasp Encarsia formosa which has long been used to manage whitefly in greenhouses. In the US, braconid wasps lay their eggs on tomato hornworms and other caterpillars, which are then eaten from the inside out as the larvae develop. Grisly but effective.

Wasp Imitators

The black and yellow striped pattern of many social wasps is such an effective warning that other bugs successfully use the same colour combination to persuade predators to keep their distance. Some species of hoverfly (also known as syrphid flies) are often mistaken for paper wasps or yellowjackets, but there are some clear differences to help you tell which is which.

You can quickly and easily recognise a hoverfly by its shape and its eyes. They lack the very pinched waist of the wasp, while their large eyes are like wraparound sunglasses. Wasps on the other hand have smaller eyes that are on the sides of their head. Hoverflies will often hover almost motionless in the air in front of flowers. They are fantastic pollinators and pest predators themselves.

Honeybees are sometimes mistaken for wasps too, but honeybees are furrier, duller in colour and fly with their legs tucked away out of sight.

“Hoverfly
Hoverflies mimic wasp coloration to deter predators

How to Live Peacefully with Wasps

Despite their reputation, wasps are not unduly aggressive. However, waving your arms, swatting at them and trying to knock down their nest can fairly be interpreted by them as antagonistic - and they are not slow to defend themselves! Wasp venom contains a pheromone which signals to other wasps that they are under attack and need backup, so if you're stung once then other nearby wasps may join the fight.

The best way to avoid being stung is to treat wasps with respect. Move calmly and deliberately, give them space to go about their business, and they will ignore you. If you do get stung, wash the area with soap and water and apply an ice-pack. You might want to take an anti-histamine tablet or use an anti-histamine lotion. If you are stung and have an extreme reaction - check the symptoms of anaphylaxis here - get to A&E fast.

Wasps' nests are problematic, especially if they are in houses or sheds. Most people don't want to have wasps living alongside them, but wasps are so beneficial for their pest control capabilities that, if you can possibly leave the nest alone, it is advisable to do so. After all, wasps are so common that even if you can't see a nest, it's probable there's one nearby.

“Wasp
Wasps are attracted to sugary substances in late summer and autumn

Wasps are more strongly attracted to sugary substances in late summer. This is because their larvae convert the protein from the insects they're fed into a sweet liquid which the worker wasps drink. In late summer, when the larvae have all grown up, the adult wasps need to look elsewhere for fuel and this is when humans and wasps most often come into conflict.

Winter freezes will kill off the workers and the old queen. The new queen will survive the winter and move on to start a new hive elsewhere, so if you want to move the nest in winter, you can safely do so.

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Comments

 
"Thanks a bunch ! I didn't know that about wasps at all . Wasps have recently built a small nest near my flower garden and didn't know if I should destroy it or least there . I'm not allergic to bee stings so for me , leaving it alone is best ."
Vanessa Dargain on Sunday 7 July 2019
"Good call. I find that they just ignore me as I go about my gardening. Give them space and they have no reason to bother you."
Ann Marie Hendry on Friday 12 July 2019
"I really appreciated this info. Paper wasps built a nest on my patio summer 2018 and since I've never had trouble e with that kind of wasp I just let them be. By fall I realized I'd had almost no flies in my yard. When summer 2019 came around I decided to let them be again. We all get along fine. This fall, I realized I don't have any house sparrows crowding my patio lubricants, whereas every single fall since I've lived here (19 years), my patio has been swarming with messy, loud sparrows eating the berries. I've realized there were very few sparrows around all year. My neighbors do have tons of sparrows in their yard right now. Not one in mine. Do you think wasps keep sparrows away? "
Andrea on Sunday 17 November 2019
"Hi Andrea. I've never heard of wasps terrorizing birds! I certainly haven't noticed a drop-off in birds in my own garden when wasp numbers are high. Perhaps your neighbors are providing the sparrows with a more tempting food source?"
Ann Marie Hendry on Tuesday 19 November 2019
"We have a wraparound deck on our house. We have an outside covered plug unit next to the enter and exit screen door of which hornets, as I have always known them to be, have taken occupancy for two or three years now. This year the house siding and all fascia boards needed replacing. With the hornet house attached to the siding, we had no choice but to remove it very carefully, and lower it to the floor of the deck. With all the sawing and work I had to move it at least five more times several feet away from the workers. Each time the hornets could not find the nest, were confused, and buzzed around the old site. I imagine they found it because several days later when I carefully opened the lid to the plug, they were all hovered over the nest. It is true they do not bother you if not provoked. We eat out there, enjoy company, or relax and they never annoy us. But tonight I had to move it again, they were annoyed and I got bit by one of our boarders. I am not allergic thank goodness but I worry that all this moving is making the hornets unable to find their home being unable to continue feeding their nest. Now, I say hornets...they are indicated as wasps! Ever since my youth when I got stung by a very black hornet, I have always known hornets to have black bodies with a very short waist. All the articles I have read indicate with pictures hornets have striped yellow and black bodies, no fur. These are completely black, so what are they? I cannot find any picture of black body bees, hornets solid black. I did see them early spring chewing on old wood items I assume to prepare a paper nest. But the nest they build is only a honeycomb nest. I’m worried about the future of these bees and I don’t want to destroy them. Can you give me some insight about their finding the nest I move and the black color please."
Claire Lemire on Saturday 1 August 2020
"Hi Claire, hornets are usually striped so I'm not sure what type of wasp or hornet you have - possibly bald faced hornets? It would be best to avoid moving their nest if possible because it will make it harder for them to find, and, as you found, will also annoy them!"
Ann Marie Hendry on Wednesday 5 August 2020
"An excellent article to stumble across! My roommate has an irrational fear of wasps, so we recently sprayed poison on a nest in the roof eave above the kitchen door. 30-40 wasps were killed by our human wrath! I have also noticed wasps in an oregano planter, but now that I know they are laying their eggs in caterpillars and eating the aphids, I am going to leave them alone (and use this article to educate my roommate). Next year I will wait until the weather gets cooler and move the inactive nest away from the house. Thanks for the info!"
Michael Flannigan on Thursday 6 August 2020
"Glad you found this useful Michael!"
Ann Marie Hendry on Friday 7 August 2020

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