Wasps: Aggressive But Beneficial

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Social wasps (the ones that live in colonies) are usually striped yellow and black or white and black, a visual warning that says “stay away, I’m aggressive”.

If you get the impression you’re seeing more social wasps (yellow jackets, paper wasps, and hornets) in your garden at this time of year, you’re absolutely right. The population of wasps in a colony keeps increasing throughout the summer and reaches its peak in the fall. But there’s no need to panic: the population will drop to zero soon enough, because the whole colony will collapse with the first hard frost.

What many gardeners don’t understand is that a wasp nest is not permanent, but rather an annual structure. Each spring, with the return of warmer temperatures, a young queen, who had overwintered in the ground or under the bark of a tree, selects a site and begins to build a new nest. She starts to lay eggs and to care for the young herself. But as worker wasps mature, they take her place, enlarging the nest, hunting for food, and feeding the larvae while the queen specializes in laying eggs. At the end of the season, one or more new queens leave the nest, mate with a male wasp, and look for a place to spend the winter. The following spring, the cycle begins again. The old nest will be abandoned and no longer used.

What to Do When You Find a Wasp Nest?

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There are many kinds of wasp nests, some covered in paper like here, but others are open to the air while others are underground.

The best (and safest) thing to do when you spot a wasp nest is… nothing, unless the nest is in a place where it’s a risk to humans, pets, or farm animals.

You see, wasps are actually beneficial insects. They are essentially predators and consume a lot of insect pests: aphids, caterpillars, beetles, whiteflies, etc. They also collect and remove dead insects. Plus, they pollinate many plants. Recently it was discovered that it’s social wasps that carry yeast spores to grapes that eventually cause them to ferment: without wasps, there would be no wine! If it weren’t for their aggressive nature, wasps would certainly be among the gardener’s best friends!

Sadly for the reputation of social wasps, though, they are quite aggressive and will sting humans who disturb them, especially when you approach their nests. And since, unlike bees, each wasp can sting more than once, you won’t want to accidentally mow down a wasp nest with your lawnmower!

Read Friend or Foe: A Closer Look at Insects if you’re not sure how to tell a wasp from a bee.

When Wasps Disturb Your Meal

Wasps like human food, especially sugary food, so often come investigate when we eat outdoors… especially in the fall when they are then particularly numerous. Since many people are afraid of wasps, that can make for a stressful snack!

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Put out a plate of sweet fruit for wasps and they’ll let you eat in peace.

The easiest thing to do in such a case is to attract the wasps elsewhere while you eat. Place a small plate of sweet fruit outdoors about 15 to 20 minutes before the meal… and at least 10 feet (3 m) from your table. Wasps will discover your “wasp buffet” first and will be too busy with it to bother you.

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Commercial wasp trap.

There are also commercial wasp traps containing a sugary liquid that also can be installed temporarily, again 15 to 20 minutes before a meal at a respectable distance from your table. They are so designed that workers wasps enter the trap looking for a meal, then can’t get out and eventually die. Don’t leave that kind of trap out permanently, though, as the wasps end up dead and, since wasps really are actually more beneficial than harmful, should be left alive where possible.

When the Nest is in the Wrong Place

When you discover a wasp nest on your lot (and it can be, among others, underground, in a hole in a wall, in a woodpile or compost bin, inside a tree trunk, exposed on a branch, attached to an overhanging roof, in a garage or shed, etc.), think first if it really is going to be bothering anybody. If it’s not located in a spot where people are likely to disturb the nest, you probably won’t have to intervene. It may be useful to mark the location with orange safety tape and put out a sign warning visitors of the location.

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If a wasp nest is too close for comfort, consider removing it.

If the nest is in a spot where humans or pets are likely to disturb and alarm the wasps, on the other hand, don’t hesitate to remove or destroy it. After all, yellow jackets, hornets, and paper wasps are not threatened insects and death of one colony is not a tragedy. Note that nests are easiest to remove in the spring when there are not many worker wasps.

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Wasp insecti-cide.

If the nest is visible, there are commercial insecticides that you can spray into the nest. Do so at night or very early morning when the wasps are asleep. You may need to repeat the treatment more than once. When you see no more wasps leaving the nest during the day, you’ll know the colony has been eliminated.

In many cases, though, the nuisance wasp nest is simply not accessible. That can be the case when it’s inside a wall. That’s the kind of situation where you need to call in an exterminator.

Note that the wasp traps described above (the kind the wasps enter and can’t get out of) will not control wasp nests. All they do is trap worker wasps, forcing the queen to lay even more eggs to replace them. To destroy a wasp nest and therefore remove all risks to humans, you have to eliminate the queen, not the workers.

Can You Keep Wasps from Nesting?

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True wasp nest built right on an artificial nest. Fake nests simply don’t work as repellents. Photo: Monique Lalonde.

Nope. At best you can chase the queen away if you catch her starting a nest. Those artificial wasp nests that are supposed to chase away wasps before they settle in, whether homemade or commercial, simply don’t work. You’ll find more information on that subject here: Wasp Repellants: Do They Really Work?

Live and Let Live

When wasp nests threaten neither humans nor their animal friends, which is the case in the vast majority of situations, the best thing to do is develop a “live and let live” attitude. And that’s doubly true in the fall, when the wasp colony has only a few weeks more to live anyway!20160509A

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