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Why Bees Are Aggressive in Late Summer and Fall | Almanac.com

Why Bees Are Aggressive in Late Summer and Fall

Yellowjacket on Leaf
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An Eastern Yellowjacket is resting on a green leaf. Taylor Creek Park, Toronto, Ontario, Canada.

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Paul Reeves Photography
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Wasps, yellow jackets, fire ants, and the stinging insects of late summer

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By late summer, stinging insects including bees such as ground wasps and yellowjackets, and those nasty fire ants are especially aggressive outdoors and in the garden. Why does this happen and what can we do about the problem? 

Why Stinging Insects Are More Aggressive 

You’ll see much more activity from stinging insects from August through October. Why?

  1. They’ve have had all summer to build up their populations. This means their nests are bigger and many new babies have been born. 
  2. At the same time, winter is around the corner and insects such as bees need to keep their queen alive so they’re on a mission to find and store food for her.
  3. Compounding this, there tend to be less flowers and nectar towards the end of summer and fall. Since these insects are in search of carbs and sugar, they may land on your cola can!

See our article on wasps, bees,and hornets to tell the difference between these stingers.

Yellowjackets can be aggressive, especially as summer winds down and their days are numbered.

Ground Wasps

My friend Laura hobbled in to work last week, her foot and ankle swollen and red. An attack by ground wasps was the cause. She was aware of the nest near her strawberry patch and was working a few feet away, cutting back wayward shrubs when the bees struck. Yelling, running, waving her arms—all actions that further inflamed them—she was chased all the way into the house, bees stinging her as they went. Days later her foot is still swollen and sore.

Ground wasps are solitary bees more interested in catching prey like this spider to feed their young rather than attacking people. They only sting when they feel threatened. Credit: Y. Shadrakhov

Yellowjackets

We all are aware of yellowjackets and when we see bees flying in and out of a 1 to 2 inch wide hole in the ground, we know to give it a wide berth. However sometimes they go unnoticed until you run the lawn mower over their nest and their “welcome committee” flies out to greet you. Unlike honeybees, each yellowjacket can sting you more than once, making an attack more dangerous, especially if you are allergic to their venom. They feed on a wide variety of insects but also have a sweet tooth and will visit flowers and your picnic table if something sugary is on the menu. 

Learn more about how to prevent and treat yellowjacket stings.

This yellowjacket nest above is easy to spot but some, like the one below, are hidden by vegetation. Credit: Pacotoscano
Southern Yellow Jackets (Vespula squamosa) at the entrance of nest hole in ground. Credit: Sean McVey

Ground Wasps

Ground wasps are usually not aggressive and live a solitary life. They are beneficial pollinators and eat garden pests. Sometimes they band together, forming a colony of nests in the same area. If they feel threatened they will sting. Like the yellowjackets they are drawn to sweets and often nest near nectar-rich flowers, fruit trees, berry bushes, and in Laura’s case, strawberries. Like yellowjackets, vibrations rile them up so don’t mow or run a chainsaw near the nest. 

The nest for a solitary bee has a smaller opening and can be hard to see unless you spot bees flying in and out. 
Credit: S.Melange/SS

If you encounter these ground-dwellers, the list of don’ts include running, yelling, waving your arms, and swatting at them but I don’t know of anyone who could calmly and quietly walk away while getting stung! 

How to Get Rid of a Nest

If you need to get rid of a yellowjacket or ground wasp nest that is located in a bad location near your house or where children play there are several ways to do it.

  1. First make sure to wait until evening when all the bees have returned to the nest for the night. They are less active, less likely to sting, and will all be in one spot to make eradicating all of them easier. Wear protective clothing, goggles, and face mask, especially if working with dusty products such as diatomaceous earth (DE.)
  2. Dust in and around the nest with the DE. It is scratchy and will pierce their exoskeletons causing them to dehydrate and die. It is not immediate and may take a few days to work and a few more applications, especially after it has rained. To make it even more effective add a little bit of pyrethrum powder to the DE
  3. Drown them by flooding the nest with water. Add a bit of dish soap to the water to keep them from flying out, then cover the hole to keep them contained. Some folks use boiling water just to make sure they are killed.

Don’t feel compelled to kill these bees unless it is necessary. Perhaps you can’t get into your home. Both types of bees will be killed by freezing weather anyway. Yellowjacket queens will winter over but they don’t return to last season’s nest and the larvae and pupae of solitary wasps survive the winter to start a new colony but they don’t reuse the previous year’s nest either.

Fire Ants

Fire ants are very aggressive and a major problem in the South. The opening to their nest is a mound of sand or clay soil and if it is disturbed they will sting to defend it. They are constantly raising queens so killing the queens is important to eradicate the whole colony.

Fire ants are known for swarming anyone they perceive as a threat and stinging the heck out them! Credit: AOKSANG/SS

Record heat and dry weather in the South have caused the ants to dig deeper nests making them harder to reach. The nests can contain as many as 200,000 ants, be as deep as ten feet under ground, and can have tunnels that extend up to 30 long. The ants will become more active as cooler fall weather sets in and they will nest closer to the surface. 

A fire ant mound can appear overnight. Unlike regular anthills, they don’t have a clear opening in the center. Credit: RGG/SS

There are many home remedies for fire ants but most don’t kill the queen so she just moves to another spot and starts a new colony. Folks at Texas A&M recommend these methods:

  1. Pouring 3 gallons of extremely hot water on a fire ant mound kills about 60% of the ants. Adding soap to the water increases the success rate up to 70%. This treatment also will kill surrounding grass and plants and you need to be careful not to burn yourself! After rain, when new mounds appear they should be shallow enough for boiling water to reach the queen.
  2. Another home remedy being evaluated and showing some promise is to flood the ant mound with a mixture of dishwashing liquid and citrus oil.
  3. The Texas Two-Step method advises homeowners to treat the mounds when they appear and also treat the entire lawn with long-lasting insecticides to prevent new fire ants from moving in. Some OMRI-rated insecticides have been shown to be effective.

Even if the colony is only weakened, it may give native ants a chance to keep populations of invasive fire ants in check. They are natural enemies and will kill new queens starting new nests.

If you have some efficient, effective remedies to share, please do tell us your tips below!

About The Author

Robin Sweetser

Robin has been a contributor to The Old Farmer’s Almanac and the All-Seasons Garden Guide for many years. Read More from Robin Sweetser

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