Grass carrying wasps, also known by their scientific name Isodontia, are a common nuisance pest that can build nests around homes. While they are generally harmless, their nests made of dried grass can be an eyesore and a hassle to clean up repeatedly. If you’ve discovered grass carrying wasp nests around windows, door frames, vents or other crevices around your home, here are some tips on how to get rid of them and prevent them from coming back.
Understanding Grass Carrying Wasps
Grass carrying wasps get their name from the female’s behavior of carrying blades of grass to construct nests. There are around 5-6 different species found in North America most being black or reddish brown in color and 12-20mm in length.
The wasp’s lifecycle begins in early summer when the adults emerge from cocoons and the females begin seeking out nesting sites. They prefer tight spaces like window tracks, folded patio umbrellas abandoned carpenter bee nests, holes in soil banks or rocks pitchers of pitcher plants, and bee hotels.
Once a suitable cavity is found, the female wasp will begin packing it tightly with dried grass, using chewed up saliva to stick the grass together. She lays a single egg within each cell and provisions it with captured and paralyzed katydids, tree crickets or other orthopterans for her young to feed on once they hatch.
The larvae are yellowish grubs with no legs that grow eating the captured insects. They eventually form an oval, papery brown cocoon, inside which they pupate before emerging as adult wasps in early summer to restart the cycle.
Why Get Rid of Grass Carrying Wasp Nests?
While grass carrying wasps are not aggressive and rarely sting, their nests can be a nuisance:
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They frequently build nests in window tracks, clogging them up and preventing windows from properly opening and closing.
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Repeatedly cleaning out dried grass from the same areas over and over can be annoying.
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The larvae feeding on captured insects can leave behind cricket carcasses and other insect parts.
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Abandoned nests with dead larvae or cocoons look unsightly.
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Over time, build up of nesting materials in certain areas could promote rot or moisture damage.
For these reasons, it’s often desirable to remove grass carrying wasp nests and deter the wasps from repeatedly nesting in the same areas around your home.
How to Get Rid of Grass Carrying Wasp Nests
Getting rid of existing grass carrying wasp nests is straightforward. Here are some tips:
Manual Removal
Simply use a stiff brush or old toothbrush to scrub out any dried grass and nesting material from window tracks or other areas wasps have been nesting. Look for larvae, cocoons or cricket carcasses and remove any you find. Vacuuming the areas afterward is also a good idea to pick up any remaining debris or grass pieces.
Seal Up Nesting Sites
Once you’ve cleared out any existing nests, deter future nesting by sealing cracks and gaps so the wasps can’t rebuild in the same areas. Use weatherstripping, caulk, insulation or other materials to close up openings around windows, doors, vents and other crevices. Plugging holes in outdoor surfaces like soil banks, rocks, or block walls can also help reduce nesting spots.
Remove Food and Water Sources
Make your home less attractive to grass carrying wasps by eliminating outdoor food and water sources. Fix leaky faucets, clean up fallen fruit from trees, and remove bird baths or pet dishes that aren’t being actively used. Installing fine mesh covers over rain barrels or buckets can allow you to keep water outside while preventing wasp access.
Use Repellents
Insect repellents made with mint, lemongrass or citronella oils can help deter grass carrying wasps. Apply these oils around doors, windowsills and other common entry points. Be aware repellents may need reapplication after heavy rain.
Call a Pest Control Professional
For severe infestations, bringing in a licensed pest control professional may be warranted. They have access to long-lasting synthetic repellents and insecticides as well as foam/sealant products that can provide a more permanent seal in problem nesting areas.
Prevention Tips
Preventing grass carrying wasps from nesting in the first place is ideal. Here are some tips:
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Keep screens in windows and doors in good repair, with no gaps or holes.
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Check window tracks and window sills frequently and clean out any nest starts before they are completed.
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Reduce clutter around the home that creates crevices for nesting, like piles of debris, deep mulch beds, unused flower pots, etc.
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Clean out bee houses or nest boxes intended for solitary bees which wasps may try to occupy.
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Seal any openings in soffits, vents, attic fans or cracks in siding.
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Caulk and seal wall cracks, holes or crevices on outdoor surfaces.
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Keep ground cover trimmed back from the foundation. Prune any shrubs or bushes touching walls.
By taking some time to proactively seal, clean and organize problem areas around your home, you can discourage grass carrying wasps and enjoy your outdoor space pest-free. Monitor for any new nests and promptly remove them before wasps have a chance to complete them. With vigilant prevention and removal of nests, you can stop grass carrying wasps from becoming a perennial nuisance around your home.
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- 1 Learn about ground digger wasps. Ground-digger wasps (GDWs) are very large (slightly larger than a green hornet) passive-aggressive wasps that “build” their nests in dry, unfertilized earth. They are typically large and black-bodied with yellow stripes on their back-end. When fully grown, they measure about one and a half inches (or more) in length with about a one and a quarter-inch wide wingspan.[1]
- 2 Know the signs of ground digger wasps infesting your lawn or garden space.[2] Youll know youve got ground-digger wasp nests when you see small granular mounds of dirt piled up anywhere from two-to-five inches in height. At the base of the mound of granular dirt will be a finger-sized hole with a “path” of dirt leading out from it.
- The nests will be sporadically built throughout your lawn or garden, but will typically be in the driest areas and/or under longer grass/weeds or under growing flowers. GDWs do not like, but can live in, moist soil.
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- 3 Find out the local life cycle. In the Northeast US, the life-cycle of a ground-digger wasp is about one month beginning in mid-July and ending around mid-to-late August (depending on where you live, their life-cycle may start earlier or later). They go from young adults buzzing about play-attacking with each other, to full-size adults in about two-to-three weeks.[3]
- 4 Its important to understand that they only sting when attacked. While very menacing looking, they are passive stingers, meaning only if very threatened will they attack and sting.[4] Youd practically have to start digging into their nests while theyre flying about for one to come at you and sting you (so, dont do that!). Otherwise, they tend to buzz about to check you out and to scare you away and they probably will the first time you encounter them. Know that theyd rather get on with their business of killing cicadas up in the trees than sting you.[5]
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- 1 While the method suggested here basically kills the wasps in their nests, there is no other (safe- for-nearby-pets) way to eradicate them. It is probable that you will still get nests from year-to-year, but only one, maybe two. The trick is to kill all of them while theyre in their nests so their babies will not come back to the same place they were born.
- 2 Get the supplies. To eradicate an infestation of ground-digger wasps (GDWs), purchase from your local party store and supermarket, the following items: a) a large bag of white plastic knives, and b) up to three or four jug gallons of regular or lemon ammonia.
- 3 During the day, when the wasps are up hunting for cicadas in the trees, mark each nest you find with one of the plastic knives pushed into the ground as close to the hole of the nest as possible (without disturbing the hole). Leave enough of the knife sticking out of the ground so you can see it.
- 4 After 10:30 or 11pm, (later is better), that evening, using a flashlight, seek out the knives you placed and carefully pour about two-to-three cups of ammonia into each of the holes. At this time the wasps are probably nesting/sleeping, so youll be catching them while in the nest. (You can stretch out the amount of ammonia by mixing a one-to-one ratio of water to ammonia. The diluted strength will still be enough to kill them.) Do not remove the knives.
- 5 The next day, repeat the process on any new nests that you find in the ground. Youll know the new nests from the old ones because youll still have the knives in place from the night before. Once youve identified the new nests, remove the old knives.You may have to continually repeat the process depending on the original amount of wasps. Or you could hit the wasps with tennis rackets, knocking them to the ground then step on them.
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- 1 Try this option if youre happy to let natures creatures follow their natural cycles without freaking. First, this is a natural cycle and is part of natures own way of dealing with a ballooning population of cicadas. Second, you can watch these interesting animals do their thing from the comfort of your own yard; theyre raising their families just as every other natural creature tries to do.[6] The way to cope if you leave them alone is very simple:[7]
- Do not aggravate them. Do not push or poke them, do not walk on them and do not attack them with anything.
- Ignore them for two months. Just let them be as they dig up cicadas to feed their children. After two months, theyll be off.
- Dont wander around with bare feet at night. Be sensible about walking in your garden; no yard is completely safe from prickles, stings and unpleasant things, so wear appropriate protection and practice sensible use of your yard.
How To Get Of Grass Carrying Wasps: Easy Tips
FAQ
What kind of wasps build nests with grass?
Grass-carrying wasps (Isodontia mexicana) are known for building nests using dried grass. These solitary wasps, belonging to the family Sphecidae, collect grass and other plant fibers to line and divide their nests within existing cavities like window tracks, hollow stems, or abandoned insect burrows.
Are grass-carrying wasps aggressive?
Grass-carrying wasps are generally not aggressive and rarely sting humans. They are solitary wasps, meaning they don’t live in colonies and are not defensive of their nests.
Why are wasps landing in my grass?
Wasps flying over your lawn could be attracted for several reasons, especially after you’ve added fertilizer: Food Sources: Many wasps are scavengers and may be searching for food. Fertilizers can sometimes attract insects, which can in turn attract wasps looking for a meal.
How to get rid of lots of wasps in grass?
Soap and Water: Mix two tablespoons of dish soap with water in a spray bottle. Spray directly on the wasps and nest. The soap clogs their breathing pores. Peppermint Oil: Mix peppermint oil with water and spray it on the nest. Wasps dislike the smell and may leave.