






⚡ Outsmart pests fast — because your space deserves zero creepy crawlies!
MGK Onslaught® FastCap Spider and Scorpion Insecticide is a commercial-grade, fast-acting concentrate combining esfenvalerate, prallethrin, and piperonyl butoxide. Designed for both indoor and outdoor use, it effectively eliminates a broad spectrum of pests including spiders, scorpions, fleas, and mosquitoes. Trusted for over a century, MGK delivers a potent, easy-to-mix formula that offers extensive coverage and rapid knockdown, ensuring your home or business stays pest-free with minimal effort.

| Active Ingredients | Esfenvalerate,Prallethrin,Piperonyl Butoxide |
| Best Sellers Rank | #11,777 in Patio, Lawn & Garden ( See Top 100 in Patio, Lawn & Garden ) #171 in Insect & Pest Repellent Sprays |
| Brand | MGK |
| Customer Reviews | 4.7 out of 5 stars 1,326 Reviews |
| Item Form | Spray |
| Item Weight | 1.2 Pounds |
| Liquid Volume | 1 Pints |
| Target Species | Insects |
N**.
It’s works for scorpions, tarantulas, and whatever else is creeping around Texas hill country
Don’t know what’s different about this year than all the others, but the scorpions are out with a vengeance. It’s seriously not fun. We’ve had them in our bed, in the dog beds, in the bathrooms, in the kitchen, in bedrooms, in the living room, on the ceiling, and the list goes on and on. Truly awful, and it was showing no signs of relief. We had been using Wondercide indoor pest control cedar scent spray, which did help, but didn’t solve. It smells great, which is a bonus, and is totally safe for us and our pets, which we love. But again, it didn’t eradicate the scorpions from our home. We tried the traps. Again, they work and serve their purpose, but they don’t stop the scorpions from entering, they only help catch them once they’re in. So problem still not solved. We’ve also tried other things: cedar wood blocks and chips everywhere, peppermint and other heavily scented scorpion deterrents, etc. No dice. We really tried to stay away from insecticide, because of how many animals we have, but we were at the very end of our rope. There aren’t many options when it comes to options that can kill scorpions. So this what we went with. We followed the directions and sprayed outside the night we received it. When we woke up the next day, it was like a graveyard out there. Dead bugs everywhere. Not just scorpions, but stick bugs, beetles, stink bugs, June bugs, a variety of spiders (including tarantulas!), mosquitos, crickets, and other things I couldn’t even begin to tell you what they were. Since then, we’ve also sprayed inside, and have found three dead scorpions, three dying scorpions, several new dead scorpions in the traps, and now, about a week in, no scorpions for two days in the house! One I found the first day that was still kicking, I grabbed him with my tweezers and put him in a bowl, then sprayed him. I watched him squirm for about 15 seconds, before he flipped over on his back and died. Just like that. Just stopped, flopped, dead. Also, we run a dog rescue here, and we have 19 dogs. During the day, the dogs are mostly outside in the yard and/or in their outdoor kennels. Since spot spraying and spraying the trees outside, there is a dramatic decrease in the amount of flying insects. >90% decrease in flies, mosquitos, moths, and June bugs. Amazing! So far, no ill effects on us, the dogs, the reptiles (snakes), amphibians (frogs), or small critters outside (bunnies) at all. No impact on the landscaping, no residue or discoloration left on the carpet, walls, or floors. No smell, except maybe a very faint buttery smell when it’s very first sprayed. It’s easy to mix, since the container has the built in measure, and you only need .5-1 ounce per gallon. That’s 16-32 gallons with this 16oz bottle. That’s a great deal for so much peace of mind! This stuff works. It’s safe and easy. Just follow the directions. Don’t over mix it (no need to waste it), make sure to let it dry completely before people or pets touch it, and you’ll be all set.
J**H
My personal experience along with an experiment and direct comparison to Harris Scorpion Killer
Scorpion season started earlier this year in South Texas. Ordered this after reading reviews for multiple days and feeling confident that it will help us. Morning started with us finding a scorpion in the laundry room. We caught it in a glass and sprayed one part of the floor with Harris scorpion killer and the other part with Fastcap scorpion killer and waited for both sides to dry. Sat the scorpion on the Harris side and turned the vase over it so it can be controlled on the treated area. Let it run around for about 30 seconds (seemed a reasonable time for it to naturally cross over) and scooped it back into the vase. Watched it for about 2 hrs happily crawling around the vase. No lameness no twitching. Just alive. Time for the second test. This time sat it on the fastcap treated area and again let it run around for 30 seconds. Scooped up and watched it. Here is what happened after exposure: After 2 minutes he got really really slow and we saw right away something is effecting him. After 5 minutes he started acting like a drunk. Uncontrolled body moving, legs kinda tried to crawl in the air and the tail bent over its body. After 10 minutes he flipped on his back and started twitching like crazy. Then nothing. Legs curled up, tail went straight and no movement at all. I moved the lifeless body around in the vase to test any reaction- NOTHING! Watched him for the next 3 hrs. Checked about all 20-40 minutes. At the beginning there was still some slight movement in the legs and pinchers here and there but you could definitely tell it’s just muscle spasms. After 3 hrs I disposed of a dead scorpion. To be fair, he was first exposed to Harris but lived on. Not saying that didn’t somehow affect him but after exposure to fastcap it went very quick. After that I sprayed my entire inside of the house. Under the sinks, behind washer/dryer and along all perimeter of the inside. It’s raining but as soon as the rain will stop I will spray generously outside up the siding and along the base and grass surrounding about 2 feet of the house. My goal is to knock em out the way I saw it happen today before they even get the chance to find an entry point. I’ll probably repeat my experiment with fastcap in about a week to see how the stuff works after some time and will update my review then. For now all I can say is I am happy seeing first hand that it kills these crustaceans fast and am looking forward to report the effectiveness in a couple of days regarding the left over strength HOPEFULLY less scorpion sightings. Before any treatment we found 6 within 7 days.
A**R
Best of the Best
Go, buy it now! I’m in a new development in TX with no houses around me yet and the scorpions are out of control. When the new houses start, it will also sent all critters fleeing to my yard. I’ve been using the recommend pest companies and it isn’t adequate. We would still get several scorpions inside each week - even having them come out every 6 weeks. I started using this a few months ago and it’s been extremely effective. I spray for the heavy application- 1 oz per 1 gallon of water with a 3 gallon sprayer. One important aspect of scorpion control is also controlling the pests they eat. This is effective at killing roaches which is one of their primary food sources. No food, less reason to come. I spray the exterior of the house perimeter, flower beds, and 5 feet around my outer property line including 3 feet up my fence. Scorpions are great climbers so you need to cover all areas. We still get the occasional scorpion inside, but it’s usually dead within a couple feet of the door. Scorpions die slowly, so they are difficult to manage. But it’s much better than the daily scorpion that’s lively and fast. I also bought some grabbers to pick them up so I don’t need to handle them. I don’t trust them even once dead… :) I spray every 4 to 6 weeks depending on how much rain we’ve had. TX monsoon rains seem to reduce the effectiveness faster than when it’s dry. As soon as I see grasshoppers or beetles twitching instead of immediately dead I know it’s time to spray again. Good luck and may the odds be ever in your favour.
J**K
Great bug killer.
I’ve been using this product for years to spray my out in the country home. Really knocks off those black stink bugs quick, spiders, black widows, ants and many other crawling insects. Those centipedes hate it, cause them to die a slow death. Safe when dry for pets, drys quick. Minor light rain does little effect on it, but heavy rain will wash it off. Use inside & outside. No oder that I can detect, no staining. Pricey but well worth it.
I**T
What they don't tell you. Now for the rest of the story.
- #1 SPIDERS ARE NOT INSECTS. Many common sprays can legitimately claim that they can kill spiders, but few can practically rid your home of them. The active ingredients that are so effective on insects are much less effective on spiders even when they kill via the same mechanism, which for both is usually taking out their nervous system. If a spider gets wet with any of them, they will kill the spider. After they dry, few will kill a spider. Diatomaceous Earth and other dusts do work but are less reliable and because spiders spend less time where the dust typically is located. - The product is micronized. Many sprays are highly effective, but for a very short time. Micronization is a type of binding, which enables it to release slowly over time, and thus lose its effectiveness slowly over time. After they internalize it, it does speed up whatever they internalize. - The results are not instant even with active ingredients that are highly effective against spiders. You may see spiders that may attack what you put next to them and are unable to run away quickly. This is because it is taking out their coordination and ability to respond normally. - DO NOT take down their webs before spraying. Spiders spend their time at or near their webs and re-process the web material to make new web, which greatly increases how much they ingest. - When it comes to getting rid of spiders, there is no such thing as cheap and effective, and the price goes up from effective when you want effective and safe, which is what your dilemma will be here.
A**R
decent pesticide
I'm terrified of spiders, bugs and anything that crawls so I purchased this because the reviews said it kills everything. I sprayed outside and inside of my home and it helped a little but not like I thought it would. I still see spiders and bugs. It's easy to mix and spray but I wasn't fully satisfied with this product.
E**R
2.5 oz/gallon works well and lasts on scorpions.
I had been using Bayer Complete from Lowes for exterior scorpion control here in central Texas. . I went to Onslaught and have found that it works way better at 2.5 oz./gallon around the perimeter than the Bayer Complete. I have sprayed it three times now at about 5 month intervals and the scorpions have simply disappeared. Not even seeing dying or dead ones on the garage floor anymore this summer. I spray the bottom 3' of the house and barndominium, then inside the barn garage doors about for about 6 feet on the concrete, and about 15' out from all exterior foundations. Sometimes I do a squirt under the house as well through the kitty doors if I know they are not under the house. We used to have many scorpions inside the back bathroom in our 1950's modernized farmhouse, say 6 a week getting stuck on the sticky pads overnight, but since the last spray, they really seen to have completely stopped coming inside the house. This is really a life saver for us, as both my wife and I have been stung before. And if you do get stung "Afterbite" roll on stick really works to kill the sting pain.
M**R
Serious Pest Control That Works
I’ve tried my fair share of pest control products over the years, and MGK Onslaught is hands-down one of the most effective I’ve used. I was battling a stubborn infestation of [insert specific pest if desired—ants, roaches, spiders, etc.] that just wouldn’t quit, even after trying multiple store-bought sprays. Within 24 hours of applying Onslaught according to the directions, I noticed a dramatic drop in activity. Within a week, the problem was nearly gone. What I like most is that it’s a microencapsulated formula, meaning it keeps working long after you spray—perfect for those pests that like to come back for round two. The application was straightforward. I diluted it in a pump sprayer and treated baseboards, entry points, and a few problem outdoor spots. The odor was minimal, and it dried without leaving residue. It also works on a wide range of pests, which saves money compared to buying multiple targeted products. Bottom line: If you want professional-grade results without hiring an exterminator, MGK Onslaught delivers. Just follow the label carefully
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