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Onslaught FastCap Spider and Scorpion Insecticide

Onslaught FastCap Spider and Scorpion Insecticide
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Onslaught FastCap Spider and Scorpion Insecticide is a fast acting microencapsulated formulation for the control of spiders and scorpions as well as a broad spectrum of other insects. This unique formulation contains Exponent synergist that enhances two other active ingredients : Esfenvalerate, and Prallethrin. Onslaught FastCap Spider and Scorpion Insecticide may be used inside or outside and has a label for food and nonfood areas in commercial structures.



Onslaught FastCap Description

Onslaught FastCap Spider and Scorpion Insecticide is a fast acting microencapsulated formulation for the control of spiders and scorpions. Onslaught FastCap also works  well as a broad spectrum of other insects.

This unique formulation contains Exponent synergist that enhances two other active ingredients : Esfenvalerate, and Prallethrin.

Onslaught FastCap Spider and Scorpion Insecticide may be used inside or outside homes and has a label for food and nonfood areas in commercial structures.

Onslaught Fastcap Yield

16-32 gallon yield

Onslaught Fastcap Residual Activity

Will last up to 12 months.

 Onslaught Mode of Action

As a pyrethroid and synergist it kills the insects by disrupting the insects' nervous systems.


Method of Onslaught FastCap Application

  • Use between 0.5 oz (light infestations ) to 1.0 oz ( heavy infestations ) per gallon of water
  • When spraying Onslaught FastCap it is not necessary to spray to point of run off, just dampen surfaces.
  • Indoor and outdoor broadcast surface treatment
  • Crack and crevice treatment
  • Spot treatment Perimeter spray
  • Foliar spray treatment
  • Tank mix with IGR's or apply alone
  • Injection into wall voids
Additional Information

Additional Information

Pro Tips Not Available
Packaging 16 oz
Manufacturer MGK (UPC: 848920000492)
Product Label Label
Technical Bulletin
More PDF's No
Target Pest Ants, Asian Lady Beetles, Bed Bugs, Boxelder Bugs, Carpenter Ants, Cockroaches, Confused Flour Beetles, Darkling Beetles (lesser mealworm), Face Flies, Fleas, Fruit Flies, Horn Flies, Hornets, House Flies, Indian Meal Moths, Lesser Grain Borers, Mosquitoes, Red Flour Beetles, Rice Weevils, Saw-tooth Grain Beetles, Scorpions, Small Flying Moths, Spiders, Stink Bugs, Swarming Termites, Ticks, Wasps, Yellow Jackets
Active Ingredient (s) Esfenvalerate 6.4%
Prallethrin - 1.6%
Piperonyl butoxide - 8%
For Use : Onslaught FastCap is labeled for Indoor in Food and Non-food Areas. Onslaught FastCap may be used in Homes, Food processing plants, Restaurants, Schools, Warehouses, Hotels Outdoor Perimeter Treatments to Areas, such as: Around garbage cans, Porches, Patios, Carports, Garages, Fence lines On Trees, Lawns, Landscapes and Turf In and Around Livestock Housing.
Yield 16-32 gallon yield
Mixture|Application Use between 0.5 oz (light infestations ) to 1.0 oz ( heavy infestations ) per gallon of water

Tips for Onslaught FastCap Microencapsulated Insecticide Usage:

  • Dilute Onslaught FastCap with water only.Do not mix wth oil.

  • Mix Onslaught FastCap with an IGR such as NyGuard IGR Concentrate to break the insect growth cycle and control future emerging insect populations as an IPM Program.
Retreatment No
Shipping Restrictions CT, NY
More Instructions

EPA Registration Number


Shelf Life

3 years in original commercial packaging


Will not stain surfaces if water will not stain. Test surfaces to see if water stains in desired location. Respirator is not required. Not classified as flammable or combustible by OSHA


Customer Reviews 22 item(s)

Get it!
Awesome product! For those of you that aren’t sure about this product? Buy it! Spray 6 inches up the wall of your house and any walls surrounding it and spray 6 inches out onto the floor. Be generous. I’ve had no issues since using it. It was recommended to me by a pest control company that uses this for everyone’s house. Quit paying somebody and do it yourself.
Review by Kirby / (Posted on 11/30/2017)
Great on Scorpions!
I've used this in a band application around the house for the past 4 years (first year was by professional exterminator). I apply it 3 ft up the side and 6 ft out from the foundation at 1 oz. per gallon.

I find no scorpions in the house for about 6 months. One 16 oz. container gives me a year of protection. Seems to work on centipedes, too. I'm happy!
Review by GeorgeC / (Posted on 9/25/2017)
Best stuff ever!!!!
We purchased some land and installed a garage. Low and behold we found scorpions & spiders after we stored our camper in there all over the floor. Purchased Onslaught FastCap Spider and Scorpion Insecticide and sprayed on the garage floor. Next week when we returned we found 10 to 15 scorpions dead. Each time we leave we spray a thin coat of this and each week we return we find dead scorpions. I can't say enough of how great this product is. I will definitely keep this on hand.
Review by Auggie / (Posted on 9/10/2017)
Good stuff!
The three days after I sprayed We found four dead scorpions..and a few half dead..I sprayed all around the doors and windows and about a foot up the side of the house [stone] . I think this is the best results we have had here in the Texas hill country
Review by Zanna / (Posted on 9/1/2017)
Scorpions- AZ Browns - Bark Scorpions
I really like this product on bark scorpions / AZ Browns scorpions. I've tried Cy Kick with okay results and a few other ones with high reviews. The OnSaulght has been the best for Scorpions, thus far. Not to mention, everyone other insect including, roaches, spiders, flies, grasshoppers, wasp are dead too!!!
We bought a new home in Las Vegas, NV and this neighborhood is infested with bark scorpions. I was even stung last year and didn't feel great for a few a days. I had a pest control agent, but I fired him after I was stung in my house. I went to war with these nasty creatures.
Is OnSlaught the perfect answer, NO, but it's 95% better. Scorpions are just hard to kill, period. This stuff does a nice job overall. They're dead in the black light up to 3 weeks after spraying.
OnSlaught Is awesome, compared to the rest.
We've had three dead ones in the house in the past 10 months. Prior we would have 2-3 a month get in and we're still alive.
We used to have 20-30 bark scorpions around the outside of the house and yard areas, each week, which I just killed manually with spray or fire :)! Now, We only see 5-6 a week, and most of them are Dead after I spray.
I've noticed it last about 3 weeks and they start coming back at night. So I spray between 3-4 weeks during the spring and summer months. I even hit my neighbors outside too, so I can try and run them off or kill them all. :)

I mix it heavy for the outside 1oz to 1gal of water.
Inside the house, i mix .5oz to 1 gal. As directed!
Review by DK2015 / (Posted on 8/8/2017)
Great product
I have been using Onslaught FastCap for a few years. We have scorpions and most the time when we see them, they are dead. Also works very well on spiders.
Review by Loren / (Posted on 7/3/2017)
Just purchased another bottle.
We live in SW FL on a bridge less barrier island. We have scorpions. This products works great! Used 2 times now and mixed up stronger than recommended. It works really well, even outside. I have just reapplied after 2 months because of all the rain we just had. Almost every morning I was finding dead scorpions. I just do the outside because I don't have any problem on the inside.
Review by Karyn / (Posted on 6/11/2017)
Weird name - awesome product
So I purchased a house in 2008 that was infested with Brown Recluses(BR)....which I did not know prior to purchase. Our house backs up to thick woods. We have an attic and a basement. The house was built in 1979. Anyone who has had to deal with an infestation like this knows the unsuspecting emotional roller coaster that it can be dealing with the BR spider. Finding them in your cabinets, bed, clothes, etc. Especially if you have small kids who root around everywhere. Hired a national professional exterminator to come on a monthly basis to spray. Realized they were basically a rip-off and through research, I found I knew more about the BR than they did! Started buying unnamed big box store products and spraying on my own. Saw some results. Came to this website and started buying these products which were WAY MORE EXPENSIVE! Started using Defense dust and Cyper WP. Started seeing much better results. But still the BR soldiered on. Purchased Fast Cap and it was game over....... clearly the best BR killer out their. I don't know what it does or how it does it but I see less than 10 BRs a year now. I was seeing hundreds........you lose count. What's weird, is this product should NOT get these results. The best stuff is supposed to be the stuff the spider gets on them. Roaches are always putting their mouths on stuff, the spider does not. They don't clean themselves like other insects either. But some how Fast Cap gets on them or in them and it just wipes them out.

Note: my dealings with BRs lasted for years. Hired unnamed pest control company for a year........that cost me 750 bucks. That was not working so did it myself. Spent who knows how much a year but hey 750 bucks will buy a lot of bug killer. Did that for several years. Everything changed when I came to this website and started using these products. Now, I probably spend 250 bucks a year here DIY. This is more for preventative maintenance than dealing with the problem. I can't ill everything around me but I'll take a BR here in the yard, in a bush, in the attic, basement to add up to 10 a year over hundreds and hundreds any day. And the ones I see, look skinny and desperate for food.

Words of advice for BR:
1. Spray these products liberally outside your home on your home and in the wooded yard. My infestations were heaviest in the attic and basement. Spraying outside kills insects coming inside and will cut off the BR food supply.

2. BRs can live up to two years without food or water and are known to eat already dead insects....although they are hunters. So, it will take some time. They will hunt if they need too. Glue Traps are key here. Buy them in bulk here. I cut Glue Traps up into smaller ones to get more out of them.

TIP: Freeze the glue traps, then cut them up frozen so that the glue does not get gummed up on your scissors. Then, let them get to room temperature before pulling the wax paper off. That way, the attracted moisture in the thaw process does not get on the glue and cause it to lose some of it's stickiness.

3. If they are not hunting, the male BR is looking for love. They will seek out the female BRs which you will rarely see. Glue Traps again!

4. use a dust like Defense dust in the attic to fog/dust the area. Buy the duster on this website. The dust will get everywhere and it will get on the Spiders. It takes a while, but the dust will kill them.

5 Remove moisture from your basement with a dehumidifier. Moisture will just attract bugs and they are BR food.

6. Seal up any access to your attic through lights and what not. Those recessed lights might be more porous than you think. Most contractors put in the cheap non insulated canned lights over the sealed insulated ones. Remember, the male BR is looking for love, food, and warmer or maybe even colder environments and will follow it's senses to find this.

7. Be patient, dealing with BRs is a long and possibly never ending process. But you, will control them to a point that like me......you see one every now and then rather than several daily.

8. Do your best to keep the insecticides out of your primary living area. Do not fog these areas. Use Glue Traps generously here. Insecticides have a high link to children with autism. The less you and your kids breath of that the better. Especially your kids for later child birth of their own.

9. Don't leave stuff on the floor in dirty areas like a basement or carport. Especially wooded, carboard, or papery items. BRs love this stuff.

10. Don't believe everything you hear or read......maybe even what I've written here. The BR is not as reclusive as you think. They will adjust to environments. I've seen them living happily in a building where a wall fan with a warped blade shook the wall and BRs sitting on the walls, in cracks, etc with all that movement. Same in my own home above the garage/attic, with a garage door that sends a lot of vibration into the attic space when it opens and closes.

11. Lot's of people incorrectly identify the BR. And yes, their are some spiders that look very similar to the BR. A magnifying glass or microscope may be on order to properly identify them.....especially the small ones. BRs have different amount of eyes than other spiders.

12. If you do use a pesticide company. Make sure to be home when they come by. Insecticide cost money. The less they spray the less they pay for product. And, the more you call them back to spray some more. Best just to DIY Pest Control!!!!!!!

Note: Don't forget the Fast Cap is expensive but it works great!!!!!!!!
Review by Jay / (Posted on 10/27/2016)
Works great for me!
When we begin to see scorpions inside I spray a 6 ft band on the ground around the perimeter of the house, going 3 ft up the outside walls. It works for ~6 months here. I've been using it for three years now with no complaints.

The first treatment was professionally applied - they recommended it to me. They never called for a follow-up, so I began to do it myself...

In Yarnell, AZ
Review by grc53 / (Posted on 10/17/2016)
Kills spiders
Works but does not seem to "knock them down". I did have some dead spiders about a few days later.
A bit expensive but it did do the job.
Review by Harley121 / (Posted on 4/3/2016)
Short lived.
After immediate application the product was great. However, only lasted about 3 months and had to reapply.
Review by Digger / (Posted on 11/4/2015)
I would recommend, very effective product.
This works great to control millipedes, ants, roaches in SW Florida. Haven't noticed dead spiders, but also haven't seen them making webs where I sprayed.
Review by SW Florida / (Posted on 10/28/2015)
works great
this stuff is fast acting
Review by easydoe / (Posted on 10/9/2015)
Great product and worth every penny
It seems it is working. The few weeks after my first application I used to find many dead/ dying scorpions in the back yard. Recently I found baby scorpions again in the back yard thought it's time for a second application which will be tonight. I used to kill up to 30 of them every weekend now I might get lucky finding one or two and most of them is dead
Review by Hannibal / (Posted on 9/8/2015)
No staying power!
Killed on contact thought I had the spiders under control but they were back in big numbers in a weeks time! Guess I'll try another product this stuff definitely not worth the money!

DIY RESPONSE: Sorry the product didn't work as expected. Spider can be very difficult to control because they don't groom often. Call us at: 1-800-476-3368 and we can help troubleshoot the application process, to ensure the best long term spider control.
Review by Ken / (Posted on 9/8/2015)
Good stuff so far!
Really knocked the spiders for a loop! We'll see how long it keeps them down. Cheaper than paying Varment Gaurd for their unreliable service! Doesn't stain the house either!
Review by Ken / (Posted on 8/24/2015)
Scorpion Killer
We live in Arizona and have a problem with bark scorpions. I've used this product now for a week, and cannot keep track of all the dead scorpions in the back yard. Product is effective, odorless, and simple to use. Highly recommend.
Review by Tim / (Posted on 8/24/2015)
Excellent product
Only used it a few times, but early results are very positive for elimination of daddy long leg spiders.
Review by gtjake / (Posted on 7/28/2015)
Onslaught FastCap Spider and Scorpion Insecticide
Used it twice so far and to date I have not seen any scorpions around my home. Before using this I used another product and I had 8 scorpions inside my garage and home - 2 alive.

Will continue to spray on a monthly basis until I am certain I have removed all scorpions near my home.
Review by npadk21 / (Posted on 4/27/2015)
Good product
Sprayed for scorpions 2 weeks ago. Haven't seen one inside or out. The question is how long it will last.
Review by TA / (Posted on 10/2/2014)
Awesome product!
Single mom with two boys living in the country. We have sprayed this chemical twice for scorpions and I have NEVER seen a product react as quick as this one does. Dead bugs everywhere. Easy to apply and can be used indoors and out. Have even sprayed around the livestock pens and barn. If you are on the fence about what to buy, jump off and hit "buy" - you will be hooked!
Review by Inky0319 / (Posted on 9/24/2014)
Hate the name but I love the product! I had a Brown Recluse Spider problem and I sprayed two times about a week apart and I have not seen one since then. Thanks!
Review by Marcel L. / (Posted on 2/4/2013)

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