Onslaught FastCap Spider and Scorpion Insecticide

4.5 out of 5 stars 195 Reviews | 129 Q&A

Onslaught FastCap Spider and Scorpion Insecticide 8 oz.
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Average Rating

4.5 out of 5 stars Rating: 4.7

195 Reviews | 129 Q&A

Product Overview

Onslaught FastCap Spider and Scorpion Insecticide is an economic and easy to use formula that provides quick knockdown and long lived residual control of scorpions, spiders, and other insects listed on the label. This one of a kind formulation is made of Exponent brand synergist, Esfenvalerate, and Prallethrin. Onslaught FastCap Spider and Scorpion Insecticide can be applied in a number of areas both indoor and outdoor, as well as food areas (see label for complete list). This product is labeled for use as an indoor broadcast treatment.

Features and Specs

Active Ingredient Esfenvalerate 6.4% Piperonyl butoxide 8% Prallethrin 1.6%
Target pests 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
For use in Commercial & Residential Indoor & Outdoor areas:
Indoor - Homes, Office Buildings, Food Processing Plants, Restaurants, Schools, Warehouses, Hotels
Outdoor Perimeter Treatments - Garbage Can areas, Porches, Patios, Carports, Garages, Fence lines
Outdoor Landscapes - Trees, Lawns, Landscape Ornamental Plants, around Livestock Housing
Application 0.5 - 1.0 oz. per gallon of water
* See label for complete application instructions
Pet safe Yes, if used as directed on Label
Formulation Professional Product
NOT FOR SALE TO CT, VT (Restricted To Licensed Applicators Only)
Shipping Weight 1.25 lbs
Manufacturer MGK
UPC 848920000492
EPA Registration 1021-2574


Onslaught FastCap Spider & Scorpion Insecticide combines fast kill (action) and long residual activity against pests listed on this label when applied as surface or spot treatments, injected into wall voids, or as a crack and crevice spray in and around residential and commercial structures, as well as on turf and landscaping. Onslaught FastCap Spider & Scorpion Insecticide may be sprayed on any surface that will not be stained by water. DO NOT use this as a fogger or apply it as a space spray. Injector application equipment that delivers low volume treatments may be used to make crack and crevice injections or spot and general surface treatments.

Spiders, scorpions and other listed crawling insects Indoors:

Apply as a course, wet spray to surfaces where these pests are normally found. Treat floors, baseboards, around doors and windows, in attics, crawl spaces, eaves, corners, closets, walls, utility pipes, storage areas, and all cracks and crevices. Treat underneath sinks, dishwashers, refrigerators, stoves, the underside of shelves, drawers, cabinets, areas behind pipes, and in all places where these insects shelter. Contact as many insects as possible with direct spray. Repeat applications as needed, but do not exceed more than one (1) application every seven (7) days.

Mixing tip. Shake Onslaught FastCap bottle well prior to mixing. Clean spray equipment before using or diluting Onslaught FastCap. For dilution, add half the required water to spray tank, then add the appropriate amount of Onslaught FastCap. Agitate the mixture, and then slowly add the remainder of the water. Agitate the spray thoroughly before using and also occasionally during use to ensure dispersion. If you use a spray filter screen, they should be 50 mesh or larger.

Use Onslaught FastCap as part of an IPM program. Tank mix Onslaught FastCap with an IGR such as NyGuard IGR Concentrate to break the insect growth cycle and control future emerging insect populations. Do not apply Onslaught FastCap as a fog or space spray. Fog first with a product such as Riptide Water-Based Pyrethrin ULV to get the quick knockdown action of the fog followed by a surface application of Onslaught FastCap for residual control.

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  • 5 of 5 Stars

    Initial review on effectiveness vs scorpions

    By Scott on 03/02/2014

    Verified Purchase

    Main Target Pest- Bark Scorpion I have used Cykick, Cyper WP, Bifen IT, Demand, and suspend polyzone for scorpion control here in AZ. Cyckick seems to be the best so far. I don't have a huge problem with them, but I have found the occasional one indoors. I black light ~ every night once the temp is warm enough at night to monitor activity. I spray onslaught for the first time in mid feb. I went out 1 week later and found a dead one against the cinder block wall. I don't normally see this even with Cykick, so I got lucky or this stuff works well. It is also cheaper than Cykick per finished gallon once the price drop to _ 60/ bottle. I will use until gone and see how well it control scorpions this summer.

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    113 of 117 people found this review helpful

  • 5 of 5 Stars


    By Mike on 11/07/2014

    Verified Purchase

    We live in a National Forest surrounded by heavy forest. After years of paying $95+ per regular scheduled visits by a pest control company, we still had scorpions inside of our home. We knew something had to be done better than a local pest control service. After web searching, we came across this company and the product Onslaught. One application of Onslaught (2tbs) per gallon wiped out the scorpions & all other creeping critters! Best pest control product we have purchased. We cancelled our pest control service! We applied Onslaught on fire ants just to see what the results would be...killed them all dead within a few minutes! We highly recommend this product.

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    104 of 106 people found this review helpful

  • 5 of 5 Stars

    Lives up to the reputation

    By John on 10/01/2015

    When I moved into my new home in central TX two years ago the first thing I saw when waking up after the first night (we all slept on the floor since we arrived with just what I could carry in the car, no furniture) was a common bark scorpion poised about 2 inches my from fingers... For the first season I just coped with these critters thinking that once the house was lived in (it had been abandoned during the housing crash in 2008) and I got everything cleaned up around the yard the problem would just go away. No such luck! We had these things in the house (sometimes I'd be removing 2 or more a day) and we've all been stung by them (hours of pain for me, but my wife ended up in the hospital). This spray worked a treat! I just do like they say, spray up the foundation a few feet, and out from the house, and around all the windows, etc. and the problem is gone gone gone. I find I need to re-apply about every other month for this to stick. Some nice side benefits include the fact no crickets have found there way inside (first season I was infested with those things during the fall, the only thing is I have piles of dead crickets I need to clean up) and if I spray the eves and on the deck it basically wipes out the wasp and fly problem as well. My wife and I try to live chemical free since she's very sensitive and she tries to be organic in the garden as much as possible, but enough was enough. We've not had any downsides to using this product as directed. My dogs sleep out on the deck I treated all night, no trouble at all. I recommend a backpack sprayer since that gets the job done faster so you don't skip out on the schedule (I was busy over the summer and pushed three months, but at that point I started to find scorpions again, I think in the three months I found 2 or three in the house, and all in the last month, so I really think bi monthly is the thing to do). plus the power of the backpack sprayer was able to hit my high eves and help me wipe out some wasp nests that got established in hard to reach areas. In general I am happy to share my land with whatever critters show up, but in the areas around the house where we like to work and chill, and particularly inside when we'd wish to relax, those have to be off limits to dangerous and messy things. This stuff is powerful and works.

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    84 of 86 people found this review helpful

  • 5 of 5 Stars


    By Wanda on 05/23/2013

    I live in an area where pests are common, this product controls them all. Bed bugs, fleas, ants, roaches, wasps, spiders scorpions... I had zero problems since I started using it. This product also lasts a long time, its around much longer than other products I have tried in the past.

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    83 of 86 people found this review helpful

  • 5 of 5 Stars

    Works Great!!!! If you have scorpions get it!

    By Dana on 09/23/2013

    Verified Purchase

    I would really recommend this product. I got it for spiders & scorpions both inside & outside the house. I've only used inside so far but it works. I don't know if this stuff calls out the scorpions but 3 are dead so far. I didn't even know i had that many scorpions around. I live in a new development in a heavily wooded area so I expected critters, never scorpions though.

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    61 of 63 people found this review helpful

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Questions & Answers

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Onslaught versus Demand, Cykick or Cyzmic for Scorpions

To eliminate scorpions, is Onslaught the strongest, most effective insecticide to spray indoors and out? My treatments have included Demand, Cysmic and Cykick CS and Aerosol (aerosol for knockdown and cracks and crevices) and now am hearing about Onslaught FastCap Spider and Scorpion insecticide and wonder if it is stronger or the strongest. My thought is, if I'm spending money on insecticide and investing time to treat my home to ward off these horrible scorpions that I fear, I want the most effective product on the market. I'd rather purchase and concentrate on the best! Thanks.

The Onslaught FastCap would definitely be the best option for your needs. It is specifically formulated to better target spiders and scorpions with a more thorough and long lasting coverage for these hard to kill pests. Keep in mind, no matter what product you are using for scorpions, you have to create a wider barrier for them than any other pest around your home. For general insects you would treat with a barrier around the foundation 2 feet up and 2 feet out. With scorpions you should be doing 2-3 feet up and 6-10 feet out on the ground. Also make sure to treat any landscape areas around your home that they would be prone to hiding in ie: mulch, bark, landscape timbers, rocks etc. You can review more information for protecting your home from scorpions in our article on Scorpion Control.

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88 of 95 people found this answer helpful

Mixing Instructions

How much water do you mix to this product? Trying to decide if a bottle is enough to spray inside and outside of my house

You want to mix 1fl oz Onslaught FastCap Spider and Scorpion Insecticide into one gallon of water. One pint will give you approx. 16000 sq feet. 

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87 of 89 people found this answer helpful

Is Onslaught FastCap safe to use in homes with dogs?
Onslaught FastCap is safe for pets when they enter the areas after the product has dried.

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76 of 83 people found this answer helpful

Is there a benefit to Onslaught FastCap vs. regular Onslaught?

I've been using regular Onslaught for residual hornet, ant, and earwig control. Is there a benefit to switching from regular Onslaught to FastCap? Either way, I need to buy another bottle, and want to make sure I'm getting the best.

The biggest difference of Onslaught Fastap and Onslaught are the Onslaught Fastcap  combines a one of a kind formulation is made of Exponent brand synergist, Esfenvalerate, and Prallethrin. So Onslaught Fastcap offers an even quicker more intense knockdown.

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73 of 78 people found this answer helpful

What's the best indoor spray for spiders?

Our church fellowship hall has an increasing amount of spiders and spider eggs. We are in a rural area of Ohio. They don't bother me that much...but a few female members are scared. What do you recommend? Please note we EAT in the fellowship hall.

The absolute best indoor/outdoor spider spray is Onslaught Fastcap. This one of a kind formulation is made of Exponent brand synergist, Esfenvalerate, and Prallethrin. Onslaught FastCap Spider and Scorpion Insecticide can be applied in a number of areas both indoor and outdoor, as well as food areas (see label for complete list).

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62 of 67 people found this answer helpful

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Onslaught FastCap Spider and Scorpion Insecticide 4.5 out of 5 stars Rating: 4.7 (195 Reviews / 129 Q&A)

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