Siphotrol Plus II Review

siphotrol plus ii review


Siphotrol Plus II by Vet Kem is an insecticidal premise spray. It controls fleas and other domestic pests. Siphnotrol contains pyrethrins to rapidly kill adult fleas. It also contains an insect growth regulator, (s)-methoprene, to prevent eggs and larvae from developing into adults. Methoprene remains residually active indoors for 7 months, effectively preventing re-infestation.

Other premise sprays are similar to Siphotrol. They all contain similar active ingredients, and in similar formulations. Thus, they all preform about the same. They all have high ratings on, as one would expect. The primary difference between premise sprays is price, and Precor 2000 Plus is the best value.


Siphotrol Plus II
Product Information Chart

Price $21
Size 16 ounces
Capacity 2000 sq ft
Application Aerosol Spray
Use On Home Premises
Kills Adults, Eggs & Larvae
Treatment Duration 7 months
Ingredients 0.085% (s)-methoprene
0.350% permethrin
0.300% phenothrin
2.000% MGK 264
1.400% piperonyl butoxide
95.865% other ingredients
Product Label view
MSDS view
Shop Amazon

*prices are based on at time of publishing

Active Ingredients


Vet Kem’s Siphotrol Plus II contains (s)-methoprene, also called Precor. This compound is an insect growth regulator (IGR). IGRs work by mimicking naturally occuring hormones in insects, specifically juvenile hormone. When an insect is exposed to an IGR, it can’t molt into the next stage of life. Flea eggs and larvae can’t complete their metamorphosis into adults. And adult female fleas are sterilized. IGRs are considered safer conventional insecticides, because they specifically mimic insect hormones.

Methoprene is the most important active ingredient in Siphotrol. 95-99% of flea populations consist of eggs, larvae and pupae. The immature fleas reside in the environment, usually at the base of carpeting. Adulticides are ineffective in killing these stages. The insecticidal spray can’t penetrate carpets to the depth where fleas live. Plus, adulticides have a short-lived effect. IGRs, such as methoprene, remain active for 7 months indoors. Because carpets are such a difficult surface to treat, long-lasting residual activity plays a crucial role is controlling fleas.

Permethrin & Phenothrin

The adulticides in Siphotrol are permethrin and phenothrin. These are two pyrethroids, synthetic compounds based on the chemical structure of a botanical insecticide found in Chrysanthemum flowers. Pyrethrins and pyrethroids are commonly employed to kill adult fleas and other insects in homes. These insecticides are neurotoxins, affecting the insect’s nervous system by causing spasms, paralysis, and death.

When Siphotrol Plus II is sprayed, exposed adult fleas will be quickly killed. Unfortunately, only 1-5% of flea infestations are adults. Some adults can be found emerging from their cocoons in the environment. However, once they find their way onto a host, the fleas stay there. Thus, there won’t be very many adult fleas in carpets at any one time.

Most of the immature fleas living deep within carpets won’t be affected. The carpeting provides refuge from insecticide penetration and vacuum removal. As a result, the fleas currently developing in the environment may survive to emerge as adults. This can confused those who just sprayed. However, the young lives in the carpet at the time of spraying will be the last generation. Any eggs thereafter will become sterilized when they fall onto the IGR-treated carpets.

Piperonyl butoxide & N-octyl bicycloheptene dicarboximide

Synergists don’t have insecticide properties, but will enhance the potency of pyrethroids. As a result, they’re often found in pest products together. Synergists allow less insecticide to be used, which results in safer and cheaper products. The two most common synergists are piperonyl butoxide and N-octyl bicycloheptene dicarboximide (MGK 264). Both are included in Siphotrol.

Comparison to Competitors

Siphotrol’s main competitors are Precor 2000 Plus, Ultracide, and Virbac Knockout. All of these products are comparable in quality and efficacy, because they’re aerosol premise sprays with similar active ingredients and concentrations. All four sprays are highly rated on reviews. Price is the most noteworthy difference between them, and Precor 2000 Plus is the cheapest.


The following instructions were taken from the product label of Siphotrol Plus II. Before using the product, view the label for the full directions and precautionary statements.

It is a violation of federal law to use this product in a manner inconsistent with its labeling.

General Information

Siphotrol® Plus II Premise Spray (Siphotrol® Plus II) kills adult fleas, hatching flea eggs, flea larvae and ticks. PRECOR®, the unique ingredient in Siphotrol® Plus II, provides 30 weeks’ protection by preventing eggs from ever developing into biting fleas. For best results, use Siphotrol® Plus II with Vet Kem® on-animal products for complete control of fleas and ticks.

For use in the home/garage/kennel. Not for use on humans or pets. Shake well before use.


Identify treatment areas, especially those where pets frequent, such as in and around pet’s sleeping and resting areas. These are the primary areas where fleas, their eggs, and ticks are found. Before treatment, make a test application to upholstery, drapery, light-colored, delicate fabrics, or wood surfaces in an inconspicuous place.

Prepare treatment areas. Cover all food processing surfaces and utensils during treatment or thoroughly wash after product use. Cover or remove exposed food. Remove pets and cover and unplug aquariums before spraying. Remove motor vehicles before using in garages. For best results with Surface/Carpet treatments, vacuum thoroughly before spraying and discard vacuum bag in outside trash. This product may also be used for infested surfaces inside motor vehicles.

Apply treatment. For flea/tick infestations, a single can treats 2,000 square feet. Hold container upside down 2-3 feet from surface, point actuator towards the surface, and push button. Using a sweeping motion, apply a light uniform spray to all surfaces of furniture, rugs, carpets, drapes, and around all pet resting areas. Avoid thoroughly wetting surfaces. Mist treated areas only until “slightly damp”. Do not over-treat. Reapply in 14 days, if necessary. IMPORTANT: Only complete and proper application to carpets, upholstery, drapes, and other fabrics will provide thorough flea/tick elimination. Keep people and pets out of areas during treatment. Vacate room after treatment and ventilate until surfaces are dry before reoccupying.

For best results, eliminate fleas/ticks on your pet with appropriate Vet Kem® on-animal products.

Storage and Disposal

Storage: Store in a cool, dry area. Do not transport or store below 32° F.

Disposal: Do Not Puncture or Incinerate! If empty: Place in trash or offer for recycling if available. If partly filled: Call your local solid waste agency for disposal instructions.

Have an unrelated question?

ask a question


  • Denise August 9, 2017, 3:08 pm

    I have a full 16oz can of Siphotrol plus ii spray. I know it’s over 1-1/2 years old.
    What is the shelf life of this product?
    Have sudden and very bad flea infestation!
    Thank you

    • Adam Retzer August 13, 2017, 5:01 pm

      I am not sure about the shelf life. The most important ingredient for flea control in the product is (s)-methoprene (also called Precor). I just did a quick Google search for “(s)-methoprene shelf life” and it looks like most products containing it state a 2 or 3 year shelf-life.

  • Barb September 18, 2017, 5:53 pm

    Does it kill the OTHER stage of a flea? The pupae stage?
    Is there anything that will

    • Adam Retzer September 29, 2017, 10:49 am

      Pupae and cocooned adults (and larvae already existing in the carpets at the time of application) are the problem stages of fleas. Unfortunately, there is little that can be done to eliminate pupal fleas besides waiting for them to emerge as adults. This is because many reside at the base of carpets (or other refuges) where the insecticides can’t penetrate. Vacuuming is the most helpful thing to do to speed up their emergence.

  • Karen Hall October 1, 2017, 12:59 pm

    If the carpet gets wet in a 3×3 area will it wash the Siphotrol away. I got the carpet wet a week after spraying. Thanks

    • Adam Retzer October 2, 2017, 10:43 am

      Wet carpet cleaning or steam cleaning can reduce the efficacy of insecticides. However, if water was simply spilled on the carpets, then I wouldn’t think the insecticides would be too diluted and it shouldn’t reduce the residual effect much. It probably depends on how the water got on the carpets, and how much water. But I have no exact answer.

  • Michelle October 4, 2017, 10:30 am

    We discovered fleas at the end of August. We’ve used 2 cans of the premise spray 2000, our cats and dog have been treated with Advantage II, (2 doses), we vacuum every other day, sometimes every day and i am still finding new fleas (around the house, and on pets). Is there something i am doing wrong? Or is it just a matter of time? I feel like i am going crazy!

    • Adam Retzer October 4, 2017, 12:40 pm

      Michelle, it sounds like you are doing everything correctly. It can take a while for the infestation to end, usually around 8 weeks. It can take longer in severe infestations or if the infestation went unnoticed for a while. Since you are only around 5 weeks in, it’s normal that you are still seeing fleas appear. However, their numbers should be diminishing. Have you noticed a decline in the number of fleas?

  • Alison November 10, 2017, 11:16 am

    SIphotrol is the only product that really got rid of the fleas.

    It also works on silverfish and ants, even pharaoh ant! and those like **&^ are harder to get rid of than fleas, but at least don’t bit.

    DAMN i hate bugs!

    Buy this, it’s AWESOME!!!

  • Shelley Thomas November 14, 2017, 10:57 am

    How long do I need to stay out of my apartment before I can go back in

    • Adam Retzer November 14, 2017, 11:23 am

      For liability reasons, I can only advise you follow the labeled instructions. The directions say: Avoid thoroughly wetting surfaces. Mist treated areas only until “slightly damp”. Do not over-treat. Keep people and pets out of areas during treatment. Vacate room after treatment and ventilate until surfaces are dry before reoccupying.

      How quickly the spray dries will vary depending on the user. Environmental conditions like ambient temperature and relative humidity will play a role. Drying time will also depend on how much individual users spray, as some will get the carpets damper than others. In general, treated carpets will likely dry in 3 to 6 hours.

  • Marie LIDSTER November 24, 2017, 12:23 pm

    I have bought Siphotrol spray , but when I spray white circles of liquid drop to the floor , leaking from the can , what am I doing wrong ?
    Thank you .

    • Adam Retzer November 29, 2017, 3:20 pm

      It sounds like it may just be an issue with the can. I won’t be able to help much. If it’s a malfunction with the can, I’d recommend contacting the retailer or the manufacturer (Wellmark International). Or, on the label, it says to call 1-800-766-7661 for product use information.

      Are you holding the can upside down, as the instructions say? “Hold container upside down 2-3 feet from surface, point actuator towards the surface, and push button.”

  • Harry Kron December 16, 2017, 9:06 pm

    I mostly have hardwood floors. How long do I need to wait before I can damp mop the floors? And basement floors? And what about having upholstery professionally cleaned?

    • Adam Retzer December 18, 2017, 1:19 pm

      It usually takes around 8 weeks for flea infestations to end. And the insect growth regulator in the spray (methoprene) will remain active for 7 months to help prevent future infestation.

      Mopping the floors (or other wet cleaning) will reduce the efficacy of the spray. I don’t have any specific, established advice for how long to wait before you clean with water. But I think it would be best to wait at least 8 weeks. If you do it sooner, it would be a good idea to re-treat the surfaces, especially flea hot-spots (cracks in the flooring, around baseboards, and other areas where debris collects, especially in rooms and locations where the dog or cat liked hanging around). In the meantime, dry vacuuming is the better option if you want to ensure the insecticides remain active.

      The same goes for getting the upholstery professionally cleaned. I am not sure the techniques they use, but if they are wet cleaning, then it would be a good idea to re-treat afterwards.