Cyfluthrin kills a wide range of insects and arthropods, from common household pests like ants, cockroaches, and bed bugs to agricultural threats like armyworms, aphids, and leafminers. It is a synthetic pyrethroid insecticide, meaning it’s a lab-made version of compounds naturally found in chrysanthemum flowers, engineered to be more potent and longer lasting.
Full List of Pests Cyfluthrin Kills
Cyfluthrin is labeled for use against dozens of pest species. The EPA-registered label includes ants (including carpenter ants and fire ants), aphids, armyworms, bed bugs, beetles, booklice, boxelder bugs, carpenter bees, carpet beetles, caterpillars, centipedes, clover mites, cluster flies, cockroaches, crickets, earwigs, elm leaf beetles, firebrats, flies, flour beetles, fruitworms, fungus gnat larvae, grasshoppers, hornets, Indian meal moths, leafminers, leafrollers, loopers, Mediterranean flour moths, millipedes, mosquitoes, rice weevils, scale insects, scorpions, silverfish, sowbugs, spiders, springtails, thrips, ticks, wasps, waterbugs, and yellowjackets.
That breadth is one reason cyfluthrin appears in so many different products. It works on crawling pests, flying pests, and everything in between. Whether you’re dealing with a scorpion in the garage or aphids on a tomato plant, cyfluthrin is formulated to handle both.
How It Kills Insects
Cyfluthrin attacks the insect nervous system. Specifically, it binds to voltage-gated sodium channels, which are tiny gates in nerve cells that open and close to transmit electrical signals. Normally these channels open briefly, send a signal, then snap shut. Cyfluthrin forces them to stay open longer than they should, which floods the nerve cell with sodium ions and triggers uncontrolled, repeated firing.
This causes a cascade of effects. The insect’s muscles begin to twitch and spasm uncontrollably. Coordination breaks down quickly, leading to what pest professionals call “knockdown,” where the insect flips onto its back and can no longer move purposefully. The sustained nerve overstimulation eventually leads to paralysis and death. Because cyfluthrin works on contact and through ingestion, insects don’t need to eat a bait. Simply walking across a treated surface is enough.
Where Cyfluthrin Is Used
Cyfluthrin pulls double duty across residential and agricultural settings. On the structural pest control side, it’s applied around home foundations, along baseboards, in cracks and crevices, and in storage areas to control cockroaches, ants, spiders, bed bugs, and pantry pests like Indian meal moths and flour beetles. Common commercial products include Tempo SC Ultra, Cy-Kick CS (a controlled-release formulation), Temprid FX (which pairs cyfluthrin with a second active ingredient), and Tempo Ultra WSP, a water-soluble packet designed for professional use.
In agriculture, cyfluthrin is registered for use on a long list of crops. The EPA maintains tolerances for residues on citrus fruits, stone fruits, pome fruits (like apples and pears), tree nuts, leafy greens, brassica vegetables (broccoli, cabbage, cauliflower), fruiting vegetables (tomatoes, peppers), and several other crop groups. Farmers use it to protect against caterpillars, aphids, armyworms, loopers, and other insects that damage yields.
How Long It Stays Active
One of cyfluthrin’s selling points is residual activity, meaning it continues killing insects for days or weeks after application. How long that lasts depends heavily on where and how it’s applied. Research testing beta-cyfluthrin on concrete surfaces found that under stable indoor laboratory conditions (around 80°F), effective knockdown of red flour beetles persisted through 10 weeks of exposure tests. But the same formulation stored in a grain bin or rice mill lost effectiveness faster as weeks progressed, with noticeably slower knockdown by the end of the study period.
The takeaway: cyfluthrin lasts longer on protected indoor surfaces and degrades faster when exposed to heat fluctuations, sunlight, and moisture. Outdoor applications generally need to be reapplied more frequently than indoor treatments. Controlled-release formulations like Cy-Kick CS are designed to extend this residual period by slowly releasing the active ingredient over time.
Risks to Beneficial Insects and Aquatic Life
Cyfluthrin is not selective. It kills beneficial insects alongside pests, and two groups are particularly vulnerable: pollinators and aquatic organisms.
Honeybees are highly sensitive to cyfluthrin, with a lethal dose of just 0.037 micrograms per bee on direct contact. That’s an extraordinarily small amount, which is why EPA registration reviews have flagged pollinator risk from both agricultural and outdoor non-agricultural uses. Applying cyfluthrin to flowering plants or during times when bees are actively foraging significantly increases the chance of killing pollinators you want to keep around.
Aquatic toxicity is even more striking. Cyfluthrin is lethal to bluegill sunfish at just 1.5 parts per billion and to rainbow trout at 0.68 parts per billion. Freshwater invertebrates like water fleas are killed at 0.14 parts per trillion, a concentration so low it’s almost undetectable. Marine organisms are similarly vulnerable: mysid shrimp die at 2.42 parts per trillion. For context, one part per trillion is roughly equivalent to a single drop in 20 Olympic swimming pools. Even tiny amounts of runoff into streams, ponds, or storm drains can be devastating to aquatic ecosystems.
Birds, by contrast, tolerate cyfluthrin well. The EPA classifies it as practically non-toxic to both upland game birds and waterfowl.
Practical Considerations for Use
If you’re using cyfluthrin products around your home, a few things matter. Apply it to cracks, crevices, and perimeters rather than broadcasting it over large open areas, especially outdoors. This limits exposure to pollinators and reduces the chance of runoff reaching water. Avoid spraying near ponds, streams, or drainage ditches entirely.
For indoor use, cyfluthrin is effective against the pests most people are trying to get rid of: roaches, ants, spiders, bed bugs, and silverfish. Its residual activity means a single application can keep working for weeks on undisturbed indoor surfaces. Reapplication timing depends on the product formulation and how much foot traffic or cleaning the treated area gets.
In agricultural settings, cyfluthrin remains widely registered for crop protection, though the EPA’s ongoing registration review has introduced updated labeling requirements around pollinator safety and aquatic buffer zones. Tolerances for residues on food crops are set at low levels, typically ranging from fractions of a part per million up to 6 ppm depending on the crop.