The label is the law. Rates and restrictions below are taken from the product labels listed under Sources. Your product's own label governs; read it before you mix or apply. Mixing calculator · Disclaimer
- Active ingredient
- Cyromazine (CAS 66215-27-8)
- Chemical class
- IRAC Group 17 moulting disruptor for Diptera (flies); cyromazine is the only active in the group.[2]
- Mode of action
- IRAC Group 17: Moulting disruptors, Dipteran: cyromazine[2]
- Signal word
- Neporex 2SG: Caution[1]
Why adult flies don't disappear overnight
Cyromazine interferes with molting, so maggots fail to develop into flies. Adults already flying aren't affected, and the label says the drop in adult numbers shows up gradually over one to two weeks.[1]
For faster relief, the label recommends using an adult fly product at the same time, along with sanitation such as removing wet manure, fixing water leaks and cleaning up spilled feed.[1]
Rules for treated manure
Manure treated with Neporex 2SG can be spread as fertilizer, but not more than 4 tons per acre per year, and never on small grain crops that will be harvested or grazed.[1]
Don't use it on manure from chickens fed Larvadex 1% Premix, a cyromazine feed additive; the label forbids combining the two.[1]
Where it is used
Treat only where flies breed, such as manure, wet spilled feed and soiled bedding. It has no effect on adult flies, so spraying walls or ceilings where flies rest is wasted.[1]
Scatter the dry granules only on wet or liquid manure. Otherwise, dissolve the product in water and apply it as a coarse, low-pressure spray.[1]
In poultry houses, spray the whole manure area about a week after manure removal. In deep-litter cattle and hog pens, spray about 3 days after cleanout and repeat after each removal or when larvae reappear.[1]
In horse barns, scatter it under bedding on cleaned stall floors and treat manure piles. Horses in treated barns must not be intended for slaughter or food.[1]
Products and registrations
| Product | Registrant | EPA Reg. No. | Active % | Formulation | Signal word |
|---|---|---|---|---|---|
| Neporex 2SG[1] | Elanco US Inc. | 70585-7 | 2.0% | water-soluble granule | Caution |
Label rates
| Product | Use | Pests | Rate |
|---|---|---|---|
| Neporex 2SG | Manure and other fly breeding sites in cattle, hog and poultry operations and in barns for horses not raised for food | House fly, lesser house fly, stable fly and soldier fly larvae | 1 lb product per 200 sq ft of breeding site[1] Scatter 1 lb dry, or dissolve 1 lb in a gallon of water and spray it, over each 200 square feet. Retreat no more often than every 21 days. |
Safety and environmental hazards
People
Signal word CAUTION: causes moderate eye irritation. Wear protective eyewear, avoid contact with skin and clothing, and wear gloves when scattering the granules by hand.[1]
Pets
Never apply it directly to livestock or their feed, never feed treated manure to animals, and keep it out of feed and water troughs. Allow one day between the last application and slaughter.[1]
Bees and pollinators
The label has no bee statement; the product goes only on manure and other fly breeding sites.[1]
Fish and water
The environmental statement says not to contaminate water when disposing of equipment washwater or rinsate.[1]
Common questions
- Does cyromazine kill adult flies?
- No. Neporex 2SG works only on fly larvae, and the label says it has no effect on adult flies.[1]
- How often can I apply Neporex 2SG?
- No more often than once every 21 days. Depending on housing, management and climate, the interval can stretch to several months.[1]
- Can I use it in my horse barn?
- Yes, in barns for horses not intended for slaughter or food. Treat stalls, manure piles and wet spots, and repeat after each cleanout or when larvae are found.[1]
Sources
- U.S. EPA Pesticide Product Label System, “Neporex 2SG label, EPA Reg. No. 70585-7 (EPA-stamped, Sept. 2, 2010).” www3.epa.gov/pesticides/chem_search/ppls/070585-00007-20100902.pdf (accessed 2026-10-06)
- Insecticide Resistance Action Committee, “IRAC Mode of Action Classification Scheme, Version 11.5 (Feb. 2026).” irac-online.org/documents/moa-classification/ (accessed 2026-10-06)