Pyriproxyfen (Nylar)

Pyriproxyfen (Nylar) — Long-Lasting IGR for Fleas & Mosquitoes

Insect Growth Regulator (Juvenile Hormone Analog) · CAS 95737-68-1

Pyriproxyfen (Nylar) is the second-generation juvenile hormone mimic after methoprene — more stable, longer-lasting, and effective at lower concentrations. It's the preferred IGR in many professional flea programs and is widely used for mosquito larval control.

Mode of Action Highly potent juvenile hormone mimic — more stable UV-stable and longer-lasting than methoprene; prevents larval maturation and induces sterility in adults at low doses

📋 Key Facts

Class

IGR — Juvenile Hormone Analog

Signal Word

Caution

Residual

Up to 7 months indoors; more UV-stable than methoprene

Adult Effect

Sterilizes adult female insects at low doses (unique)

Mosquito Use

WHO-approved for drinking water mosquito control

Key Products

Nylar, Archer IGR, Tekko, Martin's IGR

Bee Safety

Very low toxicity to bees

🎯 Primary Uses

Pyriproxyfen is used in: flea management programs (Nylar-containing sprays), mosquito larval control in standing water (more stable than methoprene in sunlight), stored product pest management, cockroach programs as a growth regulator component, and tobacco whitefly control. Its ability to sterilize adult females makes it particularly valuable.

🛡️ Safety Summary

Very low mammalian toxicity — one of the safest pesticides available. Well-tolerated by all mammal species. WHO-approved for use in drinking water containers for mosquito control in developing countries — a strong indicator of its safety profile.

🔬 Resistance Status

Very limited resistance documented. The adult sterilization effect provides population control even in populations with some larval tolerance. Considered a very durable pest management tool.

🏷️ Common Products

Nylar IGRArcher IGRTekko ProMartin's IGRZoecon RF-259

❓ FAQ

What's the difference between Nylar and Precor?

Nylar contains pyriproxyfen; Precor contains methoprene. Both are juvenile hormone mimics that prevent flea larvae from maturing. Pyriproxyfen (Nylar) is more UV-stable, longer-lasting, and also sterilizes adult females. Both are equally effective for indoor flea programs.

Is pyriproxyfen safe for fish?

Yes — pyriproxyfen is safe for fish at application rates. It's one of few pesticides approved by WHO for use in drinking water containers. It does not harm fish or other vertebrates at the concentrations used for insect control.

🦺 Personal Protective Equipment (PPE)

Required PPE varies by formulation and application method. Always read the product label — the label is the law and overrides general guidance.

Standard gloves

Low toxicity — minimal PPE required

Safe around mammals — targets only juvenile insect hormones

⚠️ Label compliance: The product label is a legal document under FIFRA. Applying any pesticide in a manner inconsistent with its label is a federal violation.

📋 Application Best Practices

Read the full label before each use — formulations change and label requirements may differ from previous products you've used.

Apply at the right rate — more is not more effective. Over-application wastes product, creates unnecessary exposure, and is illegal.

Target harborage and entry points, not just visible pest activity. Treating where pests hide is more effective than treating where you see them.

Record the application — note the product, rate, area treated, and date. Required for commercial applications; best practice for homeowners.

Ventilate the treatment area after application and before re-entry.

💡 Storage: Store in original container, away from children, in a cool dry location. Never transfer to food or beverage containers. Check local regulations for disposal — most areas have household hazardous waste collection events.

🌿 Environmental & Resistance Considerations

Responsible pesticide use protects both effectiveness and the environment:

Resistance management: Rotating to pesticides with different modes of action prevents resistance development. Avoid using the same active ingredient exclusively.

Pollinator protection: Apply in early morning or evening when bees are less active. Avoid applications to flowering plants.

Water protection: Do not apply before rain. Keep applications away from drains, waterways, and storm inlets.

Non-target species: Broad-spectrum insecticides affect beneficial insects. Consider targeted baits or dusts in sensitive areas.

❓ Frequently Asked Questions

How do I know which concentration to buy?

Consumer (RTU/concentrate) products are formulated for homeowner application rates. Professional-grade concentrates require accurate dilution — mistakes in either direction reduce effectiveness or create safety hazards. If you're new to pesticide application, start with ready-to-use formulations and work up to concentrates once you understand mixing and rates.

Can I mix this with other pesticides?

Tank mixing is common in professional applications but requires compatibility testing and label compliance. Never mix pesticides unless both labels permit it. One safe and effective combination: pair an adulticide with an IGR — they attack different life stages and don't interfere with each other.

How long does the treatment remain effective?

Residual activity depends on formulation, surface, UV exposure, and temperature. Micro-encapsulated formulations last longest (4–12 weeks). Wettable powders and emulsifiable concentrates typically last 2–6 weeks outdoors. Indoor applications on non-porous surfaces can persist significantly longer.

Is this product safe for use around pets and children?

All pesticides have some level of toxicity — 'safe' means used correctly according to the label. Keep children and pets out of treated areas until completely dry (minimum 2–4 hours for most sprays). For households with infants or chemically sensitive individuals, discuss low-exposure options (baits, dusts, IGRs) with a pest management professional.