Insect Growth Regulators (IGR)

What do they treat?

√ Premises flies √ Cattle tick √ Lice

When using the product to target a particular parasite, be aware that it will be treating any other of the above-mentioned parasites that are present. This can increase the development of pesticide resistance to all of these parasites each time an IGR product is used.

Note: √ Toxic to spiders, crustaceans and beneficial insects such as bees and predators of house fly larvae.

How can they be administered?

A variety of application methods for administering pesticide products to cattle are in use.

√ Pour-on √ Premises surface spray √ Water soluble granules for premise

Resistance

Reported in: √ Flies √ Cattle tick

What is resistance?

Safety

Everyone working in the rural industry has a ‘duty of care’; a legal obligation to provide a safe workplace for everyone on the property.

• IGRs have selective toxicity and therefore are relatively safe to human health.
• Ensure appropriate on-farm disposal of spent fluids. It is important that wastes do not enter watercourses where they may cause environmental harm, or accumulate in areas grazed by animals as IGRs bind tightly to soil and degrade slowly.

Withholding

Withholding periods are mandatory with all registered veterinary products used to treat animals for internal and external parasites.

• Always check the product label before use for specific withholding periods (WHP) and export slaughter interval (ESI) periods. Current ESI periods can be confirmed on the APVMA website.

Types of insect growth regulators

A guide to the different chemical actives and the pests they affect are in Table 1. See the Products Search Guides for FlyBoss, LiceBoss, WormBoss and TickBoss for the appropriate formulation and application method for your target pest. Note that combinations and mixtures of actives may improve treatment efficacy.

Table 1. Insect growth regulators, their actives and mixtures and a summary of the targeted parasites against which formulations are registered for.

*IRAC Mode of Action Diflubenzuron group 15; Cyromazine group 17

What are they?

Insect growth regulators (IGRs) are sometimes called development inhibitors. The chemicals interrupt insect growth and development by interfering with the production of chitin – the compound insects, ticks, lice and mites use to make their exoskeleton.

How do they work?

As arthropods grow their exoskeleton becomes too small and they have to shed this outer skin (moult) to continue growing. This new skin requires chitin synthesis and IGRs inhibit this process causing the larvae to stop growing and developing into an adult. IGRs also inhibit egg hatching.

IGRs are slow-acting compounds that eliminate infestations over many weeks. Adult stages are not killed by IGRs because they do not moult.

Diflubenzuron is a broad spectrum larvacide used in bait formulations for nuisance flies and for treating lice on cattle.

Cyromazine is a narrow spectrum larvacide that is only effective against dipteran larvae i.e. flies. As cyromazine is specific against house flies it is not toxic to the beneficial insects that live in livestock manure if used as directed.

Fluazuron is effective against ticks, but not flies.