The development of insecticide resistance allows individual insects to survive an exposure to insecticide that would kill individuals from a ‘normal’ population.
The sheep blowfly, Lucilia cuprina has developed resistance to at least three classes of insecticides that have been used to treat or prevent flystrike on sheep.
There are a number of management strategies that sheep producers can adopt to minimise the development of resistance or at least delay the onset of resistance.
- Adopt an integrated pest management strategy that incorporates non-chemical controls such as genetic selection and timing of shearing and crutching to reduce the reliance on chemicals. Only use insecticides when absolutely necessary. This reduces selection pressure.
- If treatment is needed, make sure it is applied effectively - do it right, once!
- Know which insecticides belong to which insecticide class. If treatments for lice and flystrike are deemed necessary, use different insecticides and appropriate classes for each pest. Use the FlyBoss tools (product listing) to ensure that you are using different classes of chemical for flystrike and lice treatment.
- Also use insecticides from different classes for treating and preventing flystrike. This is particularly important if relying on insecticides to kill larvae on flystruck sheep. It is important to break the cycle and ensure maggots on struck sheep do not survive. Non-insecticidal methods are more reliable than flystrike dressings for this purpose - dressings are mainly to prevent re-strike.
- Be aware that resistance to one insecticide may cause a cross-resistance to another related insecticide.
As with all chemical treatments, follow the label directions and keep a record of the product (including batch number), dose rate, date of treatment and mob treated, for future reference.
Report adverse outcomes (product failures) to the company and to the Australian Pesticides and Veterinary Products Authority (APVMA).
For detailed information on resistance in sheep blowfly larvae download the following document.