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Beyond the Bale : June 2019
40 ON FARM It is vital that sheep producers prudently manage their use of flystrike insecticides, to maintain protection for their flocks and slow the development of resistance within their local fly populations. Producers should follow the eight-step strategy below, developed by AWI’s Sheep Blowfly Resistance Management Strategy Working Group. INSECTICIDE RESISTANCE STRATEGY TO MAXIMISE FLYSTRIKE CONTROL KEY POINTS • The Australian sheep blowfly has demonstrated a capacity to develop insecticide resistance to a variety of insecticide groups, reducing their effectiveness. • There are only a limited number of insecticides registered against flystrike so increasing insecticide resistance will have a significant impact on the industry. • There is an urgent need for sheep producers to strategically manage the use of insecticides to maximise flystrike control and to maintain the efficacy of available products on their property. There have been a number of confirmed cases of the Australian sheep blowfly having developed some resistance to insecticide treatments, with some sheep producers having noticed shorter protection periods than claimed on the label of the flystrike products they have used. This is a timely reminder for sheep producers to implement strategies to manage insecticide resistance. There are only a small number of chemical groups registered for flystrike control, so it is important to prolong the useful life of these insecticides on your property for as long as possible. “Without access to effective preventative insecticide treatments to control flystrike, sheep producers would be more reliant on mulesing, crutching and continual surveillance of flocks followed by manually clipping and dressing of wounds,” explained AWI General Manager for Research Dr Jane Littlejohn. “By implementing resistance management strategies, sheep producers can slow the development of resistance, which will help increase the effective life of registered insecticide products.” AWI’s Sheep Blowfly Resistance Management Strategy Working Group members have developed the following eight steps for sheep producers to follow to slow the development of resistance. 1. USE AN INTEGRATED APPROACH TO REDUCE RELIANCE ON INSECTICIDES • Breed for resistance to all types of flystrike: poll, pizzle, body and breech (breeding for polled animals; low wrinkle, cover, urine stain, dags; and white wool colour. Cull struck sheep). • Shear or crutch at times that maximise protection against flystrike. • Dock tails to the correct length. • Manage sheep to minimise scouring. • Use breech modification if required, until sheep are genetically resistant to flystrike. • Use chemicals sparingly. • Where the above approaches are insufficient, mules with pain relief. 2. KNOW YOUR CHEMICAL GROUPS • Insecticides used for flystrike control fall into different groups or chemical families; see Table 1 below. • Flies resistant to one insecticide in a particular chemical group are likely to be resistant to other insecticides in the same group. • Different flystrike products may contain the same chemical or a related chemical from the same chemical group. When looking for alternatives, change to a different chemical group, don’t just change insecticide brands. • Use the FlyBoss Fly and Lice Products Tool at www.flyboss.com.au/tools/products. php to search for flystrike products, determine their chemical group and make your selection. 3. ROTATE CHEMICAL GROUPS WHERE PRACTICAL Insecticide choice should be tailored to your particular location and management. • Consider rotating insecticide products from different chemical groups to slow the development of resistance. • Use a different chemical group for treating struck sheep to that used for flystrike prevention. • Successive treatments within the fly season should generally be different chemical groups. • Choose a product with the appropriate protection period and time of application. – A product that provides a shorter period of protection may be sufficient in some instances. For example, when sale of sheep or lambs for slaughter is imminent, when sheep are soon to be crutched or shorn, or when close CHEMICAL GROUP CHEMICAL ACTIVE APPLICATION METHOD1 Spray-on Jetting Dipping Dressing Insect Growth Regulator (IGR) Cyromazine Yes Yes Yes Yes Dicyclanil Yes No No No Neonicotinoid Imidacloprid Yes No No No Spinosyn Spinosad No Yes No Yes Macrocyclic Lactone (ML) Ivermectin No Yes No Yes Synthetic Pyrethroid (SP) Alpha-cypermethrin2 Yes No No No Organophosphate (OP) Diazinon, Propetamphos & Chlorfenvinphos No No No Yes Table 1. Chemical groups and actives available for flystrike control and their application methods 1 Always follow label directions 2 Registered for prevention of body strike only