Flystrike occurs only when the combination of susceptible sheep, suitable weather and the presence of flies occurs at the same time.

It is impossible to control the weather, and very difficult to have an impact on fly numbers, but you can breed and manage sheep to be less susceptible to flies.

Maggots initially do not feed on skin for the first 18 hours or so after hatching until they moult. Then they start to feed on skin and the sheep will begin to show signs of irritation. Eggs hatch to larvae (maggots) in about 12 hours. First instar larvae have tiny mouthparts and feed in damp fleece, fleece rot and dermatophilosis lesions, in and around wounds or in dags. About 18 hours or more after hatching larvae moult to become second instar larvae, and start feeding and can now abrade the sheeps skin. About 36 hours or more after hatching a second moult occurs to become third instar larvae, which are very active, feed voraciously and do most damage to the sheep. When fully fed, about 3-4 days after hatching, they drop from the sheep, usually in camps at night, burrow into the top few centimetres of soil and pupate. Under ideal conditions an adult fly will emerge about 8 or 9 days later (12 days after the egg from which it was derived was laid). http://www.flyboss.com.au/susceptibility/blowfly-biology.php

By monitoring each 2-3 days (e. g By monitoring each 2-3 days (e.g. Mon, Wed, Fri), sheep that do get struck should be found when strikes are small: less than 10 cm(4”) across, and the strike itself may not be visible, but the sheep’s behaviour will indicate it is struck. If strikes are found bigger than this, monitoring is not being done frequently enough or thoroughly enough.

Flies cost the sheep industry $280 million annually in deaths and lost production, and prevention and treatment costs.

Without the 3 factors at once, strike will not occur.

Wool that retains moisture (yellower wool) (body strike) Susceptibility increases with: More skin wrinkles/folds at breech (breech strike) Wool stained by urine or dag (breech and pizzle strike) Fleece rot caused by: Conformation causing skin to remain wet (dipped back, devil’s grip) (body strike) Wool that retains moisture (yellower wool) (body strike) Dermatophilus (lumpy wool) (body strike)  Open wounds and blood (rams fighting, injuries, tail docking, castration, mulesing) (poll, body and breech strike) All have damaged weeping skin or bacterial growth or dag, which is attractive site for female flies to lay egg. This provides moisture and food for newly hatched maggots. http://www.flyboss.com.au/susceptibility.php

Hotter regions will have flies all year round. Cold regions will have a break when flies are in the ground during the cold. Flies do not travel far away from water and sheep http://www.flyboss.com.au/susceptibility/blowfly-biology.php

At the lower and upper end of the temperature range, flies are less active. When it is very windy, flies cannot beat the wind when trying to fly and land in specific places, such as landing on susceptible sheep. Wet or humid conditions will help to maintain the susceptibility of sheep, by not allowing fleece, urine stain or dag to dry out. http://www.flyboss.com.au/susceptibility/seasonal-conditions-and-geography.php

An flystrike prevention plan that integrates a number of strategies will be most effective. These will include management, breeding and chemical options. http://www.flyboss.com.au/management/annual-flystrike-management-plans.php

Management strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 1.    Shearing, crutching and lambing dates Use the FlyBoss Compare management tool to see the impact on flystrike risk from changing your shearing and crutching time. Consider these dates with the ideal lambing time for your situation and decide whether your current shearing and crutching dates should be moved for better flystrike control (depending on the practicality of moving these dates). This tool will show you the times of highest risk of flystrike.

Management strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 2.    Breech modification strategies The breech modification page describes the available options: no modification, mulesed, clips (or a combination of these). If you still mules sheep, but wish to stop, consider phasing it out in the least susceptible sheep first and assessing whether changed or extra crutching or chemical applications may be needed. Mob average breech wrinkle score 2 quite resistant to flystrike http://www.flyboss.com.au/management/breech-modification.php Ensure that the tail is docked to the correct length.   You can also change your breech modification strategy in the FlyBoss  Compare management tool to see the impact on flystrike risk. Clips are not used very much (on <2% lambs) Skin Traction still in development phase. http://www.flyboss.com.au/management/tail-length.php

Breeding strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 3.    Selection strategies (breeding for flystrike resistance) Different strategies for breeding and selection may be used for rams, ewes and retained wethers. Rams can be purchased with Australian Sheep Breeding Values for breech wrinkle, breech cover and dag, which can be used in conjunction with performance data. Be aware that housed and coated rams are less exposed to weather and this can mask their susceptibility to fleece rot and flystrike. Ewes that are less susceptible to flystrike can be chosen using Visual Sheep Scores.   The risk of flystrike can be reduced by selecting for a plainer body and breech, less or no fleece rot, whiter wool, less or no dag, and less wool around the breech. The extent of urine stain can also be used as a selection factor. THE MOST IMPORTANT ARE FLEECE ROT, BREECH WRINKLE, DAG (where it is common). Breech cover should be added as a selection criteria after breeches are plain, because improvement in wrinkle can be made a lot faster than breech cover Decide how to deal with struck sheep. As they are more likely to get struck again in the future, they are best treated and sold when beyond the withholding periods of their treatment. These sheep should not be kept as breeding stock, but could be kept as dry sheep. Image shows array of breech wrinkle on young rams in a particular flock. http://www.flyboss.com.au/breeding-and-selection/breeding-to-reduce-flystrike-susceptibility.php http://www.flyboss.com.au/breeding-and-selection/visual-sheep-scores.php http://www.flyboss.com.au/breeding-and-selection/australian-sheep-breeding-values.php http://www.flyboss.com.au/breeding-and-selection/fleece-rot-scoring-and-selection.php http://www.flyboss.com.au/breeding-and-selection/breech-wrinkle-scoring-and-selection.php http://www.flyboss.com.au/breeding-and-selection/dag-scoring-and-selection.php

Breeding strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 4.    Dag management strategies Dag is a major factor in flystrike, especially in winter rainfall areas.  Dag can be reduced by selection against it, crutching, improved scour worm control and more gradual transition onto high quality feed. http://www.flyboss.com.au/breeding-and-selection/dag-scoring-and-selection.php

Chemical strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 5.    Treatment chemical group The choice of chemical product group may determine how the product must be applied to the sheep. Resistance of flies to insecticides is present and there are management strategies that sheep producers can adopt to minimise the development of resistance or at least delay the onset of resistance. http://www.flyboss.com.au/treatment/choosing-the-right-chemical.php http://www.flyboss.com.au/treatment/insecticide-resistance.php

Chemical strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 6.    Application method The method you choose must be effective. Consider the cost of equipment and skills required for application, as well as the advantages and disadvantages of each method. Jetting should wet the sheep to the skin on the backline with the fluid running down the sides at skin level and emerging at the belly. Spray-on preventative treatments must be applied to the places on the sheep you wish to protect. Dipping not recommended for either prevention or treatment. http://www.flyboss.com.au/treatment/choosing-the-right-application-method.php

Chemical strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 7.    Commercial product Once a chemical group and application method are decided, use the FlyBoss Products Tool to see which commercial products may be suitable. This will generate a list of products including their withholding period (WHP), wool re-handling interval (WHI), export slaughter interval (ESI) and typical price per pack and per sheep. http://www.flybosstools.org.au/

Chemical strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 8.    Optimum time you apply treatment Use the FlyBoss optimize treatment tool to view how the overall risk of flystrike changes with different products used at different times. With a product in mind, review the most effective time to apply the treatment. You can choose: Shearing date, 1 or 2 crutching times Breech modification 1 or 2 treatments and their times. Select ‘optimize’ to find the most effective time to apply your chosen chemical. If treatment is needed in more than 1 in 2 years, then choose a set time to treat (Use the FlyBoss Optimise Treatment tool), rather than wait and see. http://www.flybosstools.org.au/

FlyBoss Optimise Treatments Tool example for Hamilton Victoria. This slide shows flystrike risk throughout the year with no effect from shearing, crutching or treatments. This example has no breech modification – i.e. the sheep are not mulesed.

FlyBoss Optimise Treatments Tool example for Hamilton Victoria. This slide shows a mid-February shearing selected. Flystrike risk decreases after shearing.

FlyBoss Optimise Treatments Tool example for Hamilton Victoria. This slide shows a mid-February shearing selected AND cyromazine (applied in the first week in October. This further reduces flystrike risk.

FlyBoss Optimise Treatments Tool example for Hamilton Victoria. This slide shows a mid-February shearing selected AND cyromazine applied. However, the Optimise button on the tool has been used. It moves the treatment time (won’t moveshearing or crutching) to a time that has the least overall flystrike risk for the year. In this case it has moved it to the 3rd week of November.

Chemical strategies http://www.flyboss.com.au/management/annual-flystrike-management-plans.php 9.    Predicted wool residues If you aim to sell your wool into a market sensitive for chemical residues, use the FlyBoss Wool Res tool to see whether your chosen chemical and time of application will allow your wool to remain below residue threshold levels. Most Australian wool complies with recommended maximum residue levels, however, some lots exceed these levels and there is the risk that these could be tested by buyers and rejected. http://www.flybosstools.org.au/

In areas with low annual rates of flystrike, mob preventative treatments are not warranted. In these areas sheep should be monitored each 2-3 days during risk periods, so that sheep with early signs of strike can be treated. Should conditions become higher risk, undertake a mob treatment. http://www.flyboss.com.au/treatment.php

Treating struck sheep: Machine shearing generally does a better job than hand shearing a strike IGR chemicals (cyromazine and dicyclanil) are not suitable dressings on welfare reasons as their mode of action takes up to 4 days for maggots to be killed. http://www.flyboss.com.au/treatment/treatment-of-struck-sheep.php

For districts where an annual mob treatment in required in fewer than half the years: Monitor during risk periods and treat individual struck sheep Apply a mob treatment when Weather becomes favourable for flystrike Strikes are already occurring Unable to monitor each 2 days when there is flystrike risk PUBLIC PERCEPTION ISSUE Once about 1 in 200 sheep are being struck in one week, and favourable conditions for flystrike are continuing, mob treatment should be applied simply on an economic basis. However, any level of strike used as a trigger for mob treatment could be seen as unacceptable on welfare grounds. http://www.flyboss.com.au/treatment.php

http://www.flyboss.com.au/news/flyboss-online-learning.php http://www.makingmorefromsheep.com.au

Question 1. At which lower temperature do flies typically become active? 9°C 13°C 17°C (correct answer) 21°C Unsure

Question 2. What two characteristics are the most important to select against when breeding for reduced breech strike? Breech cover and breech wrinkle Breech cover and dag Breech cover and urine stain Breech wrinkle and dag (correct answer) Unsure

Question 3. Which insecticide chemical group is good for preventative treatments but not considered ideal for treating struck sheep? Insect growth regulator (correct answer) Macrocyclic lactone Spinosyn Synthetic pyrethroid Unsure

Question 4. Which of the following statements is false? Spray on flystrike preventative treatments take 4-6 weeks to spread and protect the whole sheep (correct answer) Hand-jetting is very effective for flystrike prevention Plunge dipping long-wool sheep provides poor flystrike prevention Resistance of maggots to flystrike products is not common Unsure

Question 5. In regions where a flystrike preventative is applied in most years, for the best economic and welfare result, what should determine it’s timing in most years? Treat the mob once strike reaches a trigger level (1 in 200 sheep struck in one week) Treat once there has been more than 25 mm rainfall in one week and daily temperatures are greater than 20°C Treat 6 weeks after shearing or crutching Treat at a set time each year based on long term weather records (correct answer) Unsure

Question 6. How confident are you that you can select sheep resistant to flystrike? (choose the number corresponding to your level of confidence)

Question 7. How confident are you that you can prevent any deaths from flystrike in your flock? (choose the number corresponding to your level of confidence)