Although daily temperatures remain low, we are entering the time of year when the blowfly threat becomes real. Blowfly becomes active from mid-May to autumn.

The main factors to consider when choosing the product to cope with blowfly are the length of prevention offered and the withdrawal period associated with each product.

There are a number of factors that may increase the risk of a blowfly attack. The first is temperature. As temperatures start to rise in mid to late May, fly activity

increases which can bring about the onset of fly strike. Scouring and dirty lambs pose the highest risk for fly strike.

Another factor that will influence it is shearing. Although shearing will protect ewes to some extent by removing wool cover and dirty wool on the rear, skin damage caused by shearing may attract flies to the area and give grounds for an initial strike.

The female fly can lay close to 3,000 eggs. Generally, these will be laid in numerous clumps.

Sheep should be checked daily during periods of high risk to ensure that if fly strike has occurred that it is detected and treated quickly. An obvious sign of fly strike is

agitated sheep that walk quickly with tail swishing or biting at the affected area. The presence of maggots will generally only be detected by close examination.

Prevention

Prevention is always better than fire-fighting the problem with treatment. Prevention can be carried out using either a pour on or a dip. Cost should not be looked at as the sole concern when selecting a product. The duration of cover and method of application should also be taken into account when choosing the correct product for you.

Products available for prevention and treatment of fly strike include those with control periods of up to 9 weeks, Cyperguard and Ecofleece, control periods of up to 8 weeks, Ectoflits, Ectofly and CLiKZiN, control periods of 5-8 weeks, Summer Dip, control periods of up to 16 weeks, CLiK, and control periods of up to 10 weeks, Youngs Vector.

Pour-ons

The most common preventative treatments used are pour-ons due to their easy administration. Over the last few years there has been an increasing variety of pour-ons available on the market. CLiK, CLiKZiN and Ectofly are the most common products used for preventing blowfly strikes.

CLiK has a long withdrawal period of 40 days. CLiKZiN is a more recent product and comes with a much shorter withholding period of seven days. CLiKZiN and Ectofly

have control periods of up to eight weeks. CLiK has a much longer control period of up to 16 weeks, but this comes with a longer withdrawal period.

Because of this, CLiK may not be preferred for use on lambs from early lambing flocks that will have a shorter period to slaughter.

Farmers more commonly use CLiK on younger or lighter lambs where the 40 day withdrawal period will not be an issue.

Youngs vector is the final pour-on product available on the market. However, this has a wider range of parasitic control. It is active against ticks, headlice and biting flies.

It can also be used to both prevent and treat fly strike. It has a control period for the prevention of fly strikes for up to ten weeks and comes with a withdrawal period of

seven days which is similar to CLiKZiN.

Dipping

Although pour-ons are more commonly used, dipping offers the added benefit of being able to target a wider range of external parasites and sheep scab.

However, where farmers are considering dipping, they should be aware that the control period with dipping products is generally shorter than pour-ons. There are

several methods of dipping available, plunge dipping, shower and spray units. It is essential when mixing the dip solution to do so to the correct concentration as specified on each product and have extra on hand to allow for losses and top-up of dip bath.

Dagging

There are several management practices that can be adopted that will lessen the risk of a blowfly attack. Sheep should be dagged before the risk period to reduce the risk of flies laying eggs. Scouring sheep and lambs can also result in them having dirty and wet flanks which can attract flies. It is essential the lambs are dosed in advance of the risk period to reduce the risk of scouring.