Given the terrible weather experienced in recent months and the fact that temperatures have only really increased significantly last week, it is no wonder that for many farmers blowfly control considerations are not even on their radar.

However, this could quickly change with the high-risk season for tick-borne diseases also hitting at an earlier stage for hill sheep producers in recent years.

There are no significant changes in the range of products available to farmers to treat and prevent these ailments with the only developments in this area being a significant increase in the cost of products.

Table 1 details external parasite control options taking blowfly strike as the focal point and including other external parasites in the column on the right.

For easier interpretation, the table has been split into products licensed for plunge dipping and pour-on products.

The list is not exhaustive and includes the main options available to farmers in Ireland and Northern Ireland.

There are numerous other products licensed in the UK but, similar to Ireland, sales of CLiK-brand products are big business.

The data for the majority of products has been extracted from the Summary of Product Characteristics (SPC) published by the Health Products Regulatory Authority (HPRA) and, where applicable for UK-only products, from the Veterinary Medicines Directorate (VMD) Product Information Database. It is important that farmers are cognisant of any differences between product characteristics across different veterinary jurisdictions.

Important considerations

As can be seen, the products differ significantly with regards the suite of external parasites covered, the length of protection claimed and level of cover.

The other factor which is gaining in importance as lambs get older is withdrawal dates.

It is not surprising that plunge-dipping products offer the most extensive range of cover with control of sheep scab the big beneficiary from correct dipping. In the context of blowfly strike, dipping often faces criticism for the level of protection offered.

The product listings have a claim period typically ranging from five to eight weeks. However, the length of protection depends on a number of factors including weather, the efficacy of dip in the tub and the correct procedure being adopted.

Some farmers have moved away from dipping earlier in the season and are adopting a programme of dipping later in the season when products offering a longer period of protection are waning in cover and there is a greater focus on other external parasites.

Cyperguard is the only product in Ireland with a claim to treat ticks.


The convenience of pour-ons has largely replaced dipping earlier in the season as the main form of preventative control for blowfly strike.

There are big difference in the level of protection offered with CLiK products providing the longest duration of protection, but also possessing the longest withdrawal rates.

It is worth noting that an earlier application can often work better in providing cover earlier in the season, suit withdrawal dates and require less product, as lambs are treated at lighter weights.

The product of choice for many hill sheep farmers in Ireland located in areas where ticks are an ongoing challenge is Youngs Vector due to the fact it targets blowfly strike, ticks and headflies. Farmers in the UK have access to a much wider range of products although many possess the same treatment properties, for example Vectocert.

Its SPC advises that for tick control for lambs less than 10kg, you should apply a 5ml treatment followed by 10ml three weeks later.

Dysect/Zermasect, which are also only available to farmers in the UK, have a different active ingredient to Youngs Vector and Vectocert but offers a similarly broad range of cover and two weeks longer blowfly protection.

The big difference however is a 49-day withdrawal period.

Ectofly is also similar to the above named products but its claim for tick control extends just to treatment and not preventative control.

It is a common product in Ireland for shorter-term protection due to its short withdrawal date.

Top application tips

The mode of action in products such as CLiK is insect growth regulators (IGRs), which essentially stifle any development.

The UK body SCOPS explain that such products allow the female blowfly to lay her eggs but then prevent the larvae developing, stopping the lifecycle.

They prevent strike for eight to 16 weeks depending on product choice. They do not treat an existing strike.

Products with an active ingredient of cypermethrin/alphamethrin are pyrethroids and work by disrupting an insect’s nervous system, ultimately leading to death.

The method of application for pour-ons and condition of the fleece of sheep can have a big influence of the length of cover achieved.

  • Apply product to a clean, dry fleece and time the application to avoid contact with rain for six to 12 hours post-application.
  • Refrain from applying products during periods of intense heat where there is a risk of product evaporating before binding with the fleece. If product is being applied, do so indoors or late in the evening.
  • Many products provide protection where product comes in to contact with the fleece. As such, abide by manufacturers’ guidelines and cover high-risk areas such as the shoulder, back and rump regions.
  • Dag dirty tailends before applying to extend the period of cover.
  • Take note that some products have different applicators for blowfly, ticks, headflies.
  • Read manufacturer’s guidelines or seek advice when purchasing.
  • Tick-borne diseases

    As mentioned earlier, tick-borne diseases are becoming a greater issue earlier in the season, partly due to changing weather patterns. It is important to note that it is not just sheep health at risk. Farmers and members of the public traversing vegetation where ticks are present are also at risk.

    There has been a rise in the number of people contracting Lyme disease in recent years with the month of May designated as an awareness month for Lyme disease and other tick-borne diseases.

    It is important for farmers to be aware of the risks, including identifying areas of the farm where the environment sustains a tick population, and to tailor their external parasite control programme appropriately.

    With tick-borne diseases, the greatest risks for farmers in Ireland and Northern Ireland are typically tick-borne fever and louping ill. For tick-borne fever, the clinical symptoms are sheep being lethargic and stiff when moved, a reluctance to eat and running a high temperature.

    Clinical symptoms

    Louping ill is characterised by a nervous disposition in affected sheep due to the fact it causes neurological issues.

    The clinical symptoms to look out for with tick-borne fever include sheep being lethargic and stiff when moved, failing to eat and running a high temperature.

    Sheep in such habitats tend to develop immunity to disease, but young lambs and naïve sheep which have been introduced to the environment face a high risk.

    Life cycle

    As a tick progress through its three stages of development, it needs to feed on blood on a host such as sheep, cattle, dogs, humans, etc. It is during this period that disease spreads, with a feeding period lasting anywhere from four to 14 days.

    If animals are grazing areas with a very high tick infestation, anaemia or occasional blood loss can also occur. In such instances, ticks can be readily seen on the inner legs and belly region of lambs when turned over.

    Organic farming

    It is estimated that there is likely to be well in excess of 2,000 sheep farmers converting or farming in full organic status in 2024.

    The objective for external parasite control is to control blowfly strike by mechanical means, including shearing and regular crutching, dagging etc.

    However, chemical control options are permitted, if recommended and approved by your veterinary practitioner, for the prevention and treatment of blowfly strike and other external parasites.

    Plunge dipping can be carried out on-farm, where facilities are available or by a mobile plunge dipping service operator

    With regards dipping, the use of organophosphate-based dips are not permitted with the non-organophosphate based dip, Cyperguard, the only plunge-dipping product permitted.

    Scheme considerations

    Flystrike control is an annual action in the Sheep Improvement Scheme for lowland flocks but has only been selected by a small number of participants.

    There will be a greater focus on sheep dipping in 2024, as it is included as one of two options along with clostridial vaccination in the National Sheep Welfare Scheme.

    Plunge dipping can be carried out on-farm, where facilities are available or by a mobile plunge dipping service operator. Documentary evidence of completion of this action will include but is not been limited to, completion of the scheme action record sheets, receipts from a contractor and/or receipts for the purchase of appropriate dipping material.

    The action must be carried out on the number of breeding ewes selected by the farmer as a payable number at application stage.

    The deadline is 15 October 2024 or 25 November 2024 where farmers notify the Department of later dipping by 15 September 2024.

  • Control options should take into account the external parasites of risk, the length of protection required and withdrawal dates.
  • Protection will be optimised by applying product in the correct manner and to clean fleeces.
  • Take care to avoid applying product during periods of rainfall and to avoid letting sheep near water sources following dipping/application of pour-ons.