Buyer Beware

shorn sheep

Resistance by worms, blowflies and lice is real and poses a significant threat to the ongoing viability of livestock farms in New Zealand. The issues around drench resistance are well documented with recent laboratory testing data showing approximately 30% of farms tested had triple drench-resistant parasites.

Less well-known is the situation around ectoparasites and in particular, blowflies and lice. This is in part due to AgResearch disestablishing its highly regarded entomology unit over twenty years ago. Since then, we have had to rely on Australian data and scientists for guidance.  

What is known is that the European Green blowfly was proven to be highly resistant to triflumuron, the active ingredient in Zapp in 2010-11, with the North Waikato/South Auckland region being particularly affected. This resistance showed up as a very reduced protection period. The active ingredient diflubenzuron, found in Magnum and Unlock Pour On and Unlock Concentrate, is very similar to triflumuron. It is important to note that neither of these active ingredients is used for blowfly or louse control in Australia, due to the widespread and high-level resistance by both parasites (triflumuron was never used for fly control in Australia but is no longer sold for louse control).

Using products containing these actives will put your sheep at risk this summer.

It is important to know what active ingredients are in your flystrike prevention products and understand any resistance issues. We believe using Magnum (Ewe & Lamb), Unlock (Pour on, Concentrate & Combo) & Zapp Encore poses a risk to your stock and, importantly, peace of mind.

We recommend that you use Clikzin for docking and medium-term fly protection, which has a short withholding period and no known resistance in NZ. Clik Extra is recommended for unmatched long-term protection. Cyrex is a proven combination jetting liquid on the market, which covers off flies, maggots and lice. The active ingredients of CLiKZiN, CLiK Extra and Cyrex are unrelated to triflumuron and diflubenzuron and have a different IGR mode of action

If you would like more information on what products would suit your sheep’s needs best, please get in contact with your local Franklin Vets Clinic.

Matt Airey – Sales Manager


Franklin Vets

Franklin Vets - excellence in veterinary care for dairy, farming, lifestyle, equine and household pets. BESTPRACTICE ACCREDITED NZ.