Effective flystrike prevention in a wet spring

FLYSTRIKE in sheep is one of those things where it is best to put the effort into prevention. Coming back from Christmas holidays to find flyblown lambs and ewes is very demoralising.

Even a 50¢piecesize area of flystrike can stop a ewe cycling for a month. In lambs, the loss of growth, suffering and deaths along with the time dealing with the mess are enough for many to vow to get things sorted before Christmas next year.

The obvious measures are to ensure stock are clean and don’t get wormy. So crutching and a regular effective drenching programme are essential pillars to preventing fly-stike. This wet spring, with rampant growth, has also been ideal for internal parasite development and there appear to be a lot of daggy ewes around. Dags create the perfect environment for fly-breeding.

There are generally three waves of fly pressure, the first few appearing around December, then the second and bigger wave in midsummer, and the third wave midautumn.

This is important when planning your programme, when to apply a product, and what chemical to choose, especially in relation to persistent activity.

Your fly/lice programme for your sheep flock is complex. There are new chemicals on the market to consider and we have to be more aware of chemical resistance and using these resources in an effective and sustainable way.

Mode of delivery and class of stock is one place to start a discussion on fly control.

SPRAYON TREATMENTS

Sprayon products are generally used for lambs at tailing or weaning where you don’t have a jetter/or shower dip. CLiKR sprayon at tailing has been a revolution for lamb fly control, especially finewool lambs giving four to five months protection, but it does have longer meat withhold, which is not ideal for fattening lambs. Cyromazine-based sprayons, such as VetrazinR or CyrazinR, are popular for crossbreds.

JETTING TREATMENTS

Jetting can work out cheaper and faster, and achieves full body coverage. As with all chemical protection, effectiveness depends on the amount and volume applied. Chemical does not work in dags. Single active IGR chemicals such as ZenithR and CyrazinR have claims of up to 12 weeks. These only work as preventatives and do not kill existing strike. Checking to ensure animals are saturated to the skin is important.

EARLY STRIKE

If early strike is already present, then a combination product is advised. CyrexR or CyrazinKO are options, both containing Cyromazine, an IGR for longterm preventative treatment. In addition, they also contain an instantkill chemical. Cyrex contains Spinosad, which is the active ingredient of Extinosad, a widely used lice treatment with good kill of existing maggots. If you do repeatedly use Extinosad at other times, then CyrazinKO could be considered, which contains Ivermectin and has a claim for up to 14 weeks fly protection. Ivermectin does strip out of solution so is not considered for shower dips or where fluid is recycled.

There are, of course, many other finer points to discuss with a veterinarian around fly prevention programmes. The main thing is to make some time to discuss a programme and get the right chemical when (or before) the first wave of fly pressure hits.