The best control is a program to reduce immature cattle tick numbers on the paddock. The following strategies can help to achieve this:
Cattle tick can be challenging to control in Australia due to increasing chemical resistance, changes to land use, increased feral animal movements and limited availability of cattle dips. A solution to more effective tick control can be found by understanding weaknesses in the tick life cycle and implementing strategic treatments that reduce paddock contamination. Cattle tick control needs to focus not just on occasional removal of ticks from the cattle, but instead a well-planned program that aims to reduce future tick burdens by lowering the number of immature ticks in pasture. See also the section on moving cattle.
A weakness in the tick life cycle is the delay before female ticks fall off cattle and lay their eggs. The cattle tick life cycle is an average of 21 days. Female cattle ticks feed on blood for 7 to 12 days. By the 19th day after attachment as larvae, the females start to mature, once they reach 4-5mm long they engorge overnight and drop to the ground early the next morning. Once on the ground, the females commence egg laying within a few days and can lay up to 2500 eggs. The more female ticks that can be prevented from surviving to produce eggs, the cleaner the pastures will be. Research has indicated that intermittent or unplanned treatment of cattle does little to control tick problems.
Instead, controlling ticks to a level that will promote increased productivity needs a planned program that consecutively suppresses at least 4-5 female tick cycles i.e. chemical suppression for at least 100 days. If a plunge dip or spray race is used, it is best practice to implement 5 consecutive treatments 18-21 days apart. This will then allow a long break in treatment. When pour-on or injectable treatments are used, the re-treatment interval and frequency will depend on the label claims of the product. Pour-on products also are ideally used for 5 consecutive treatments, 21 days apart, while with some macrocyclic lactone (ML) injections, 4 treatments 28 days apart can be used. A long-acting moxidectin injection used twice 56 days apart will suppress egg laying for at least 121 days. Up to three treatments of fluazuron (a growth inhibitor, IGR) can be used to suppress female tick reproduction throughout the season.
The timing of treatments is essential for a successful program. Treatments should begin when tick numbers are first observed to be increasing in spring. By implementing a planned program at this time, it is possible to prevent the typical rapid rise in adult tick numbers throughout summer and early autumn. Autumn is also a strategic time for treatment to reduce the number of eggs that will be laid in pasture to survive and hatch the next spring. For more regional information see the section on best time to count cattle ticks.
Strategic timing of different treatments in a program can improve tick control and reduce the risk of chemical resistance. For example, repeated macrocyclic lactone (ML) tick treatments in early spring may be followed by different chemical classes in late spring such as fluazuron or amitraz. Combining chemicals from different classes prevents the survival of resistant ticks. For example, when attempting to clear cattle of tick burdens, it is best practice to combine an ML injection initially with a clearance dip about a week later. The delay in dipping ensures that the ML and dip actives are timed for maximum efficacy. It is important before designing a program with multiple chemicals that you have up-to-date information on what chemicals are still working on your farm. You can do this by submitting ticks to a laboratory for resistance testing.
You can reduce your reliance on chemicals by using different strategies for younger and older cattle. A highly effective strategy for very contaminated paddocks is to use a ‘paddock sweeping’ approach where heifers and/or steers are placed at a high stocking rate and are protected by a suppressive chemical program as explained previously. Ticks are attracted, attach and remain on the young cattle, ‘sweeping’ the paddocks clean, and the chemical treatment prevents the ticks from egg laying. Once a paddock is considered to have a low tick burden, the younger stock can be moved to another paddock and cow and calf units moved in. This approach decreases the frequency of chemical treatment of cows and calves.
Another weaknesses in the cattle tick life cycle is that immature, or seed ticks, cannot survive forever on pasture. How long they survive depends on local climatic conditions, but it is never more than 8-9 months. Seed-ticks do not survive as well in hot and dry conditions. For example, when maximum temperatures are above 25 degrees, 90% of seed ticks will die within a month. This is compared to maximum temperatures less than 20 degrees where only 50% of seed ticks die within a month. Paddock spelling, where one or more paddocks are kept free of cattle for a period of time greatly assists tick control. It may not be practical for all farms, but whenever possible it is a good practice. Spelling some paddocks in summer for at least 3 months will remove many seed ticks — five months is needed in winter. Paddock spelling can be combined with a rotational grazing strategy, where treated cattle are moved into a paddock that is likely to only have a small tick burden. This will reduce the number of chemical treatments needed. Cattle need to be kept in their original paddock for 3-5 days after treatment, before being moved to the lower tick burden paddock to allow the chemical to work and to prevent the spread of viable ticks to the new paddock.