Brown Besier, DAFWA, Albany (firstname.lastname@example.org):
With hot weather finally general across the state, worm control will become easier after the problems experienced by many farmers in December and even January. The continued bouts of rain over summer not only interrupted the harvest, but delayed the traditional drenching onto crop stubbles. In the Great Southern region, especially, leaving weaner sheep longer than normal for a summer drench allowed worm burdens to rise well above levels usually seen at this time of year, with severe disease and losses in many cases.
The risk will be swiftly removed when sheep are drenched onto stubble paddocks, provided that the drench was effective. Where sheep went onto a pasture paddock after a summer drench, the outcome depends on the amount of green pasture left. In most cases, the only green to be seen will be summer weeds, which are not usually a major risk for worms. Typical summer temperatures usually kill worm eggs rapidly, and limit the period of survival of any larvae that do develop.
However, a risk of further worm pick-up remains where there are significant areas of dense green pasture (or heavy weed infestations), and there are periods of relatively mild weather (maximum temperatures below about 25°C). This may occur to a small extent in niche areas in inland areas, but will not usually lead to a significant worm problem. Along the South Coast, however, there is likely to be a continued intake of low to moderate levels of worm larvae from pasture. Conducing worm egg counts in late summer is recommended to ensure that sheep don’t enter autumn carrying more worms that it is realised - these are the source of worm disease outbreaks in winter.
Of particular significance, we have seen many more outbreaks of disease due to Barber’s Pole worm than for several years. Even where it has not been seen for some time, this worm species often hangs on at low levels until conditions are suitable, and unexpected and rapid increases can occur. Again, a worm egg count is mid-late summer is recommended in areas where Barber’s Pole has been present in the past, especially in weaners and hogget-age sheep.
Reports of Barber’s Pole worm in inland areas where it has not been seen in past years have proved incorrect - the high worm egg counts have been almost entirely due to “Scour worms” types, but at far higher levels than seen for many years.
With the continued and often heavy summer rains, pasture nutritional quality has been significantly eroded in much of the major sheep areas. This will be a year for particular vigilance regarding worms, to ensure that nutritional limitations are not compounded by unexpected worm problems.