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South Australia worms, flies and lice update - January 2015

Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (trengovet@icloud.com)

Dorothea McKellar once penned (1904)….”I love a sunburnt country……A land…. of droughts and flood rains"….well we have started 2015 with fires and flooding rains and don’t need the other bit. Falls of 100–200 mm were received across much of SA in the second week of January ending 2 months of mild dry weather, which allowed uninterrupted harvest and shearing as well as sustained dry feed quality at least into early summer. While rainfall of this magnitude is not the preferred option for grape growers or horticulturalists, it will give a big boost to pastoralists and graziers—especially some in northern SA receiving their annual rainfall in one episode. The downside is the first law of physics—for every action there is an equal an opposite reaction or “what goes around comes around". In this case the sudden influx of copious soil moisture combined with summer heat will promote abundant summer weeds such as melons and heliotrope. These will only serve to eventually clog cultivators or cause liver damage to grazing sheep respectively. In addition, worm larvae will emerge in their droves with the optional fate of death by dehydration or finding refuge in the belly of an unsuspecting ruminant. It is the latter option that graziers need to be monitoring as a sudden outbreak of Barber’s pole worm (Haemonchus contortus) 4–6 weeks after 50+mm is a real possibility. This can be averted by monitoring at-risk populations around 4 weeks after such deluges.

Recent monitoring has been scant as presumably harvest combined with the dry lead up to Christmas and scant need for supplementary feed has led to many/most stock owners leaving sheep to graze undisturbed. The reports of what monitoring has been done indicates a third of mobs, especially weaners and hoggets, had counts high enough to warrant a drench. This would indicate those who routinely drench in early summer may not have needed to. Alternatively, those who haven’t bothered to monitor may have needed to. Either way if you have received 50+mm rain in early January it will pay to check worm egg counts at month's end to ensure a scouring or blood sucking scourge is not about to wreak havoc in your flock.