Chemical options for flystrike
An animal health scientist is urging sheep farmers to use different chemicals to prevent and treat flystrike.
Different chemicals should be used to protect sheep from lice and flies, and farmers should avoid repeat use of the same chemical, Novartis Animal Health technical services manager Colin McKay says.
He was speaking to about 30 people at last week's Taranaki Sheep Focus Day, organised at Tikorangi by Inglewood Veterinary Services and Beef + Lamb NZ. McKay said farmers should seek veterinary advice on why their sheep suffered flystrike, and talk with vets if they had problems controlling flies.
Research showed that when blowflies developed resistance to chemicals, it was rapid, and the loss of protection sheep received was dramatic, he said.
Flies caused sheep extra stress, which led to production losses, loss of libido in rams, decreased fertility in ewes, loss of wool quality, and increased labour costs.
The Australian green blowfly, which targets live sheep to lay its maggots, established itself in this country in the 1980s.
After becoming established in the Waikato, the fly hitch-hiked on sheep as they were transported, and is now found throughout New Zealand. With the blowfly becoming established here, sheep farmers had to adopt new dipping practices.
During the average two to four- week life cycle of blowflies, eggs hatch if there is moisture in the sheep's fleece. The second and third stages of the larvae are the most harmful and cause major tissue damage in a short time.
Risk factors for flystrike are odour, wet or wrinkled fleece, diarrhoea, dags, and docking ewe lamb tails too short. McKay said the two types of insect growth regulator chemicals used to prevent flystrike affected the ability of the maggot to moult and form an external skeleton.
Taranaki Daily News