Australian mouse plague: ‘napalming’ rodents may kill native and home animals too | Surroundings

Leading rodent experts say they are “not convinced” that a new poison injected by the New South Wales government as “napalm” for mice will seriously affect the state’s plague and warn that the risk of killing native and domestic animals is significantly higher.

Rodents are still prevalent in much of interior New South Wales and southern Queensland, costing some farmers more than $ 100,000 in destroyed crops and damage to stored hay and grain. Cases of leptospirosis – a potentially fatal disease that can be transmitted from mice to humans – have nearly doubled this year in Queensland, with health officials citing the increased numbers of rodents as a possible cause.

NSW Agriculture Secretary Adam Marshall announced on Thursday a $ 50 million support package promising to “forget about these things.”

The government had hoped heavy rains and the winter cold would dampen the numbers before new crops were planted, but populations have really recovered in some areas since the autumn floods. This led the NSW Farmers Association and the Country Women’s Association of NSW to designate the plague as an urgent economic and health emergency and call for government intervention.

In response, the state government has filed an urgent petition with the Australian Federal Government’s Pesticides and Veterinary Medicines Agency to approve widespread agricultural use of the anticoagulant bait bromadiolone, which is currently banned from use in fields.

“It will be the equivalent of napalming mice in rural NSW,” Marshall told ABC. “This chemical, this poison, kills mice that take this bait within 24 hours.”

Bromadiolone is the central component in most household and industrial rodent baits, but is generally not used on an agricultural scale.

Dr. Peter Brown, head of the rodent management research team at CSIRO, said that unlike zinc nitrate baits commonly used in grain fields, bromadiolone remains in the body of mice after they die.

“The anticoagulants can build up in the food chain so that birds of prey or other animals can feed on dead mice and possibly receive a lethal dose themselves from secondary poisoning.”

Brown said killing other animals isn’t the only possible environmental impact from using the poison.

“There have been published studies dealing with owls. They eat dead mice that have been poisoned by anticoagulants [and then] They are unable to hatch young ones successfully because something is wrong with the way the eggshells form, for example, ”he said.

“[Anticoagulant rodenticides] were not so widespread, so widespread that the effects are unknown. ”

A vet in South Tamworth, Dr. Peter Best said his practice had been treating bait-poisoned animals – “the whole crowd, pets, working dogs” – for the past few months of mouse plague. He estimated that one in 15 shots was due to bait poisoning.

Bromadiolone has not yet received federal regulator approval, but Marshall told ABC that he was confident it would be granted.

The state government’s plan envisages the establishment of eight grain treatment stations across NSW, where farmers can treat their grain with the poison free of charge.

James Jackson, president of the NSW Farmers Association, welcomed the announcement, saying the possibility that native animals could be affected was “the lesser of two evils”.

“It will cause poisoning in animals that eat the dead mice, yes, while zinc phosphide does not,” he said.

“The problem is that the mice already have a significant impact. It is the lesser of two evils right now. Yes, it may have an impact on other animals, but that’s one of the reasons we need some new tools. “

Jackson said this was why his organization was delighted to hear that the government bailout package included funding research into new kills for mice.

“[Bromadiolone] is certainly a useful tool, but it is not the silver bullet that solves the plague overnight, ”he said.

Growing numbers of farmers have urged bromadiolone to be approved for use because of widespread concern that the traditional rodenticide zinc phosphide is not effective in controlling large numbers of mice.

Anticoagulant toxins have two main benefits: a single grain of bait wheat is generally enough to deliver a lethal dose, and it has delayed effectiveness. This means that the mouse will not feel sick for several days. Even if a single dose isn’t enough to kill them, they likely have time to eat more poisoned grains before they become suspicious.

“When a rodent eats poison and gets really sick [temporarily]They won’t keep eating it because they may associate illness with eating this poison, “Brown said.

On the recommendation of the CSIRO, the pesticides and federal veterinary authorities have now approved an emergency permit for double-strength zinc phosphide, which means that a single grain of this poison is now enough to deliver a lethal dose. As soon as this new starch zinc phosphide hits the market, its effectiveness on farms should increase dramatically.

Brown said it was now unclear what the benefits would be of adding the more environmentally destructive bromadiolone bait.

“I don’t think I’m convinced that taking another bite alongside something we know should work would actually help solve the problem on such a large scale.”

But he said farmers’ personal perceptions of which baits are effective is also an important factor.

“We have to give the farmers tools to do something because the last thing we want is for them to make their own preparations and then birds will fall from the sky which has happened in the past,” he said.

“But we still have a tool that should work, namely zinc phosphide.”

The government support package also includes discounts of up to $ 500 for households and $ 1,000 for small businesses for bait deliveries.

The government has also hired a mouse expert and CSIRO research officer, Steve Henry, to run training workshops to help people understand the number of mice in their area and spot any signs of a mouse problem early on to avoid the numbers in the Spring hits rise again.

Guardian Australia has requested an answer from the NSW Secretary of Agriculture’s office.