Poisoning Possums

Poisons are often the most effective way for landowners to control possums over large areas. They are usually less labour intensive than trapping or shooting.


On this page:

• Using poisons
  
• Poisons used in New Zealand
  
• Brodifacoum
  
• Cyanide
  
• Cholecalciferol
  
• Useful contacts
  

Using poisons

When using poisons:

• READ THE LABEL thoroughly and follow all instructions and safety requirements.
  
• Make sure children recognise poison warning signs and know not to enter control areas.
  
• Seek medical assistance immediately if bait is eaten. Follow the first aid instructions supplied with the bait.
  
• Set bait stations in a tree so they are accessible to possums but away from pets and stock.
  
• Keep pets well fed so they are less likely to scavenge and check them regularly for symptoms, such as loss of appetite or vomiting. Use a mix of flour and curry powder around the bait station to discourage curious cats.

Poisons used in New Zealand

Six poisons are currently registered for possum control in New Zealand.

• 1080
  
• cyanide
  
• cholecalciferol
  
• phosphorus
  
• brodifacoum
  
• pindone.

Only brodifacoum, cyanide and cholecalciferol are commonly used by landowners. Poisons are usually put in bait stations, which helps keep the bait dry and away from non-target animals. By initially filling bait stations with a non-toxic form of the bait you intend to use (pre-feeding), you’ll get a higher kill rate when using fast acting poisons, such as cyanide and cholecalciferol. A pre-feed around one week before placing poison baits should be enough.

Most baits used in pest control are not designed to last for long periods in bait stations. If not clearly stated on the product label, remove and bury remaining bait after about one month.

Brodifacoum

Pestoff™ is a brand name for green dyed cereal pellets containing brodifacoum. You do not require a license to use this bait, which can also be used to control rats, stoats and feral cats. Brodifacoum can be expensive, but is a good option once possum numbers are low.

Brodifacoum bait must be placed in a bait station, which is usually nailed to a suitable tree or post. Keep bait stations out of the reach of stock. To use brodifacoum:

• Place the bait stations 50 to 150 metres apart (one or two bait stations per hectare of bush).
  
• For the first feed, fill the bait stations with about one kilogram of bait.
  
• Refill the bait stations a month later with about 500 grams of bait.
  
• You may have to refill the bait stations again the next month with another 500 grams of bait to get rid of remaining possums.

Brodifacoum safety

• Seek medical advice immediately if you suspect that bait has been consumed.
  
• Repeat doses will be harmful to pets. A vet can give an antidote (Vitamin K1) for brodifacoum poisoning. Symptoms of poisoning include green dye around the mouth, bleeding around the mouth, anus or eyes, blood in the urine and faeces and excessive bleeding from cuts.
  
• Pestoff™ pellets break down quickly to harmless residues on contact with moisture and the brodifacoum slowly breaks down in soil. Brodifacoum is not soluble in water so is not likely to contaminate it.

Cyanide

Cyanide is a deadly poison. A license is required to store, handle and use cyanide. For more information on obtaining a licence contact your local AgriQuality New Zealand Ltd office.

Encapsulated cyanide

Feratox™ is the trade name for encapsulated pellets containing potassium cyanide. This is an effective option for controlling high possum numbers. Cyanide pellets can be placed in bait stations or small, specially labeled bags stapled to trees. Space the bait stations or bags 75 to 150 metres apart:

• Bait stations - place about six poison baits in each station. Before using the bait, use non-toxic feed pellets to encourage possums to feed.
  
• Bags - place one or more pellets in the bag along with some non-toxic lure, such as peanut butter or Ferafeed ™ paste.

Cyanide paste

• Place pea-sized baits of cyanide paste on a handful of flour ‘lure’ on the ground or at the base of trees. Smaller baits generally work better than large baits.
  
• Create a 'line' of baits, about 20 metres apart, depending on how many possums are around.
  
• Remove baits following the operation (around three days). This prevents possums from becoming bait shy from eating ‘sub-lethal’ baits that have started to break down.

Cyanide safety

Cyanide may be used by biosecurity pest officers and approved contractors on private or public land, or by licensed individuals on private land. Wherever cyanide is used, you must seek permission from the Medical Officer of Health, advertise the project publicly (if used on public land) and post warning signs. On private land, you must seek the owner’s consent and put up warning signs.

Cyanide breaks down rapidly in the carcass so scavenging animals are not at risk. It also ‘detoxifies’ very quickly when exposed to the environment. It does not build up in soil or the food chain, or contaminate water. Feratox™ pellets deteriorate on contact with moisture and break down in 6 to 14 weeks. Cyanide paste baits break down much faster.

Cholecalciferol

Feracol™ is the brand name for cholecalciferol paste otherwise known as Vitamin D paste. You do not require a licence to buy or use this product. Cholecalciferol baits can be expensive to buy, but are effective in low doses and can be reasonably cost-effective.

Feracol™ paste can be put into bait stations but is often put into specially labeled bags and stapled to trees or posts, 20 to 30 metres apart. Around 25 grams of bait should be enough to kill one possum. Keep livestock well away from poison baits.

Cholecalciferol baits may also control rats but are unlikely to also kill animals feeding on poisoned rats or possums. Birds are very resistant to the effects of cholecalciferol.

Cholecalciferol safety

• Cholecalciferol is harmful to people if swallowed repeatedly in large doses. Seek medical assistance immediately if you suspect poisoning. Symptoms include headache, nausea, loss of appetite, excessive thirst and muscle weakness.
  
• Cholecalciferol will be harmful and possibly fatal to pets if eaten. Symptoms include loss of appetite, tiredness and vomiting. Take your pet to a vet as quickly as possible if you suspect poisoning.

Useful contacts

Contact your local Biosecurity Animal Pest Contractor for additional advice and information on effective methods of control.

For enquiries on policy and procedural matters, call Environment Waikato’s Freephone 0800 800 401.

You can buy possum control products from the following suppliers.