Managing risk when controlling vermin
'Vermin' is a broad term that generally relates to a range of vertebrate pests such as rats and mice, foxes, wild dogs, rabbits and hares.
The control of any pest is best achieved with an Integrated Pest Management (IPM) plan that utilises a range of strategies to achieve the best possible level of control. IPM strategies include:
- Physical control (e.g. using a bulldozer with rippers to destroy harbour, warrens, or dens)
- Cultural control (e.g. changing lambing paddocks to a paddock that offers less cover for foxes)
- Biological control (e.g. Rabbit Calicivirus Disease used to control rabbits)
- Genetic control (e.g. resistant varieties - not yet used for vermin control in Victoria)
- Quarantine (e.g. fencing out a forest block to 'quarantine' the paddock from the pests)
- Chemical control (e.g. using poison baits to control a range of vertebrate pests).
Assuming that an IPM plan is implemented using a range of the strategies listed above, it is reasonable that chemical control may play a part in the program.
Chemicals used for vermin control are formulated in a number of ways. For example, aluminium phosphide tablets used in rabbit control react with moisture in the air to release toxic phosphine gas that fumigates the treated warren. Other chemicals produce carbon monoxide gas or chloropicrin gas to fumigate the burrow or den.
These chemicals require a high level of expertise and diligence in their use, as fumigant gases can have significant and acute adverse effects on the user when things go wrong. In addition, most of these fumigant chemicals are Schedule 7 Poisons (Dangerous Poisons), and require the user to have completed a course in safe chemical use and hold a proper authorisation for their use.
Bait formulations are often used as part of IPM, because it is not always easy or possible to identify a den, nest or warren. The pest may also be transient in an area, as in the case of foxes, and in the case of mice infestations there may simply be too many holes in a paddock to treat each one individually.
Baits are a concern because by their nature, they contain a food source to attract the pest, and a poison to kill the pest. We don't want to be attracting non-target animals such as native marsupials, or the neighbour's dog to the bait. To overcome this potential concern, registered baits are formulated to deter or limit their attractiveness to non-target animals.
This is achieved through a range of strategies such as:
- formulating the bait using a chemical that is more selective to the pest than to non-target animals
- the addition of bittering agents to limit bait intake by non-target animals
- colouring the bait to make it unattractive to non-target animals
- using only a certain amount of bait
- leaving the husk on grain bait, or removing it depending on the nature of the target animal
- burying the bait to make it unavailable to non-target animals
- covering the bait after a certain period of time to limit access by non-target animals.
For some bait formulations, there is also a requirement to post warning signs and to notify neighbours so they can take precautions to prevent any unwanted access to the baits. Each strategy works to ensure that the pest animal is targeted, and that the risks to non-target animals are minimised.
Illegal bait issues
Unfortunately, there have been instances where people have illegally used chemicals they had access to, and made baits to control animals they viewed as vermin.
In these cases, the illegal bait has not been formulated to limit access by non-target animals, and the Department of Economic Development, Jobs, Transport and Resources(DEDJTR) has received complaints in relation to the poisoning of non-target animals, including domestic animals and protected wildlife.
Experience shows that when illegal baits are used, their effects are generally non-selective to the targeted pest, and the negative outcomes can be frightening.
For example, a person laid a home-made grain bait to control corellas (which is illegal in any case, because these birds are protected), and killed not only corellas, but cockatoos, ducks, magpies, mudlarks, brown hawks, kookaburras and a range of other bird species. Not all of these birds eat grain, and it is likely that the raptors, like the hawks and kookaburras, were poisoned after feeding on other birds (or animals) that had died after consuming the home-made grain bait.
In another example of illegal baiting, a person who lived on the outskirts of a sizeable rural city prepared and laid baits made from meat, laced with strychnine to poison foxes. Instead of killing foxes, he killed a number of his neighbour's domestic dogs. The grief this caused the local residents was both considerable and unwarranted.
Bait formulations must be used strictly according to the label Directions for Use to ensure the best possible outcome. Many of these products are 'restricted supply' (high risk chemicals such as 1080), 'restricted use' chemicals, or both.
- 'Restricted use' chemicals are agricultural chemical products that:
- are Schedule 7 Poisons (Dangerous Poisons)
- contain atrazine, metham sodium or ester formulations of 2,4-D, 2,4-DB, MCPA or triclopyr.
In Victoria, an Agricultural Chemical User Permit (ACUP) must be held to purchase 'restricted supply' chemical products and use 'restricted use' chemical products.
Specified records must be made within 48 hours of using an agricultural chemical product, and kept for a period of two years. This applies to all agricultural chemicals used, including poison baits used for pest animal control. This requirement came into effect on 24 July 2007 and excludes the use of household or home garden products.
In addition, the penalties for misuse of vermin baits are significant, and if non-vermin animals are targeted, the penalties are even more significant, and can include the imposition of heavy fines and in some cases, even imprisonment.
Chemicals can play an important role in IPM in helping to ensure the best possible outcome is achieved. Whenever using chemicals to control vermin, remember that these chemicals need to be used carefully, and always in accordance with the label Directions for Use.
DEPI Chemical Standards Officers
Fax: (03) 5430 4590
|Steve Field||(03) 5430 4463|
|Alex Perera||(03) 5430 4591|
|Felicity Collins||(03) 5833 5203|
|Neil Harrison||(03) 5336 6616|
|Jane Rhodes||(03) 5147 0832|
Enquiries from other regions should be directed to the nearest of the above-named regional officers.
Published and Authorised by:
Department of Environment and Primary Industries
1 Spring Street
This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication