Bait Shy?

In response to issues with the use of 1080 and brodifacoum for possum control, a momentum is developing to enable the introduction of alternative toxins, baits and delivery systems. 

by Professor Charles Eason and Dr Shaun Ogilvie, Lincoln University.

Considerable effort has been put into improving and refining the use of 1080. While there are no “silver bullet replacements”, we are now moving to a time for new product registration advancement.

Collaboration between Lincoln, Otago and Auckland universities, the Department of Conservation, regional councils, pest control professionals and community groups – coupled with Animal Health Board and Foundation for Research, Science and Technology (FRST) support – is accelerating the development of new toxin research and new product registrations.

Research on biocontrol of vertebrate pests remains an important and major focus. But there is a gap between conventional poisons and hopes for the future that needs to be filled.

In response to issues with the use of 1080 and brodifacoum for possum control, a momentum is developing to enable the introduction of alternative toxins, baits and delivery systems within one-to-six years for the control of possums, rodents, other predators such as stoats and rabbits.

New tools require approval from the Environmental Risk Management Authority (ERMA) and New Zealand Food Safety Authority (NZFSA). Consultation with Maori is a prerequisite. Welfare considerations, and the need for demonstrating effective control of pests with minimum non-target impacts, are key components.

The new tools pipeline includes: products that contain vertebrate pesticides already in use in New Zealand; products that contain vertebrate pesticides not already in use in New Zealand; and registration in New Zealand of a new generation of vertebrate pesticides.

Efforts to extend existing registrations have focused on cyanide, because, in appropriate doses, cyanide kills possums humanely without risk of secondary poisoning. Feratox® (cyanide pellets) is now also under development for control of wallabies, while work continues to produce effective formulations for ferret control. New “low residue” poisons – zinc phosphide and a combination of coumatetrayly and cholecalciferol – are being developed in multi-species bait formulations to target both possums and rodents. These are being developed as potential alternatives to 1080 and brodifacoum, respectively, and are effective for possum, rodent and rabbit control with low secondary poisoning risks and limited environmental persistence.

Zinc phosphide has been favoured for field use in the United States, as well as in Australia, China and the Asia–Pacific region for field control of rodents and some larger pests. It is quick acting in possums, rabbits and rodents and would make a suitable back-up to 1080. The first zinc phosphide containing product could be available next year, subject of course to ERMA approval. Less expensive formulations of cholecalciferol should also be well advanced by next year.

In parallel, efforts to complete the registration of completely novel humane poisons have accelerated. For example, para aminopropiophenone (PAPP) – has the potential to become the second vertebrate pesticide product designed with humaneness as a primary consideration and the first new compound to be developed for 30 years. PAPP could become an important tool for stoat control and kiwi protection, it is humane, not persistent, has an antidote and does not cause secondary poisoning. Dossiers for chemistry and manufacturing, toxicology, efficacy, ecotoxicology and non-target impacts, and welfare were filed with NZFSA last year and ERMA this year. New initiatives in the FRST programme “Pest Control for the 21st Century”, which started on 1 October this year, also include screening of PAPP analogues with a similar mode of action for rodents and possums, and identifying other active ingredients that cause rapid death.
Looking to the future, we anticipate more and better control tools combining “low residue” characteristics with humaneness.